问题
I am trying to create my first Android app. I would like a main-thread Activity (in my case: an ActionBarActivity) to receive notification of an event from a background Activity (in my case: an IntentService). I've read that using broadcasts should be the best way to do this.
To register a Broadcast Receiver for listening to broadcasts sent from the background activity, I am using the following code inside the main-thread activity:
// Register broadcast receiver
LocalBroadcastManager bManager = LocalBroadcastManager.getInstance(this);
IntentFilter intentFilter = new IntentFilter();
intentFilter.addAction("com.me.myBroadcast");
bManager.registerReceiver(bReceiver, intentFilter);
I tried putting this in the onCreate() method of my main-thread activity, but I quickly discovered that every time I restart the activity (e.g. closing the app and re-opening it), it seems to create "duplicate" broadcast receivers, which then trigger the Broadcast Receiver's onReceive() method multiple times whenever a single broadcast is sent. This is causing problems.
So I created a SharedPreferences file to save a boolean which remembers whether or not I have already created a Broadcast Receiver, so as to avoid creating duplicates. This works exactly as hoped, until I restart the device of course, after which the Broadcast Receiver is destroyed, and the app doesn't create a new one because the SharedPreferences boolean says it already has one.
I'm guessing I could patch this issue by setting up a new broadcast receiver to listen for a device reboot, which resets the SharedPreferences boolean, but I have this nagging feeling that I am overcomplicating things massively. What am I missing? Thanks for any help offered!!
回答1:
To answer your question, you can ignore sharedprefs and register the broadcast receiver in onResume and unregister the receiver in onPause. This method is well described in Reporting Work Status(1) android doc. Note that, this way, you will get status updates only if Activity is in foreground. Use appropriate life cycle methods depending on your needs.
To report status back to foreground activity from service, my preference would have been ResultReceiver(2) class which feels natural compared to a broadcast. Also, if you need to report multiple status messages back, it will be clearer with statusCode param in onReceiveResult method of ResultReceiver class.
来源：https://stackoverflow.com/questions/30414410/avoid-registering-duplicate-broadcast-receivers-in-android