android - How do I pass data from a BroadcastReceiver through to an Activity being started?

Question

I've got an Android application which needs to be woken up sporadically throughout the day.

To do this, I'm using the AlarmManager to set up a PendingIntent and have this trigger a BroadcastReceiver. This BroadcastReceiver then starts an Activity to bring the UI to the foreground.

All of the above seems to work, in that the Activity launches itself correctly; but I'd like the BroadcastReceiver to notify the Activity that it was started by the alarm (as opposed to being started by the user). To do this I'm trying, from the onReceive() method of the BroadcastReceiver to set a variable in the extras bundle of the intent, thus:

    Intent i = new Intent(context, MyActivity.class);
    i.putExtra(wakeupKey, true);
    i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
    context.startActivity(i);

In the onResume() method of my Activity, I then look for the existence of this boolean variable:

protected void onResume() {
    super.onResume();

    String wakeupKey = "blah";      
    if (getIntent()!=null && getIntent().getExtras()!=null)
        Log.d("app", "onResume at " + System.currentTimeMillis() + ":" + getIntent().getExtras().getBoolean(wakeupKey));
    else
        Log.d("app", "onResume at " + System.currentTimeMillis() + ": null");
}

The getIntent().getExtras() call in onResume() always returns null - I don't seem to be able to pass any extras through at all in this bundle.

If I use the same method to bind extras to the PendingIntent which triggers the BroadcastReceiver however, the extras come through just fine.

Can anyone tell me what's different about passing a bundle from a BroadcastReceiver to an Activity, as opposed to passing the bundle from an Activity to a BroadcastReceiver? I fear I may be doing something very very obvious wrong here...

Answer 1

Just to make it clear (because I used a lot of time figuring out how to make it work)

In the service class that extends BroadcastReceiver. Put in the following code in onReceive()

Intent intent2open = new Intent(context, YourActivity.class);
intent2open.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
intent2open.addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP);
String name = "KEY";
String value = "String you want to pass";
intent2open.putExtra(name, value);
context.startActivity(intent2open);

The FLAG_ACTIVITY_SINGLE_TOP makes sure the apps doesn't re-open if already open. This means that the "old" intent that opened YourActivity in the first place is re-used and it will NOT contain the extra values. You have to catch them in another method called onNewIntent() in YourActivity.

public class YourActivity extends Activity {
    private String memberFieldString;

    @Override
    public void onCreate(Bundle savedInstanceState) { 
         super.onCreate(savedInstanceState);
         setContentView(R.layout.main);

         // Code doing your thing...
    } // End of onCreate()

    @Override
    protected void onNewIntent(Intent intent) {
    Log.d("YourActivity", "onNewIntent is called!");

    memberFieldString = intent.getStringExtra("KEY");

    super.onNewIntent(intent);
} // End of onNewIntent(Intent intent)

    @Override
    protected void onResume() {
        if (memberFieldString != null) {
            if (opstartsIntent.getStringExtra(KEY) != null) {
               Log.d("YourActivity", "memberFieldString: "+ memberFieldString);
            } else {
               Log.d("YourActivity", "The intent that started YourActivity did not have an extra string value");
            }
        }
    } // End of onResume()

}  // End of YourActivity

Please note the two if statements - the onResume() does not know if it's called after OnCreate()->OnStart() OR onRestart()->onStart()
Please see: http://www.anddev.org/images/android/activity_lifecycle.png

It's just used to test if the app is launched by the user (intent with no extras) OR by the BroadcastReceiver (intent with extras).