Revert "Issues/39832 reland (#13642)" (#13720)

This reverts commit 1bfb928e.

lib/ui/window.dart

@@ -171,16 +171,18 @@ enum AppLifecycleState {
   ///
   /// When the application is in this state, the engine will not call the
   /// [Window.onBeginFrame] and [Window.onDrawFrame] callbacks.
+  ///
+  /// Android apps in this state should assume that they may enter the
+  /// [suspending] state at any time.
   paused,
 
-  /// The application is still hosted on a flutter engine but is detached from
-  /// any host views.
+  /// The application will be suspended momentarily.
+  ///
+  /// When the application is in this state, the engine will not call the
+  /// [Window.onBeginFrame] and [Window.onDrawFrame] callbacks.
   ///
-  /// When the application is in this state, the engine is running without
-  /// a view. It can either be in the progress of attaching a view when engine
-  /// was first initializes, or after the view being destroyed due to a Navigator
-  /// pop.
-  detached,
+  /// On iOS, this state is currently unused.
+  suspending,
 }
 
 /// A representation of distances for each of the four edges of a rectangle,

lib/web_ui/lib/src/ui/window.dart

@@ -73,13 +73,18 @@ enum AppLifecycleState {
   ///
   /// When the application is in this state, the engine will not call the
   /// [Window.onBeginFrame] and [Window.onDrawFrame] callbacks.
+  ///
+  /// Android apps in this state should assume that they may enter the
+  /// [suspending] state at any time.
   paused,
 
-  /// The application is detached from view.
+  /// The application will be suspended momentarily.
+  ///
+  /// When the application is in this state, the engine will not call the
+  /// [Window.onBeginFrame] and [Window.onDrawFrame] callbacks.
   ///
-  /// When the application is in this state, the engine is running without
-  /// a platform UI.
-  detached,
+  /// On iOS, this state is currently unused.
+  suspending,
 }
 
 /// A representation of distances for each of the four edges of a rectangle,

runtime/runtime_controller.h

@@ -120,7 +120,7 @@ class RuntimeController final : public WindowClient {
     std::string variant_code;
     std::vector<std::string> locale_data;
     std::string user_settings_data = "{}";
-    std::string lifecycle_state = "AppLifecycleState.detached";
+    std::string lifecycle_state;
     bool semantics_enabled = false;
     bool assistive_technology_enabled = false;
     int32_t accessibility_feature_flags_ = 0;

shell/common/engine.cc

@@ -311,7 +311,7 @@ bool Engine::HandleLifecyclePlatformMessage(PlatformMessage* message) {
   const auto& data = message->data();
   std::string state(reinterpret_cast<const char*>(data.data()), data.size());
   if (state == "AppLifecycleState.paused" ||
-      state == "AppLifecycleState.detached") {
+      state == "AppLifecycleState.suspending") {
     activity_running_ = false;
     StopAnimator();
   } else if (state == "AppLifecycleState.resumed" ||

shell/platform/android/io/flutter/embedding/android/FlutterActivityAndFragmentDelegate.java

@@ -461,8 +461,6 @@ import static android.content.ComponentCallbacks2.TRIM_MEMORY_RUNNING_LOW;
       platformPlugin = null;
     }
 
-    flutterEngine.getLifecycleChannel().appIsDetached();
-
     // Destroy our FlutterEngine if we're not set to retain it.
     if (host.shouldDestroyEngineWithHost()) {
       flutterEngine.destroy();

shell/platform/android/io/flutter/embedding/engine/systemchannels/LifecycleChannel.java

@@ -39,8 +39,4 @@ public class LifecycleChannel {
     channel.send("AppLifecycleState.paused");
   }
 
-  public void appIsDetached() {
-    Log.v(TAG, "Sending AppLifecycleState.detached message.");
-    channel.send("AppLifecycleState.detached");
-  }
 }

shell/platform/android/test/io/flutter/embedding/android/FlutterActivityAndFragmentDelegateTest.java

@@ -85,21 +85,18 @@ public class FlutterActivityAndFragmentDelegateTest {
     verify(mockFlutterEngine.getLifecycleChannel(), never()).appIsResumed();
     verify(mockFlutterEngine.getLifecycleChannel(), never()).appIsPaused();
     verify(mockFlutterEngine.getLifecycleChannel(), never()).appIsInactive();
-    verify(mockFlutterEngine.getLifecycleChannel(), never()).appIsDetached();
 
     // When the Activity/Fragment is resumed, a resumed message should have been sent to Flutter.
     delegate.onResume();
     verify(mockFlutterEngine.getLifecycleChannel(), times(1)).appIsResumed();
     verify(mockFlutterEngine.getLifecycleChannel(), never()).appIsInactive();
     verify(mockFlutterEngine.getLifecycleChannel(), never()).appIsPaused();
-    verify(mockFlutterEngine.getLifecycleChannel(), never()).appIsDetached();
 
     // When the Activity/Fragment is paused, an inactive message should have been sent to Flutter.
     delegate.onPause();
     verify(mockFlutterEngine.getLifecycleChannel(), times(1)).appIsResumed();
     verify(mockFlutterEngine.getLifecycleChannel(), times(1)).appIsInactive();
     verify(mockFlutterEngine.getLifecycleChannel(), never()).appIsPaused();
-    verify(mockFlutterEngine.getLifecycleChannel(), never()).appIsDetached();
 
     // When the Activity/Fragment is stopped, a paused message should have been sent to Flutter.
     // Notice that Flutter uses the term "paused" in a different way, and at a different time
@@ -108,14 +105,6 @@ public class FlutterActivityAndFragmentDelegateTest {
     verify(mockFlutterEngine.getLifecycleChannel(), times(1)).appIsResumed();
     verify(mockFlutterEngine.getLifecycleChannel(), times(1)).appIsInactive();
     verify(mockFlutterEngine.getLifecycleChannel(), times(1)).appIsPaused();
-    verify(mockFlutterEngine.getLifecycleChannel(), never()).appIsDetached();
-
-    // When activity detaches, a detached message should have been sent to Flutter.
-    delegate.onDetach();
-    verify(mockFlutterEngine.getLifecycleChannel(), times(1)).appIsResumed();
-    verify(mockFlutterEngine.getLifecycleChannel(), times(1)).appIsInactive();
-    verify(mockFlutterEngine.getLifecycleChannel(), times(1)).appIsPaused();
-    verify(mockFlutterEngine.getLifecycleChannel(), times(1)).appIsDetached();
   }
 
   @Test

shell/platform/darwin/ios/framework/Source/FlutterEngine.mm

@@ -175,23 +175,18 @@ NSString* const FlutterDefaultDartEntrypoint = nil;
 
 - (void)setViewController:(FlutterViewController*)viewController {
   FML_DCHECK(self.iosPlatformView);
-  _viewController =
-      viewController ? [viewController getWeakPtr] : fml::WeakPtr<FlutterViewController>();
+  _viewController = [viewController getWeakPtr];
   self.iosPlatformView->SetOwnerViewController(_viewController);
   [self maybeSetupPlatformViewChannels];
 
-  if (viewController) {
-    __block FlutterEngine* blockSelf = self;
-    self.flutterViewControllerWillDeallocObserver =
-        [[NSNotificationCenter defaultCenter] addObserverForName:FlutterViewControllerWillDealloc
-                                                          object:viewController
-                                                           queue:[NSOperationQueue mainQueue]
-                                                      usingBlock:^(NSNotification* note) {
-                                                        [blockSelf notifyViewControllerDeallocated];
-                                                      }];
-  } else {
-    self.flutterViewControllerWillDeallocObserver = nil;
-  }
+  __block FlutterEngine* blockSelf = self;
+  self.flutterViewControllerWillDeallocObserver =
+      [[NSNotificationCenter defaultCenter] addObserverForName:FlutterViewControllerWillDealloc
+                                                        object:viewController
+                                                         queue:[NSOperationQueue mainQueue]
+                                                    usingBlock:^(NSNotification* note) {
+                                                      [blockSelf notifyViewControllerDeallocated];
+                                                    }];
 }
 
 - (void)setFlutterViewControllerWillDeallocObserver:(id<NSObject>)observer {
@@ -206,7 +201,6 @@ NSString* const FlutterDefaultDartEntrypoint = nil;
 }
 
 - (void)notifyViewControllerDeallocated {
-  [[self lifecycleChannel] sendMessage:@"AppLifecycleState.detached"];
   if (!_allowHeadlessExecution) {
     [self destroyContext];
   } else {

testing/scenario_app/ios/Scenarios/ScenariosTests/AppLifecycleTests.m

@@ -225,70 +225,4 @@
   [engine setViewController:nil];
 }
 
-- (void)testFlutterViewControllerDetachingSendsApplicationLifecycle {
-  XCTestExpectation* engineStartedExpectation = [self expectationWithDescription:@"Engine started"];
-
-  // Let the engine finish booting (at the end of which the channels are properly set-up) before
-  // moving onto the next step of showing the next view controller.
-  ScreenBeforeFlutter* rootVC = [[ScreenBeforeFlutter alloc] initWithEngineRunCompletion:^void() {
-    [engineStartedExpectation fulfill];
-  }];
-
-  [self waitForExpectationsWithTimeout:5 handler:nil];
-
-  UIApplication* application = UIApplication.sharedApplication;
-  application.delegate.window.rootViewController = rootVC;
-  FlutterEngine* engine = rootVC.engine;
-
-  NSMutableArray* lifecycleExpectations = [NSMutableArray arrayWithCapacity:10];
-
-  // Expected sequence from showing the FlutterViewController is inactive and resumed.
-  [lifecycleExpectations addObjectsFromArray:@[
-    [[XCAppLifecycleTestExpectation alloc] initForLifecycle:@"AppLifecycleState.inactive"
-                                                    forStep:@"showing a FlutterViewController"],
-    [[XCAppLifecycleTestExpectation alloc] initForLifecycle:@"AppLifecycleState.resumed"
-                                                    forStep:@"showing a FlutterViewController"]
-  ]];
-  // At the end of Flutter VC, we want to make sure it deallocs and sends detached signal.
-  // Using autoreleasepool will guarantee that.
-  FlutterViewController* flutterVC;
-  @autoreleasepool {
-    flutterVC = [rootVC showFlutter];
-    [engine.lifecycleChannel setMessageHandler:^(id message, FlutterReply callback) {
-      if (lifecycleExpectations.count == 0) {
-        XCTFail(@"Unexpected lifecycle transition: %@", message);
-        return;
-      }
-      XCAppLifecycleTestExpectation* nextExpectation = [lifecycleExpectations objectAtIndex:0];
-      if (![[nextExpectation expectedLifecycle] isEqualToString:message]) {
-        XCTFail(@"Expected lifecycle %@ but instead received %@",
-                [nextExpectation expectedLifecycle], message);
-        return;
-      }
-
-      [nextExpectation fulfill];
-      [lifecycleExpectations removeObjectAtIndex:0];
-    }];
-
-    [self waitForExpectations:lifecycleExpectations timeout:5];
-
-    // Starts dealloc flutter VC.
-    [lifecycleExpectations addObjectsFromArray:@[
-      [[XCAppLifecycleTestExpectation alloc] initForLifecycle:@"AppLifecycleState.inactive"
-                                                      forStep:@"detaching a FlutterViewController"],
-      [[XCAppLifecycleTestExpectation alloc] initForLifecycle:@"AppLifecycleState.paused"
-                                                      forStep:@"detaching a FlutterViewController"],
-      [[XCAppLifecycleTestExpectation alloc]
-          initForLifecycle:@"AppLifecycleState.detached"
-                   forStep:@"detaching a FlutterViewController"]
-    ]];
-    [flutterVC dismissViewControllerAnimated:NO completion:nil];
-    flutterVC = nil;
-  }
-  [self waitForExpectations:lifecycleExpectations timeout:5];
-
-  [engine.lifecycleChannel setMessageHandler:nil];
-  [engine setViewController:nil];
-}
-
 @end