Notify current Activity which background function has finished running Android

Question

I have a class that looks for a list of clients in the background with a AsyncTask. She can be called any Activity, and returns nothing, just looks for the list of customers that comes in json and saves that list as string in a SharedPreferences.
Initially, I’m sending to search the list on my login screen, so when I bring the user data from the database, it already sends to search the client list (to reduce the data search wait), but I needed when this class saved the list on SharedPreferences my Activity which opens after the login is notified so I fill a RecyclerView with her. I thought of Implementing a Interface in AsyncTask but she returns to the Activity who called her.
Do you have any method to notify Activity even if the function was not started by it?

Note: If you do not understand the question, comment before negative that I will be happy to clarify your doubts.

Answer 1

Good afternoon,

It has how to do what you want in various ways, for a simpler solution I use a BroadCastReceiver but if you’re going to use it in multiple classes, you might want to create an interface for this.

Here’s an example from Braodcast:

In the Activity

BroadCastReceiver myReceiver;
 protected void onCreate(Bundle savedInstanceState) {

 IntentFilter filter = new IntentFilter();

            filter.addAction("lista.atualizada");

            myReceiver = new BroadcastReceiver() {  //  < ------ Declare o Bradcast como global

                @Override
                public void onReceive(Context context, Intent intent) {
                   // Atualize o que quiser, foi atualizado

                }
            };
            registerReceiver(myReceiver, filter);

}


 @Override
    protected void onDestroy() {
        super.onDestroy();
        unregisterReceiver(myReceiver); // <---- não esqueça de destruir o receiver junto com a activity
    }

So in your task:

Intent atualizouLista = new Intent();

atualizouLista.setAction("lista.atualizada"); // < ---- aqui é o nome da sua "ação" a mesma que você registrou no receiver
mContext.sendBroadcast(atualizouLista); // < --- repare que estou passando mContext, na sua Task você precisa manter uma referência do seu contexto.