Add support for more Scroll Events to Android

Summary:
public
This adds support for
onScrollBeginDrag/End
onMomentumScrolBegin/End

Reviewed By: astreet

Differential Revision: D2739035

fb-gh-sync-id: 2a49d1df54e5f5cd82008bdb0ffde0881ba39aff

ReactAndroid/src/main/java/com/facebook/react/views/recyclerview/RecyclerViewBackedScrollView.java

@@ -19,6 +19,7 @@ import com.facebook.react.common.annotations.VisibleForTesting;
 import com.facebook.react.uimanager.UIManagerModule;
 import com.facebook.react.uimanager.events.NativeGestureUtil;
 import com.facebook.react.views.scroll.ScrollEvent;
+import com.facebook.react.views.scroll.ScrollEventType;
 
 /**
  * Wraps {@link RecyclerView} providing interface similar to `ScrollView.js` where each children
@@ -311,6 +312,7 @@ public class RecyclerViewBackedScrollView extends RecyclerView {
         .dispatchEvent(ScrollEvent.obtain(
                 getId(),
                 SystemClock.uptimeMillis(),
+                ScrollEventType.SCROLL,
                 0, /* offsetX = 0, horizontal scrolling only */
                 calculateAbsoluteOffset(),
                 getWidth(),

ReactAndroid/src/main/java/com/facebook/react/views/recyclerview/RecyclerViewBackedScrollViewManager.java

@@ -14,7 +14,7 @@ import com.facebook.react.uimanager.ReactProp;
 import com.facebook.react.uimanager.ThemedReactContext;
 import com.facebook.react.uimanager.ViewGroupManager;
 import com.facebook.react.views.scroll.ReactScrollViewCommandHelper;
-import com.facebook.react.views.scroll.ScrollEvent;
+import com.facebook.react.views.scroll.ScrollEventType;
 
 /**
  * View manager for {@link RecyclerViewBackedScrollView}.
@@ -91,7 +91,7 @@ public class RecyclerViewBackedScrollViewManager extends
   public @Nullable
   Map getExportedCustomDirectEventTypeConstants() {
     return MapBuilder.builder()
-        .put(ScrollEvent.EVENT_NAME, MapBuilder.of("registrationName", "onScroll"))
+        .put(ScrollEventType.SCROLL.getJSEventName(), MapBuilder.of("registrationName", "onScroll"))
         .put(
             ContentSizeChangeEvent.EVENT_NAME,
             MapBuilder.of("registrationName", "onContentSizeChange"))

ReactAndroid/src/main/java/com/facebook/react/views/scroll/ReactHorizontalScrollView.java

@@ -23,10 +23,19 @@ public class ReactHorizontalScrollView extends HorizontalScrollView {
 
   private final OnScrollDispatchHelper mOnScrollDispatchHelper = new OnScrollDispatchHelper();
 
+  private boolean mSendMomentumEvents;
+  private boolean mDragging;
+  private boolean mFlinging;
+  private boolean mDoneFlinging;
+
   public ReactHorizontalScrollView(Context context) {
     super(context);
   }
 
+  public void setSendMomentumEvents(boolean sendMomentumEvents) {
+    mSendMomentumEvents = sendMomentumEvents;
+  }
+
   @Override
   protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
     MeasureSpecAssertions.assertExplicitMeasureSpec(widthMeasureSpec, heightMeasureSpec);
@@ -47,7 +56,10 @@ public class ReactHorizontalScrollView extends HorizontalScrollView {
     super.onScrollChanged(x, y, oldX, oldY);
 
     if (mOnScrollDispatchHelper.onScrollChanged(x, y)) {
-      ReactScrollViewHelper.emitScrollEvent(this, x, y);
+      if (mFlinging) {
+        mDoneFlinging = false;
+      }
+      ReactScrollViewHelper.emitScrollEvent(this);
     }
   }
 
@@ -55,9 +67,43 @@ public class ReactHorizontalScrollView extends HorizontalScrollView {
   public boolean onInterceptTouchEvent(MotionEvent ev) {
     if (super.onInterceptTouchEvent(ev)) {
       NativeGestureUtil.notifyNativeGestureStarted(this, ev);
+      ReactScrollViewHelper.emitScrollBeginDragEvent(this);
+      mDragging = true;
       return true;
     }
 
     return false;
   }
+
+  @Override
+  public boolean onTouchEvent(MotionEvent ev) {
+    int action = ev.getAction() & MotionEvent.ACTION_MASK;
+    if (action == MotionEvent.ACTION_UP && mDragging) {
+      ReactScrollViewHelper.emitScrollEndDragEvent(this);
+      mDragging = false;
+    }
+    return super.onTouchEvent(ev);
+  }
+
+  @Override
+  public void fling(int velocityX) {
+    super.fling(velocityX);
+    if (mSendMomentumEvents) {
+      mFlinging = true;
+      ReactScrollViewHelper.emitScrollMomentumBeginEvent(this);
+      Runnable r = new Runnable() {
+        @Override
+        public void run() {
+          if (mDoneFlinging) {
+            mFlinging = false;
+            ReactScrollViewHelper.emitScrollMomentumEndEvent(ReactHorizontalScrollView.this);
+          } else {
+            mDoneFlinging = true;
+            ReactHorizontalScrollView.this.postOnAnimationDelayed(this, ReactScrollViewHelper.MOMENTUM_DELAY);
+          }
+        }
+      };
+      postOnAnimationDelayed(r, ReactScrollViewHelper.MOMENTUM_DELAY);
+    }
+  }
 }

ReactAndroid/src/main/java/com/facebook/react/views/scroll/ReactHorizontalScrollViewManager.java

@@ -43,6 +43,19 @@ public class ReactHorizontalScrollViewManager
     view.setHorizontalScrollBarEnabled(value);
   }
 
+  /**
+   * Computing momentum events is potentially expensive since we post a runnable on the UI thread
+   * to see when it is done.  We only do that if {@param sendMomentumEvents} is set to true.  This
+   * is handled automatically in js by checking if there is a listener on the momentum events.
+   *
+   * @param view
+   * @param sendMomentumEvents
+   */
+  @ReactProp(name = "sendMomentumEvents")
+  public void setSendMomentumEvents(ReactHorizontalScrollView view, boolean sendMomentumEvents) {
+    view.setSendMomentumEvents(sendMomentumEvents);
+  }
+
   @Override
   public void receiveCommand(
       ReactHorizontalScrollView scrollView,

ReactAndroid/src/main/java/com/facebook/react/views/scroll/ReactScrollView.java

@@ -36,11 +36,19 @@ public class ReactScrollView extends ScrollView implements ReactClippingViewGrou
 
   private boolean mRemoveClippedSubviews;
   private @Nullable Rect mClippingRect;
+  private boolean mSendMomentumEvents;
+  private boolean mDragging;
+  private boolean mFlinging;
+  private boolean mDoneFlinging;
 
   public ReactScrollView(Context context) {
     super(context);
   }
 
+  public void setSendMomentumEvents(boolean sendMomentumEvents) {
+    mSendMomentumEvents = sendMomentumEvents;
+  }
+
   @Override
   protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
     MeasureSpecAssertions.assertExplicitMeasureSpec(widthMeasureSpec, heightMeasureSpec);
@@ -73,7 +81,11 @@ public class ReactScrollView extends ScrollView implements ReactClippingViewGrou
         updateClippingRect();
       }
 
-      ReactScrollViewHelper.emitScrollEvent(this, x, y);
+      if (mFlinging) {
+        mDoneFlinging = false;
+      }
+
+      ReactScrollViewHelper.emitScrollEvent(this);
     }
   }
 
@@ -81,12 +93,24 @@ public class ReactScrollView extends ScrollView implements ReactClippingViewGrou
   public boolean onInterceptTouchEvent(MotionEvent ev) {
     if (super.onInterceptTouchEvent(ev)) {
       NativeGestureUtil.notifyNativeGestureStarted(this, ev);
+      ReactScrollViewHelper.emitScrollBeginDragEvent(this);
+      mDragging = true;
       return true;
     }
 
     return false;
   }
 
+  @Override
+  public boolean onTouchEvent(MotionEvent ev) {
+    int action = ev.getAction() & MotionEvent.ACTION_MASK;
+    if (action == MotionEvent.ACTION_UP && mDragging) {
+      ReactScrollViewHelper.emitScrollEndDragEvent(this);
+      mDragging = false;
+    }
+    return super.onTouchEvent(ev);
+  }
+
   @Override
   public void setRemoveClippedSubviews(boolean removeClippedSubviews) {
     if (removeClippedSubviews && mClippingRect == null) {
@@ -120,4 +144,26 @@ public class ReactScrollView extends ScrollView implements ReactClippingViewGrou
   public void getClippingRect(Rect outClippingRect) {
     outClippingRect.set(Assertions.assertNotNull(mClippingRect));
   }
+
+  @Override
+  public void fling(int velocityY) {
+    super.fling(velocityY);
+    if (mSendMomentumEvents) {
+      mFlinging = true;
+      ReactScrollViewHelper.emitScrollMomentumBeginEvent(this);
+      Runnable r = new Runnable() {
+        @Override
+        public void run() {
+          if (mDoneFlinging) {
+            mFlinging = false;
+            ReactScrollViewHelper.emitScrollMomentumEndEvent(ReactScrollView.this);
+          } else {
+            mDoneFlinging = true;
+            ReactScrollView.this.postOnAnimationDelayed(this, ReactScrollViewHelper.MOMENTUM_DELAY);
+          }
+        }
+      };
+      postOnAnimationDelayed(r, ReactScrollViewHelper.MOMENTUM_DELAY);
+    }
+  }
 }

ReactAndroid/src/main/java/com/facebook/react/views/scroll/ReactScrollViewHelper.java

@@ -21,18 +21,41 @@ import com.facebook.react.uimanager.UIManagerModule;
  */
 public class ReactScrollViewHelper {
 
+  public static final long MOMENTUM_DELAY = 20;
+
   /**
    * Shared by {@link ReactScrollView} and {@link ReactHorizontalScrollView}.
    */
-  public static void emitScrollEvent(ViewGroup scrollView, int scrollX, int scrollY) {
+  public static void emitScrollEvent(ViewGroup scrollView) {
+    emitScrollEvent(scrollView, ScrollEventType.SCROLL);
+  }
+
+  public static void emitScrollBeginDragEvent(ViewGroup scrollView) {
+    emitScrollEvent(scrollView, ScrollEventType.BEGIN_DRAG);
+  }
+
+  public static void emitScrollEndDragEvent(ViewGroup scrollView) {
+    emitScrollEvent(scrollView, ScrollEventType.END_DRAG);
+  }
+
+  public static void emitScrollMomentumBeginEvent(ViewGroup scrollView) {
+    emitScrollEvent(scrollView, ScrollEventType.MOMENTUM_BEGIN);
+  }
+
+  public static void emitScrollMomentumEndEvent(ViewGroup scrollView) {
+    emitScrollEvent(scrollView, ScrollEventType.MOMENTUM_END);
+  }
+
+  private static void emitScrollEvent(ViewGroup scrollView, ScrollEventType scrollEventType) {
     View contentView = scrollView.getChildAt(0);
     ReactContext reactContext = (ReactContext) scrollView.getContext();
     reactContext.getNativeModule(UIManagerModule.class).getEventDispatcher().dispatchEvent(
         ScrollEvent.obtain(
             scrollView.getId(),
             SystemClock.uptimeMillis(),
-            scrollX,
-            scrollY,
+            scrollEventType,
+            scrollView.getScrollX(),
+            scrollView.getScrollY(),
             contentView.getWidth(),
             contentView.getHeight(),
             scrollView.getWidth(),

ReactAndroid/src/main/java/com/facebook/react/views/scroll/ReactScrollViewManager.java

@@ -52,6 +52,19 @@ public class ReactScrollViewManager
     view.setRemoveClippedSubviews(removeClippedSubviews);
   }
 
+  /**
+   * Computing momentum events is potentially expensive since we post a runnable on the UI thread
+   * to see when it is done.  We only do that if {@param sendMomentumEvents} is set to true.  This
+   * is handled automatically in js by checking if there is a listener on the momentum events.
+   *
+   * @param view
+   * @param sendMomentumEvents
+   */
+  @ReactProp(name = "sendMomentumEvents")
+  public void setSendMomentumEvents(ReactScrollView view, boolean sendMomentumEvents) {
+    view.setSendMomentumEvents(sendMomentumEvents);
+  }
+
   @Override
   public @Nullable Map<String, Integer> getCommandsMap() {
     return ReactScrollViewCommandHelper.getCommandsMap();
@@ -86,12 +99,12 @@ public class ReactScrollViewManager
 
   public static Map createExportedCustomDirectEventTypeConstants() {
     return MapBuilder.builder()
-        .put(ScrollEvent.EVENT_NAME, MapBuilder.of("registrationName", "onScroll"))
-        .put("topScrollBeginDrag", MapBuilder.of("registrationName", "onScrollBeginDrag"))
-        .put("topScrollEndDrag", MapBuilder.of("registrationName", "onScrollEndDrag"))
-        .put("topScrollAnimationEnd", MapBuilder.of("registrationName", "onScrollAnimationEnd"))
-        .put("topMomentumScrollBegin", MapBuilder.of("registrationName", "onMomentumScrollBegin"))
-        .put("topMomentumScrollEnd", MapBuilder.of("registrationName", "onMomentumScrollEnd"))
+        .put(ScrollEventType.SCROLL.getJSEventName(), MapBuilder.of("registrationName", "onScroll"))
+        .put(ScrollEventType.BEGIN_DRAG.getJSEventName(), MapBuilder.of("registrationName", "onScrollBeginDrag"))
+        .put(ScrollEventType.END_DRAG.getJSEventName(), MapBuilder.of("registrationName", "onScrollEndDrag"))
+        .put(ScrollEventType.ANIMATION_END.getJSEventName(), MapBuilder.of("registrationName", "onScrollAnimationEnd"))
+        .put(ScrollEventType.MOMENTUM_BEGIN.getJSEventName(), MapBuilder.of("registrationName", "onMomentumScrollBegin"))
+        .put(ScrollEventType.MOMENTUM_END.getJSEventName(), MapBuilder.of("registrationName", "onMomentumScrollEnd"))
         .build();
   }
 }

ReactAndroid/src/main/java/com/facebook/react/views/scroll/ScrollEvent.java

@@ -9,10 +9,13 @@
 
 package com.facebook.react.views.scroll;
 
+import javax.annotation.Nullable;
+
 import java.lang.Override;
 
 import android.support.v4.util.Pools;
 
+import com.facebook.infer.annotation.Assertions;
 import com.facebook.react.bridge.Arguments;
 import com.facebook.react.bridge.WritableMap;
 import com.facebook.react.uimanager.PixelUtil;
@@ -27,18 +30,18 @@ public class ScrollEvent extends Event<ScrollEvent> {
   private static final Pools.SynchronizedPool<ScrollEvent> EVENTS_POOL =
       new Pools.SynchronizedPool<>(3);
 
-  public static final String EVENT_NAME = "topScroll";
-
   private int mScrollX;
   private int mScrollY;
   private int mContentWidth;
   private int mContentHeight;
   private int mScrollViewWidth;
   private int mScrollViewHeight;
+  private @Nullable ScrollEventType mScrollEventType;
 
   public static ScrollEvent obtain(
       int viewTag,
       long timestampMs,
+      ScrollEventType scrollEventType,
       int scrollX,
       int scrollY,
       int contentWidth,
@@ -52,6 +55,7 @@ public class ScrollEvent extends Event<ScrollEvent> {
     event.init(
         viewTag,
         timestampMs,
+        scrollEventType,
         scrollX,
         scrollY,
         contentWidth,
@@ -72,6 +76,7 @@ public class ScrollEvent extends Event<ScrollEvent> {
   private void init(
       int viewTag,
       long timestampMs,
+      ScrollEventType scrollEventType,
       int scrollX,
       int scrollY,
       int contentWidth,
@@ -79,6 +84,7 @@ public class ScrollEvent extends Event<ScrollEvent> {
       int scrollViewWidth,
       int scrollViewHeight) {
     super.init(viewTag, timestampMs);
+    mScrollEventType = scrollEventType;
     mScrollX = scrollX;
     mScrollY = scrollY;
     mContentWidth = contentWidth;
@@ -89,7 +95,7 @@ public class ScrollEvent extends Event<ScrollEvent> {
 
   @Override
   public String getEventName() {
-    return EVENT_NAME;
+    return Assertions.assertNotNull(mScrollEventType).getJSEventName();
   }
 
   @Override
@@ -98,6 +104,15 @@ public class ScrollEvent extends Event<ScrollEvent> {
     return 0;
   }
 
+  @Override
+  public boolean canCoalesce() {
+    // Only SCROLL events can be coalesced, all others can not be
+    if (mScrollEventType == ScrollEventType.SCROLL) {
+      return true;
+    }
+    return false;
+  }
+
   @Override
   public void dispatch(RCTEventEmitter rctEventEmitter) {
     rctEventEmitter.receiveEvent(getViewTag(), getEventName(), serializeEventData());

ReactAndroid/src/main/java/com/facebook/react/views/scroll/ScrollEventType.java

@@ -0,0 +1,32 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+package com.facebook.react.views.scroll;
+
+/**
+ * Scroll event types that JS module RCTEventEmitter can understand
+ */
+public enum ScrollEventType {
+  BEGIN_DRAG("topScrollBeginDrag"),
+  END_DRAG("topScrollEndDrag"),
+  SCROLL("topScroll"),
+  MOMENTUM_BEGIN("topMomentumScrollBegin"),
+  MOMENTUM_END("topMomentumScrollEnd"),
+  ANIMATION_END("topScrollAnimationEnd");
+
+  private final String mJSEventName;
+
+  ScrollEventType(String jsEventName) {
+    mJSEventName = jsEventName;
+  }
+
+  public String getJSEventName() {
+    return mJSEventName;
+  }
+}