Add setPageWithoutAnimation

Summary: In some cases it's desirable to set the page in the ViewPager without animating it -- we have this in ScrollView with `scrollWithoutAnimationTo`. This PR adds `setPageWithoutAnimation` on ViewPager.

cc ide kmagiera
Closes https://github.com/facebook/react-native/pull/3621

Reviewed By: svcscm

Differential Revision: D2652056

Pulled By: mkonicek

fb-gh-sync-id: 6f1f38558c41ffdd863c0ebb2f046c75b5c0392c

Examples/UIExplorer/ViewPagerAndroidExample.android.js

@@ -96,23 +96,39 @@ var ViewPagerAndroidExample = React.createClass({
     description: 'Container that allows to flip left and right between child views.'
   },
   getInitialState: function() {
-    return {page: 0, progress: {position: 0, offset: 0}};
+    return {
+      page: 0,
+      animationsAreEnabled: true,
+      progress: {
+        position: 0,
+        offset: 0,
+      },
+    };
   },
+
   onPageSelected: function(e) {
     this.setState({page: e.nativeEvent.position});
   },
+
   onPageScroll: function(e) {
     this.setState({progress: e.nativeEvent});
   },
+
   move: function(delta) {
     var page = this.state.page + delta;
-    this.viewPager && this.viewPager.setPage(page);
-    this.setState({page});
+    this.go(page);
   },
+
   go: function(page) {
-    this.viewPager && this.viewPager.setPage(page);
+    if (this.state.animationsAreEnabled) {
+      this.viewPager.setPage(page);
+    } else {
+      this.viewPager.setPageWithoutAnimation(page);
+    }
+
     this.setState({page});
   },
+
   render: function() {
     var pages = [];
     for (var i = 0; i < PAGES; i++) {
@@ -131,7 +147,7 @@ var ViewPagerAndroidExample = React.createClass({
        </View>
       );
     }
-    var page = this.state.page;
+    var { page, animationsAreEnabled } = this.state;
     return (
       <View style={styles.container}>
         <ViewPagerAndroid
@@ -142,6 +158,19 @@ var ViewPagerAndroidExample = React.createClass({
           ref={viewPager => { this.viewPager = viewPager; }}>
           {pages}
         </ViewPagerAndroid>
+        <View style={styles.buttons}>
+          { animationsAreEnabled ?
+            <Button
+              text="Turn off animations"
+              enabled={true}
+              onPress={() => this.setState({animationsAreEnabled: false})}
+            /> :
+            <Button
+              text="Turn animations back on"
+              enabled={true}
+              onPress={() => this.setState({animationsAreEnabled: true})}
+            /> }
+        </View>
         <View style={styles.buttons}>
           <Button text="Start" enabled={page > 0} onPress={() => this.go(0)}/>
           <Button text="Prev" enabled={page > 0} onPress={() => this.move(-1)}/>