Expose rootViewTag for ReactRootView

Reviewed By: AaaChiuuu

Differential Revision: D3630452

fbshipit-source-id: 9e7e750051b8bd5c60971a82740916e2e5faf6f6

ReactAndroid/src/main/java/com/facebook/react/ReactInstanceManagerImpl.java

@@ -773,6 +773,7 @@ import static com.facebook.react.bridge.ReactMarkerConstants.RUN_JS_BUNDLE_START
 
     UIManagerModule uiManagerModule = catalystInstance.getNativeModule(UIManagerModule.class);
     int rootTag = uiManagerModule.addMeasuredRootView(rootView);
+    rootView.setRootViewTag(rootTag);
     @Nullable Bundle launchOptions = rootView.getLaunchOptions();
     WritableMap initialProps = launchOptions != null
         ? Arguments.fromBundle(launchOptions)

ReactAndroid/src/main/java/com/facebook/react/ReactRootView.java

@@ -58,6 +58,7 @@ public class ReactRootView extends SizeMonitoringFrameLayout implements RootView
   private @Nullable Bundle mLaunchOptions;
   private @Nullable KeyboardListener mKeyboardListener;
   private @Nullable OnGenericMotionListener mOnGenericMotionListener;
+  private int mRootViewTag;
   private boolean mWasMeasured = false;
   private boolean mIsAttachedToInstance = false;
   private final JSTouchDispatcher mJSTouchDispatcher = new JSTouchDispatcher(this);
@@ -281,6 +282,14 @@ public class ReactRootView extends SizeMonitoringFrameLayout implements RootView
         "of your hosting Activity or in the onDestroyView() of your hosting Fragment.");
   }
 
+  public int getRootViewTag() {
+    return mRootViewTag;
+  }
+
+  public void setRootViewTag(int rootViewTag) {
+    mRootViewTag = rootViewTag;
+  }
+
   private class KeyboardListener implements ViewTreeObserver.OnGlobalLayoutListener {
     private final Rect mVisibleViewArea;
     private final int mMinKeyboardHeightDetected;

ReactAndroid/src/main/java/com/facebook/react/XReactInstanceManagerImpl.java

@@ -765,6 +765,7 @@ import static com.facebook.systrace.Systrace.TRACE_TAG_REACT_JAVA_BRIDGE;
 
     UIManagerModule uiManagerModule = catalystInstance.getNativeModule(UIManagerModule.class);
     int rootTag = uiManagerModule.addMeasuredRootView(rootView);
+    rootView.setRootViewTag(rootTag);
     @Nullable Bundle launchOptions = rootView.getLaunchOptions();
     WritableMap initialProps = Arguments.makeNativeMap(launchOptions);
     String jsAppModuleName = rootView.getJSModuleName();