Strange CoordinatorLayout/AppBarLayout behavior

Question

<?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.support.design.widget.AppBarLayout
        android:id="@+id/app_bar"
        android:layout_width="match_parent"
        android:layout_height="200dp">

        <android.support.design.widget.CollapsingToolbarLayout
            android:id="@+id/toolbar_layout"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:minHeight="100dp"
            app:contentScrim="?attr/colorPrimary"
            app:layout_scrollFlags="scroll|exitUntilCollapsed">
        </android.support.design.widget.CollapsingToolbarLayout>
    </android.support.design.widget.AppBarLayout>

    <View
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:background="@color/colorAccent"
        app:layout_anchor="@id/app_bar"
        app:layout_anchorGravity="bottom"/>

    <include layout="@layout/content_scrolling"/>
</android.support.design.widget.CoordinatorLayout>

Seems, the AppBarLayout becomes "ontop" view once the CollapsingToolbarLayout reaches the minHeight height. See the screenshots:

Question 1: Why it behaves like that?

Question 2: Is it possible to prevent that? I need that the square was on top while the CollapsingToolbarLayout is collapsed to its minimum height.

Answer 1

ANCHORS

I think the reason for your problem is the anchor and the height attribute of the AppBarLayout. What I suggest doing:

• Set the height attribute of the AppBarLayout to wrap_content

• Set the max_height or height of your CollapsingToolbarLayout to 200dp

• Set the anchor of your View to the CollapsingToolbarLayout

I honestly hope I helped, I'm still quite new to Android but if I have figured it out for you let me know. -Daniel