CODEWITHSUNDEEP
androidandroid-activitycallback
Shailesh
Shailesh

Reputation: 717

implementing a callback in android with Activities

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
   }
}

Upvotes: 2

Views: 3254

Answers (3)

Sarthak Gandhi
Sarthak Gandhi

Reputation: 2170

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.

Upvotes: 5

Tanay Mondal
Tanay Mondal

Reputation: 147

For this purpose I use Singleton approach.

class ActivityCommunication {
private static ActivityCommunication instance = null;
private MainCallback mainCallback = null;

private ActivityCommunication() {
}

public static ActivityCommunication getInstance() {
    if (instance == null) {
        instance = new ActivityCommunication();
    }
    return instance;
}

public void setMainCallBackListener(MainCallback mainCallback) {
    this.mainCallback = mainCallback;
}

public void sendDataToMainActivity(Data data) {
    if (mainCallback != null) {
        mainCallback.onMainCallBack(data);
    }
}

public interface MainCallback {
    void onMainCallBack(Data data);
}
}

On MainActivity set the listener

 ActivityCommunication.getInstance().setMainCallBackListener();

On from ActivityB, send the data when you need

 ActivityCommunication.getInstance().sendDataToMainActivity(myData);

Implemented onMainCallBack method will be then called.

Upvotes: 2

Abdul Waheed
Abdul Waheed

Reputation: 4688

You can do one thing. Create an object of your library when activity starts and pass the reference of your activity to that object instantiation. And implement that interface call back to the activity. And internally in your library, you will have activity reference cast that to your interface callback and call interface method that will give you call back at your activity level.

Upvotes: 0

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