Displaying a Delayed Toast from a BroadcastReceiver

Question

Hi,

I'm trying to display a message to the user some time after an event is received by a BroadcastReceiver.

public class MyReceiver extends BroadcastReceiver {

  private Timer timer = new Timer();

  @Override
  public void onReceive(Context context, Intent intent) {
      // Display message in 10 sec.
      timer.schedule(new MessageTask(context, "Test Message"), 10 * 1000);
  }

  private static class MessageTask extends TimerTask {
    public MessageTask(Context context, String message) {
      this.context = context;
      this.message = message;
    }

    public void run() {
      Toast.makeText(context, message, Toast.LENGTH_SHORT).show();
    }
  }
}

When I run this I get the following exception:

java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()

Is this the right way to do something like this? Should I be using something other then a Timer? And what is the right way to get a Context object in this situation?

Thank you

Answer 1

This won't work. Once your onReceive() method is complete, the phone is free to go back to sleep or do whatever it wants. You have to implement a wakelock.

Answer 2

You might try using my Toaster class. Use it like a Thread:

new Toaster(yourContext, yourMessageResId, Toast.LENGTH_LONG).start();

Answer 3

Guided by the example posted by Kevin Gaudin bellow, I realize that in order to interact with the UI from a different thread, one needs to manage the Android message loop manually.

In pseudo this looks something like this:

import android.content.Context;
import android.os.Looper;

public class MyUIThread extends Thread {

    public MyUIThread(Context context) {
      // Probably going to need a context to do anything useful.  So
      // pass it in.
      this.context = context;
    }

    public void run() {
      Looper.prepare();
      // Do some UI stuff, e.g. Toast.makeText
      Looper.loop();
    }

}