[android] Open application after clicking on Notification

Thanks to above posts, here's the main lines - distilled from the longer code answers - that are necessary to connect a notification with click listener set to open some app Activity.

private Notification getNotification(String messageText) {

    Notification.Builder builder = new Notification.Builder(this);
    builder.setContentText(messageText);
    // ...

    Intent appActivityIntent = new Intent(this, SomeAppActivity.class);

    PendingIntent contentAppActivityIntent =
            PendingIntent.getActivity(
                            this,  // calling from Activity
                            0,
                            appActivityIntent,
                            PendingIntent.FLAG_UPDATE_CURRENT);

    builder.setContentIntent(contentAppActivityIntent);

    return builder.build();
}