Listen to device orientation changes

Summary:
Similar to iOS, send device orientation changes events. This does not have the
`getCurrentOrientation` method, because it's not used. If necessary, we'll
add it separately.
This also adds a simple example for testing.

We listen to orientation changes in `onGlobalLayout`, and check if the rotation of the device has changed. If it has, we emit the event.
But:
- `onGlobalLayout` (and `onConfigurationChanged` - which is the method usually used for checking for device orientation changes) is *not* called when the device goes from landscape
  to reverse landscape (same with portrait), as that is not a relayout / configuration change. We could detect if this happens with the help of an `OrientationEventListener`. However, this listener notifies you if the degree
  of the phone changes by a single degree, which means that you need to know by how many degrees the phone needs to change in order for the orientation to change. I haven't looked into how accurate this could be, but I suspect that in practice it would cause a lot of bugs. A simple `abgs` and google search reveals that everybody uses a different margin for detecting a rotation change (from 30 to 45 degrees), so I suspect that this won't work
  as expected in practice. Therefore, we're not using this here, and we're sticking to what android provides via `onConfigurationChanged`. If we find that we have issues because users need to know when the user goes
  from landscape to reverse landscape, then we'll have to revisit this.

Reviewed By: foghina

Differential Revision: D3797521

fbshipit-source-id: 62508efd342a9a4b41b42b6138c73553cfdefebc

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

@@ -11,14 +11,17 @@ package com.facebook.react;
 
 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.view.MotionEvent;
+import android.view.Surface;
 import android.view.View;
 import android.view.ViewGroup;
 import android.view.ViewTreeObserver;
+import android.view.WindowManager;
 
 import com.facebook.common.logging.FLog;
 import com.facebook.infer.annotation.Assertions;
@@ -30,10 +33,10 @@ import com.facebook.react.common.ReactConstants;
 import com.facebook.react.common.annotations.VisibleForTesting;
 import com.facebook.react.modules.core.DeviceEventManagerModule;
 import com.facebook.react.uimanager.DisplayMetricsHolder;
+import com.facebook.react.uimanager.JSTouchDispatcher;
 import com.facebook.react.uimanager.PixelUtil;
 import com.facebook.react.uimanager.RootView;
 import com.facebook.react.uimanager.SizeMonitoringFrameLayout;
-import com.facebook.react.uimanager.JSTouchDispatcher;
 import com.facebook.react.uimanager.UIManagerModule;
 import com.facebook.react.uimanager.events.EventDispatcher;
 
@@ -56,7 +59,7 @@ public class ReactRootView extends SizeMonitoringFrameLayout implements RootView
   private @Nullable ReactInstanceManager mReactInstanceManager;
   private @Nullable String mJSModuleName;
   private @Nullable Bundle mLaunchOptions;
-  private @Nullable KeyboardListener mKeyboardListener;
+  private @Nullable CustomGlobalLayoutListener mCustomGlobalLayoutListener;
   private @Nullable OnGenericMotionListener mOnGenericMotionListener;
   private int mRootViewTag;
   private boolean mWasMeasured = false;
@@ -171,7 +174,7 @@ public class ReactRootView extends SizeMonitoringFrameLayout implements RootView
   protected void onAttachedToWindow() {
     super.onAttachedToWindow();
     if (mIsAttachedToInstance) {
-      getViewTreeObserver().addOnGlobalLayoutListener(getKeyboardListener());
+      getViewTreeObserver().addOnGlobalLayoutListener(getCustomGlobalLayoutListener());
     }
   }
 
@@ -179,7 +182,7 @@ public class ReactRootView extends SizeMonitoringFrameLayout implements RootView
   protected void onDetachedFromWindow() {
     super.onDetachedFromWindow();
     if (mIsAttachedToInstance) {
-      getViewTreeObserver().removeOnGlobalLayoutListener(getKeyboardListener());
+      getViewTreeObserver().removeOnGlobalLayoutListener(getCustomGlobalLayoutListener());
     }
   }
 
@@ -255,11 +258,11 @@ public class ReactRootView extends SizeMonitoringFrameLayout implements RootView
     mWasMeasured = true;
   }
 
-  private KeyboardListener getKeyboardListener() {
-    if (mKeyboardListener == null) {
-      mKeyboardListener = new KeyboardListener();
+  private CustomGlobalLayoutListener getCustomGlobalLayoutListener() {
+    if (mCustomGlobalLayoutListener == null) {
+      mCustomGlobalLayoutListener = new CustomGlobalLayoutListener();
     }
-    return mKeyboardListener;
+    return mCustomGlobalLayoutListener;
   }
 
   private void attachToReactInstanceManager() {
@@ -269,7 +272,7 @@ public class ReactRootView extends SizeMonitoringFrameLayout implements RootView
 
     mIsAttachedToInstance = true;
     Assertions.assertNotNull(mReactInstanceManager).attachMeasuredRootView(this);
-    getViewTreeObserver().addOnGlobalLayoutListener(getKeyboardListener());
+    getViewTreeObserver().addOnGlobalLayoutListener(getCustomGlobalLayoutListener());
   }
 
   @Override
@@ -291,13 +294,14 @@ public class ReactRootView extends SizeMonitoringFrameLayout implements RootView
     mRootViewTag = rootViewTag;
   }
 
-  private class KeyboardListener implements ViewTreeObserver.OnGlobalLayoutListener {
+  private class CustomGlobalLayoutListener implements ViewTreeObserver.OnGlobalLayoutListener {
     private final Rect mVisibleViewArea;
     private final int mMinKeyboardHeightDetected;
 
     private int mKeyboardHeight = 0;
+    private int mDeviceRotation = 0;
 
-    /* package */ KeyboardListener() {
+    /* package */ CustomGlobalLayoutListener() {
       mVisibleViewArea = new Rect();
       mMinKeyboardHeightDetected = (int) PixelUtil.toPixelFromDIP(60);
     }
@@ -305,16 +309,17 @@ public class ReactRootView extends SizeMonitoringFrameLayout implements RootView
     @Override
     public void onGlobalLayout() {
       if (mReactInstanceManager == null || !mIsAttachedToInstance ||
-          mReactInstanceManager.getCurrentReactContext() == null) {
-        FLog.w(
-            ReactConstants.TAG,
-            "Unable to dispatch keyboard events in JS as the react instance has not been attached");
+        mReactInstanceManager.getCurrentReactContext() == null) {
         return;
       }
+      checkForKeyboardEvents();
+      checkForDeviceOrientationChanges();
+    }
 
+    private void checkForKeyboardEvents() {
       getRootView().getWindowVisibleDisplayFrame(mVisibleViewArea);
       final int heightDiff =
-          DisplayMetricsHolder.getWindowDisplayMetrics().heightPixels - mVisibleViewArea.bottom;
+        DisplayMetricsHolder.getWindowDisplayMetrics().heightPixels - mVisibleViewArea.bottom;
       if (mKeyboardHeight != heightDiff && heightDiff > mMinKeyboardHeightDetected) {
         // keyboard is now showing, or the keyboard height has changed
         mKeyboardHeight = heightDiff;
@@ -333,6 +338,52 @@ public class ReactRootView extends SizeMonitoringFrameLayout implements RootView
       }
     }
 
+    private void checkForDeviceOrientationChanges() {
+      final int rotation =
+        ((WindowManager) getContext().getSystemService(Context.WINDOW_SERVICE))
+          .getDefaultDisplay().getRotation();
+      if (mDeviceRotation == rotation) {
+        return;
+      }
+      mDeviceRotation = rotation;
+      emitOrientationChanged(rotation);
+    }
+
+    private void emitOrientationChanged(final int newRotation) {
+      String name;
+      double rotationDegrees;
+      boolean isLandscape = false;
+
+      switch (newRotation) {
+        case Surface.ROTATION_0:
+          name = "portrait-primary";
+          rotationDegrees = 0.0;
+          break;
+        case Surface.ROTATION_90:
+          name = "landscape-primary";
+          rotationDegrees = -90.0;
+          isLandscape = true;
+          break;
+        case Surface.ROTATION_180:
+          name = "portrait-secondary";
+          rotationDegrees = 180.0;
+          break;
+        case Surface.ROTATION_270:
+          name = "landscape-secondary";
+          rotationDegrees = 90.0;
+          isLandscape = true;
+          break;
+        default:
+          return;
+      }
+      WritableMap map = Arguments.createMap();
+      map.putString("name", name);
+      map.putDouble("rotationDegrees", rotationDegrees);
+      map.putBoolean("isLandscape", isLandscape);
+
+      sendEvent("namedOrientationDidChange", map);
+    }
+
     private void sendEvent(String eventName, @Nullable WritableMap params) {
       if (mReactInstanceManager != null) {
         mReactInstanceManager.getCurrentReactContext()