Implement native Animated value listeners on Android

Summary:
Adds support for `Animated.Value#addListener` for native driven nodes on Android. This is based on work by skevy in the exponent RN fork. Also adds a UIExplorer example.

** Test plan **
Run unit tests

Tested that by adding a listener to a native driven animated node and checked that the listener callback is called properly.

Also tested that it doesn't crash on iOS that doesn't support this yet.
Closes #8844

Differential Revision: D3670906

fbshipit-source-id: 15700ed7b93db140d907ce80af4dae6be3102135

Author: janicduplessis

Examples/UIExplorer/js/NativeAnimationsExample.js

@@ -22,16 +22,15 @@
  */
 'use strict';
 
-var React = require('react');
-var ReactNative = require('react-native');
-var {
+const React = require('react');
+const ReactNative = require('react-native');
+const {
   View,
   Text,
   Animated,
   StyleSheet,
   TouchableWithoutFeedback,
 } = ReactNative;
-var UIExplorerButton = require('./UIExplorerButton');
 
 class Tester extends React.Component {
   state = {
@@ -47,12 +46,8 @@ class Tester extends React.Component {
       ...this.props.config,
       toValue: this.current,
     };
-    try {
-      Animated[this.props.type](this.state.native, { ...config, useNativeDriver: true }).start();
-    } catch (e) {
-      // uncomment this if you want to get the redbox errors!
-      throw e;
-    }
+
+    Animated[this.props.type](this.state.native, { ...config, useNativeDriver: true }).start();
     Animated[this.props.type](this.state.js, { ...config, useNativeDriver: false }).start();
   };
 
@@ -78,6 +73,52 @@ class Tester extends React.Component {
   }
 }
 
+class ValueListenerExample extends React.Component {
+  state = {
+    anim: new Animated.Value(0),
+    progress: 0,
+  };
+  _current = 0;
+
+  componentDidMount() {
+    this.state.anim.addListener((e) => this.setState({ progress: e.value }));
+  }
+
+  componentWillUnmount() {
+    this.state.anim.removeAllListeners();
+  }
+
+  _onPress = () => {
+    this._current = this._current ? 0 : 1;
+    const config = {
+      duration: 1000,
+      toValue: this._current,
+    };
+
+    Animated.timing(this.state.anim, { ...config, useNativeDriver: true }).start();
+  };
+
+  render() {
+    return (
+      <TouchableWithoutFeedback onPress={this._onPress}>
+        <View>
+          <View style={styles.row}>
+            <Animated.View
+              style={[
+                styles.block,
+                {
+                  opacity: this.state.anim,
+                }
+              ]}
+            />
+          </View>
+          <Text>Value: {this.state.progress}</Text>
+        </View>
+      </TouchableWithoutFeedback>
+    );
+  }
+}
+
 const styles = StyleSheet.create({
   row: {
     padding: 10,
@@ -304,4 +345,13 @@ exports.examples = [
       );
     },
   },
+  {
+    title: 'Animated value listener',
+    platform: 'android',
+    render: function() {
+      return (
+        <ValueListenerExample />
+      );
+    },
+  },
 ];

Libraries/Animated/src/AnimatedImplementation.js

@@ -11,6 +11,7 @@
  */
 'use strict';
 
+var DeviceEventEmitter = require('RCTDeviceEventEmitter');
 var InteractionManager = require('InteractionManager');
 var Interpolation = require('Interpolation');
 var React = require('React');
@@ -634,6 +635,7 @@ class AnimatedValue extends AnimatedWithChildren {
   _animation: ?Animation;
   _tracking: ?Animated;
   _listeners: {[key: string]: ValueListenerCallback};
+  __nativeAnimatedValueListener: ?any;
 
   constructor(value: number) {
     super();
@@ -652,6 +654,14 @@ class AnimatedValue extends AnimatedWithChildren {
     return this._value + this._offset;
   }
 
+  __makeNative() {
+    super.__makeNative();
+
+    if (Object.keys(this._listeners).length) {
+      this._startListeningToNativeValueUpdates();
+    }
+  }
+
   /**
    * Directly set the value.  This will stop any animations running on the value
    * and update all the bound properties.
@@ -693,15 +703,49 @@ class AnimatedValue extends AnimatedWithChildren {
   addListener(callback: ValueListenerCallback): string {
     var id = String(_uniqueId++);
     this._listeners[id] = callback;
+    if (this.__isNative) {
+      this._startListeningToNativeValueUpdates();
+    }
     return id;
   }
 
   removeListener(id: string): void {
     delete this._listeners[id];
+    if (this.__isNative && Object.keys(this._listeners).length === 0) {
+      this._stopListeningForNativeValueUpdates();
+    }
   }
 
   removeAllListeners(): void {
     this._listeners = {};
+    if (this.__isNative) {
+      this._stopListeningForNativeValueUpdates();
+    }
+  }
+
+  _startListeningToNativeValueUpdates() {
+    if (this.__nativeAnimatedValueListener ||
+        !NativeAnimatedHelper.supportsNativeListener()) {
+      return;
+    }
+
+    NativeAnimatedAPI.startListeningToAnimatedNodeValue(this.__getNativeTag());
+    this.__nativeAnimatedValueListener = DeviceEventEmitter.addListener('onAnimatedValueUpdate', (data) => {
+      if (data.tag !== this.__getNativeTag()) {
+        return;
+      }
+      this._updateValue(data.value, false /* flush */);
+    });
+  }
+
+  _stopListeningForNativeValueUpdates() {
+    if (!this.__nativeAnimatedValueListener ||
+        !NativeAnimatedHelper.supportsNativeListener()) {
+      return;
+    }
+
+    this.__nativeAnimatedValueListener.remove();
+    NativeAnimatedAPI.stopListeningToAnimatedNodeValue(this.__getNativeTag());
   }
 
   /**
@@ -1204,7 +1248,7 @@ class AnimatedStyle extends AnimatedWithChildren {
       if (value instanceof Animated) {
         if (!value.__isNative) {
           // We cannot use value of natively driven nodes this way as the value we have access from JS
-          // may not be up to date
+          // may not be up to date.
           style[key] = value.__getValue();
         }
       } else {
@@ -1296,9 +1340,9 @@ class AnimatedProps extends Animated {
     for (var key in this._props) {
       var value = this._props[key];
       if (value instanceof Animated) {
-        if (!value.__isNative) {
+        if (!value.__isNative || value instanceof AnimatedStyle) {
           // We cannot use value of natively driven nodes this way as the value we have access from JS
-          // may not be up to date
+          // may not be up to date.
           props[key] = value.__getValue();
         }
       } else {

Libraries/Animated/src/NativeAnimatedHelper.js

@@ -30,6 +30,14 @@ var API = {
     assertNativeAnimatedModule();
     NativeAnimatedModule.createAnimatedNode(tag, config);
   },
+  startListeningToAnimatedNodeValue: function(tag: number) {
+    assertNativeAnimatedModule();
+    NativeAnimatedModule.startListeningToAnimatedNodeValue(tag);
+  },
+  stopListeningToAnimatedNodeValue: function(tag: number) {
+    assertNativeAnimatedModule();
+    NativeAnimatedModule.stopListeningToAnimatedNodeValue(tag);
+  },
   connectAnimatedNodes: function(parentTag: number, childTag: number): void {
     assertNativeAnimatedModule();
     NativeAnimatedModule.connectAnimatedNodes(parentTag, childTag);
@@ -144,6 +152,11 @@ function assertNativeAnimatedModule(): void {
   invariant(NativeAnimatedModule, 'Native animated module is not available');
 }
 
+// TODO: remove this when iOS supports native listeners.
+function supportsNativeListener(): bool {
+  return !!NativeAnimatedModule.startListeningToAnimatedNodeValue;
+}
+
 module.exports = {
   API,
   validateProps,
@@ -153,4 +166,5 @@ module.exports = {
   generateNewNodeTag,
   generateNewAnimationId,
   assertNativeAnimatedModule,
+  supportsNativeListener,
 };

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

@@ -0,0 +1,17 @@
+/**
+ * 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.animated;
+
+/**
+ * Interface used to listen to {@link ValueAnimatedNode} updates.
+ */
+public interface AnimatedNodeValueListener {
+  void onValueUpdate(double value);
+}

ReactAndroid/src/main/java/com/facebook/react/animated/BUCK

@@ -7,8 +7,8 @@ android_library(
   ]),
   deps = [
     react_native_target('java/com/facebook/react/bridge:bridge'),
+    react_native_target('java/com/facebook/react/modules/core:core'),
     react_native_target('java/com/facebook/react/uimanager:uimanager'),
-
     react_native_target('java/com/facebook/react/uimanager/annotations:annotations'),
     react_native_dep('third-party/java/infer-annotations:infer-annotations'),
     react_native_dep('third-party/java/jsr-305:jsr-305'),

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

@@ -12,13 +12,16 @@
 import javax.annotation.Nullable;
 
 import com.facebook.infer.annotation.Assertions;
+import com.facebook.react.bridge.Arguments;
 import com.facebook.react.bridge.Callback;
 import com.facebook.react.bridge.LifecycleEventListener;
 import com.facebook.react.bridge.OnBatchCompleteListener;
 import com.facebook.react.bridge.ReactApplicationContext;
 import com.facebook.react.bridge.ReactContextBaseJavaModule;
 import com.facebook.react.bridge.ReactMethod;
 import com.facebook.react.bridge.ReadableMap;
+import com.facebook.react.bridge.WritableMap;
+import com.facebook.react.modules.core.DeviceEventManagerModule;
 import com.facebook.react.uimanager.GuardedChoreographerFrameCallback;
 import com.facebook.react.uimanager.ReactChoreographer;
 import com.facebook.react.uimanager.UIImplementation;
@@ -190,6 +193,36 @@ public void execute(NativeAnimatedNodesManager animatedNodesManager) {
     });
   }
 
+  @ReactMethod
+  public void startListeningToAnimatedNodeValue(final int tag) {
+    final AnimatedNodeValueListener listener = new AnimatedNodeValueListener() {
+      public void onValueUpdate(double value) {
+        WritableMap onAnimatedValueData = Arguments.createMap();
+        onAnimatedValueData.putInt("tag", tag);
+        onAnimatedValueData.putDouble("value", value);
+        getReactApplicationContext().getJSModule(DeviceEventManagerModule.RCTDeviceEventEmitter.class)
+            .emit("onAnimatedValueUpdate", onAnimatedValueData);
+      }
+    };
+
+    mOperations.add(new UIThreadOperation() {
+      @Override
+      public void execute(NativeAnimatedNodesManager animatedNodesManager) {
+        animatedNodesManager.startListeningToAnimatedNodeValue(tag, listener);
+      }
+    });
+  }
+
+  @ReactMethod
+  public void stopListeningToAnimatedNodeValue(final int tag) {
+    mOperations.add(new UIThreadOperation() {
+      @Override
+      public void execute(NativeAnimatedNodesManager animatedNodesManager) {
+        animatedNodesManager.stopListeningToAnimatedNodeValue(tag);
+      }
+    });
+  }
+
   @ReactMethod
   public void dropAnimatedNode(final int tag) {
     mOperations.add(new UIThreadOperation() {

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

@@ -89,6 +89,24 @@ public void dropAnimatedNode(int tag) {
     mAnimatedNodes.remove(tag);
   }
 
+  public void startListeningToAnimatedNodeValue(int tag, AnimatedNodeValueListener listener) {
+    AnimatedNode node = mAnimatedNodes.get(tag);
+    if (node == null || !(node instanceof ValueAnimatedNode)) {
+      throw new JSApplicationIllegalArgumentException("Animated node with tag " + tag +
+              " does not exists or is not a 'value' node");
+    }
+    ((ValueAnimatedNode) node).setValueListener(listener);
+  }
+
+  public void stopListeningToAnimatedNodeValue(int tag) {
+    AnimatedNode node = mAnimatedNodes.get(tag);
+    if (node == null || !(node instanceof ValueAnimatedNode)) {
+      throw new JSApplicationIllegalArgumentException("Animated node with tag " + tag +
+              " does not exists or is not a 'value' node");
+    }
+    ((ValueAnimatedNode) node).setValueListener(null);
+  }
+
   public void setAnimatedNodeValue(int tag, double value) {
     AnimatedNode node = mAnimatedNodes.get(tag);
     if (node == null || !(node instanceof ValueAnimatedNode)) {
@@ -324,6 +342,10 @@ public void runUpdates(long frameTimeNanos) {
         // Send property updates to native view manager
         ((PropsAnimatedNode) nextNode).updateView(mUIImplementation);
       }
+      if (nextNode instanceof ValueAnimatedNode) {
+        // Potentially send events to JS when the node's value is updated
+        ((ValueAnimatedNode) nextNode).onValueUpdate();
+      }
       if (nextNode.mChildren != null) {
         for (int i = 0; i < nextNode.mChildren.size(); i++) {
           AnimatedNode child = nextNode.mChildren.get(i);

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

@@ -11,13 +11,15 @@
 
 import com.facebook.react.bridge.ReadableMap;
 
+import javax.annotation.Nullable;
+
 /**
  * Basic type of animated node that maps directly from {@code Animated.Value(x)} of Animated.js
  * library.
  */
 /*package*/ class ValueAnimatedNode extends AnimatedNode {
-
   /*package*/ double mValue = Double.NaN;
+  private @Nullable AnimatedNodeValueListener mValueListener;
 
   public ValueAnimatedNode() {
     // empty constructor that can be used by subclasses
@@ -26,4 +28,15 @@ public ValueAnimatedNode() {
   public ValueAnimatedNode(ReadableMap config) {
     mValue = config.getDouble("value");
   }
+
+  public void onValueUpdate() {
+    if (mValueListener == null) {
+      return;
+    }
+    mValueListener.onValueUpdate(mValue);
+  }
+
+  public void setValueListener(@Nullable AnimatedNodeValueListener listener) {
+    mValueListener = listener;
+  }
 }