Fix dimensions on orientation change

Summary:
This adds the `didUpdateDimensions` event that already exists on iOS, and
updates the internal native dimensions data that needs repopulation after
orientation change.

Reviewed By: foghina

Differential Revision: D3819364

fbshipit-source-id: fc2b3b4d1991d101e5de4439ccef2189bc65fd58

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

@@ -11,11 +11,11 @@
 
 import javax.annotation.Nullable;
 
-import android.app.Activity;
 import android.content.Context;
 import android.graphics.Rect;
 import android.os.Bundle;
 import android.util.AttributeSet;
+import android.util.DisplayMetrics;
 import android.view.MotionEvent;
 import android.view.Surface;
 import android.view.View;
@@ -346,6 +346,10 @@ private void checkForDeviceOrientationChanges() {
         return;
       }
       mDeviceRotation = rotation;
+      // It's important to repopulate DisplayMetrics and export them before emitting the
+      // orientation change event, so that the Dimensions object returns the correct new values.
+      DisplayMetricsHolder.initDisplayMetrics(getContext());
+      emitUpdateDimensionsEvent();
       emitOrientationChanged(rotation);
     }
 
@@ -384,6 +388,30 @@ private void emitOrientationChanged(final int newRotation) {
       sendEvent("namedOrientationDidChange", map);
     }
 
+    private void emitUpdateDimensionsEvent() {
+      DisplayMetrics windowDisplayMetrics = DisplayMetricsHolder.getWindowDisplayMetrics();
+      DisplayMetrics screenDisplayMetrics = DisplayMetricsHolder.getScreenDisplayMetrics();
+
+      WritableMap windowDisplayMetricsMap = Arguments.createMap();
+      windowDisplayMetricsMap.putInt("width", windowDisplayMetrics.widthPixels);
+      windowDisplayMetricsMap.putInt("height", windowDisplayMetrics.heightPixels);
+      windowDisplayMetricsMap.putDouble("scale", windowDisplayMetrics.density);
+      windowDisplayMetricsMap.putDouble("fontScale", windowDisplayMetrics.scaledDensity);
+      windowDisplayMetricsMap.putDouble("densityDpi", windowDisplayMetrics.densityDpi);
+
+      WritableMap screenDisplayMetricsMap = Arguments.createMap();
+      screenDisplayMetricsMap.putInt("width", screenDisplayMetrics.widthPixels);
+      screenDisplayMetricsMap.putInt("height", screenDisplayMetrics.heightPixels);
+      screenDisplayMetricsMap.putDouble("scale", screenDisplayMetrics.density);
+      screenDisplayMetricsMap.putDouble("fontScale", screenDisplayMetrics.scaledDensity);
+      screenDisplayMetricsMap.putDouble("densityDpi", screenDisplayMetrics.densityDpi);
+
+      WritableMap dimensionsMap = Arguments.createMap();
+      dimensionsMap.putMap("windowPhysicalPixels", windowDisplayMetricsMap);
+      dimensionsMap.putMap("screenPhysicalPixels", screenDisplayMetricsMap);
+      sendEvent("didUpdateDimensions", dimensionsMap);
+    }
+
     private void sendEvent(String eventName, @Nullable WritableMap params) {
       if (mReactInstanceManager != null) {
         mReactInstanceManager.getCurrentReactContext()

ReactAndroid/src/main/java/com/facebook/react/uimanager/DisplayMetricsHolder.java

@@ -9,17 +9,17 @@
 
 package com.facebook.react.uimanager;
 
+import javax.annotation.Nullable;
+
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+
 import android.content.Context;
 import android.os.Build;
 import android.util.DisplayMetrics;
 import android.view.Display;
 import android.view.WindowManager;
 
-import java.lang.reflect.InvocationTargetException;
-import java.lang.reflect.Method;
-
-import javax.annotation.Nullable;
-
 import com.facebook.infer.annotation.Assertions;
 
 /**
@@ -43,11 +43,15 @@ public class DisplayMetricsHolder {
   public static void setWindowDisplayMetrics(DisplayMetrics displayMetrics) {
     sWindowDisplayMetrics = displayMetrics;
   }
-  
+
   public static void initDisplayMetricsIfNotInitialized(Context context) {
     if (DisplayMetricsHolder.getScreenDisplayMetrics() != null) {
       return;
     }
+    initDisplayMetrics(context);
+  }
+
+  public static void initDisplayMetrics(Context context) {
     DisplayMetrics displayMetrics = context.getResources().getDisplayMetrics();
     DisplayMetricsHolder.setWindowDisplayMetrics(displayMetrics);