IssueTracker

Component used: ViewPager2 + Fragment

Version used: viewpager2:1.1.0-beta01 fragment:1.2.5

Devices/Android versions reproduced on: Android Emulator API 16

Description: I have a DialogFragment, it will show as a Dialog on Pad and as a normal Fragment on Phone. After update from ViewPager to ViewPager2, it will crash.

WorkAround: DialogFragment.setShowsDialog(false)

Stack:

E/AndroidRuntime: FATAL EXCEPTION: main
    java.lang.IllegalStateException: DialogFragment can not be attached to a container view
        at androidx.fragment.app.DialogFragment.onActivityCreated(DialogFragment.java:501)
        at androidx.fragment.app.Fragment.performActivityCreated(Fragment.java:2718)
        at androidx.fragment.app.FragmentStateManager.activityCreated(FragmentStateManager.java:346)
        at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1200)
        at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1368)
        at androidx.fragment.app.FragmentManager.moveFragmentToExpectedState(FragmentManager.java:1446)
        at androidx.fragment.app.BackStackRecord.executeOps(BackStackRecord.java:442)
        at androidx.fragment.app.FragmentManager.executeOps(FragmentManager.java:2181)
        at androidx.fragment.app.FragmentManager.executeOpsTogether(FragmentManager.java:2004)
        at androidx.fragment.app.FragmentManager.removeRedundantOperationsAndExecute(FragmentManager.java:1959)
        at androidx.fragment.app.FragmentManager.execSingleAction(FragmentManager.java:1830)
        at androidx.fragment.app.BackStackRecord.commitNow(BackStackRecord.java:297)
        at androidx.viewpager2.adapter.FragmentStateAdapter.placeFragmentInViewHolder(FragmentStateAdapter.java:353)
        at androidx.viewpager2.adapter.FragmentStateAdapter.onViewAttachedToWindow(FragmentStateAdapter.java:284)
        at androidx.viewpager2.adapter.FragmentStateAdapter.onViewAttachedToWindow(FragmentStateAdapter.java:72)
        at androidx.recyclerview.widget.RecyclerView.dispatchChildAttached(RecyclerView.java:7867)
        at androidx.recyclerview.widget.RecyclerView$5.addView(RecyclerView.java:893)
        at androidx.recyclerview.widget.ChildHelper.addView(ChildHelper.java:107)
        at androidx.recyclerview.widget.RecyclerView$LayoutManager.addViewInt(RecyclerView.java:8902)
        at androidx.recyclerview.widget.RecyclerView$LayoutManager.addView(RecyclerView.java:8860)
        at androidx.recyclerview.widget.RecyclerView$LayoutManager.addView(RecyclerView.java:8848)
        at androidx.recyclerview.widget.LinearLayoutManager.layoutChunk(LinearLayoutManager.java:1645)
        at androidx.recyclerview.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1591)
        at androidx.recyclerview.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:668)
...

Sample Code:

// FragmentStateAdapter
class TestFragmentAdapter extends FragmentStateAdapter {
    ...
    @NonNull
    @Override
    public Fragment createFragment(int position) {
        switch (position) {
            case 0:
                return new Fragment0();
            case 1:
                // work
                // return new DialogFragment0().forceNotShowDialog();
                // crash!!
                return new DialogFragment0();
            case 2:
                return new Fragment1();
        }

        return new Fragment0();
    }

    @Override
    public int getItemCount() {
        return 3;
    }
}

// DialogFragment0
class DialogFragment0 extends DialogFragment{
    public static final String SHOW_DIALOG = "SHOW_DIALOG";

    public DialogFragment forceNotShowDialog() {
        Bundle bundle = getArguments();
        if (bundle == null) {
            bundle = new Bundle();
        }
        bundle.putBoolean(SHOW_DIALOG, false);
        setArguments(bundle);
        return this;
    }

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if (getArguments() != null) {
            Bundle bundle = getArguments();
            if (bundle.containsKey(SHOW_DIALOG)) {
                boolean showDialog = bundle.getBoolean(SHOW_DIALOG, false);
                Log.i(TAG, "use bundle showDialog " + showDialog);
                setShowsDialog(showDialog);
            }
        }
    }
}

If call DialogFragment.setShowsDialog(false), will not crash

look like in FragmentStateAdapter.placeFragmentInViewHolder(FragmentStateAdapter.java:351), it call add(fragment, "f" + holder.getItemId()), not provide a container View ID.