Can I use a callback method from a BroadcastReceiver?

Question

Learning to use the BroadcastReceiver class in Android, I have written a small program to receive the battery charge state and write it to three TextView fields in an activity.

However, I have made the BroadcastReceiver as a separate class to make it more simple and separate from the activity. Therefore I have to find a method to tell my Activity class that the battery data has been updated, or, which is my solution, to pass in references to the TextView fields from the Activity to the BroadcastReceiver class.

Does anyone know whether it is possible to make a callback method from the BroadcastReceiver to start a function, f.ex. updateTextViews(); in the Activity?

Here is the source code - note there are two java files: http://pastebin.com/qjCTsSuH

Regards, Niels.

Answer 1

What worked a charm for me is simply declaring the interface objects as static. Bear in mind though that statics can cause as many problems as they solve as statics persist therir values accross instances.

public class MainActivity extends AppCompatActivity implements SocketMessageReceiver.ISocketMessageReceiver {

    //Declare the cb interface static in your activity
    private static SocketMessageReceiver.ISocketMessageReceiver iSocketMessageReceiver;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main_activity);

        //Assign this
        iSocketMessageReceiver = this;
        socketMessageReceiver.registerCallback(iSocketMessageReceiver);
    }

    @Override
    public void sendSocketMessage(String socketMessage) {
        lblEchoMessage.setText(socketMessage);
    }

}

And in your Receiver ....

public class SocketMessageReceiver extends BroadcastReceiver {

    interface ISocketMessageReceiver {
        void sendSocketMessage(String socketMessage);
    }

    //Also declare the interface in your BroadcastReceiver as static
    private static ISocketMessageReceiver iSocketMessageReceiver;

    @Override
    public void onReceive(Context context, Intent intent) {

        if(intent.getAction().equals("com.WarwickWestonWright.SocketExample.RECEIVE")) {
            iSocketMessageReceiver.sendSocketMessage(intent.getBundleExtra("DATA").getString("DATA"));
        }

    }

    public void registerCallback(ISocketMessageReceiver iSocketMessageReceiver) {
        this.iSocketMessageReceiver = iSocketMessageReceiver;
    }

}