ViewPager Fragments getting destroyed while app is in background?

Question

I can't for the life of me figure out why sometimes my Fragments become uncontrollable after my app has been launched, paused, and then resumed.

I hold references to my Fragments like this:

public class MainActivity ... {

    public static AccountFragment accountFragment;
    ....

    @Override
    protected void onCreate( ... {

        accountFragment = new AccountFragment(this);
        ...
    }

I have a custom toolbar with a Spinner which theoretically should allow the user to cause an AsyncTask in the AccountFragment to run. This is implemented like so:

if (accountFragment.getView() != null) {

    accountFragment.load()
}

I then create a ViewPager, a FragmentPagerAdapter, etc.

This works completely fine most of the time. The user can select a new item in the Spinner and the AccountFragment will update accordingly. However, sometimes after the app has been stopped and then later resumed, the AccountFragment will not respond at all to anything. Even other views in the app which should affect the AccountFragment are useless. It makes no sense to me because the AccountFragment's view cannot be null, and the AsyncTask which is executed by accountFragment.load() makes some very simple changes to the UI in its onPreExecute which should be very apparent (e.g. Everything disappears and a ProgressBar appears) which is simply not happening.

Any ideas?

Answer 1

There's not enough code to know exactly what's going wrong here, but there are also a bunch of stuff you're doing wrong.

1) Don't store fragment reference in a public static field. Make it just private, or protected at most. Read basic Java manuals for explanation.

2) Don't overload Fragment's constructor, it's discouraged by design. If you need to pass some values to it, do it by using arguments.

3) I guess you're not performing a check during onCreate() method in your Activity if it's being recreated or freshly created. You could end up with two instances of AccountFragment where one of them is in some weird detached state.

...

You should probably spend more time researching basics about Fragment/Activity relationship and how to avoid situations like this.