Add support for animated events

Summary:
This adds support for `Animated.event` driven natively. This is WIP and would like feedback on how this is implemented.

At the moment, it works by providing a mapping between a view tag, an event name, an event path and an animated value when a view has a prop with a `AnimatedEvent` object. Then we can hook into `EventDispatcher`, check for events that target our view + event name and update the animated value using the event path.

For now it works with the onScroll event but it should be generic enough to work with anything.
Closes https://github.com/facebook/react-native/pull/9253

Differential Revision: D3759844

Pulled By: foghina

fbshipit-source-id: 86989c705847955bd65e6cf5a7d572ec7ccd3eb4

ReactAndroid/src/main/java/com/facebook/react/animated/NativeAnimatedNodesManager.java

@@ -11,16 +11,24 @@ package com.facebook.react.animated;
 
 import android.util.SparseArray;
 
+import com.facebook.infer.annotation.Assertions;
 import com.facebook.react.bridge.Arguments;
 import com.facebook.react.bridge.Callback;
 import com.facebook.react.bridge.JSApplicationIllegalArgumentException;
+import com.facebook.react.bridge.ReadableArray;
 import com.facebook.react.bridge.ReadableMap;
 import com.facebook.react.bridge.UiThreadUtil;
 import com.facebook.react.bridge.WritableMap;
 import com.facebook.react.uimanager.UIImplementation;
+import com.facebook.react.uimanager.UIManagerModule;
+import com.facebook.react.uimanager.events.Event;
+import com.facebook.react.uimanager.events.EventDispatcherListener;
 
 import java.util.ArrayDeque;
 import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
 import java.util.Queue;
 
 import javax.annotation.Nullable;
@@ -38,16 +46,21 @@ import javax.annotation.Nullable;
  *
  * IMPORTANT: This class should be accessed only from the UI Thread
  */
-/*package*/ class NativeAnimatedNodesManager {
+/*package*/ class NativeAnimatedNodesManager implements EventDispatcherListener {
 
   private final SparseArray<AnimatedNode> mAnimatedNodes = new SparseArray<>();
   private final ArrayList<AnimationDriver> mActiveAnimations = new ArrayList<>();
   private final ArrayList<AnimatedNode> mUpdatedNodes = new ArrayList<>();
+  private final Map<String, EventAnimationDriver> mEventDrivers = new HashMap<>();
+  private final Map<String, Map<String, String>> mCustomEventTypes;
   private final UIImplementation mUIImplementation;
   private int mAnimatedGraphBFSColor = 0;
 
-  public NativeAnimatedNodesManager(UIImplementation uiImplementation) {
-    mUIImplementation = uiImplementation;
+  public NativeAnimatedNodesManager(UIManagerModule uiManager) {
+    mUIImplementation = uiManager.getUIImplementation();
+    uiManager.getEventDispatcher().addListener(this);
+    Object customEventTypes = Assertions.assertNotNull(uiManager.getConstants()).get("customDirectEventTypes");
+    mCustomEventTypes = (Map<String, Map<String, String>>) customEventTypes;
   }
 
   /*package*/ @Nullable AnimatedNode getNodeById(int id) {
@@ -238,6 +251,58 @@ import javax.annotation.Nullable;
     propsAnimatedNode.mConnectedViewTag = -1;
   }
 
+  public void addAnimatedEventToView(int viewTag, String eventName, ReadableMap eventMapping) {
+    int nodeTag = eventMapping.getInt("animatedValueTag");
+    AnimatedNode node = mAnimatedNodes.get(nodeTag);
+    if (node == null) {
+      throw new JSApplicationIllegalArgumentException("Animated node with tag " + nodeTag +
+        " does not exists");
+    }
+    if (!(node instanceof ValueAnimatedNode)) {
+      throw new JSApplicationIllegalArgumentException("Animated node connected to event should be" +
+        "of type " + ValueAnimatedNode.class.getName());
+    }
+
+    ReadableArray path = eventMapping.getArray("nativeEventPath");
+    List<String> pathList = new ArrayList<>(path.size());
+    for (int i = 0; i < path.size(); i++) {
+      pathList.add(path.getString(i));
+    }
+
+    EventAnimationDriver event = new EventAnimationDriver(pathList, (ValueAnimatedNode) node);
+    mEventDrivers.put(viewTag + eventName, event);
+  }
+
+  public void removeAnimatedEventFromView(int viewTag, String eventName) {
+    mEventDrivers.remove(viewTag + eventName);
+  }
+
+  @Override
+  public boolean onEventDispatch(Event event) {
+    // Only support events dispatched from the UI thread.
+    if (!UiThreadUtil.isOnUiThread()) {
+      return false;
+    }
+
+    if (!mEventDrivers.isEmpty()) {
+      // If the event has a different name in native convert it to it's JS name.
+      String eventName = event.getEventName();
+      Map<String, String> customEventType = mCustomEventTypes.get(eventName);
+      if (customEventType != null) {
+        eventName = customEventType.get("registrationName");
+      }
+
+      EventAnimationDriver eventDriver = mEventDrivers.get(event.getViewTag() + eventName);
+      if (eventDriver != null) {
+        event.dispatch(eventDriver);
+        mUpdatedNodes.add(eventDriver.mValueNode);
+        return true;
+      }
+    }
+
+    return false;
+  }
+
   /**
    * Animation loop performs two BFSes over the graph of animated nodes. We use incremented
    * {@code mAnimatedGraphBFSColor} to mark nodes as visited in each of the BFSes which saves