CoordinatorLayout causes FrameLayout to fall behind the navigation bar at the bottom

Question

This is my activity XML:

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@android:color/white"
    android:fitsSystemWindows="true">

    <include layout="@layout/toolbar" />

    <FrameLayout
        android:id="@+id/frameLayoutContainer"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_behavior="@string/appbar_scrolling_view_behavior" />

</android.support.design.widget.CoordinatorLayout>

I replace frameLayoutContainer with a ConstraintLayout-rooted Fragment. It has a Button view at the bottom constrained with app:layout_constraintBottom_toBottomOf="parent"

But the Button view falls behind the navigation bar. I have many activities almost the same structure with this, but they don't have such a problem.

When I replace CoordinatorLayout with a LinearLayout, the problem is solved, but I want to know what is wrong with CoordinatorLayout?

Answer 1

The line app:layout_behavior="@string/appbar_scrolling_view_behavior" does all the job. Try to remove this line from your XML file and you will see that the problem happens even if you do not replace frameLayoutContainer with Fragment.

Thus, the solution is to add this line app:layout_behavior="@string/appbar_scrolling_view_behavior" to your root of Fragment (either in your XML or programmatically) and check it.