Android embedding API updates for plugin ecosystem

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

@@ -399,6 +399,7 @@ protected void onCreate(@Nullable Bundle savedInstanceState) {
 
     delegate = new FlutterActivityAndFragmentDelegate(this);
     delegate.onAttach(this);
+    delegate.onActivityCreated(savedInstanceState);
 
     configureWindowForTransparency();
     setContentView(createFlutterView());
@@ -557,6 +558,12 @@ protected void onStop() {
     lifecycle.handleLifecycleEvent(Lifecycle.Event.ON_STOP);
   }
 
+  @Override
+  protected void onSaveInstanceState(Bundle outState) {
+    super.onSaveInstanceState(outState);
+    delegate.onSaveInstanceState(outState);
+  }
+
   @Override
   protected void onDestroy() {
     super.onDestroy();

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

@@ -257,6 +257,15 @@ View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nulla
     return flutterSplashView;
   }
 
+  void onActivityCreated(@Nullable Bundle bundle) {
+    Log.v(TAG, "onActivityCreated. Giving plugins an opportunity to restore state.");
+    ensureAlive();
+
+    if (host.shouldAttachEngineToActivity()) {
+      flutterEngine.getActivityControlSurface().onRestoreInstanceState(bundle);
+    }
+  }
+
   /**
    * Invoke this from {@code Activity#onStart()} or {@code Fragment#onStart()}.
    * <p>
@@ -404,6 +413,15 @@ void onDestroyView() {
     flutterView.removeOnFirstFrameRenderedListener(flutterUiDisplayListener);
   }
 
+  void onSaveInstanceState(@Nullable Bundle bundle) {
+    Log.v(TAG, "onSaveInstanceState. Giving plugins an opportunity to save state.");
+    ensureAlive();
+
+    if (host.shouldAttachEngineToActivity()) {
+      flutterEngine.getActivityControlSurface().onSaveInstanceState(bundle);
+    }
+  }
+
   /**
    * Invoke this from {@code Activity#onDestroy()} or {@code Fragment#onDetach()}.
    * <p>

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

@@ -586,6 +586,12 @@ public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container,
     return delegate.onCreateView(inflater, container, savedInstanceState);
   }
 
+  @Override
+  public void onActivityCreated(@Nullable Bundle savedInstanceState) {
+    super.onActivityCreated(savedInstanceState);
+    delegate.onActivityCreated(savedInstanceState);
+  }
+
   @Override
   public void onStart() {
     super.onStart();
@@ -622,6 +628,12 @@ public void onDestroyView() {
     delegate.onDestroyView();
   }
 
+  @Override
+  public void onSaveInstanceState(Bundle outState) {
+    super.onSaveInstanceState(outState);
+    delegate.onSaveInstanceState(outState);
+  }
+
   @Override
   public void onDetach() {
     super.onDetach();

shell/platform/android/io/flutter/embedding/engine/FlutterEnginePluginRegistry.java

@@ -11,6 +11,7 @@
 import android.content.ContentProvider;
 import android.content.Context;
 import android.content.Intent;
+import android.os.Bundle;
 import android.support.annotation.NonNull;
 import android.support.annotation.Nullable;
 
@@ -49,6 +50,8 @@ class FlutterEnginePluginRegistry implements PluginRegistry,
 
   // Standard FlutterPlugin
   @NonNull
+  private final FlutterEngine flutterEngine;
+  @NonNull
   private final FlutterPlugin.FlutterPluginBinding pluginBinding;
   @NonNull
   private final FlutterEngineAndroidLifecycle flutterEngineAndroidLifecycle;
@@ -91,10 +94,14 @@ class FlutterEnginePluginRegistry implements PluginRegistry,
       @NonNull FlutterEngine flutterEngine,
       @NonNull FlutterEngineAndroidLifecycle lifecycle
   ) {
+    this.flutterEngine = flutterEngine;
     flutterEngineAndroidLifecycle = lifecycle;
     pluginBinding = new FlutterPlugin.FlutterPluginBinding(
         appContext,
         flutterEngine,
+        flutterEngine.getDartExecutor(),
+        flutterEngine.getRenderer(),
+        flutterEngine.getPlatformViewsController().getRegistry(),
         lifecycle
     );
   }
@@ -288,16 +295,16 @@ public void attachToActivity(
     detachFromAndroidComponent();
 
     this.activity = activity;
-    this.activityPluginBinding = new FlutterEngineActivityPluginBinding(activity);
+    this.activityPluginBinding = new FlutterEngineActivityPluginBinding(activity, lifecycle);
     this.flutterEngineAndroidLifecycle.setBackingLifecycle(lifecycle);
 
     // Activate the PlatformViewsController. This must happen before any plugins attempt
     // to use it, otherwise an error stack trace will appear that says there is no
     // flutter/platform_views channel.
-    pluginBinding.getFlutterEngine().getPlatformViewsController().attach(
+    flutterEngine.getPlatformViewsController().attach(
         activity,
-        pluginBinding.getFlutterEngine().getRenderer(),
-        pluginBinding.getFlutterEngine().getDartExecutor()
+        flutterEngine.getRenderer(),
+        flutterEngine.getDartExecutor()
     );
 
     // Notify all ActivityAware plugins that they are now attached to a new Activity.
@@ -322,7 +329,7 @@ public void detachFromActivityForConfigChanges() {
       }
 
       // Deactivate PlatformViewsController.
-      pluginBinding.getFlutterEngine().getPlatformViewsController().detach();
+      flutterEngine.getPlatformViewsController().detach();
 
       flutterEngineAndroidLifecycle.setBackingLifecycle(null);
       activity = null;
@@ -341,7 +348,7 @@ public void detachFromActivity() {
       }
 
       // Deactivate PlatformViewsController.
-      pluginBinding.getFlutterEngine().getPlatformViewsController().detach();
+      flutterEngine.getPlatformViewsController().detach();
 
       flutterEngineAndroidLifecycle.setBackingLifecycle(null);
       activity = null;
@@ -392,6 +399,26 @@ public void onUserLeaveHint() {
       Log.e(TAG, "Attempted to notify ActivityAware plugins of onUserLeaveHint, but no Activity was attached.");
     }
   }
+
+  @Override
+  public void onSaveInstanceState(@NonNull Bundle bundle) {
+    Log.v(TAG, "Forwarding onSaveInstanceState() to plugins.");
+    if (isAttachedToActivity()) {
+      activityPluginBinding.onSaveInstanceState(bundle);
+    } else {
+      Log.e(TAG, "Attempted to notify ActivityAware plugins of onSaveInstanceState, but no Activity was attached.");
+    }
+  }
+
+  @Override
+  public void onRestoreInstanceState(@Nullable Bundle bundle) {
+    Log.v(TAG, "Forwarding onRestoreInstanceState() to plugins.");
+    if (isAttachedToActivity()) {
+      activityPluginBinding.onRestoreInstanceState(bundle);
+    } else {
+      Log.e(TAG, "Attempted to notify ActivityAware plugins of onRestoreInstanceState, but no Activity was attached.");
+    }
+  }
   //------- End ActivityControlSurface -----
 
   //----- Start ServiceControlSurface ----
@@ -400,13 +427,13 @@ private boolean isAttachedToService() {
   }
 
   @Override
-  public void attachToService(@NonNull Service service, @NonNull Lifecycle lifecycle, boolean isForeground) {
+  public void attachToService(@NonNull Service service, @Nullable Lifecycle lifecycle, boolean isForeground) {
     Log.v(TAG, "Attaching to a Service: " + service);
     // If we were already attached to an Android component, detach from it.
     detachFromAndroidComponent();
 
     this.service = service;
-    this.servicePluginBinding = new FlutterEngineServicePluginBinding(service);
+    this.servicePluginBinding = new FlutterEngineServicePluginBinding(service, lifecycle);
     flutterEngineAndroidLifecycle.setBackingLifecycle(lifecycle);
 
     // Notify all ServiceAware plugins that they are now attached to a new Service.
@@ -523,16 +550,21 @@ private static class FlutterEngineActivityPluginBinding implements ActivityPlugi
     @NonNull
     private final Activity activity;
     @NonNull
+    private final Lifecycle lifecycle;
+    @NonNull
     private final Set<io.flutter.plugin.common.PluginRegistry.RequestPermissionsResultListener> onRequestPermissionsResultListeners = new HashSet<>();
     @NonNull
     private final Set<io.flutter.plugin.common.PluginRegistry.ActivityResultListener> onActivityResultListeners = new HashSet<>();
     @NonNull
     private final Set<io.flutter.plugin.common.PluginRegistry.NewIntentListener> onNewIntentListeners = new HashSet<>();
     @NonNull
     private final Set<io.flutter.plugin.common.PluginRegistry.UserLeaveHintListener> onUserLeaveHintListeners = new HashSet<>();
+    @NonNull
+    private final Set<OnSaveInstanceStateListener> onSaveInstanceStateListeners = new HashSet<>();
 
-    public FlutterEngineActivityPluginBinding(@NonNull Activity activity) {
+    public FlutterEngineActivityPluginBinding(@NonNull Activity activity, @NonNull Lifecycle lifecycle) {
       this.activity = activity;
+      this.lifecycle = lifecycle;
     }
 
     @Override
@@ -541,6 +573,12 @@ public Activity getActivity() {
       return activity;
     }
 
+    @NonNull
+    @Override
+    public Lifecycle getLifecycle() {
+      return lifecycle;
+    }
+
     @Override
     public void addRequestPermissionsResultListener(@NonNull io.flutter.plugin.common.PluginRegistry.RequestPermissionsResultListener listener) {
       onRequestPermissionsResultListeners.add(listener);
@@ -615,6 +653,16 @@ public void removeOnUserLeaveHintListener(@NonNull io.flutter.plugin.common.Plug
       onUserLeaveHintListeners.remove(listener);
     }
 
+    @Override
+    public void addOnSaveStateListener(@NonNull OnSaveInstanceStateListener listener) {
+      onSaveInstanceStateListeners.add(listener);
+    }
+
+    @Override
+    public void removeOnSaveStateListener(@NonNull OnSaveInstanceStateListener listener) {
+      onSaveInstanceStateListeners.remove(listener);
+    }
+
     /**
      * Invoked by the {@link FlutterEngine} that owns this {@code ActivityPluginBinding} when its
      * associated {@link Activity} has its {@code onUserLeaveHint()} method invoked.
@@ -624,16 +672,41 @@ void onUserLeaveHint() {
         listener.onUserLeaveHint();
       }
     }
+
+    /**
+     * Invoked by the {@link FlutterEngine} that owns this {@code ActivityPluginBinding} when its
+     * associated {@link Activity} or {@code Fragment} has its {@code onSaveInstanceState(Bundle)}
+     * method invoked.
+     */
+    void onSaveInstanceState(@NonNull Bundle bundle) {
+      for (OnSaveInstanceStateListener listener : onSaveInstanceStateListeners) {
+        listener.onSaveInstanceState(bundle);
+      }
+    }
+
+    /**
+     * Invoked by the {@link FlutterEngine} that owns this {@code ActivityPluginBinding} when its
+     * associated {@link Activity} has its {@code onCreate(Bundle)} method invoked, or its
+     * associated {@code Fragment} has its {@code onActivityCreated(Bundle)} method invoked.
+     */
+    void onRestoreInstanceState(@Nullable Bundle bundle) {
+      for (OnSaveInstanceStateListener listener : onSaveInstanceStateListeners) {
+        listener.onRestoreInstanceState(bundle);
+      }
+    }
   }
 
   private static class FlutterEngineServicePluginBinding implements ServicePluginBinding {
     @NonNull
     private final Service service;
+    @Nullable
+    private final Lifecycle lifecycle;
     @NonNull
     private final Set<ServiceAware.OnModeChangeListener> onModeChangeListeners = new HashSet<>();
 
-    FlutterEngineServicePluginBinding(@NonNull Service service) {
+    FlutterEngineServicePluginBinding(@NonNull Service service, @Nullable Lifecycle lifecycle) {
       this.service = service;
+      this.lifecycle = lifecycle;
     }
 
     @Override
@@ -642,6 +715,12 @@ public Service getService() {
       return service;
     }
 
+    @Nullable
+    @Override
+    public Lifecycle getLifecycle() {
+      return lifecycle;
+    }
+
     @Override
     public void addOnModeChangeListener(@NonNull ServiceAware.OnModeChangeListener listener) {
       onModeChangeListeners.add(listener);