[android] Childview will process its motion events

Prior to this change the parent view, i.e, FlutterView intercepts
all the MotionEvents and sent them to the framework for processing,
after this it makes it so that the ChildView processes the event.

Author: Kaushik Iska

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

@@ -69,15 +69,18 @@ public class AndroidTouchProcessor {
 
   private static final int _POINTER_BUTTON_PRIMARY = 1;
 
+  private final boolean trackMotionEvents;
+
   /**
    * Constructs an {@code AndroidTouchProcessor} that will send touch event data to the Flutter
    * execution context represented by the given {@link FlutterRenderer}.
    */
   // TODO(mattcarroll): consider moving packet behavior to a FlutterInteractionSurface instead of
   // FlutterRenderer
-  public AndroidTouchProcessor(@NonNull FlutterRenderer renderer) {
+  public AndroidTouchProcessor(@NonNull FlutterRenderer renderer, boolean trackMotionEvents) {
     this.renderer = renderer;
     this.motionEventTracker = MotionEventTracker.getInstance();
+    this.trackMotionEvents = trackMotionEvents;
   }
 
   /** Sends the given {@link MotionEvent} data to Flutter in a format that Flutter understands. */
@@ -176,8 +179,11 @@ private void addPointerForIndex(
       return;
     }
 
-    // TODO (kaushikiska) : pass this in when we have a way to evict framework only events.
-    // MotionEventTracker.MotionEventId motionEventId = motionEventTracker.track(event);
+    long motionEventId = 0;
+    if (trackMotionEvents) {
+      MotionEventTracker.MotionEventId trackedEvent = motionEventTracker.track(event);
+      motionEventId = trackedEvent.getId();
+    }
 
     int pointerKind = getPointerDeviceTypeForToolType(event.getToolType(pointerIndex));
 
@@ -188,15 +194,15 @@ private void addPointerForIndex(
 
     long timeStamp = event.getEventTime() * 1000; // Convert from milliseconds to microseconds.
 
-    packet.putLong(0); // motionEventId
+    packet.putLong(motionEventId); // motionEventId
     packet.putLong(timeStamp); // time_stamp
     packet.putLong(pointerChange); // change
     packet.putLong(pointerKind); // kind
     packet.putLong(signalKind); // signal_kind
     packet.putLong(event.getPointerId(pointerIndex)); // device
     packet.putLong(0); // pointer_identifier, will be generated in pointer_data_packet_converter.cc.
-    packet.putDouble(event.getX(pointerIndex)); // physical_x
-    packet.putDouble(event.getY(pointerIndex)); // physical_y
+    packet.putDouble(event.getRawX(pointerIndex)); // physical_x
+    packet.putDouble(event.getRawY(pointerIndex)); // physical_y
     packet.putDouble(
         0.0); // physical_delta_x, will be generated in pointer_data_packet_converter.cc.
     packet.putDouble(

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

@@ -782,11 +782,6 @@ public AccessibilityNodeProvider getAccessibilityNodeProvider() {
     }
   }
 
-  @Override
-  public boolean onInterceptTouchEvent(MotionEvent ev) {
-    return true;
-  }
-
   // TODO(mattcarroll): Confer with Ian as to why we need this method. Delete if possible, otherwise
   // add comments.
   private void resetWillNotDraw(boolean isAccessibilityEnabled, boolean isTouchExplorationEnabled) {
@@ -857,7 +852,8 @@ public void attachToFlutterEngine(@NonNull FlutterEngine flutterEngine) {
     localizationPlugin = this.flutterEngine.getLocalizationPlugin();
     androidKeyProcessor =
         new AndroidKeyProcessor(this.flutterEngine.getKeyEventChannel(), textInputPlugin);
-    androidTouchProcessor = new AndroidTouchProcessor(this.flutterEngine.getRenderer());
+    androidTouchProcessor =
+        new AndroidTouchProcessor(this.flutterEngine.getRenderer(), /*trackMotionEvents=*/ false);
     accessibilityBridge =
         new AccessibilityBridge(
             this,
@@ -873,6 +869,9 @@ public void attachToFlutterEngine(@NonNull FlutterEngine flutterEngine) {
     // Connect AccessibilityBridge to the PlatformViewsController within the FlutterEngine.
     // This allows platform Views to hook into Flutter's overall accessibility system.
     this.flutterEngine.getPlatformViewsController().attachAccessibilityBridge(accessibilityBridge);
+    this.flutterEngine
+        .getPlatformViewsController()
+        .attachToFlutterRenderer(this.flutterEngine.getRenderer());
 
     // Inform the Android framework that it should retrieve a new InputConnection
     // now that an engine is attached.

shell/platform/android/io/flutter/embedding/engine/mutatorsstack/FlutterMutatorView.java

@@ -4,8 +4,10 @@
 import android.graphics.Canvas;
 import android.graphics.Matrix;
 import android.graphics.Path;
+import android.view.MotionEvent;
 import android.widget.FrameLayout;
 import androidx.annotation.NonNull;
+import io.flutter.embedding.android.AndroidTouchProcessor;
 
 /**
  * A view that applies the {@link io.flutter.embedding.engine.mutatorsstack.MutatorsStack} to its
@@ -17,19 +19,24 @@ public class FlutterMutatorView extends FrameLayout {
   private int left;
   private int top;
 
+  private final AndroidTouchProcessor androidTouchProcessor;
+
   /**
    * Initialize the FlutterMutatorView. Use this to set the screenDensity, which will be used to
    * correct the final transform matrix.
    */
-  public FlutterMutatorView(@NonNull Context context, float screenDensity) {
+  public FlutterMutatorView(
+      @NonNull Context context, float screenDensity, AndroidTouchProcessor androidTouchProcessor) {
     super(context, null);
     this.screenDensity = screenDensity;
+    this.androidTouchProcessor = androidTouchProcessor;
   }
 
   /** Initialize the FlutterMutatorView. */
-  public FlutterMutatorView(@NonNull Context context) {
+  public FlutterMutatorView(@NonNull Context context, AndroidTouchProcessor androidTouchProcessor) {
     super(context, null);
     this.screenDensity = 1;
+    this.androidTouchProcessor = androidTouchProcessor;
   }
 
   /**
@@ -92,4 +99,15 @@ public void dispatchDraw(Canvas canvas) {
     super.dispatchDraw(canvas);
     canvas.restore();
   }
+
+  @Override
+  // Intercept the events here and do not propagate them to the child platform views.
+  public boolean onInterceptTouchEvent(MotionEvent event) {
+    return true;
+  }
+
+  @Override
+  public boolean onTouchEvent(MotionEvent event) {
+    return androidTouchProcessor.onTouchEvent(event);
+  }
 }

shell/platform/android/io/flutter/plugin/platform/PlatformViewsController.java

@@ -19,12 +19,14 @@
 import androidx.annotation.NonNull;
 import androidx.annotation.UiThread;
 import androidx.annotation.VisibleForTesting;
+import io.flutter.embedding.android.AndroidTouchProcessor;
 import io.flutter.embedding.android.FlutterImageView;
 import io.flutter.embedding.android.FlutterView;
 import io.flutter.embedding.android.MotionEventTracker;
 import io.flutter.embedding.engine.FlutterOverlaySurface;
 import io.flutter.embedding.engine.dart.DartExecutor;
 import io.flutter.embedding.engine.mutatorsstack.*;
+import io.flutter.embedding.engine.renderer.FlutterRenderer;
 import io.flutter.embedding.engine.systemchannels.PlatformViewsChannel;
 import io.flutter.plugin.editing.TextInputPlugin;
 import io.flutter.view.AccessibilityBridge;
@@ -45,6 +47,8 @@ public class PlatformViewsController implements PlatformViewsAccessibilityDelega
 
   private final PlatformViewRegistryImpl registry;
 
+  private AndroidTouchProcessor androidTouchProcessor;
+
   // The context of the Activity or Fragment hosting the render target for the Flutter engine.
   private Context context;
 
@@ -325,10 +329,12 @@ public MotionEvent toMotionEvent(
             .toArray(new PointerCoords[touch.pointerCount]);
 
     if (!usingVirtualDiplays && trackedEvent != null) {
+      // TODO (kaushikiska): investigate why we can not use the tracked
+      // event directly.
       return MotionEvent.obtain(
           trackedEvent.getDownTime(),
           trackedEvent.getEventTime(),
-          trackedEvent.getAction(),
+          touch.action,
           touch.pointerCount,
           pointerProperties,
           pointerCoords,
@@ -673,12 +679,17 @@ private void initializePlatformViewIfNeeded(int viewId) {
     platformViews.put(viewId, view);
 
     FlutterMutatorView mutatorView =
-        new FlutterMutatorView(context, context.getResources().getDisplayMetrics().density);
+        new FlutterMutatorView(
+            context, context.getResources().getDisplayMetrics().density, androidTouchProcessor);
     mutatorViews.put(viewId, mutatorView);
     mutatorView.addView(platformView.getView());
     ((FlutterView) flutterView).addView(mutatorView);
   }
 
+  public void attachToFlutterRenderer(FlutterRenderer flutterRenderer) {
+    androidTouchProcessor = new AndroidTouchProcessor(flutterRenderer, /*trackMotionEvents=*/ true);
+  }
+
   public void onDisplayPlatformView(
       int viewId,
       int x,

shell/platform/android/io/flutter/view/FlutterView.java

@@ -232,7 +232,9 @@ public void onPostResume() {
     }
     mLocalizationPlugin = new LocalizationPlugin(context, localizationChannel);
     androidKeyProcessor = new AndroidKeyProcessor(keyEventChannel, mTextInputPlugin);
-    androidTouchProcessor = new AndroidTouchProcessor(flutterRenderer);
+    androidTouchProcessor =
+        new AndroidTouchProcessor(flutterRenderer, /*trackMotionEvents=*/ false);
+    platformViewsController.attachToFlutterRenderer(flutterRenderer);
     mNativeView
         .getPluginRegistry()
         .getPlatformViewsController()