How to remove specific activity from the stack

Question

Lets put we 3 activates that may follow the stack A->B->C

How can I close A and keep B->C, but only if B opens C?

C is not always opened, but if it gets opened only then A should be removed, leaving the stack as B->C. Otherwise will remain as A->B.

I don't see the possibility of using finish() in A, as it should be closed from B when opening C.

By the way A is a single instance with its own affinity.

Answer 1

Write an abstract BaseActivity class and implement a LocalBroadcastManager in it and register a BroadcastReceiver. Note that we have also introduced an abstract onFinishReceived method.

public abstract class BaseActivity extends AppCompatActivity {

  private LocalBroadcastManager mLBM;
  private final BroadcastReceiver receiver = new BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent intent) {
      onFinishReceived(intent.getStringExtra("activity"));
    }
  }

  protected void onCreate(@Nullable Bundle savedInstanceState) {
    ...
    mLBM = LocalBroadcastManager.getInstance(this);
    IntentFilter filter = new IntentFilter();
    filter.addAction(...);
    mLBM.registerReceiver(receiver, filter);
  }

  protected void onDestroy() {
    mLBM.unregisterReceiver(receiver);
    mLBM = null;
  }

  abstract void onFinishReceived(String activity);
}

Then, extend all A, B and C Activities from the BaseActivity and override the onFinishReceived() method.

public class A extends BaseActivity {

  void onFinishReceived(String activity) {
    if (activity.equals("A") { // or "B" or "C"
        finish();
      }
    }
  }
}

Now, whenever you want to finish a specific activity use,

LocalBroadcastManager.getInstance(context)
    .sendBroadcast(new Intent()
        .setAction(...)
        .putExtra("activity", "A") // or "B" or "C"
    );

---

LocalBroadcastManager is now deprecated. It's better if you can use something like RxJava. The idea is to use an asynchronous and event-based mechanism rather than going for a simple ugly solution like storing the Activity in a static variable.