Implement complete Android app code

- Add models: Note, SyncStatus
- Add storage: NotesStorage for local file system
- Add sync: WebDavSyncService, SyncWorker, WifiSyncReceiver
- Add UI: MainActivity, NoteEditorActivity, SettingsActivity
- Add adapters: NotesAdapter
- Add utils: Constants, DeviceIdGenerator, Extensions, NotificationHelper
- Add layouts: activity_main, activity_editor, activity_settings, item_note
- Add menus and strings

android/app/src/main/java/dev/dettmer/simplenotes/MainActivity.kt

@@ -1,20 +1,160 @@
 package dev.dettmer.simplenotes
 
+import android.Manifest
+import android.content.Intent
+import android.content.pm.PackageManager
+import android.os.Build
 import android.os.Bundle
-import androidx.activity.enableEdgeToEdge
+import android.view.Menu
+import android.view.MenuItem
 import androidx.appcompat.app.AppCompatActivity
-import androidx.core.view.ViewCompat
+import androidx.recyclerview.widget.LinearLayoutManager
-import androidx.core.view.WindowInsetsCompat
+import androidx.recyclerview.widget.RecyclerView
+import com.google.android.material.appbar.MaterialToolbar
+import com.google.android.material.floatingactionbutton.FloatingActionButton
+import dev.dettmer.simplenotes.adapters.NotesAdapter
+import dev.dettmer.simplenotes.storage.NotesStorage
+import dev.dettmer.simplenotes.utils.NotificationHelper
+import dev.dettmer.simplenotes.utils.showToast
+import android.widget.TextView
 
 class MainActivity : AppCompatActivity() {
+    
+    private lateinit var recyclerViewNotes: RecyclerView
+    private lateinit var textViewEmpty: TextView
+    private lateinit var fabAddNote: FloatingActionButton
+    private lateinit var toolbar: MaterialToolbar
+    
+    private lateinit var adapter: NotesAdapter
+    private val storage by lazy { NotesStorage(this) }
+    
+    companion object {
+        private const val REQUEST_NOTIFICATION_PERMISSION = 1001
+    }
+    
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
-        enableEdgeToEdge()
         setContentView(R.layout.activity_main)
-        ViewCompat.setOnApplyWindowInsetsListener(findViewById(R.id.main)) { v, insets ->
+        
-            val systemBars = insets.getInsets(WindowInsetsCompat.Type.systemBars())
+        // Notification Channel erstellen
-            v.setPadding(systemBars.left, systemBars.top, systemBars.right, systemBars.bottom)
+        NotificationHelper.createNotificationChannel(this)
-            insets
+        
+        // Permission für Notifications (Android 13+)
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
+            requestNotificationPermission()
+        }
+        
+        findViews()
+        setupToolbar()
+        setupRecyclerView()
+        setupFab()
+        
+        loadNotes()
+    }
+    
+    override fun onResume() {
+        super.onResume()
+        loadNotes()
+    }
+    
+    private fun findViews() {
+        recyclerViewNotes = findViewById(R.id.recyclerViewNotes)
+        textViewEmpty = findViewById(R.id.textViewEmpty)
+        fabAddNote = findViewById(R.id.fabAddNote)
+        toolbar = findViewById(R.id.toolbar)
+    }
+    
+    private fun setupToolbar() {
+        setSupportActionBar(toolbar)
+    }
+    
+    private fun setupRecyclerView() {
+        adapter = NotesAdapter { note ->
+            openNoteEditor(note.id)
+        }
+        recyclerViewNotes.adapter = adapter
+        recyclerViewNotes.layoutManager = LinearLayoutManager(this)
+    }
+    
+    private fun setupFab() {
+        fabAddNote.setOnClickListener {
+            openNoteEditor(null)
+        }
+    }
+    
+    private fun loadNotes() {
+        val notes = storage.loadAllNotes()
+        adapter.submitList(notes)
+        
+        // Empty state
+        textViewEmpty.visibility = if (notes.isEmpty()) {
+            android.view.View.VISIBLE
+        } else {
+            android.view.View.GONE
+        }
+    }
+    
+    private fun openNoteEditor(noteId: String?) {
+        val intent = Intent(this, NoteEditorActivity::class.java)
+        noteId?.let {
+            intent.putExtra(NoteEditorActivity.EXTRA_NOTE_ID, it)
+        }
+        startActivity(intent)
+    }
+    
+    private fun openSettings() {
+        startActivity(Intent(this, SettingsActivity::class.java))
+    }
+    
+    override fun onCreateOptionsMenu(menu: Menu): Boolean {
+        menuInflater.inflate(R.menu.menu_main, menu)
+        return true
+    }
+    
+    override fun onOptionsItemSelected(item: MenuItem): Boolean {
+        return when (item.itemId) {
+            R.id.action_settings -> {
+                openSettings()
+                true
+            }
+            R.id.action_sync -> {
+                // Manual sync trigger could be added here
+                showToast("Sync wird in den Einstellungen gestartet")
+                true
+            }
+            else -> super.onOptionsItemSelected(item)
+        }
+    }
+    
+    private fun requestNotificationPermission() {
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
+            if (checkSelfPermission(Manifest.permission.POST_NOTIFICATIONS) 
+                != PackageManager.PERMISSION_GRANTED) {
+                requestPermissions(
+                    arrayOf(Manifest.permission.POST_NOTIFICATIONS),
+                    REQUEST_NOTIFICATION_PERMISSION
+                )
+            }
+        }
+    }
+    
+    override fun onRequestPermissionsResult(
+        requestCode: Int,
+        permissions: Array<out String>,
+        grantResults: IntArray
+    ) {
+        super.onRequestPermissionsResult(requestCode, permissions, grantResults)
+        
+        when (requestCode) {
+            REQUEST_NOTIFICATION_PERMISSION -> {
+                if (grantResults.isNotEmpty() && 
+                    grantResults[0] == PackageManager.PERMISSION_GRANTED) {
+                    showToast("Benachrichtigungen aktiviert")
+                } else {
+                    showToast("Benachrichtigungen deaktiviert. " +
+                        "Du kannst sie in den Einstellungen aktivieren.")
+                }
+            }
         }
     }
 }

android/app/src/main/java/dev/dettmer/simplenotes/NoteEditorActivity.kt

@@ -0,0 +1,134 @@
+package dev.dettmer.simplenotes
+
+import android.os.Bundle
+import android.view.Menu
+import android.view.MenuItem
+import androidx.appcompat.app.AlertDialog
+import androidx.appcompat.app.AppCompatActivity
+import dev.dettmer.simplenotes.models.Note
+import dev.dettmer.simplenotes.models.SyncStatus
+import dev.dettmer.simplenotes.storage.NotesStorage
+import dev.dettmer.simplenotes.utils.DeviceIdGenerator
+import dev.dettmer.simplenotes.utils.showToast
+import com.google.android.material.textfield.TextInputEditText
+
+class NoteEditorActivity : AppCompatActivity() {
+    
+    private lateinit var editTextTitle: TextInputEditText
+    private lateinit var editTextContent: TextInputEditText
+    private lateinit var storage: NotesStorage
+    
+    private var existingNote: Note? = null
+    
+    companion object {
+        const val EXTRA_NOTE_ID = "extra_note_id"
+    }
+    
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        setContentView(R.layout.activity_editor)
+        
+        storage = NotesStorage(this)
+        
+        // Setup toolbar
+        supportActionBar?.apply {
+            setDisplayHomeAsUpEnabled(true)
+            setHomeAsUpIndicator(android.R.drawable.ic_menu_close_clear_cancel)
+        }
+        
+        // Find views
+        editTextTitle = findViewById(R.id.editTextTitle)
+        editTextContent = findViewById(R.id.editTextContent)
+        
+        // Load existing note if editing
+        val noteId = intent.getStringExtra(EXTRA_NOTE_ID)
+        if (noteId != null) {
+            existingNote = storage.loadNote(noteId)
+            existingNote?.let {
+                editTextTitle.setText(it.title)
+                editTextContent.setText(it.content)
+                supportActionBar?.title = "Notiz bearbeiten"
+            }
+        } else {
+            supportActionBar?.title = "Neue Notiz"
+        }
+    }
+    
+    override fun onCreateOptionsMenu(menu: Menu): Boolean {
+        menuInflater.inflate(R.menu.menu_editor, menu)
+        
+        // Show delete only for existing notes
+        menu.findItem(R.id.action_delete)?.isVisible = existingNote != null
+        
+        return true
+    }
+    
+    override fun onOptionsItemSelected(item: MenuItem): Boolean {
+        return when (item.itemId) {
+            android.R.id.home -> {
+                finish()
+                true
+            }
+            R.id.action_save -> {
+                saveNote()
+                true
+            }
+            R.id.action_delete -> {
+                confirmDelete()
+                true
+            }
+            else -> super.onOptionsItemSelected(item)
+        }
+    }
+    
+    private fun saveNote() {
+        val title = editTextTitle.text?.toString()?.trim() ?: ""
+        val content = editTextContent.text?.toString()?.trim() ?: ""
+        
+        if (title.isEmpty() && content.isEmpty()) {
+            showToast("Titel oder Inhalt darf nicht leer sein")
+            return
+        }
+        
+        val note = if (existingNote != null) {
+            // Update existing note
+            existingNote!!.copy(
+                title = title,
+                content = content,
+                updatedAt = System.currentTimeMillis(),
+                syncStatus = SyncStatus.PENDING
+            )
+        } else {
+            // Create new note
+            Note(
+                title = title,
+                content = content,
+                deviceId = DeviceIdGenerator.getDeviceId(this),
+                syncStatus = SyncStatus.LOCAL_ONLY
+            )
+        }
+        
+        storage.saveNote(note)
+        showToast("Notiz gespeichert")
+        finish()
+    }
+    
+    private fun confirmDelete() {
+        AlertDialog.Builder(this)
+            .setTitle("Notiz löschen?")
+            .setMessage("Diese Aktion kann nicht rückgängig gemacht werden.")
+            .setPositiveButton("Löschen") { _, _ ->
+                deleteNote()
+            }
+            .setNegativeButton("Abbrechen", null)
+            .show()
+    }
+    
+    private fun deleteNote() {
+        existingNote?.let {
+            storage.deleteNote(it.id)
+            showToast("Notiz gelöscht")
+            finish()
+        }
+    }
+}

android/app/src/main/java/dev/dettmer/simplenotes/SettingsActivity.kt

@@ -0,0 +1,159 @@
+package dev.dettmer.simplenotes
+
+import android.net.wifi.WifiManager
+import android.os.Bundle
+import android.view.MenuItem
+import android.widget.Button
+import android.widget.EditText
+import androidx.appcompat.app.AppCompatActivity
+import androidx.appcompat.widget.SwitchCompat
+import androidx.lifecycle.lifecycleScope
+import dev.dettmer.simplenotes.sync.WebDavSyncService
+import dev.dettmer.simplenotes.utils.Constants
+import dev.dettmer.simplenotes.utils.showToast
+import kotlinx.coroutines.launch
+
+class SettingsActivity : AppCompatActivity() {
+    
+    private lateinit var editTextServerUrl: EditText
+    private lateinit var editTextUsername: EditText
+    private lateinit var editTextPassword: EditText
+    private lateinit var editTextHomeSSID: EditText
+    private lateinit var switchAutoSync: SwitchCompat
+    private lateinit var buttonTestConnection: Button
+    private lateinit var buttonSyncNow: Button
+    private lateinit var buttonDetectSSID: Button
+    
+    private val prefs by lazy {
+        getSharedPreferences(Constants.PREFS_NAME, MODE_PRIVATE)
+    }
+    
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        setContentView(R.layout.activity_settings)
+        
+        supportActionBar?.apply {
+            setDisplayHomeAsUpEnabled(true)
+            title = "Einstellungen"
+        }
+        
+        findViews()
+        loadSettings()
+        setupListeners()
+    }
+    
+    private fun findViews() {
+        editTextServerUrl = findViewById(R.id.editTextServerUrl)
+        editTextUsername = findViewById(R.id.editTextUsername)
+        editTextPassword = findViewById(R.id.editTextPassword)
+        editTextHomeSSID = findViewById(R.id.editTextHomeSSID)
+        switchAutoSync = findViewById(R.id.switchAutoSync)
+        buttonTestConnection = findViewById(R.id.buttonTestConnection)
+        buttonSyncNow = findViewById(R.id.buttonSyncNow)
+        buttonDetectSSID = findViewById(R.id.buttonDetectSSID)
+    }
+    
+    private fun loadSettings() {
+        editTextServerUrl.setText(prefs.getString(Constants.KEY_SERVER_URL, ""))
+        editTextUsername.setText(prefs.getString(Constants.KEY_USERNAME, ""))
+        editTextPassword.setText(prefs.getString(Constants.KEY_PASSWORD, ""))
+        editTextHomeSSID.setText(prefs.getString(Constants.KEY_HOME_SSID, ""))
+        switchAutoSync.isChecked = prefs.getBoolean(Constants.KEY_AUTO_SYNC, false)
+    }
+    
+    private fun setupListeners() {
+        buttonTestConnection.setOnClickListener {
+            saveSettings()
+            testConnection()
+        }
+        
+        buttonSyncNow.setOnClickListener {
+            saveSettings()
+            syncNow()
+        }
+        
+        buttonDetectSSID.setOnClickListener {
+            detectCurrentSSID()
+        }
+    }
+    
+    private fun saveSettings() {
+        prefs.edit().apply {
+            putString(Constants.KEY_SERVER_URL, editTextServerUrl.text.toString().trim())
+            putString(Constants.KEY_USERNAME, editTextUsername.text.toString().trim())
+            putString(Constants.KEY_PASSWORD, editTextPassword.text.toString().trim())
+            putString(Constants.KEY_HOME_SSID, editTextHomeSSID.text.toString().trim())
+            putBoolean(Constants.KEY_AUTO_SYNC, switchAutoSync.isChecked)
+            apply()
+        }
+    }
+    
+    private fun testConnection() {
+        lifecycleScope.launch {
+            try {
+                showToast("Teste Verbindung...")
+                val syncService = WebDavSyncService(this@SettingsActivity)
+                val result = syncService.syncNotes()
+                
+                if (result.isSuccess) {
+                    showToast("Verbindung erfolgreich! ${result.syncedCount} Notizen synchronisiert")
+                } else {
+                    showToast("Verbindung fehlgeschlagen: ${result.errorMessage}")
+                }
+            } catch (e: Exception) {
+                showToast("Fehler: ${e.message}")
+            }
+        }
+    }
+    
+    private fun syncNow() {
+        lifecycleScope.launch {
+            try {
+                showToast("Synchronisiere...")
+                val syncService = WebDavSyncService(this@SettingsActivity)
+                val result = syncService.syncNotes()
+                
+                if (result.isSuccess) {
+                    if (result.hasConflicts) {
+                        showToast("Sync abgeschlossen. ${result.conflictCount} Konflikte erkannt!")
+                    } else {
+                        showToast("Erfolgreich! ${result.syncedCount} Notizen synchronisiert")
+                    }
+                } else {
+                    showToast("Sync fehlgeschlagen: ${result.errorMessage}")
+                }
+            } catch (e: Exception) {
+                showToast("Fehler: ${e.message}")
+            }
+        }
+    }
+    
+    private fun detectCurrentSSID() {
+        val wifiManager = applicationContext.getSystemService(WIFI_SERVICE) as WifiManager
+        val wifiInfo = wifiManager.connectionInfo
+        val ssid = wifiInfo.ssid.replace("\"", "")
+        
+        if (ssid.isNotEmpty() && ssid != "<unknown ssid>") {
+            editTextHomeSSID.setText(ssid)
+            showToast("SSID erkannt: $ssid")
+        } else {
+            showToast("Nicht mit WLAN verbunden")
+        }
+    }
+    
+    override fun onOptionsItemSelected(item: MenuItem): Boolean {
+        return when (item.itemId) {
+            android.R.id.home -> {
+                saveSettings()
+                finish()
+                true
+            }
+            else -> super.onOptionsItemSelected(item)
+        }
+    }
+    
+    override fun onPause() {
+        super.onPause()
+        saveSettings()
+    }
+}

android/app/src/main/java/dev/dettmer/simplenotes/adapters/NotesAdapter.kt

@@ -0,0 +1,66 @@
+package dev.dettmer.simplenotes.adapters
+
+import android.view.LayoutInflater
+import android.view.View
+import android.view.ViewGroup
+import android.widget.ImageView
+import android.widget.TextView
+import androidx.recyclerview.widget.DiffUtil
+import androidx.recyclerview.widget.ListAdapter
+import androidx.recyclerview.widget.RecyclerView
+import dev.dettmer.simplenotes.R
+import dev.dettmer.simplenotes.models.Note
+import dev.dettmer.simplenotes.models.SyncStatus
+import dev.dettmer.simplenotes.utils.toReadableTime
+import dev.dettmer.simplenotes.utils.truncate
+
+class NotesAdapter(
+    private val onNoteClick: (Note) -> Unit
+) : ListAdapter<Note, NotesAdapter.NoteViewHolder>(NoteDiffCallback()) {
+    
+    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): NoteViewHolder {
+        val view = LayoutInflater.from(parent.context)
+            .inflate(R.layout.item_note, parent, false)
+        return NoteViewHolder(view)
+    }
+    
+    override fun onBindViewHolder(holder: NoteViewHolder, position: Int) {
+        holder.bind(getItem(position))
+    }
+    
+    inner class NoteViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
+        private val textViewTitle: TextView = itemView.findViewById(R.id.textViewTitle)
+        private val textViewContent: TextView = itemView.findViewById(R.id.textViewContent)
+        private val textViewTimestamp: TextView = itemView.findViewById(R.id.textViewTimestamp)
+        private val imageViewSyncStatus: ImageView = itemView.findViewById(R.id.imageViewSyncStatus)
+        
+        fun bind(note: Note) {
+            textViewTitle.text = note.title.ifEmpty { "Ohne Titel" }
+            textViewContent.text = note.content.truncate(100)
+            textViewTimestamp.text = note.updatedAt.toReadableTime()
+            
+            // Sync status icon
+            val syncIcon = when (note.syncStatus) {
+                SyncStatus.SYNCED -> android.R.drawable.ic_menu_upload
+                SyncStatus.PENDING -> android.R.drawable.ic_popup_sync
+                SyncStatus.CONFLICT -> android.R.drawable.ic_dialog_alert
+                SyncStatus.LOCAL_ONLY -> android.R.drawable.ic_menu_save
+            }
+            imageViewSyncStatus.setImageResource(syncIcon)
+            
+            itemView.setOnClickListener {
+                onNoteClick(note)
+            }
+        }
+    }
+    
+    private class NoteDiffCallback : DiffUtil.ItemCallback<Note>() {
+        override fun areItemsTheSame(oldItem: Note, newItem: Note): Boolean {
+            return oldItem.id == newItem.id
+        }
+        
+        override fun areContentsTheSame(oldItem: Note, newItem: Note): Boolean {
+            return oldItem == newItem
+        }
+    }
+}

android/app/src/main/java/dev/dettmer/simplenotes/models/Note.kt

@@ -0,0 +1,48 @@
+package dev.dettmer.simplenotes.models
+
+import java.util.UUID
+
+data class Note(
+    val id: String = UUID.randomUUID().toString(),
+    val title: String,
+    val content: String,
+    val createdAt: Long = System.currentTimeMillis(),
+    val updatedAt: Long = System.currentTimeMillis(),
+    val deviceId: String,
+    val syncStatus: SyncStatus = SyncStatus.LOCAL_ONLY
+) {
+    fun toJson(): String {
+        return """
+        {
+            "id": "$id",
+            "title": "${title.escapeJson()}",
+            "content": "${content.escapeJson()}",
+            "createdAt": $createdAt,
+            "updatedAt": $updatedAt,
+            "deviceId": "$deviceId",
+            "syncStatus": "${syncStatus.name}"
+        }
+        """.trimIndent()
+    }
+    
+    companion object {
+        fun fromJson(json: String): Note? {
+            return try {
+                val gson = com.google.gson.Gson()
+                gson.fromJson(json, Note::class.java)
+            } catch (e: Exception) {
+                null
+            }
+        }
+    }
+}
+
+// Extension für JSON-Escaping
+fun String.escapeJson(): String {
+    return this
+        .replace("\\", "\\\\")
+        .replace("\"", "\\\"")
+        .replace("\n", "\\n")
+        .replace("\r", "\\r")
+        .replace("\t", "\\t")
+}

android/app/src/main/java/dev/dettmer/simplenotes/models/SyncStatus.kt

@@ -0,0 +1,8 @@
+package dev.dettmer.simplenotes.models
+
+enum class SyncStatus {
+    LOCAL_ONLY,   // Noch nie gesynct
+    SYNCED,       // Erfolgreich gesynct
+    PENDING,      // Wartet auf Sync
+    CONFLICT      // Konflikt erkannt
+}

android/app/src/main/java/dev/dettmer/simplenotes/storage/NotesStorage.kt

@@ -0,0 +1,41 @@
+package dev.dettmer.simplenotes.storage
+
+import android.content.Context
+import dev.dettmer.simplenotes.models.Note
+import java.io.File
+
+class NotesStorage(private val context: Context) {
+    
+    private val notesDir: File = File(context.filesDir, "notes").apply {
+        if (!exists()) mkdirs()
+    }
+    
+    fun saveNote(note: Note) {
+        val file = File(notesDir, "${note.id}.json")
+        file.writeText(note.toJson())
+    }
+    
+    fun loadNote(id: String): Note? {
+        val file = File(notesDir, "$id.json")
+        return if (file.exists()) {
+            Note.fromJson(file.readText())
+        } else {
+            null
+        }
+    }
+    
+    fun loadAllNotes(): List<Note> {
+        return notesDir.listFiles()
+            ?.filter { it.extension == "json" }
+            ?.mapNotNull { Note.fromJson(it.readText()) }
+            ?.sortedByDescending { it.updatedAt }
+            ?: emptyList()
+    }
+    
+    fun deleteNote(id: String): Boolean {
+        val file = File(notesDir, "$id.json")
+        return file.delete()
+    }
+    
+    fun getNotesDir(): File = notesDir
+}

android/app/src/main/java/dev/dettmer/simplenotes/sync/SyncResult.kt

@@ -0,0 +1,11 @@
+package dev.dettmer.simplenotes.sync
+
+data class SyncResult(
+    val isSuccess: Boolean,
+    val syncedCount: Int = 0,
+    val conflictCount: Int = 0,
+    val errorMessage: String? = null
+) {
+    val hasConflicts: Boolean
+        get() = conflictCount > 0
+}

android/app/src/main/java/dev/dettmer/simplenotes/sync/SyncWorker.kt

@@ -0,0 +1,65 @@
+package dev.dettmer.simplenotes.sync
+
+import android.content.Context
+import androidx.work.CoroutineWorker
+import androidx.work.WorkerParameters
+import dev.dettmer.simplenotes.utils.NotificationHelper
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.withContext
+
+class SyncWorker(
+    context: Context,
+    params: WorkerParameters
+) : CoroutineWorker(context, params) {
+    
+    override suspend fun doWork(): Result = withContext(Dispatchers.IO) {
+        // Progress Notification zeigen
+        val notificationId = NotificationHelper.showSyncProgressNotification(applicationContext)
+        
+        return@withContext try {
+            val syncService = WebDavSyncService(applicationContext)
+            val syncResult = syncService.syncNotes()
+            
+            // Progress Notification entfernen
+            NotificationHelper.dismissNotification(applicationContext, notificationId)
+            
+            when {
+                syncResult.hasConflicts -> {
+                    // Konflikt-Notification
+                    NotificationHelper.showConflictNotification(
+                        applicationContext,
+                        syncResult.conflictCount
+                    )
+                    Result.success()
+                }
+                syncResult.isSuccess -> {
+                    // Erfolgs-Notification
+                    NotificationHelper.showSyncSuccessNotification(
+                        applicationContext,
+                        syncResult.syncedCount
+                    )
+                    Result.success()
+                }
+                else -> {
+                    // Fehler-Notification
+                    NotificationHelper.showSyncFailureNotification(
+                        applicationContext,
+                        syncResult.errorMessage ?: "Unbekannter Fehler"
+                    )
+                    Result.retry()
+                }
+            }
+            
+        } catch (e: Exception) {
+            // Fehler-Notification
+            NotificationHelper.dismissNotification(applicationContext, notificationId)
+            NotificationHelper.showSyncFailureNotification(
+                applicationContext,
+                e.message ?: "Sync fehlgeschlagen"
+            )
+            
+            // Retry mit Backoff
+            Result.retry()
+        }
+    }
+}

android/app/src/main/java/dev/dettmer/simplenotes/sync/WebDavSyncService.kt

@@ -0,0 +1,178 @@
+package dev.dettmer.simplenotes.sync
+
+import android.content.Context
+import com.thegrizzlylabs.sardineandroid.Sardine
+import com.thegrizzlylabs.sardineandroid.impl.OkHttpSardine
+import dev.dettmer.simplenotes.models.Note
+import dev.dettmer.simplenotes.models.SyncStatus
+import dev.dettmer.simplenotes.storage.NotesStorage
+import dev.dettmer.simplenotes.utils.Constants
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.withContext
+import java.io.ByteArrayInputStream
+
+class WebDavSyncService(private val context: Context) {
+    
+    private val storage = NotesStorage(context)
+    private val prefs = context.getSharedPreferences(Constants.PREFS_NAME, Context.MODE_PRIVATE)
+    
+    private fun getSardine(): Sardine? {
+        val username = prefs.getString(Constants.KEY_USERNAME, null) ?: return null
+        val password = prefs.getString(Constants.KEY_PASSWORD, null) ?: return null
+        
+        return OkHttpSardine().apply {
+            setCredentials(username, password)
+        }
+    }
+    
+    private fun getServerUrl(): String? {
+        return prefs.getString(Constants.KEY_SERVER_URL, null)
+    }
+    
+    suspend fun syncNotes(): SyncResult = withContext(Dispatchers.IO) {
+        return@withContext try {
+            val sardine = getSardine() ?: return@withContext SyncResult(
+                isSuccess = false,
+                errorMessage = "Server-Zugangsdaten nicht konfiguriert"
+            )
+            
+            val serverUrl = getServerUrl() ?: return@withContext SyncResult(
+                isSuccess = false,
+                errorMessage = "Server-URL nicht konfiguriert"
+            )
+            
+            var syncedCount = 0
+            var conflictCount = 0
+            
+            // Ensure server directory exists
+            if (!sardine.exists(serverUrl)) {
+                sardine.createDirectory(serverUrl)
+            }
+            
+            // Upload local notes
+            val uploadedCount = uploadLocalNotes(sardine, serverUrl)
+            syncedCount += uploadedCount
+            
+            // Download remote notes
+            val downloadResult = downloadRemoteNotes(sardine, serverUrl)
+            syncedCount += downloadResult.downloadedCount
+            conflictCount += downloadResult.conflictCount
+            
+            // Update last sync timestamp
+            saveLastSyncTimestamp()
+            
+            SyncResult(
+                isSuccess = true,
+                syncedCount = syncedCount,
+                conflictCount = conflictCount
+            )
+            
+        } catch (e: Exception) {
+            SyncResult(
+                isSuccess = false,
+                errorMessage = when (e) {
+                    is java.net.UnknownHostException -> "Server nicht erreichbar"
+                    is java.net.SocketTimeoutException -> "Verbindungs-Timeout"
+                    is javax.net.ssl.SSLException -> "SSL-Fehler"
+                    is com.thegrizzlylabs.sardineandroid.impl.SardineException -> {
+                        when (e.statusCode) {
+                            401 -> "Authentifizierung fehlgeschlagen"
+                            403 -> "Zugriff verweigert"
+                            404 -> "Server-Pfad nicht gefunden"
+                            500 -> "Server-Fehler"
+                            else -> "HTTP-Fehler: ${e.statusCode}"
+                        }
+                    }
+                    else -> e.message ?: "Unbekannter Fehler"
+                }
+            )
+        }
+    }
+    
+    private fun uploadLocalNotes(sardine: Sardine, serverUrl: String): Int {
+        var uploadedCount = 0
+        val localNotes = storage.loadAllNotes()
+        
+        for (note in localNotes) {
+            try {
+                if (note.syncStatus == SyncStatus.LOCAL_ONLY || note.syncStatus == SyncStatus.PENDING) {
+                    val noteUrl = "$serverUrl/${note.id}.json"
+                    val jsonBytes = note.toJson().toByteArray()
+                    
+                    sardine.put(noteUrl, ByteArrayInputStream(jsonBytes), "application/json")
+                    
+                    // Update sync status
+                    val updatedNote = note.copy(syncStatus = SyncStatus.SYNCED)
+                    storage.saveNote(updatedNote)
+                    uploadedCount++
+                }
+            } catch (e: Exception) {
+                // Mark as pending for retry
+                val updatedNote = note.copy(syncStatus = SyncStatus.PENDING)
+                storage.saveNote(updatedNote)
+            }
+        }
+        
+        return uploadedCount
+    }
+    
+    private data class DownloadResult(
+        val downloadedCount: Int,
+        val conflictCount: Int
+    )
+    
+    private fun downloadRemoteNotes(sardine: Sardine, serverUrl: String): DownloadResult {
+        var downloadedCount = 0
+        var conflictCount = 0
+        
+        try {
+            val resources = sardine.list(serverUrl)
+            
+            for (resource in resources) {
+                if (resource.isDirectory || !resource.name.endsWith(".json")) {
+                    continue
+                }
+                
+                val noteUrl = resource.href.toString()
+                val jsonContent = sardine.get(noteUrl).bufferedReader().use { it.readText() }
+                val remoteNote = Note.fromJson(jsonContent) ?: continue
+                
+                val localNote = storage.loadNote(remoteNote.id)
+                
+                when {
+                    localNote == null -> {
+                        // New note from server
+                        storage.saveNote(remoteNote.copy(syncStatus = SyncStatus.SYNCED))
+                        downloadedCount++
+                    }
+                    localNote.updatedAt < remoteNote.updatedAt -> {
+                        // Remote is newer
+                        if (localNote.syncStatus == SyncStatus.PENDING) {
+                            // Conflict detected
+                            storage.saveNote(localNote.copy(syncStatus = SyncStatus.CONFLICT))
+                            conflictCount++
+                        } else {
+                            // Safe to overwrite
+                            storage.saveNote(remoteNote.copy(syncStatus = SyncStatus.SYNCED))
+                            downloadedCount++
+                        }
+                    }
+                }
+            }
+        } catch (e: Exception) {
+            // Log error but don't fail entire sync
+        }
+        
+        return DownloadResult(downloadedCount, conflictCount)
+    }
+    
+    private fun saveLastSyncTimestamp() {
+        prefs.edit()
+            .putLong(Constants.KEY_LAST_SYNC, System.currentTimeMillis())
+            .apply()
+    }
+    
+    fun getLastSyncTimestamp(): Long {
+        return prefs.getLong(Constants.KEY_LAST_SYNC, 0)
+    }
+}

android/app/src/main/java/dev/dettmer/simplenotes/sync/WifiSyncReceiver.kt

@@ -0,0 +1,62 @@
+package dev.dettmer.simplenotes.sync
+
+import android.content.BroadcastReceiver
+import android.content.Context
+import android.content.Intent
+import android.net.ConnectivityManager
+import android.net.NetworkCapabilities
+import android.net.wifi.WifiManager
+import androidx.work.OneTimeWorkRequestBuilder
+import androidx.work.WorkManager
+import dev.dettmer.simplenotes.utils.Constants
+import java.util.concurrent.TimeUnit
+
+class WifiSyncReceiver : BroadcastReceiver() {
+    
+    override fun onReceive(context: Context, intent: Intent) {
+        // Check if auto-sync is enabled
+        val prefs = context.getSharedPreferences(Constants.PREFS_NAME, Context.MODE_PRIVATE)
+        val autoSyncEnabled = prefs.getBoolean(Constants.KEY_AUTO_SYNC, false)
+        
+        if (!autoSyncEnabled) {
+            return
+        }
+        
+        // Check if connected to home WiFi
+        if (isConnectedToHomeWifi(context)) {
+            scheduleSyncWork(context)
+        }
+    }
+    
+    private fun isConnectedToHomeWifi(context: Context): Boolean {
+        val prefs = context.getSharedPreferences(Constants.PREFS_NAME, Context.MODE_PRIVATE)
+        val homeSSID = prefs.getString(Constants.KEY_HOME_SSID, null) ?: return false
+        
+        val connectivityManager = context.getSystemService(Context.CONNECTIVITY_SERVICE) 
+            as ConnectivityManager
+        
+        val network = connectivityManager.activeNetwork ?: return false
+        val capabilities = connectivityManager.getNetworkCapabilities(network) ?: return false
+        
+        if (!capabilities.hasTransport(NetworkCapabilities.TRANSPORT_WIFI)) {
+            return false
+        }
+        
+        // Get current SSID
+        val wifiManager = context.applicationContext.getSystemService(Context.WIFI_SERVICE) 
+            as WifiManager
+        val wifiInfo = wifiManager.connectionInfo
+        val currentSSID = wifiInfo.ssid.replace("\"", "")
+        
+        return currentSSID == homeSSID
+    }
+    
+    private fun scheduleSyncWork(context: Context) {
+        val syncRequest = OneTimeWorkRequestBuilder<SyncWorker>()
+            .setInitialDelay(Constants.SYNC_DELAY_SECONDS, TimeUnit.SECONDS)
+            .addTag(Constants.SYNC_WORK_TAG)
+            .build()
+        
+        WorkManager.getInstance(context).enqueue(syncRequest)
+    }
+}

android/app/src/main/java/dev/dettmer/simplenotes/utils/Constants.kt

@@ -0,0 +1,20 @@
+package dev.dettmer.simplenotes.utils
+
+object Constants {
+    // SharedPreferences
+    const val PREFS_NAME = "simple_notes_prefs"
+    const val KEY_SERVER_URL = "server_url"
+    const val KEY_USERNAME = "username"
+    const val KEY_PASSWORD = "password"
+    const val KEY_HOME_SSID = "home_ssid"
+    const val KEY_AUTO_SYNC = "auto_sync_enabled"
+    const val KEY_LAST_SYNC = "last_sync_timestamp"
+    
+    // WorkManager
+    const val SYNC_WORK_TAG = "notes_sync"
+    const val SYNC_DELAY_SECONDS = 5L
+    
+    // Notifications
+    const val NOTIFICATION_CHANNEL_ID = "notes_sync_channel"
+    const val NOTIFICATION_ID = 1001
+}

android/app/src/main/java/dev/dettmer/simplenotes/utils/DeviceIdGenerator.kt

@@ -0,0 +1,39 @@
+package dev.dettmer.simplenotes.utils
+
+import android.content.Context
+import android.provider.Settings
+import java.util.UUID
+
+object DeviceIdGenerator {
+    
+    private const val PREF_NAME = "simple_notes_prefs"
+    private const val KEY_DEVICE_ID = "device_id"
+    
+    fun getDeviceId(context: Context): String {
+        val prefs = context.getSharedPreferences(PREF_NAME, Context.MODE_PRIVATE)
+        
+        // Check if already generated
+        var deviceId = prefs.getString(KEY_DEVICE_ID, null)
+        
+        if (deviceId == null) {
+            // Try Android ID
+            deviceId = Settings.Secure.getString(
+                context.contentResolver,
+                Settings.Secure.ANDROID_ID
+            )
+            
+            // Fallback to UUID if Android ID not available
+            if (deviceId.isNullOrEmpty()) {
+                deviceId = UUID.randomUUID().toString()
+            }
+            
+            // Prefix for identification
+            deviceId = "android-$deviceId"
+            
+            // Save for future use
+            prefs.edit().putString(KEY_DEVICE_ID, deviceId).apply()
+        }
+        
+        return deviceId
+    }
+}

android/app/src/main/java/dev/dettmer/simplenotes/utils/Extensions.kt

@@ -0,0 +1,48 @@
+package dev.dettmer.simplenotes.utils
+
+import android.content.Context
+import android.widget.Toast
+import java.text.SimpleDateFormat
+import java.util.Date
+import java.util.Locale
+import java.util.concurrent.TimeUnit
+
+// Toast Extensions
+fun Context.showToast(message: String, duration: Int = Toast.LENGTH_SHORT) {
+    Toast.makeText(this, message, duration).show()
+}
+
+// Timestamp to readable format
+fun Long.toReadableTime(): String {
+    val now = System.currentTimeMillis()
+    val diff = now - this
+    
+    return when {
+        diff < TimeUnit.MINUTES.toMillis(1) -> "Gerade eben"
+        diff < TimeUnit.HOURS.toMillis(1) -> {
+            val minutes = TimeUnit.MILLISECONDS.toMinutes(diff)
+            "Vor $minutes Min"
+        }
+        diff < TimeUnit.DAYS.toMillis(1) -> {
+            val hours = TimeUnit.MILLISECONDS.toHours(diff)
+            "Vor $hours Std"
+        }
+        diff < TimeUnit.DAYS.toMillis(7) -> {
+            val days = TimeUnit.MILLISECONDS.toDays(diff)
+            "Vor $days Tagen"
+        }
+        else -> {
+            val sdf = SimpleDateFormat("dd.MM.yyyy", Locale.GERMAN)
+            sdf.format(Date(this))
+        }
+    }
+}
+
+// Truncate long strings
+fun String.truncate(maxLength: Int): String {
+    return if (length > maxLength) {
+        substring(0, maxLength - 3) + "..."
+    } else {
+        this
+    }
+}

android/app/src/main/java/dev/dettmer/simplenotes/utils/NotificationHelper.kt

@@ -0,0 +1,192 @@
+package dev.dettmer.simplenotes.utils
+
+import android.app.NotificationChannel
+import android.app.NotificationManager
+import android.app.PendingIntent
+import android.content.Context
+import android.content.Intent
+import android.os.Build
+import androidx.core.app.NotificationCompat
+import androidx.core.app.NotificationManagerCompat
+import dev.dettmer.simplenotes.MainActivity
+
+object NotificationHelper {
+    
+    private const val CHANNEL_ID = "notes_sync_channel"
+    private const val CHANNEL_NAME = "Notizen Synchronisierung"
+    private const val CHANNEL_DESCRIPTION = "Benachrichtigungen über Sync-Status"
+    private const val NOTIFICATION_ID = 1001
+    
+    /**
+     * Erstellt Notification Channel (Android 8.0+)
+     * Muss beim App-Start aufgerufen werden
+     */
+    fun createNotificationChannel(context: Context) {
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
+            val importance = NotificationManager.IMPORTANCE_DEFAULT
+            
+            val channel = NotificationChannel(CHANNEL_ID, CHANNEL_NAME, importance).apply {
+                description = CHANNEL_DESCRIPTION
+                enableVibration(true)
+                enableLights(true)
+            }
+            
+            val notificationManager = context.getSystemService(Context.NOTIFICATION_SERVICE) 
+                as NotificationManager
+            notificationManager.createNotificationChannel(channel)
+        }
+    }
+    
+    /**
+     * Zeigt Erfolgs-Notification nach Sync
+     */
+    fun showSyncSuccessNotification(context: Context, syncedCount: Int) {
+        val intent = Intent(context, MainActivity::class.java).apply {
+            flags = Intent.FLAG_ACTIVITY_NEW_TASK or Intent.FLAG_ACTIVITY_CLEAR_TASK
+        }
+        
+        val pendingIntent = PendingIntent.getActivity(
+            context, 0, intent,
+            PendingIntent.FLAG_IMMUTABLE or PendingIntent.FLAG_UPDATE_CURRENT
+        )
+        
+        val notification = NotificationCompat.Builder(context, CHANNEL_ID)
+            .setSmallIcon(android.R.drawable.ic_menu_upload)
+            .setContentTitle("Sync erfolgreich")
+            .setContentText("$syncedCount Notiz(en) synchronisiert")
+            .setPriority(NotificationCompat.PRIORITY_DEFAULT)
+            .setContentIntent(pendingIntent)
+            .setAutoCancel(true)
+            .build()
+        
+        with(NotificationManagerCompat.from(context)) {
+            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
+                if (androidx.core.app.ActivityCompat.checkSelfPermission(
+                    context,
+                    android.Manifest.permission.POST_NOTIFICATIONS
+                ) == android.content.pm.PackageManager.PERMISSION_GRANTED
+                ) {
+                    notify(NOTIFICATION_ID, notification)
+                }
+            } else {
+                notify(NOTIFICATION_ID, notification)
+            }
+        }
+    }
+    
+    /**
+     * Zeigt Fehler-Notification bei fehlgeschlagenem Sync
+     */
+    fun showSyncFailureNotification(context: Context, errorMessage: String) {
+        val notification = NotificationCompat.Builder(context, CHANNEL_ID)
+            .setSmallIcon(android.R.drawable.ic_dialog_alert)
+            .setContentTitle("Sync fehlgeschlagen")
+            .setContentText(errorMessage)
+            .setStyle(NotificationCompat.BigTextStyle()
+                .bigText(errorMessage))
+            .setPriority(NotificationCompat.PRIORITY_HIGH)
+            .setAutoCancel(true)
+            .build()
+        
+        with(NotificationManagerCompat.from(context)) {
+            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
+                if (androidx.core.app.ActivityCompat.checkSelfPermission(
+                    context,
+                    android.Manifest.permission.POST_NOTIFICATIONS
+                ) == android.content.pm.PackageManager.PERMISSION_GRANTED
+                ) {
+                    notify(NOTIFICATION_ID, notification)
+                }
+            } else {
+                notify(NOTIFICATION_ID, notification)
+            }
+        }
+    }
+    
+    /**
+     * Zeigt Progress-Notification während Sync läuft
+     */
+    fun showSyncProgressNotification(context: Context): Int {
+        val notification = NotificationCompat.Builder(context, CHANNEL_ID)
+            .setSmallIcon(android.R.drawable.ic_popup_sync)
+            .setContentTitle("Synchronisiere...")
+            .setContentText("Notizen werden synchronisiert")
+            .setPriority(NotificationCompat.PRIORITY_LOW)
+            .setOngoing(true)
+            .setProgress(0, 0, true)
+            .build()
+        
+        with(NotificationManagerCompat.from(context)) {
+            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
+                if (androidx.core.app.ActivityCompat.checkSelfPermission(
+                    context,
+                    android.Manifest.permission.POST_NOTIFICATIONS
+                ) == android.content.pm.PackageManager.PERMISSION_GRANTED
+                ) {
+                    notify(NOTIFICATION_ID, notification)
+                }
+            } else {
+                notify(NOTIFICATION_ID, notification)
+            }
+        }
+        
+        return NOTIFICATION_ID
+    }
+    
+    /**
+     * Zeigt Notification bei erkanntem Konflikt
+     */
+    fun showConflictNotification(context: Context, conflictCount: Int) {
+        val intent = Intent(context, MainActivity::class.java)
+        val pendingIntent = PendingIntent.getActivity(
+            context, 0, intent,
+            PendingIntent.FLAG_IMMUTABLE or PendingIntent.FLAG_UPDATE_CURRENT
+        )
+        
+        val notification = NotificationCompat.Builder(context, CHANNEL_ID)
+            .setSmallIcon(android.R.drawable.ic_dialog_info)
+            .setContentTitle("Sync-Konflikt erkannt")
+            .setContentText("$conflictCount Notiz(en) haben Konflikte")
+            .setPriority(NotificationCompat.PRIORITY_HIGH)
+            .setContentIntent(pendingIntent)
+            .setAutoCancel(true)
+            .build()
+        
+        with(NotificationManagerCompat.from(context)) {
+            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
+                if (androidx.core.app.ActivityCompat.checkSelfPermission(
+                    context,
+                    android.Manifest.permission.POST_NOTIFICATIONS
+                ) == android.content.pm.PackageManager.PERMISSION_GRANTED
+                ) {
+                    notify(NOTIFICATION_ID + 1, notification)
+                }
+            } else {
+                notify(NOTIFICATION_ID + 1, notification)
+            }
+        }
+    }
+    
+    /**
+     * Entfernt aktive Notification
+     */
+    fun dismissNotification(context: Context, notificationId: Int = NOTIFICATION_ID) {
+        with(NotificationManagerCompat.from(context)) {
+            cancel(notificationId)
+        }
+    }
+    
+    /**
+     * Prüft ob Notification-Permission vorhanden (Android 13+)
+     */
+    fun hasNotificationPermission(context: Context): Boolean {
+        return if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
+            androidx.core.app.ActivityCompat.checkSelfPermission(
+                context,
+                android.Manifest.permission.POST_NOTIFICATIONS
+            ) == android.content.pm.PackageManager.PERMISSION_GRANTED
+        } else {
+            true
+        }
+    }
+}

android/app/src/main/res/layout/activity_editor.xml

@@ -0,0 +1,52 @@
+<?xml version="1.0" encoding="utf-8"?>
+<LinearLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:orientation="vertical">
+
+    <com.google.android.material.appbar.MaterialToolbar
+        android:id="@+id/toolbar"
+        android:layout_width="match_parent"
+        android:layout_height="?attr/actionBarSize"
+        app:navigationIcon="@android:drawable/ic_menu_close_clear_cancel"
+        app:title="@string/edit_note" />
+
+    <com.google.android.material.textfield.TextInputLayout
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:layout_margin="16dp"
+        android:hint="@string/title"
+        style="@style/Widget.Material3.TextInputLayout.OutlinedBox">
+
+        <com.google.android.material.textfield.TextInputEditText
+            android:id="@+id/editTextTitle"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:inputType="text"
+            android:maxLines="2" />
+
+    </com.google.android.material.textfield.TextInputLayout>
+
+    <com.google.android.material.textfield.TextInputLayout
+        android:layout_width="match_parent"
+        android:layout_height="0dp"
+        android:layout_weight="1"
+        android:layout_marginStart="16dp"
+        android:layout_marginEnd="16dp"
+        android:layout_marginBottom="16dp"
+        android:hint="@string/content"
+        style="@style/Widget.Material3.TextInputLayout.OutlinedBox">
+
+        <com.google.android.material.textfield.TextInputEditText
+            android:id="@+id/editTextContent"
+            android:layout_width="match_parent"
+            android:layout_height="match_parent"
+            android:gravity="top|start"
+            android:inputType="textMultiLine"
+            android:scrollbars="vertical" />
+
+    </com.google.android.material.textfield.TextInputLayout>
+
+</LinearLayout>

android/app/src/main/res/layout/activity_main.xml

@@ -1,19 +1,48 @@
 <?xml version="1.0" encoding="utf-8"?>
-<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+<androidx.coordinatorlayout.widget.CoordinatorLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto"
-    xmlns:tools="http://schemas.android.com/tools"
-    android:id="@+id/main"
     android:layout_width="match_parent"
-    android:layout_height="match_parent"
+    android:layout_height="match_parent">
-    tools:context=".MainActivity">
+
+    <com.google.android.material.appbar.AppBarLayout
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content">
+
+        <com.google.android.material.appbar.MaterialToolbar
+            android:id="@+id/toolbar"
+            android:layout_width="match_parent"
+            android:layout_height="?attr/actionBarSize"
+            app:title="@string/app_name" />
+
+    </com.google.android.material.appbar.AppBarLayout>
+
+    <androidx.recyclerview.widget.RecyclerView
+        android:id="@+id/recyclerViewNotes"
+        android:layout_width="match_parent"
+        android:layout_height="match_parent"
+        android:clipToPadding="false"
+        android:padding="8dp"
+        app:layout_behavior="@string/appbar_scrolling_view_behavior" />
 
     <TextView
+        android:id="@+id/textViewEmpty"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
-        android:text="Hello World!"
+        android:layout_gravity="center"
-        app:layout_constraintBottom_toBottomOf="parent"
+        android:text="@string/no_notes_yet"
-        app:layout_constraintEnd_toEndOf="parent"
+        android:textSize="18sp"
-        app:layout_constraintStart_toStartOf="parent"
+        android:textColor="?android:attr/textColorSecondary"
-        app:layout_constraintTop_toTopOf="parent" />
+        android:gravity="center"
+        android:visibility="gone" />
 
-</androidx.constraintlayout.widget.ConstraintLayout>
+    <com.google.android.material.floatingactionbutton.FloatingActionButton
+        android:id="@+id/fabAddNote"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_gravity="bottom|end"
+        android:layout_margin="16dp"
+        android:contentDescription="@string/add_note"
+        app:srcCompat="@android:drawable/ic_input_add" />
+
+</androidx.coordinatorlayout.widget.CoordinatorLayout>

android/app/src/main/res/layout/activity_settings.xml

@@ -0,0 +1,150 @@
+<?xml version="1.0" encoding="utf-8"?>
+<ScrollView
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+    <LinearLayout
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:orientation="vertical"
+        android:padding="16dp">
+
+        <!-- Server Settings -->
+        <TextView
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:text="@string/server_settings"
+            android:textSize="18sp"
+            android:textStyle="bold"
+            android:layout_marginBottom="16dp" />
+
+        <com.google.android.material.textfield.TextInputLayout
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:hint="@string/server_url"
+            android:layout_marginBottom="8dp"
+            style="@style/Widget.Material3.TextInputLayout.OutlinedBox">
+
+            <com.google.android.material.textfield.TextInputEditText
+                android:id="@+id/editTextServerUrl"
+                android:layout_width="match_parent"
+                android:layout_height="wrap_content"
+                android:inputType="textUri" />
+
+        </com.google.android.material.textfield.TextInputLayout>
+
+        <com.google.android.material.textfield.TextInputLayout
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:hint="@string/username"
+            android:layout_marginBottom="8dp"
+            style="@style/Widget.Material3.TextInputLayout.OutlinedBox">
+
+            <com.google.android.material.textfield.TextInputEditText
+                android:id="@+id/editTextUsername"
+                android:layout_width="match_parent"
+                android:layout_height="wrap_content"
+                android:inputType="text" />
+
+        </com.google.android.material.textfield.TextInputLayout>
+
+        <com.google.android.material.textfield.TextInputLayout
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:hint="@string/password"
+            android:layout_marginBottom="16dp"
+            style="@style/Widget.Material3.TextInputLayout.OutlinedBox"
+            app:endIconMode="password_toggle">
+
+            <com.google.android.material.textfield.TextInputEditText
+                android:id="@+id/editTextPassword"
+                android:layout_width="match_parent"
+                android:layout_height="wrap_content"
+                android:inputType="textPassword" />
+
+        </com.google.android.material.textfield.TextInputLayout>
+
+        <!-- WiFi Settings -->
+        <TextView
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:text="@string/wifi_settings"
+            android:textSize="18sp"
+            android:textStyle="bold"
+            android:layout_marginTop="16dp"
+            android:layout_marginBottom="16dp" />
+
+        <LinearLayout
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:orientation="horizontal"
+            android:layout_marginBottom="8dp">
+
+            <com.google.android.material.textfield.TextInputLayout
+                android:layout_width="0dp"
+                android:layout_height="wrap_content"
+                android:layout_weight="1"
+                android:hint="@string/home_ssid"
+                android:layout_marginEnd="8dp"
+                style="@style/Widget.Material3.TextInputLayout.OutlinedBox">
+
+                <com.google.android.material.textfield.TextInputEditText
+                    android:id="@+id/editTextHomeSSID"
+                    android:layout_width="match_parent"
+                    android:layout_height="wrap_content"
+                    android:inputType="text" />
+
+            </com.google.android.material.textfield.TextInputLayout>
+
+            <Button
+                android:id="@+id/buttonDetectSSID"
+                android:layout_width="wrap_content"
+                android:layout_height="wrap_content"
+                android:layout_gravity="center_vertical"
+                android:text="Detect"
+                style="@style/Widget.Material3.Button.OutlinedButton" />
+
+        </LinearLayout>
+
+        <LinearLayout
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:orientation="horizontal"
+            android:layout_marginBottom="16dp">
+
+            <TextView
+                android:layout_width="0dp"
+                android:layout_height="wrap_content"
+                android:layout_weight="1"
+                android:text="@string/auto_sync"
+                android:textSize="16sp"
+                android:layout_gravity="center_vertical" />
+
+            <androidx.appcompat.widget.SwitchCompat
+                android:id="@+id/switchAutoSync"
+                android:layout_width="wrap_content"
+                android:layout_height="wrap_content" />
+
+        </LinearLayout>
+
+        <!-- Actions -->
+        <Button
+            android:id="@+id/buttonTestConnection"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:text="@string/test_connection"
+            android:layout_marginTop="8dp"
+            style="@style/Widget.Material3.Button.OutlinedButton" />
+
+        <Button
+            android:id="@+id/buttonSyncNow"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:text="@string/sync_now"
+            android:layout_marginTop="8dp" />
+
+    </LinearLayout>
+
+</ScrollView>

android/app/src/main/res/layout/item_note.xml

@@ -0,0 +1,65 @@
+<?xml version="1.0" encoding="utf-8"?>
+<com.google.android.material.card.MaterialCardView
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:layout_margin="4dp"
+    app:cardElevation="2dp"
+    app:cardCornerRadius="8dp">
+
+    <LinearLayout
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:orientation="vertical"
+        android:padding="16dp">
+
+        <TextView
+            android:id="@+id/textViewTitle"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:text="Note Title"
+            android:textSize="18sp"
+            android:textStyle="bold"
+            android:maxLines="2"
+            android:ellipsize="end" />
+
+        <TextView
+            android:id="@+id/textViewContent"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:layout_marginTop="4dp"
+            android:text="Note content preview..."
+            android:textSize="14sp"
+            android:textColor="?android:attr/textColorSecondary"
+            android:maxLines="3"
+            android:ellipsize="end" />
+
+        <LinearLayout
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:layout_marginTop="8dp"
+            android:orientation="horizontal">
+
+            <TextView
+                android:id="@+id/textViewTimestamp"
+                android:layout_width="0dp"
+                android:layout_height="wrap_content"
+                android:layout_weight="1"
+                android:text="Vor 2 Std"
+                android:textSize="12sp"
+                android:textColor="?android:attr/textColorTertiary" />
+
+            <ImageView
+                android:id="@+id/imageViewSyncStatus"
+                android:layout_width="16dp"
+                android:layout_height="16dp"
+                android:layout_gravity="center_vertical"
+                android:src="@android:drawable/ic_popup_sync"
+                android:contentDescription="@string/sync_status" />
+
+        </LinearLayout>
+
+    </LinearLayout>
+
+</com.google.android.material.card.MaterialCardView>

android/app/src/main/res/menu/menu_editor.xml

@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="utf-8"?>
+<menu xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto">
+
+    <item
+        android:id="@+id/action_save"
+        android:title="@string/save"
+        android:icon="@android:drawable/ic_menu_save"
+        app:showAsAction="always" />
+
+    <item
+        android:id="@+id/action_delete"
+        android:title="@string/delete"
+        android:icon="@android:drawable/ic_menu_delete"
+        app:showAsAction="never" />
+
+</menu>

android/app/src/main/res/menu/menu_main.xml

@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="utf-8"?>
+<menu xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto">
+
+    <item
+        android:id="@+id/action_sync"
+        android:title="@string/sync"
+        android:icon="@android:drawable/ic_popup_sync"
+        app:showAsAction="ifRoom" />
+
+    <item
+        android:id="@+id/action_settings"
+        android:title="@string/settings"
+        android:icon="@android:drawable/ic_menu_preferences"
+        app:showAsAction="ifRoom" />
+
+</menu>

android/app/src/main/res/values/strings.xml

@@ -1,3 +1,23 @@
 <resources>
     <string name="app_name">Simple Notes</string>
+    <string name="no_notes_yet">Noch keine Notizen.\nTippe + um eine zu erstellen.</string>
+    <string name="add_note">Notiz hinzufügen</string>
+    <string name="sync">Synchronisieren</string>
+    <string name="settings">Einstellungen</string>
+    <string name="edit_note">Notiz bearbeiten</string>
+    <string name="new_note">Neue Notiz</string>
+    <string name="title">Titel</string>
+    <string name="content">Inhalt</string>
+    <string name="save">Speichern</string>
+    <string name="delete">Löschen</string>
+    <string name="server_settings">Server-Einstellungen</string>
+    <string name="server_url">Server URL</string>
+    <string name="username">Benutzername</string>
+    <string name="password">Passwort</string>
+    <string name="wifi_settings">WLAN-Einstellungen</string>
+    <string name="home_ssid">Heim-WLAN SSID</string>
+    <string name="auto_sync">Auto-Sync aktiviert</string>
+    <string name="test_connection">Verbindung testen</string>
+    <string name="sync_now">Jetzt synchronisieren</string>
+    <string name="sync_status">Sync-Status</string>
 </resources>