LockScreen : avoid removing from composition the LoggedInFlowNode.Children when LockScreen is displayed.

app/src/main/kotlin/io/element/android/x/MainActivity.kt

@@ -33,6 +33,7 @@ import com.bumble.appyx.core.integration.NodeHost
 import com.bumble.appyx.core.integrationpoint.NodeActivity
 import com.bumble.appyx.core.plugin.NodeReadyObserver
 import io.element.android.features.lockscreen.api.handleSecureFlag
+import io.element.android.features.lockscreen.api.isLocked
 import io.element.android.libraries.architecture.bindings
 import io.element.android.libraries.core.log.logger.LoggerTag
 import io.element.android.libraries.designsystem.utils.snackbar.LocalSnackbarDispatcher
@@ -46,7 +47,6 @@ private val loggerTag = LoggerTag("MainActivity")
 class MainActivity : NodeActivity() {
 
     private lateinit var mainNode: MainNode
-
     private lateinit var appBindings: AppBindings
 
     override fun onCreate(savedInstanceState: Bundle?) {
@@ -61,6 +61,19 @@ class MainActivity : NodeActivity() {
         }
     }
 
+    @Deprecated("")
+    override fun onBackPressed() {
+        // If the app is locked, we need to intercept onBackPressed before it goes to OnBackPressedDispatcher.
+        // Indeed, otherwise we would need to trick Appyx backstack management everywhere.
+        // Without this trick, we would get pop operations on the hidden backstack.
+        if (appBindings.lockScreenService().isLocked) {
+            //Do not kill the app in this case, just go to background.
+            moveTaskToBack(false)
+        } else {
+            super.onBackPressed()
+        }
+    }
+
     @Composable
     private fun MainContent(appBindings: AppBindings) {
         ElementTheme {

appnav/src/main/kotlin/io/element/android/appnav/LoggedInFlowNode.kt

@@ -362,23 +362,18 @@ class LoggedInFlowNode @AssistedInject constructor(
     override fun View(modifier: Modifier) {
         Box(modifier = modifier) {
             val lockScreenState by lockScreenStateService.lockState.collectAsState()
-            when (lockScreenState) {
-                LockScreenLockState.Unlocked -> {
-                    Children(
-                        navModel = backstack,
-                        modifier = Modifier,
-                        // Animate navigation to settings and to a room
-                        transitionHandler = rememberDefaultTransitionHandler(),
-                    )
-                    val isFtueDisplayed by ftueState.shouldDisplayFlow.collectAsState()
-                    if (!isFtueDisplayed) {
-                        PermanentChild(permanentNavModel = permanentNavModel, navTarget = NavTarget.LoggedInPermanent)
-                    }
-                }
-                LockScreenLockState.Locked -> {
-                    MoveActivityToBackgroundBackHandler()
-                    PermanentChild(permanentNavModel = permanentNavModel, navTarget = NavTarget.LockPermanent)
-                }
+            Children(
+                navModel = backstack,
+                modifier = Modifier,
+                // Animate navigation to settings and to a room
+                transitionHandler = rememberDefaultTransitionHandler(),
+            )
+            val isFtueDisplayed by ftueState.shouldDisplayFlow.collectAsState()
+            if (!isFtueDisplayed) {
+                PermanentChild(permanentNavModel = permanentNavModel, navTarget = NavTarget.LoggedInPermanent)
+            }
+            if (lockScreenState == LockScreenLockState.Locked) {
+                PermanentChild(permanentNavModel = permanentNavModel, navTarget = NavTarget.LockPermanent)
             }
         }
     }

appnav/src/main/kotlin/io/element/android/appnav/MoveActivityToBackgroundBackHandler.kt

@@ -1,39 +0,0 @@
-/*
- * Copyright (c) 2023 New Vector Ltd
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package io.element.android.appnav
-
-import android.content.Context
-import android.content.ContextWrapper
-import androidx.activity.ComponentActivity
-import androidx.activity.compose.BackHandler
-import androidx.compose.runtime.Composable
-import androidx.compose.ui.platform.LocalContext
-
-@Composable
-fun MoveActivityToBackgroundBackHandler(enabled: Boolean = true) {
-
-    fun Context.findActivity(): ComponentActivity? = when (this) {
-        is ComponentActivity -> this
-        is ContextWrapper -> baseContext.findActivity()
-        else -> null
-    }
-
-    val context = LocalContext.current
-    BackHandler(enabled = enabled) {
-        context.findActivity()?.moveTaskToBack(false)
-    }
-}

features/lockscreen/api/src/main/kotlin/io/element/android/features/lockscreen/api/LockScreenService.kt

@@ -44,6 +44,12 @@ interface LockScreenService {
     fun isPinSetup(): Flow<Boolean>
 }
 
+/**
+ * Check if the app is currently locked.
+ */
+val LockScreenService.isLocked: Boolean
+    get() = lockState.value == LockScreenLockState.Locked
+
 /**
  * Makes sure the secure flag is set on the activity if the pin is setup.
  * @param activity the activity to set the flag on.