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 facebook/react-native#8844

Differential Revision: D3670906

fbshipit-source-id: 15700ed7b93db140d907ce80af4dae6be3102135

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 />
+      );
+    },
+  },
 ];