How to bind Service if it's in another process?

Question

Manifest:

 <service android:name="com.example.MainService" android:process=":main_service"/>

Trying to bind service in Activity:

public class MainActivity extends Activity {
    MainService mMainService;

    private boolean mBound;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        bindService(intentForMainService, mConnection, Context.BIND_AUTO_CREATE)
    }

    private ServiceConnection mConnection = new ServiceConnection() {
        public void onServiceConnected(ComponentName className,
                                       IBinder service) {
            MainService.MainServiceBinder binder = (MainService.MainServiceBinder) service;//HERE IS EXCEPTION
            mMainService = (MainService) binder.getService();
            mBound = true;
        }

        public void onServiceDisconnected(ComponentName className) {
            mMainService = null;
            mBound = false;
        }
    };

    @Override
    protected void onStop() {
        doUnbindService();
        super.onStop();
    }

    void doUnbindService() {
        if (mBound) {
          unbindService(mConnection);
        }
    }
}

Error:

    FATAL EXCEPTION: main
 Process: com.hos.android, PID: 9001
   java.lang.ClassCastException: android.os.BinderProxy cannot be cast to com.example.service.main.MainService$MainServiceBinder
   at com.example.ui.base.BaseServiceActivity$1.onServiceConnected(MainActivity.java:34)
   at android.app.LoadedApk$ServiceDispatcher.doConnected(LoadedApk.java:1335)
   at android.app.LoadedApk$ServiceDispatcher$RunConnection.run(LoadedApk.java:1352)
   at android.os.Handler.handleCallback(Handler.java:739)
   at android.os.Handler.dispatchMessage(Handler.java:95)
   at android.os.Looper.loop(Looper.java:158)
   at android.app.ActivityThread.main(ActivityThread.java:7224)

But when I delete this android:process=":main_service" all works properly

Answer 1

Step #1: Write an AIDL file that describes the interface to be exported by the service that clients can bind to. For the purposes of this answer, I will call this interface Foo, and so the AIDL file would be Foo.aidl. Note that if the client and service are in separate Android Studio modules that both need the same Foo.aidl content.

Step #2: Have your service's binder extend Foo.Stub and override the methods on Foo.Stub, instead of extending IBinder.

Step #3: In your client, in onServiceConnected(), convert the raw binder to a Foo instance via Foo.Stub.asInterface(service), and Foo has the client side of the AIDL-defined API.

This pair of sample projects illustrates this, where in my case the client and the service are in separate apps.