How can I globally detect when the screen rotation changes?

Question

In an Android service, I want to detect whenever the screen rotation changes. By rotation, I don't just mean portrait versus landscape; I mean any change to the screen rotation. Examples of such changes are changes to:

• Portrait
• Reverse portrait
• Landscape
• Reverse landscape

Note that this question is not about changes to the device orientation. It's only about the screen orientation/rotation.

What I've Tried

• Listening for Configuration changes via ACTION_CONFIGURATION_CHANGED. This only covers changes between portrait and landscape, so 180° changes don't trigger this.

Why I'm Doing This

I'm developing a custom screen orientation management app.

Use the hidden API

You can do this using a hidden API called IWindowManager.watchRotation(IRotationWatcher). From my testing, it seems to take a callback that is called every time the screen rotation changes. The callback also seems to be given the current screen rotation.

Being a hidden API, you can't just call it directly. How to use hidden APIs is a topic of its own. And, of course, this might not be as reliable from a maintainability perspective as normal APIs.

Also, onRotationChanged isn't called in the same thread you used to call watchRotation. You'll probably want to delegate some work to a different thread such as the UI thread once you're in onRotationChanged.

Compatibility

Tested and working in API 14 - 28.

Example

Here's one way to get it to work:

1. Copy android.view.IRotationWatcher into your app. Make sure to keep it in its original package. This seems to cause the development tools to think your code has access to it while also causing the operating system to still use the real one rather than your own copy.

2. Use reflection to call watchRotation:

   try {
       Class<?> serviceManager = Class.forName("android.os.ServiceManager");
       IBinder serviceBinder = (IBinder)serviceManager.getMethod("getService", String.class).invoke(serviceManager, "window");
       Class<?> stub = Class.forName("android.view.IWindowManager$Stub");
       Object windowManagerService = stub.getMethod("asInterface", IBinder.class).invoke(stub, serviceBinder);
       Method watchRotation;
       if (Build.VERSION.SDK_INT >= 26)
           watchRotation = windowManagerService.getClass().getMethod("watchRotation", IRotationWatcher.class, int.class);
       else
           watchRotation = windowManagerService.getClass().getMethod("watchRotation", IRotationWatcher.class);
   
       //This method seems to have been introduced in Android 4.3, so don't expect to always find it
       Method removeRotationWatcher = null;
       try {
           removeRotationWatcher = windowManagerService.getClass().getMethod("removeRotationWatcher", IRotationWatcher.class);
       }
       catch (NoSuchMethodException ignored) {}
   
       IRotationWatcher.Stub screenRotationChanged = new IRotationWatcher.Stub() {
           @Override
           public void onRotationChanged(int rotation) throws RemoteException {
               //Do what you want here
               //WARNING: This isn't called in the same thread you were in when you called watchRotation
           }
       };
   
       //Start monitoring for changes
       if (Build.VERSION.SDK_INT >= 26)
           watchRotation.invoke(windowManagerService, screenRotationChanged, Display.DEFAULT_DISPLAY);
       else
           watchRotation.invoke(windowManagerService, screenRotationChanged);
   
       //Stop monitoring for changes when you're done
       if (removeRotationWatcher != null) {
           removeRotationWatcher.invoke(windowManagerService, screenRotationChanged);
   } catch (ClassNotFoundException | ClassCastException | InvocationTargetException | NoSuchMethodException | IllegalAccessException e) {
       throw new RuntimeException(e);
   }