Question

I’m trying to use TaskStackBuilder with notifications to create a back stack for the back button to go through. Normal flow of my app:

1. Activity A is launched from the launcher.
2. User selects an item from A, which launches B with extras for what to load.
3. User selects an item from B, this launches C with extras for what to load.

Sometimes, after a background update when the user isn’t using my app, I generate a notification. If they click this notification, it launches Activity C, skipping A and B. I’m trying to follow the design guidelines and create a back stack, so when they press back it will go to Activity B instead of the home screen. My problem is that Activity B requires an extra in its launch intent to tell it what to grab from the database.

My current TaskStackBuilder code:

TaskStackBuilder sBuilder = TaskStackBuilder.create( this );
sBuilder.addParentStack( ActivityC.class );
sBuilder.addNextIntent( launchIntent );

pIntent = sBuilder.getPendingIntent( 0, PendingIntent.FLAG_ONE_SHOT );

Clicking on the notification launches Activity C just fine, but when I press back it explodes with an IllegalArgumentException from my ContentProvider because Activity B doesn’t know what ID to request. Is there any way to get this extra into the back stack or am I stuck?

Answer 1

This line:

sBuilder.addParentStack( ActivityC.class );

adds all parents declared for ActivityC in AndroidManifest.xml in <meta-data>. I don’t know what it is, I haven’t used it. I doubt you need it.

This line adds intent to an array:

sBuilder.addNextIntent(launchIntent);

then the array of intents is used to create PendingIntent, probably with PendingIntent.getActivities, I couldn’t find the implementation, which is then started somewhere with Context.startActivities.

I think you just need to create set of intents, there you can add extras:

Intent activityA = new Intent(context, ActivityA.class);
activityA.putExtra(key, valueA);
Intent activityB = new Intent(context, ActivityB.class);
activityB.putExtra(key, valueB);
Intent activityC = new Intent(context, ActivityC.class);
activityC.putExtra(key, valueC);

and add them to builder:

sBuilder.addNextIntent(activityA);
sBuilder.addNextIntent(activityB);
sBuilder.addNextIntent(activityC);
pIntent = sBuilder.getPendingIntent( 0, PendingIntent.FLAG_ONE_SHOT );

I haven’t tested it, this is only a result of my fast research, I hope someone will correct me if I’m wrong.