Optionally ignore @UIThread call when @EFragment is detached from Activity?

[vincentjames501]

When using @Background in conjunction with @UIThread annotations on an @EFragment, it's possible that many developers don't want to run the method annotated with the @UIThread annotation if the Fragment is no longer attached to the activity. I think it would be great to add an annotation (something like @IgnoredWhenDetached) with the following rules:

1. Must also have the @UIThread annotation
2. Can only be used in conjunction with @EFragment classes
3. Simply wraps the @UIThreadmethod call in an if block like so

if(isAdded()) {
    //executable code
}

or

if(getActivity() != null) {
    //executable code
}

Here is a simple example and in my application I have dozens of things similar to this

@EFragment
public class LoaderFragment extends Fragment {

    @Background
    void longTask() {
        try {
            updateProgress(0);
            Thread.sleep(1000);
            updateProgress(50);
            Thread.sleep(1000);
            updateProgress(100);
        } catch (InterruptedException e) {
            killActivity()        
        }
    }

    @IgnoredWhenDetached
    @UiThread
    void updateProgress(int progress) {
        getActivity().setProgress(progress);
    }

    @IgnoredWhenDetached
    @UiThread
    void killActivity(int progress) {
        getActivity().finish();
    }

This essentially prevents the two @UIThread methods from getting a NPE if the Fragment were to have been destroyed at any point during the execution of the @Background method. While I realize this is something that can be easily guarded against by a simple null check, it makes the code much cleaner and is a very common use case in conjunction with Fragments. I would be more than happy to submit a pull request pending thoughts/comments about this. This could also be useful in conjunction with @Background on an @EFragment as well, but not a very common use case.

Vince

[WonderCsabo]

Actually #823 proposed the same, but it was rejected.

[vincentjames501]

I read his actually before posting this. This is slightly different in that I'm not proposing making it the default behavior of @UIThread for @EFragment classes.

[WonderCsabo]

Yes, you are right.

[DayS]

Yeah, I prefer this solution as the developer still have the choice to handle theses cases as he want.
This may be in 3.1 :)

[WonderCsabo]

I tought about the API, and bringed up a version which uses a parameter in the @UiThread and not a new annotation. But i changed my mind since this feature is only for Fragments, @UiThread API should not be affected.
I think you can start to implement this if you want. :)

[yDelouis]

I think we could use this annotation even on methods which are not annotated with @UIThread or @Background.

[vincentjames501]

I think you may be right. I'll look at doing another pull request then let the authors decide which, if any, they would like to merge.

[DayS]

@yDelouis > Good idea 👍

[toshe]

This is an extremely good idea!
I'm currently using

if(isAdded()) {
    //executable code
}

in order to avoid the problem when switching really fast through fragments. An annotation like that makes total sense.

[DayS]

Merged. Thanks to @yDelouis and @vincentjames501 for this