implementing a callback in android with Activities

Question

I am developing an library for Android and have following scenario, I want a response back to MainActivity. How could I do it? I have tried with callbacks but could not as I could not create an object of Activity class by myself. is there any other way to achieve it? in AsyncTaskListener implementation I am doing some network operation. I could not use startActivityForResult as it's not according to my library specification.

public class MainActivity extends AppCompatActivity implements MyReceiver{

    @Override
    protected void onCreate(Bundle savedInstanceState) {
    MyServiceImpl b = new MyServiceImpl();
    String request = "123";
    b.request(this,request);
    }

    @Override
    public void completed(String result) {        
        Log.d("MainActivity","Result - "+result);
    }
}

public class MyServiceImpl{

   public void request(Activity appActivity,String req){
        Intent intent = new Intent(appActivity, ActivityB.class);
        appActivity.startActivity(intent);
   } 
}

public class ActivityB extends AppCompatActivity imnplements AsyncTaskListener{

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // shows UI 
        // network operations
    }

   @Override
   public void taskFinish(String response) {
     //  my result comes here
     //  now  i want this result to propagated to MainActiviy
   }
}

Answer 1

I would do it like this :

Create an interface :

public interface MyReceiver {
  public void onReceive();
}

In you activity :

public class MyActivity implements MyReceiver{

public static MyReceiver myReceiver;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
    setContentView(R.layout.activity_new_booking);        
    super.onCreate(savedInstanceState);
    myReceiver = this;
    }
    
    @Override
    protected void onDestroy() {
        myReceiver = null;
    }


    @Override
    public void onReceive(){
       //Implement your code here or send objects in the parameters
    }

}

To Call it just use this:

if(MyActivity.myReceiver!=null){
  MyActivity.myReceiver.onReceive();
}

No need to create activity instances.

In this case i would also suggest you to use startActivityForResult.

Hope this helps.