CODEWITHSUNDEEP
javaandroid
Doug
Doug

Reputation: 5318

How to show DialogFragment from within the onLoadFinished method of LoaderCallbacks

I receive an exception when trying to show a DialogFragment from within the onLoadFinished method of a Fragment that implements the LoaderCallbacks interface. Basically I am using the LoaderCallbacks to get some data from a rest service and then on the onLoadFinished I am trying to show a custom DialogFragment that contains a ListVeiw to allow the user to make a selection. Everything works great except when I try to launch the dialog from within the onLoadFinished. How can I accomplish this..and is this the correct approach to the problem.

Here is an example of what I am trying to do:

public class EventFragment extends Fragment implements LoaderCallbacks<someresponse> {

    @Override
    public void onLoadFinished(Loader<someresponse> arg0, someresponse data) {
        //an exception is generated when trying to launch a dialog fragment from 
        //within the onLoadFinished
        FragmentManager manager = getFragmentManager();             
        ListViewDialogFragment dialog = ListViewDialogFragment.newInstance(data);   
        dialog.show(manager, "event_list_dialog");  

    }
}

Thanks!

Upvotes: 2

Views: 2838

Answers (2)

Doug
Doug

Reputation: 5318

So after some research, I have determined that my approach was incorrect. You should never try to launch a new fragment from within the onLoadFinished method of an LoaderCallbacks async task. The framework tries to keep you from doing this because the state of the currently running fragment or activity, that implements the LoaderCallbacks is indeterminate and therefore not guaranteed to be there when the async task finishes.

Additionally trying to separate a processing dialog state and data display state into two separate fragments is a bit counter to the MVC design pattern that the android framework supports. That said, my new approach consisted of dynamically changing the view for the fragment implenting LoaderCallbacks to hide or show a specific linear layout, one for the process indicator and one for the display of the data. This approach left me modifying an existing fragment instead of launching a new one which worked out great.

Here is a link to the discussion that finally gave me clarity.

https://groups.google.com/forum/#!topic/android-developers/dXZZjhRjkMk/discussion

Upvotes: 5

AlexN
AlexN

Reputation: 2554

The approach you define is quite good, except one case - what will happen if your activity had already gone from the screen, when loading operation got finished? How it will show dialog in this case?

So generally, I would appreciate if you'll tell which exactly exception did you get. However, as a general approach, it can be useful to check is the activity holding the fragment is still on top or even was it finished or not. Even better - you should consider cancelling all background operations when activity/fragment is destroying, in this case you'll have no problems with showing dialogs.

Good luck!

Upvotes: 1

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