Initial implementation of iOS bindings to Lifecycle (#1043)

Initial implementation of iOS bindings to Lifecycle. <img width="836" alt="ios_lifecycle" src="https://github.com/JetBrains/compose-multiplatform-core/assets/4167681/ec73ed26-5435-43e7-a4cf-5d3b9fe91693">
JetBrains · Mar 16, 2024 · 0b9a5c8 · 0b9a5c8
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diff --git a/compose/mpp/demo/src/uikitMain/kotlin/NativePopupExample.kt b/compose/mpp/demo/src/uikitMain/kotlin/NativePopupExample.kt
@@ -3,15 +3,20 @@ import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.lazy.LazyRow
 import androidx.compose.foundation.lazy.grid.GridCells
 import androidx.compose.foundation.lazy.grid.LazyVerticalGrid
 import androidx.compose.material.Button
 import androidx.compose.material.Text
 import androidx.compose.mpp.demo.Screen
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.DisposableEffect
+import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateListOf
 import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
 import androidx.compose.runtime.setValue
@@ -20,8 +25,10 @@ import androidx.compose.ui.Modifier
 import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.interop.LocalUIViewController
 import androidx.compose.ui.interop.UIKitView
+import androidx.compose.ui.platform.LocalLifecycleOwner
 import androidx.compose.ui.unit.dp
 import androidx.compose.ui.window.ComposeUIViewController
+import androidx.lifecycle.LifecycleEventObserver
 import platform.UIKit.*
 import platform.Foundation.*
 import platform.darwin.dispatch_async
@@ -64,9 +71,35 @@ private fun NativeModalWithNavigation() {
 
 @Composable
 private fun NativeNavigationPage() {
+    val lifecycleOwner = LocalLifecycleOwner.current
+
+    val states = remember { mutableStateListOf<String>() }
+
+    val observer = remember {
+        LifecycleEventObserver { _, event ->
+            println(event)
+            states.add("${states.size} ${event.name}")
+        }
+    }
+
+    DisposableEffect(lifecycleOwner) {
+        lifecycleOwner.lifecycle.addObserver(observer)
+        onDispose {
+            lifecycleOwner.lifecycle.removeObserver(observer)
+        }
+    }
+
     Column(Modifier.fillMaxSize().background(Color.DarkGray), verticalArrangement = Arrangement.Center, horizontalAlignment = Alignment.CenterHorizontally) {
         val navigationController = LocalUIViewController.current.navigationController
 
+        LazyRow(Modifier.height(50.dp).fillMaxWidth()) {
+            items(states.size) { index ->
+                Box(Modifier.background(Color.White).padding(16.dp)) {
+                    Text(states[index], color = Color.Black)
+                }
+            }
+        }
+
         Button(onClick = {
             navigationController?.pushViewController(
                 ComposeUIViewController {

diff --git a/...e/ui/ui/src/uikitMain/kotlin/androidx/compose/ui/window/ApplicationStateListener.uikit.kt b/...e/ui/ui/src/uikitMain/kotlin/androidx/compose/ui/window/ApplicationStateListener.uikit.kt
@@ -0,0 +1,76 @@
+/*
+ * Copyright 2024 The Android Open Source Project
+ *
+ * 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 androidx.compose.ui.window
+
+import kotlinx.cinterop.ObjCAction
+import platform.Foundation.NSNotificationCenter
+import platform.Foundation.NSSelectorFromString
+import platform.UIKit.UIApplication
+import platform.UIKit.UIApplicationDidEnterBackgroundNotification
+import platform.UIKit.UIApplicationState
+import platform.UIKit.UIApplicationWillEnterForegroundNotification
+import platform.darwin.NSObject
+
+internal class ApplicationStateListener(
+    /**
+     * Callback which will be called with `true` when the app becomes active, and `false` when the app goes background
+     */
+    private val callback: (Boolean) -> Unit
+) : NSObject() {
+    init {
+        val notificationCenter = NSNotificationCenter.defaultCenter
+
+        notificationCenter.addObserver(
+            this,
+            NSSelectorFromString(::applicationWillEnterForeground.name),
+            UIApplicationWillEnterForegroundNotification,
+            null
+        )
+
+        notificationCenter.addObserver(
+            this,
+            NSSelectorFromString(::applicationDidEnterBackground.name),
+            UIApplicationDidEnterBackgroundNotification,
+            null
+        )
+    }
+
+    @ObjCAction
+    fun applicationWillEnterForeground() {
+        callback(true)
+    }
+
+    @ObjCAction
+    fun applicationDidEnterBackground() {
+        callback(false)
+    }
+
+    /**
+     * Deregister from [NSNotificationCenter]
+     */
+    fun dispose() {
+        val notificationCenter = NSNotificationCenter.defaultCenter
+
+        notificationCenter.removeObserver(this, UIApplicationWillEnterForegroundNotification, null)
+        notificationCenter.removeObserver(this, UIApplicationDidEnterBackgroundNotification, null)
+    }
+
+    companion object {
+        val isApplicationActive: Boolean
+            get() = UIApplication.sharedApplication.applicationState != UIApplicationState.UIApplicationStateBackground
+    }
+}
diff --git a/compose/ui/ui/src/uikitMain/kotlin/androidx/compose/ui/window/ComposeContainer.uikit.kt b/compose/ui/ui/src/uikitMain/kotlin/androidx/compose/ui/window/ComposeContainer.uikit.kt
@@ -26,6 +26,7 @@ import androidx.compose.runtime.mutableStateOf
 import androidx.compose.ui.LocalSystemTheme
 import androidx.compose.ui.SystemTheme
 import androidx.compose.ui.interop.LocalUIViewController
+import androidx.compose.ui.platform.LocalLifecycleOwner
 import androidx.compose.ui.platform.PlatformContext
 import androidx.compose.ui.platform.PlatformWindowContext
 import androidx.compose.ui.scene.ComposeScene
@@ -92,6 +93,8 @@ internal class ComposeContainer(
     private val configuration: ComposeUIViewControllerConfiguration,
     private val content: @Composable () -> Unit,
 ) : CMPViewController(nibName = null, bundle = null) {
+    val lifecycleOwner = ViewControllerBasedLifecycleOwner()
+
     private var isInsideSwiftUI = false
     private var mediator: ComposeSceneMediator? = null
     private val layers: MutableList<UIViewComposeSceneLayer> = mutableListOf()
@@ -234,6 +237,8 @@ internal class ComposeContainer(
 
         isInsideSwiftUI = checkIfInsideSwiftUI()
         createMediatorIfNeeded()
+
+        lifecycleOwner.handleViewWillAppear()
         configuration.delegate.viewWillAppear(animated)
     }
 
@@ -263,6 +268,7 @@ internal class ComposeContainer(
             kotlin.native.internal.GC.collect()
         }
 
+        lifecycleOwner.handleViewDidDisappear()
         configuration.delegate.viewDidDisappear(animated)
     }
 
@@ -337,6 +343,7 @@ internal class ComposeContainer(
     }
 
     private fun dispose() {
+        lifecycleOwner.dispose()
         mediator?.dispose()
         mediator = null
         layers.fastForEach {
@@ -420,6 +427,7 @@ internal fun ProvideContainerCompositionLocals(
         LocalUIViewController provides this,
         LocalInterfaceOrientation provides interfaceOrientationState.value,
         LocalSystemTheme provides systemThemeState.value,
+        LocalLifecycleOwner provides lifecycleOwner,
         content = content
     )
 }

diff --git a/compose/ui/ui/src/uikitMain/kotlin/androidx/compose/ui/window/MetalRedrawer.uikit.kt b/compose/ui/ui/src/uikitMain/kotlin/androidx/compose/ui/window/MetalRedrawer.uikit.kt
@@ -25,14 +25,11 @@ import androidx.compose.ui.util.trace
 import kotlin.math.roundToInt
 import kotlinx.cinterop.*
 import org.jetbrains.skia.*
-import platform.Foundation.NSNotificationCenter
 import platform.Foundation.NSRunLoop
 import platform.Foundation.NSSelectorFromString
 import platform.Foundation.NSThread
 import platform.Metal.MTLCommandBufferProtocol
 import platform.QuartzCore.*
-import platform.UIKit.UIApplicationDidEnterBackgroundNotification
-import platform.UIKit.UIApplicationWillEnterForegroundNotification
 import platform.darwin.*
 import org.jetbrains.skia.Rect
 import platform.Foundation.NSLock
@@ -109,51 +106,6 @@ private class DisplayLinkConditions(
     }
 }
 
-private class ApplicationStateListener(
-    /**
-     * Callback which will be called with `true` when the app becomes active, and `false` when the app goes background
-     */
-    private val callback: (Boolean) -> Unit
-) : NSObject() {
-    init {
-        val notificationCenter = NSNotificationCenter.defaultCenter
-
-        notificationCenter.addObserver(
-            this,
-            NSSelectorFromString(::applicationWillEnterForeground.name),
-            UIApplicationWillEnterForegroundNotification,
-            null
-        )
-
-        notificationCenter.addObserver(
-            this,
-            NSSelectorFromString(::applicationDidEnterBackground.name),
-            UIApplicationDidEnterBackgroundNotification,
-            null
-        )
-    }
-
-    @ObjCAction
-    fun applicationWillEnterForeground() {
-        callback(true)
-    }
-
-    @ObjCAction
-    fun applicationDidEnterBackground() {
-        callback(false)
-    }
-
-    /**
-     * Deregister from [NSNotificationCenter]
-     */
-    fun dispose() {
-        val notificationCenter = NSNotificationCenter.defaultCenter
-
-        notificationCenter.removeObserver(this, UIApplicationWillEnterForegroundNotification, null)
-        notificationCenter.removeObserver(this, UIApplicationDidEnterBackgroundNotification, null)
-    }
-}
-
 internal interface MetalRedrawerCallbacks {
     /**
      * Perform time step and encode draw operations into canvas.
@@ -292,7 +244,7 @@ internal class MetalRedrawer(
         // and won't receive UIApplicationWillEnterForegroundNotification
         // so we compare the state with UIApplicationStateBackground instead of UIApplicationStateActive
         displayLinkConditions.isApplicationActive =
-            UIApplication.sharedApplication.applicationState != UIApplicationState.UIApplicationStateBackground
+            ApplicationStateListener.isApplicationActive
 
         caDisplayLink.addToRunLoop(NSRunLoop.mainRunLoop, NSRunLoopCommonModes)