Add mobile app switcher privacy setting

android/app/src/main/kotlin/chat/fluffy/fluffychat/MainActivity.kt

@@ -1,27 +1,64 @@
 package chat.fluffy.fluffychat
 
+import android.content.Context
+import android.os.Build
+import android.view.WindowManager
 import io.flutter.embedding.android.FlutterActivity
 import io.flutter.embedding.engine.FlutterEngine
-
-import android.content.Context
+import io.flutter.plugin.common.MethodChannel
 
 class MainActivity : FlutterActivity() {
+    private var appSwitcherPrivacyEnabled = false
+    private var appSwitcherPrivacyForeground = true
 
     override fun attachBaseContext(base: Context) {
         super.attachBaseContext(base)
     }
 
-
     override fun provideFlutterEngine(context: Context): FlutterEngine? {
         return provideEngine(this)
     }
 
     override fun configureFlutterEngine(flutterEngine: FlutterEngine) {
-        // do nothing, because the engine was been configured in provideEngine
+        MethodChannel(
+            flutterEngine.dartExecutor.binaryMessenger,
+            APP_SWITCHER_PRIVACY_CHANNEL
+        ).setMethodCallHandler { call, result ->
+            when (call.method) {
+                "setState" -> {
+                    appSwitcherPrivacyEnabled = call.argument<Boolean>("enabled") ?: false
+                    appSwitcherPrivacyForeground = call.argument<Boolean>("foreground") ?: true
+                    applyAppSwitcherPrivacy()
+                    result.success(null)
+                }
+                else -> result.notImplemented()
+            }
+        }
+    }
+
+    private fun applyAppSwitcherPrivacy() {
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
+            setRecentsScreenshotEnabled(!appSwitcherPrivacyEnabled)
+            window.clearFlags(WindowManager.LayoutParams.FLAG_SECURE)
+            return
+        }
+
+        if (appSwitcherPrivacyEnabled && !appSwitcherPrivacyForeground) {
+            window.setFlags(
+                WindowManager.LayoutParams.FLAG_SECURE,
+                WindowManager.LayoutParams.FLAG_SECURE
+            )
+        } else {
+            window.clearFlags(WindowManager.LayoutParams.FLAG_SECURE)
+        }
     }
 
     companion object {
+        private const val APP_SWITCHER_PRIVACY_CHANNEL =
+            "chat.fluffy/app_switcher_privacy"
+
         var engine: FlutterEngine? = null
+
         fun provideEngine(context: Context): FlutterEngine {
             val eng = engine ?: FlutterEngine(context, emptyArray(), true, false)
             engine = eng

lib/config/setting_keys.dart

@@ -45,6 +45,7 @@ enum AppSettings<T> {
   sendOnEnter<bool>('chat.fluffy.send_on_enter', false),
   displayNavigationRail<bool>('chat.fluffy.display_navigation_rail', false),
   experimentalVoip<bool>('chat.fluffy.experimental_voip', false),
+  appSwitcherPrivacy<String>('chat.fluffy.app_switcher_privacy', 'always'),
   shareKeysWith<String>('chat.fluffy.share_keys_with_2', 'all'),
   noEncryptionWarningShown<bool>(
     'chat.fluffy.no_encryption_warning_shown',

lib/l10n/intl_en.arb

@@ -143,6 +143,31 @@
         "placeholders": {}
     },
     "appLockDescription": "Lock the app when not using with a pin code",
+    "appSwitcherPrivacy": "App switcher privacy",
+    "@appSwitcherPrivacy": {
+        "type": "String",
+        "placeholders": {}
+    },
+    "appSwitcherPrivacyDescription": "Hide app content in the app switcher and recents screen",
+    "@appSwitcherPrivacyDescription": {
+        "type": "String",
+        "placeholders": {}
+    },
+    "appSwitcherPrivacyOff": "Off",
+    "@appSwitcherPrivacyOff": {
+        "type": "String",
+        "placeholders": {}
+    },
+    "appSwitcherPrivacyAppLock": "When app lock is enabled",
+    "@appSwitcherPrivacyAppLock": {
+        "type": "String",
+        "placeholders": {}
+    },
+    "appSwitcherPrivacyAlways": "Always",
+    "@appSwitcherPrivacyAlways": {
+        "type": "String",
+        "placeholders": {}
+    },
     "archive": "Archive",
     "@archive": {
         "type": "String",
@@ -2785,4 +2810,4 @@
         }
     },
     "deviceIdentityKey": "Device identity key"
-}
+}

lib/pages/settings_security/settings_security.dart

@@ -5,6 +5,7 @@
 
 import 'package:fluffychat/config/setting_keys.dart';
 import 'package:fluffychat/l10n/l10n.dart';
+import 'package:fluffychat/utils/app_switcher_privacy.dart';
 import 'package:fluffychat/widgets/adaptive_dialogs/show_ok_cancel_alert_dialog.dart';
 import 'package:fluffychat/widgets/adaptive_dialogs/show_text_input_dialog.dart';
 import 'package:fluffychat/widgets/app_lock.dart';
@@ -52,6 +53,14 @@ class SettingsSecurityController extends State<SettingsSecurity> {
     }
   }
 
+  Future<void> setAppSwitcherPrivacyMode(AppSwitcherPrivacyMode? mode) async {
+    if (mode == null) return;
+    await AppSettings.appSwitcherPrivacy.setAppSwitcherPrivacyMode(mode);
+    if (!mounted) return;
+    await AppLock.of(context).syncAppSwitcherPrivacy();
+    setState(() {});
+  }
+
   Future<void> deleteAccountAction() async {
     final l10n = L10n.of(context);
     final matrix = Matrix.of(context);

lib/pages/settings_security/settings_security_view.dart

@@ -7,6 +7,7 @@ import 'package:fluffychat/config/app_config.dart';
 import 'package:fluffychat/config/setting_keys.dart';
 import 'package:fluffychat/config/themes.dart';
 import 'package:fluffychat/l10n/l10n.dart';
+import 'package:fluffychat/utils/app_switcher_privacy.dart';
 import 'package:fluffychat/utils/beautify_string_extension.dart';
 import 'package:fluffychat/utils/platform_infos.dart';
 import 'package:fluffychat/widgets/layouts/max_width_body.dart';
@@ -27,6 +28,8 @@ class SettingsSecurityView extends StatelessWidget {
   Widget build(BuildContext context) {
     final theme = Theme.of(context);
     final client = Matrix.of(context).client;
+    final appSwitcherPrivacyMode =
+        AppSettings.appSwitcherPrivacy.appSwitcherPrivacyMode;
     final publicMasterKey =
         client.userDeviceKeys[client.userID]?.masterKey?.publicKey;
 
@@ -77,6 +80,42 @@ class SettingsSecurityView extends StatelessWidget {
                     subtitle: L10n.of(context).sendReadReceiptsDescription,
                     setting: AppSettings.sendPublicReadReceipts,
                   ),
+                  if (PlatformInfos.isMobile) ...[
+                    ListTile(
+                      title: Text(L10n.of(context).appSwitcherPrivacy),
+                      subtitle: Text(
+                        L10n.of(context).appSwitcherPrivacyDescription,
+                      ),
+                    ),
+                    Padding(
+                      padding: const EdgeInsets.symmetric(horizontal: 16.0),
+                      child: Material(
+                        borderRadius: BorderRadius.circular(
+                          AppConfig.borderRadius / 2,
+                        ),
+                        color: theme.colorScheme.onInverseSurface,
+                        child: DropdownButton<AppSwitcherPrivacyMode>(
+                          isExpanded: true,
+                          padding: const EdgeInsets.symmetric(horizontal: 8.0),
+                          borderRadius: BorderRadius.circular(
+                            AppConfig.borderRadius / 2,
+                          ),
+                          underline: const SizedBox.shrink(),
+                          value: appSwitcherPrivacyMode,
+                          items: [
+                            for (final mode in AppSwitcherPrivacyMode.values)
+                              DropdownMenuItem<AppSwitcherPrivacyMode>(
+                                value: mode,
+                                child: Text(
+                                  _appSwitcherPrivacyModeLabel(context, mode),
+                                ),
+                              ),
+                          ],
+                          onChanged: controller.setAppSwitcherPrivacyMode,
+                        ),
+                      ),
+                    ),
+                  ],
                   ListTile(
                     trailing: const Icon(Icons.chevron_right_outlined),
                     title: Text(L10n.of(context).blockedUsers),
@@ -197,6 +236,20 @@ class SettingsSecurityView extends StatelessWidget {
       ),
     );
   }
+
+  String _appSwitcherPrivacyModeLabel(
+    BuildContext context,
+    AppSwitcherPrivacyMode mode,
+  ) {
+    switch (mode) {
+      case AppSwitcherPrivacyMode.off:
+        return L10n.of(context).appSwitcherPrivacyOff;
+      case AppSwitcherPrivacyMode.appLock:
+        return L10n.of(context).appSwitcherPrivacyAppLock;
+      case AppSwitcherPrivacyMode.always:
+        return L10n.of(context).appSwitcherPrivacyAlways;
+    }
+  }
 }
 
 extension on ShareKeysWith {

lib/utils/app_switcher_privacy.dart

@@ -0,0 +1,61 @@
+// SPDX-FileCopyrightText: 2019-Present Christian Kußowski
+// SPDX-FileCopyrightText: 2019-Present Contributors to FluffyChat
+//
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+import 'package:fluffychat/config/setting_keys.dart';
+import 'package:fluffychat/utils/platform_infos.dart';
+import 'package:flutter/foundation.dart';
+import 'package:flutter/services.dart';
+
+enum AppSwitcherPrivacyMode {
+  off,
+  appLock,
+  always;
+
+  static AppSwitcherPrivacyMode fromSetting(String setting) {
+    for (final mode in AppSwitcherPrivacyMode.values) {
+      if (mode.name == setting) {
+        return mode;
+      }
+    }
+    return AppSwitcherPrivacyMode.always;
+  }
+}
+
+extension AppSwitcherPrivacySetting on AppSettings<String> {
+  AppSwitcherPrivacyMode get appSwitcherPrivacyMode =>
+      AppSwitcherPrivacyMode.fromSetting(value);
+
+  Future<void> setAppSwitcherPrivacyMode(AppSwitcherPrivacyMode mode) =>
+      setItem(mode.name);
+}
+
+class AppSwitcherPrivacy {
+  static const _channelName = 'chat.fluffy/app_switcher_privacy';
+
+  @visibleForTesting
+  static const channel = MethodChannel(_channelName);
+
+  @visibleForTesting
+  static bool? debugIsAndroid;
+
+  @visibleForTesting
+  static bool? debugIsMobile;
+
+  static bool get isAndroid => debugIsAndroid ?? PlatformInfos.isAndroid;
+
+  static bool get isMobile => debugIsMobile ?? PlatformInfos.isMobile;
+
+  static Future<void> setState({
+    required bool enabled,
+    required bool foreground,
+  }) async {
+    if (!isAndroid) return;
+
+    await channel.invokeMethod<void>('setState', {
+      'enabled': enabled,
+      'foreground': foreground,
+    });
+  }
+}