Current Fragment null after switching mode from FragmentStatePagerAdapter /Get Current Fragment

Question

I have an issue when I came back after switching mode either dark/light mode, then the current fragment is null. I want to get back my current fragment (not new fragment) after switching mode/after recreating activity. I am using FragmentStatePagerAdapter. I already tried with InstantiateItem method like this. But I found that the method creates a new fragment. And using SetRetainInstance but, I think SetRetainInstance is not the best way. I already searching the information but, still don't get it. I am using GetItem to declare the fragment inside the adapter. Currently I have 3 tabs/ 3 fragments.

public override Fragment GetItem(int position)
    {
        switch (position)
        {
            case 1:
                if (fragment1 == null)
                {
                    fragment1 = new FragmentOne(_parentActivity);
                }
                else
                {
                    fragment1.RefreshPage();
                }
                return fragment1;

            case 2:
                if (fragment2 == null)
                {
                    fragment2 = new FragmentTwo(_parentActivity);
                }
                return fragment2;

            case 3:
                if (fragment3 == null)
                {
                    fragment3 = new FragmentThree(_parentActivity);
                }
                else
                {
                    fragment3.fragment3Adapter.UpdateData();
                }
                return fragment3;

            default:
                throw new Exception("Unrecognized fragments!!!");
        }
    }

Then, in the Activity, I am using OnPageSelected(position) to get/know the selected tab/ clicked tab.

 public void OnPageSelected(int position)
    {
        if (position == 1)
        {
            fragmentAdapter.RefreshPage();
        }
        else if (position == 3)
        {
            fragmentAdapter.fragment3.UpdateData();
        }
    }

Nah, in the OnPageSelected, my Fragment3 is null but the adapter is not null(fragmentAdapter.fragment3.UpdateData();). And FYI, I dont use FragmentTransaction to switch/get my fragments. So, is there a way to get current fragment without create a new fragment? Please help me! Thank you!

score 0 · Answer 1 · answered Jan 25 '21 at 06:28

I think this is cause of using FragmentStatePagerAdapter.

It's inherited from the PagerAdapter,This PagerAdapter implementation will keep only the current page, and when the page is out of sight, it will be removed, freeing up its resources.

If the you only requires a small number of fixed fragments, FragmentPagerAdapter is a safe and appropriate choice.

So you could try to change using FragmentPagerAdapter.

Current Fragment null after switching mode from FragmentStatePagerAdapter /Get Current Fragment

1 Answers1