feat: added backup and restored functionality

mobile/src/main/AndroidManifest.xml

@@ -8,6 +8,11 @@
         android:roundIcon="@mipmap/ic_launcher_round"
         android:supportsRtl="true"
         android:theme="@style/Theme.OmniCards">
+        <activity
+            android:name=".BackupActivity"
+            android:exported="false"
+            android:label="@string/title_activity_backup"
+            android:theme="@style/Theme.OmniCards" />
         <activity
             android:name=".EditCardActivity"
             android:exported="false"

mobile/src/main/java/ru/omni_devel/cards/BackupActivity.kt

@@ -0,0 +1,150 @@
+package ru.omni_devel.cards
+
+import android.net.Uri
+import android.os.Bundle
+import android.widget.Toast
+import androidx.activity.ComponentActivity
+import androidx.activity.compose.LocalActivity
+import androidx.activity.compose.rememberLauncherForActivityResult
+import androidx.activity.compose.setContent
+import androidx.activity.enableEdgeToEdge
+import androidx.activity.result.contract.ActivityResultContracts
+import androidx.compose.foundation.layout.PaddingValues
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.material3.AlertDialog
+import androidx.compose.material3.Scaffold
+import androidx.compose.material3.Text
+import androidx.compose.material3.TextButton
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.saveable.rememberSaveable
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.platform.LocalContext
+import kotlinx.serialization.json.Json
+import ru.omni_devel.cards.ui.theme.OmniCardsTheme
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.setValue
+import kotlinx.serialization.decodeFromString
+
+class BackupActivity : ComponentActivity() {
+    private lateinit var db: DbHelper
+
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        enableEdgeToEdge()
+
+        db = DbHelper(this, null)
+
+        setContent {
+            OmniCardsTheme {
+                Scaffold(modifier = Modifier.fillMaxSize()) { innerPadding ->
+                    BackupPage(innerPadding = innerPadding, getDbFun = {
+                        return@BackupPage db
+                    })
+                }
+            }
+        }
+    }
+}
+
+@Composable
+fun BackupPage(innerPadding: PaddingValues, getDbFun: () -> DbHelper) {
+    val context = LocalContext.current
+    val activityContext = LocalActivity.current
+
+    val showImportDialog = rememberSaveable { mutableStateOf(false) }
+    var pendingUri by rememberSaveable { mutableStateOf<Uri?>(null) }
+
+    val createBackupLauncher = rememberLauncherForActivityResult(
+        contract = ActivityResultContracts.CreateDocument("application/json")
+    ) { uri ->
+        uri?.let {
+            try {
+                val jsonData = Json.encodeToString(getDbFun().getCards())
+
+                context.contentResolver.openOutputStream(it)?.use { outputStream ->
+                    outputStream.write(jsonData.toByteArray())
+
+                    Toast.makeText(context, "Backup successfully saved", Toast.LENGTH_SHORT).show()
+
+                    activityContext!!.finish()
+                }
+            } catch (e: Exception) {
+                Toast.makeText(context, "Failed to save backup: $e", Toast.LENGTH_LONG).show()
+            }
+        }
+    }
+
+    val restoreFromBackupLauncher = rememberLauncherForActivityResult(
+        contract = ActivityResultContracts.GetContent()
+    ) { uri ->
+        uri?.let {
+            pendingUri = it
+            showImportDialog.value = true
+        }
+    }
+
+    if (showImportDialog.value) {
+        AlertDialog(
+            title = { Text("Restore backup") },
+            text = { Text("This will replace existing cards by data from backup file. Continue?") },
+            confirmButton = {
+                TextButton(
+                    onClick = {
+                        showImportDialog.value = false
+
+                        pendingUri?.let { uri ->
+                            try {
+                                context.contentResolver.openInputStream(uri)?.use { stream ->
+                                    val json = stream.bufferedReader().use { it.readText() }
+
+                                    val cards = Json.decodeFromString<List<CardInfo>>(json)
+
+                                    val db = getDbFun()
+
+                                    db.clearDatabase()
+                                    db.addCards(cards)
+
+                                    Toast.makeText(context, "Data successfully restored from backup", Toast.LENGTH_SHORT).show()
+
+                                    activityContext!!.finish()
+                                }
+                            } catch (e: Exception) {
+                                Toast.makeText(context, "Failed to restore data from backup: $e", Toast.LENGTH_LONG).show()
+                            }
+                        }
+                    }
+                ) {
+                    Text("Yes")
+                }
+            },
+            dismissButton = {
+                TextButton(
+                    onClick = {
+                        showImportDialog.value = false
+                    }
+                ) {
+                    Text("No")
+                }
+            },
+            onDismissRequest = { showImportDialog.value = false },
+        )
+    }
+
+    Page("Backup", innerPadding) {
+        FullWidthButton(
+            onClick = {
+                createBackupLauncher.launch("omnicards-backup.json")
+            }
+        ) {
+            Text("Backup to file")
+        }
+        FullWidthButton(
+            onClick = {
+                restoreFromBackupLauncher.launch("application/json")
+            }
+        ) {
+            Text("Restore from file")
+        }
+    }
+}

mobile/src/main/java/ru/omni_devel/cards/DbHelper.kt

@@ -106,4 +106,28 @@ class DbHelper(val context: Context, val factory: SQLiteDatabase.CursorFactory?)
 
         db.close()
     }
+
+    fun clearDatabase() {
+        val db = this.writableDatabase
+
+        db.execSQL("DELETE FROM cards")
+    }
+
+    fun addCards(cards: List<CardInfo>) {
+        val db = this.writableDatabase
+
+        for (card in cards) {
+            val values = ContentValues()
+
+            values.put("id", card.id)
+            values.put("name", card.name)
+            values.put("codeValue", card.codeValue)
+            values.put("codeType", card.codeType.name)
+            values.put("color", card.color)
+
+            db.insert("cards", null, values)
+        }
+
+        db.close()
+    }
 }

mobile/src/main/java/ru/omni_devel/cards/EditCardActivity.kt

@@ -1,6 +1,5 @@
 package ru.omni_devel.cards
 
-import android.app.Activity
 import android.os.Bundle
 import android.widget.Toast
 import androidx.activity.ComponentActivity
@@ -23,7 +22,6 @@ import androidx.compose.foundation.verticalScroll
 import androidx.compose.material3.Button
 import androidx.compose.material3.DropdownMenu
 import androidx.compose.material3.DropdownMenuItem
-import androidx.compose.material3.IconButton
 import androidx.compose.material3.OutlinedTextField
 import androidx.compose.material3.Scaffold
 import androidx.compose.material3.Switch
@@ -32,12 +30,10 @@ import androidx.compose.runtime.Composable
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.setValue
 import androidx.compose.runtime.mutableStateOf
-import androidx.compose.runtime.remember
 import androidx.compose.runtime.saveable.rememberSaveable
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.graphics.Color
-import androidx.compose.ui.platform.LocalContext
 import androidx.compose.ui.unit.dp
 import androidx.core.graphics.toColorInt
 import com.github.skydoves.colorpicker.compose.ColorEnvelope

mobile/src/main/java/ru/omni_devel/cards/MainActivity.kt

@@ -145,9 +145,22 @@ fun MainPage(
                 ) {
                     Text("Sync with WearOS")
                 }
+                FullWidthButton(
+                    onClick = {
+                        val intent = Intent(context, BackupActivity::class.java)
+
+                        context.startActivity(intent)
+
+                        isActionBarShowed = false
+                    }
+                ) {
+                    Text("Backup")
+                }
                 FullWidthButton(
                     onClick = {
                         uriHandler.openUri("https://github.com/omni-devel/OmniCards")
+
+                        isActionBarShowed = false
                     }
                 ) {
                     Text("Source code")

mobile/src/main/res/values/strings.xml

@@ -45,4 +45,5 @@
     <string name="title_activity_show_card">ShowCardActivity</string>
     <string name="title_activity_add_card">AddCardActivity</string>
     <string name="title_activity_edit_card">EditCardActivity</string>
+    <string name="title_activity_backup">BackupActivity</string>
 </resources>