系统何时将开始考虑动态注册的BroadcastReceiver？

Question

My question is about: "when will my postbox be noticed by the postman", not "when will I be able to read any letters"?

I have an Activity which allows the user to edit a list. As soon as the user commits the edit, an IntentService is started which in turn calls a database helper to change the database entries as required.

As soon as the database is updated successfully (nothing crashed until then), the database helper writes "ok" to SharedPreferences and returns to the IntentService . The IntentService sends a message to a BroadcastReceiver which now causes the list to be reloaded from db with the current data.

The BroadcastReceiver is an inner class of the Activity and it is registered dynamically in onCreate() :

    mReceiver = new MyMessageReceiver();
    IntentFilter iFilter = new IntentFilter();
    iFilter.addAction("com.example.mycoolapp.LOCALINTENT");
    LocalBroadcastManager.getInstance(this).registerReceiver(mReceiver, iFilter);

If the user stayed in my Activity until the list could be reloaded, there would be no problem at all. But imagine the user moving around and somehow causing an orientation change... that's why I have the "ok" in SharedPeferences :

In onCreate() , after registering the receiver, I check whether there is an action pending:

If the database was updated successfully, I can load the data and just set a flag for my receiver to ignore the next message. Which will come, as the IntentService was configured with setIntentRedelivery(true) .

If I find that the database is not yet updated, I decide to wait for the broadcast from the IntentService .

The one thing I'm extremely uncertain of is the following:

From which moment on will the system consider my receiver to be "up and running"? I know that onReceive() can only be called after onCreate() is finished.

Is it possible that while onCreate() is being executed, the IntentService fires the local Broadcast ("too soon") and my receiver will never get it?

Then that list would never be refreshed until the user left the Activity (which is quite likely) and returned once more (then not so likely).

Answer 1

The Broadcast Receiver is not registered in the Activity but in the main application thread. The registerReceiver method is defined in the Context class.

That means that your Broadcast receiver will remain registered until you un-register it or your application is destroyed (ie. not having the receiver in a Service )

Check the documentation

From which moment on will the system consider my receiver to be "up and running"? I know that onReceive() can only be called after onCreate() is finished.

From the moment registerReceiver() returns

Is it possible that while onCreate() is being executed, the IntentService fires the local Broadcast ("too soon") and my receiver will never get it?

You can avoid this by registering the receiver in the onCreate method of a class that extends Application . That's how you can make sure that the broadcast receiver is the first thing done.