add peeking feature in AndroidViewPage(RN)

Reviewed By: sahrens

Differential Revision: D5340198

fbshipit-source-id: b2986a320a39225882d4289b193e1d22e9e7547e

Libraries/Components/ViewPager/ViewPagerAndroid.android.js

@@ -75,6 +75,7 @@ class ViewPagerAndroid extends React.Component {
     onPageScrollStateChanged?: Function,
     onPageSelected?: Function,
     pageMargin?: number,
+    peekEnabled?: boolean,
     keyboardDismissMode?: 'none' | 'on-drag',
     scrollEnabled?: boolean,
   };
@@ -137,6 +138,12 @@ class ViewPagerAndroid extends React.Component {
     * The default value is true.
     */
     scrollEnabled: PropTypes.bool,
+
+    /**
+     * Whether enable showing peekFraction or not. If this is true, the preview of
+     * last and next page will show in current screen. Defaults to false.
+     */
+     peekEnabled: PropTypes.bool,
   };
 
   componentDidMount() {

ReactAndroid/src/main/java/com/facebook/react/views/viewpager/ReactViewPagerManager.java

@@ -120,4 +120,9 @@ public class ReactViewPagerManager extends ViewGroupManager<ReactViewPager> {
   public void setPageMargin(ReactViewPager pager, float margin) {
     pager.setPageMargin((int) PixelUtil.toPixelFromDIP(margin));
   }
+
+  @ReactProp(name = "peekEnabled", defaultBoolean = false)
+  public void setPeekEnabled(ReactViewPager pager, boolean peekEnabled) {
+    pager.setClipToPadding(!peekEnabled);
+  }
 }