视图位于父级的最后位置，但仍被阻止

Question

What I want to do

In a BottomSheetDialogFragment , I want to inflate a view that always stick at the bottom of the screen, no matter what state (collapsed / expanded) the BottomSheetBehavior is in.

What I have done

In a subclass of BottomSheetDialogFragment , I inflate a view from XML and add it as a child of CoordinatorLayout (which is BottomSheetDialogFragment 's parent's parent):

@Override
public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    setupBottomBar(getView());
}

private void setupBottomBar (View rootView) {
    CoordinatorLayout parentView = (CoordinatorLayout) ((FrameLayout)rootView.getParent()).getParent();
    parentView.addView(LayoutInflater.from(getContext()).inflate(R.layout.item_selection_bar, parentView, false), -1);
}

The code runs without error.
And when I use Layout Inspector to look at the View hierarchy, the view structure is also correct:

You can also download the layout inspector result here , and open it using your own Android Studio.

The problem

However, even though it is inserted as the last child of the CoordinatorLayout , it is still being blocked by the BottomSheetDialogFragment .
When I slowly scroll the BottomSheetDialogFragemnt downwards (from collapsed state to hidden state), I can finally see the view that I want to inflate behind the fragment.

Why is this happening?

The answer

As @GoodDev pointed out correctly, it is because the root view (design_bottom_sheet) has been set a Z translation by BottomSheetDialog .
This provides an important information that - not only sequence in a View hierarchy will determine its visibility, but also its Z translation.

The best way is to get the Z value of design_bottom_sheet and set it to the bottom bar layout.

private void setupBottomBar (View rootView) {
    CoordinatorLayout parentView = (CoordinatorLayout) (rootView.getParent().getParent());
    View barView = LayoutInflater.from(getContext()).inflate(R.layout.item_selection_bar, parentView, false);
    ViewCompat.setTranslationZ(barView, ViewCompat.getZ((View)rootView.getParent()));
    parentView.addView(barView, -1);
}

Answer 1

EDIT 2

Ok, now I see your requirement, try this one:

private void setupBottomBar (View rootView) {
    CoordinatorLayout parentView = (CoordinatorLayout) ((FrameLayout)rootView.getParent()).getParent();
    View view = LayoutInflater.from(getContext()).inflate(R.layout.item_selection_bar, parentView, false);
    // using TranslationZ to put the view on top of bottom sheet layout
    view.setTranslationZ(100);
    parentView.addView(view, -1);
}

---

EDIT:

OK, I check your layout and check the BottomSheetDialogFragment source code, found the reason:

In BottomSheetDialogFragment using BottomSheetDialog dialog, the method setContentView in BottomSheetDialog using wrapInBottomSheet to put the content view in R.id.design_bottom_sheet layout. So you need override the BottomSheetDialogFragment 's public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) to fix your problem.

Or, change your setupBottomBar method to:

private void setupBottomBar (View rootView) {
    FrameLayout frame = (FrameLayout)rootView.getParent();
    frame.addView(LayoutInflater.from(getContext()).inflate(R.layout.item_selection_bar, frame, false), -1);
}

and in your item_selection_bar layout file, change height and layout_gravity:

<android.support.constraint.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_gravity="bottom"
    android:layout_width="match_parent"
    android:layout_height="wrap_content">

---

BottomSheetDialogFragment doc says: Modal bottom sheet. This is a version of DialogFragment that shows a bottom sheet using BottomSheetDialog instead of a floating dialog.

So the BottomSheetDialogFragment is a Dialog , Dialog is a floating view, so will cover the Activity content when BottomSheetDialogFragment is showing.

Answer 2

@goodev has give a nice answer.

Your problem

View's Z position causes this problem. Although the TextView is the last position you still can not see it.

How to solve

You can set design_sheet_bottom's Z to TextView.

 private void setupBottomBar (View rootView) {
    CoordinatorLayout parentView = (CoordinatorLayout) ((FrameLayout)rootView.getParent()).getParent();
    View view = LayoutInflater.from(getContext()).inflate(R.layout.item_selection_bar, parentView, false);
    view.setZ(((View)rootView.getParent()).getZ());
    parentView.addView(view, -1);
}

And I think above way is very boring, can you put your two view RecyclerView and TextView into a layout ? Then you can inflate theme together in onCreateView() method.