Revert "Enforce exclusivity for activity and fragments attached to the FlutterEngine"

ci/licenses_golden/licenses_flutter

@@ -708,7 +708,6 @@ FILE: ../../../flutter/shell/platform/android/io/flutter/app/FlutterPluginRegist
 FILE: ../../../flutter/shell/platform/android/io/flutter/embedding/android/AndroidKeyProcessor.java
 FILE: ../../../flutter/shell/platform/android/io/flutter/embedding/android/AndroidTouchProcessor.java
 FILE: ../../../flutter/shell/platform/android/io/flutter/embedding/android/DrawableSplashScreen.java
-FILE: ../../../flutter/shell/platform/android/io/flutter/embedding/android/ExclusiveAppComponent.java
 FILE: ../../../flutter/shell/platform/android/io/flutter/embedding/android/FlutterActivity.java
 FILE: ../../../flutter/shell/platform/android/io/flutter/embedding/android/FlutterActivityAndFragmentDelegate.java
 FILE: ../../../flutter/shell/platform/android/io/flutter/embedding/android/FlutterActivityLaunchConfigs.java
@@ -728,7 +727,7 @@ FILE: ../../../flutter/shell/platform/android/io/flutter/embedding/android/Splas
 FILE: ../../../flutter/shell/platform/android/io/flutter/embedding/android/TransparencyMode.java
 FILE: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/FlutterEngine.java
 FILE: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/FlutterEngineCache.java
-FILE: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/FlutterEngineConnectionRegistry.java
+FILE: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/FlutterEnginePluginRegistry.java
 FILE: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/FlutterJNI.java
 FILE: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/FlutterOverlaySurface.java
 FILE: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/FlutterShellArgs.java

shell/platform/android/BUILD.gn

@@ -128,7 +128,6 @@ android_java_sources = [
   "io/flutter/embedding/android/AndroidKeyProcessor.java",
   "io/flutter/embedding/android/AndroidTouchProcessor.java",
   "io/flutter/embedding/android/DrawableSplashScreen.java",
-  "io/flutter/embedding/android/ExclusiveAppComponent.java",
   "io/flutter/embedding/android/FlutterActivity.java",
   "io/flutter/embedding/android/FlutterActivityAndFragmentDelegate.java",
   "io/flutter/embedding/android/FlutterActivityLaunchConfigs.java",
@@ -148,7 +147,7 @@ android_java_sources = [
   "io/flutter/embedding/android/TransparencyMode.java",
   "io/flutter/embedding/engine/FlutterEngine.java",
   "io/flutter/embedding/engine/FlutterEngineCache.java",
-  "io/flutter/embedding/engine/FlutterEngineConnectionRegistry.java",
+  "io/flutter/embedding/engine/FlutterEnginePluginRegistry.java",
   "io/flutter/embedding/engine/FlutterJNI.java",
   "io/flutter/embedding/engine/FlutterOverlaySurface.java",
   "io/flutter/embedding/engine/FlutterShellArgs.java",
@@ -430,7 +429,7 @@ action("robolectric_tests") {
     "test/io/flutter/embedding/android/FlutterViewTest.java",
     "test/io/flutter/embedding/android/RobolectricFlutterActivity.java",
     "test/io/flutter/embedding/engine/FlutterEngineCacheTest.java",
-    "test/io/flutter/embedding/engine/FlutterEngineConnectionRegistryTest.java",
+    "test/io/flutter/embedding/engine/FlutterEnginePluginRegistryTest.java",
     "test/io/flutter/embedding/engine/FlutterEngineTest.java",
     "test/io/flutter/embedding/engine/FlutterJNITest.java",
     "test/io/flutter/embedding/engine/FlutterShellArgsTest.java",

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

@@ -560,102 +560,56 @@ protected void onPause() {
   @Override
   protected void onStop() {
     super.onStop();
-    if (stillAttachedForEvent("onStop")) {
-      delegate.onStop();
-    }
+    delegate.onStop();
     lifecycle.handleLifecycleEvent(Lifecycle.Event.ON_STOP);
   }
 
   @Override
   protected void onSaveInstanceState(Bundle outState) {
     super.onSaveInstanceState(outState);
-    if (stillAttachedForEvent("onSaveInstanceState")) {
-      delegate.onSaveInstanceState(outState);
-    }
-  }
-
-  /**
-   * Irreversibly release this activity's control of the {@link FlutterEngine} and its
-   * subcomponents.
-   *
-   * <p>Calling will disconnect this activity's view from the Flutter renderer, disconnect this
-   * activity from plugins' {@link ActivityControlSurface}, and stop system channel messages from
-   * this activity.
-   *
-   * <p>After calling, this activity should be disposed immediately and not be re-used.
-   */
-  private void release() {
-    delegate.onDestroyView();
-    delegate.onDetach();
-    delegate.release();
-    delegate = null;
-  }
-
-  @Override
-  public void detachFromFlutterEngine() {
-    Log.v(
-        TAG,
-        "FlutterActivity "
-            + this
-            + " connection to the engine "
-            + getFlutterEngine()
-            + " evicted by another attaching activity");
-    release();
+    delegate.onSaveInstanceState(outState);
   }
 
   @Override
   protected void onDestroy() {
     super.onDestroy();
-    if (stillAttachedForEvent("onDestroy")) {
-      release();
-    }
+    delegate.onDestroyView();
+    delegate.onDetach();
     lifecycle.handleLifecycleEvent(Lifecycle.Event.ON_DESTROY);
   }
 
   @Override
   protected void onActivityResult(int requestCode, int resultCode, Intent data) {
-    if (stillAttachedForEvent("onActivityResult")) {
-      delegate.onActivityResult(requestCode, resultCode, data);
-    }
+    delegate.onActivityResult(requestCode, resultCode, data);
   }
 
   @Override
   protected void onNewIntent(@NonNull Intent intent) {
     // TODO(mattcarroll): change G3 lint rule that forces us to call super
     super.onNewIntent(intent);
-    if (stillAttachedForEvent("onNewIntent")) {
-      delegate.onNewIntent(intent);
-    }
+    delegate.onNewIntent(intent);
   }
 
   @Override
   public void onBackPressed() {
-    if (stillAttachedForEvent("onBackPressed")) {
-      delegate.onBackPressed();
-    }
+    delegate.onBackPressed();
   }
 
   @Override
   public void onRequestPermissionsResult(
       int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
-    if (stillAttachedForEvent("onRequestPermissionsResult")) {
-      delegate.onRequestPermissionsResult(requestCode, permissions, grantResults);
-    }
+    delegate.onRequestPermissionsResult(requestCode, permissions, grantResults);
   }
 
   @Override
   public void onUserLeaveHint() {
-    if (stillAttachedForEvent("onUserLeaveHint")) {
-      delegate.onUserLeaveHint();
-    }
+    delegate.onUserLeaveHint();
   }
 
   @Override
   public void onTrimMemory(int level) {
     super.onTrimMemory(level);
-    if (stillAttachedForEvent("onTrimMemory")) {
-      delegate.onTrimMemory(level);
-    }
+    delegate.onTrimMemory(level);
   }
 
   /**
@@ -954,7 +908,7 @@ public void cleanUpFlutterEngine(@NonNull FlutterEngine flutterEngine) {
    * <p>Returning false from this method does not preclude a {@link FlutterEngine} from being
    * attaching to a {@code FlutterActivity} - it just prevents the attachment from happening
    * automatically. A developer can choose to subclass {@code FlutterActivity} and then invoke
-   * {@link ActivityControlSurface#attachToActivity(ExclusiveAppComponent, Lifecycle)} and {@link
+   * {@link ActivityControlSurface#attachToActivity(Activity, Lifecycle)} and {@link
    * ActivityControlSurface#detachFromActivity()} at the desired times.
    *
    * <p>One reason that a developer might choose to manually manage the relationship between the
@@ -1007,12 +961,4 @@ public boolean shouldRestoreAndSaveState() {
     }
     return true;
   }
-
-  private boolean stillAttachedForEvent(String event) {
-    if (delegate == null) {
-      Log.v(TAG, "FlutterActivity " + hashCode() + " " + event + " called after release.");
-      return false;
-    }
-    return true;
-  }
 }

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

@@ -62,7 +62,7 @@
  * the same form. <strong>Do not use this class as a convenient shortcut for any other
  * behavior.</strong>
  */
-/* package */ class FlutterActivityAndFragmentDelegate implements ExclusiveAppComponent<Activity> {
+/* package */ final class FlutterActivityAndFragmentDelegate {
   private static final String TAG = "FlutterActivityAndFragmentDelegate";
   private static final String FRAMEWORK_RESTORATION_BUNDLE_KEY = "framework";
   private static final String PLUGINS_RESTORATION_BUNDLE_KEY = "plugins";
@@ -154,6 +154,14 @@ void onAttach(@NonNull Context context) {
       setupFlutterEngine();
     }
 
+    // Regardless of whether or not a FlutterEngine already existed, the PlatformPlugin
+    // is bound to a specific Activity. Therefore, it needs to be created and configured
+    // every time this Fragment attaches to a new Activity.
+    // TODO(mattcarroll): the PlatformPlugin needs to be reimagined because it implicitly takes
+    //                    control of the entire window. This is unacceptable for non-fullscreen
+    //                    use-cases.
+    platformPlugin = host.providePlatformPlugin(host.getActivity(), flutterEngine);
+
     if (host.shouldAttachEngineToActivity()) {
       // Notify any plugins that are currently attached to our FlutterEngine that they
       // are now attached to an Activity.
@@ -164,32 +172,15 @@ void onAttach(@NonNull Context context) {
       // which means there shouldn't be any possibility for the Fragment Lifecycle to get out of
       // sync with the Activity. We use the Fragment's Lifecycle because it is possible that the
       // attached Activity is not a LifecycleOwner.
-      Log.v(TAG, "Attaching FlutterEngine to the Activity that owns this delegate.");
-      flutterEngine.getActivityControlSurface().attachToActivity(this, host.getLifecycle());
+      Log.v(TAG, "Attaching FlutterEngine to the Activity that owns this Fragment.");
+      flutterEngine
+          .getActivityControlSurface()
+          .attachToActivity(host.getActivity(), host.getLifecycle());
     }
 
-    // Regardless of whether or not a FlutterEngine already existed, the PlatformPlugin
-    // is bound to a specific Activity. Therefore, it needs to be created and configured
-    // every time this Fragment attaches to a new Activity.
-    // TODO(mattcarroll): the PlatformPlugin needs to be reimagined because it implicitly takes
-    //                    control of the entire window. This is unacceptable for non-fullscreen
-    //                    use-cases.
-    platformPlugin = host.providePlatformPlugin(host.getActivity(), flutterEngine);
-
     host.configureFlutterEngine(flutterEngine);
   }
 
-  @Override
-  public @NonNull Activity getAppComponent() {
-    final Activity activity = host.getActivity();
-    if (activity == null) {
-      throw new AssertionError(
-          "FlutterActivityAndFragmentDelegate's getAppComponent should only "
-              + "be queried after onAttach, when the host's activity should always be non-null");
-    }
-    return activity;
-  }
-
   /**
    * Obtains a reference to a FlutterEngine to back this delegate and its {@code host}.
    *
@@ -489,24 +480,6 @@ void onSaveInstanceState(@Nullable Bundle bundle) {
     }
   }
 
-  @Override
-  public void detachFromFlutterEngine() {
-    if (host.shouldDestroyEngineWithHost()) {
-      // The host owns the engine and should never have its engine taken by another exclusive
-      // activity.
-      throw new AssertionError(
-          "The internal FlutterEngine created by "
-              + host
-              + " has been attached to by another activity. To persist a FlutterEngine beyond the "
-              + "ownership of this activity, explicitly create a FlutterEngine");
-    }
-
-    // Default, but customizable, behavior is for the host to call {@link #onDetach}
-    // deterministically as to not mix more events during the lifecycle of the next exclusive
-    // activity.
-    host.detachFromFlutterEngine();
-  }
-
   /**
    * Invoke this from {@code Activity#onDestroy()} or {@code Fragment#onDetach()}.
    *
@@ -768,15 +741,6 @@ private void ensureAlive() {
      */
     boolean shouldDestroyEngineWithHost();
 
-    /**
-     * Callback called when the {@link FlutterEngine} has been attached to by another activity
-     * before this activity was destroyed.
-     *
-     * <p>The expected behavior is for this activity to synchronously stop using the {@link
-     * FlutterEngine} to avoid lifecycle crosstalk with the new activity.
-     */
-    void detachFromFlutterEngine();
-
     /** Returns the Dart entrypoint that should run when a new {@link FlutterEngine} is created. */
     @NonNull
     String getDartEntrypointFunctionName();

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

@@ -4,6 +4,7 @@
 
 package io.flutter.embedding.android;
 
+import android.app.Activity;
 import androidx.annotation.NonNull;
 import androidx.lifecycle.Lifecycle;
 import io.flutter.embedding.engine.FlutterEngine;
@@ -20,8 +21,8 @@ public interface FlutterEngineConfigurator {
    *
    * <p>This method is called after the given {@link FlutterEngine} has been attached to the owning
    * {@code FragmentActivity}. See {@link
-   * io.flutter.embedding.engine.plugins.activity.ActivityControlSurface#attachToActivity(
-   * ExclusiveAppComponent, Lifecycle)}.
+   * io.flutter.embedding.engine.plugins.activity.ActivityControlSurface#attachToActivity(Activity,
+   * Lifecycle)}.
    *
    * <p>It is possible that the owning {@code FragmentActivity} opted not to connect itself as an
    * {@link io.flutter.embedding.engine.plugins.activity.ActivityControlSurface}. In that case, any