让活动知道片段何时完成操作

Question

I have an activity with two fragments.

Fragment A does a complex operation during onResume(), and Fragment B needs fragment A to be finished the complex operation, or else user interaction with Fragment B will cause a crash.

I want to put a progressbar spinning object in this activity until Fragment A is complete, and then reveal the layout with Fragment A and Fragment B side by side.

But I am unsure how to expose the completion of Fragment A's onResume to the activity.

In Fragment AI do have a fragmentlistener set up

public void onAttach(final Activity activity) {
    super.onAttach(activity);
    try {
        this.mListener = (TopicListener) activity;
    } catch (ClassCastException e) {
        throw new ClassCastException(activity.getClass().getName()
                + " must implement TopicListener");
    }
}

But now what, thanks.

Answer 1

作为Android开发者建议在这里 ，我建议你不要夫妇的片段，并通过你的活动类使用回调。

Answer 2

Use your callback to send you to the activity.

Example of using callbacks with a map fragment

private MapListeners mLocation;

public interface MapListeners{
    public void onMarkerClick(Marker m);
    public void onLocationChanged(Location location);
}

@Override
public void onAttach(Activity activity){
    super.onAttach(activity);
    try{
        mLocation = (MapListeners)activity;
    }catch(ClassCastException e){
        throw new ClassCastException(activity.toString() + " must implement OnMarkerClick and OnLocationChanged");
    }
}

public boolean onMarkerClick(Marker marker) {
//marker is clicked so send a call to the activity like this
    mLocation.onMarkerClick(marker);
    return true;
}

In the activity make sure you implement the interface, in this case it would be MapListeners

then when a marker was clicked the onMarkerClick method you created gets called

public void onMarkerClick(Marker m) {

    //do something
}

Answer 3

do this:

public class MyFragmentOne extends Fragment{ 
 @Override 
 onResume()
 {
   //Do the complex task
     ((MyActivity)getActivity()).fragmentTaskCompleted();
  }
 }


 public class MyActivity extends Activity
 {
  public void fragmentTaskCompleted()
  {
    //Show second fragment
   }
  }