当CollapsingToolbarLayout折叠时，锚定图像会被工具栏重叠

Question

I am using CollapsingToolbarLayout in one of my layouts, I anchored an image (id=event_logo) on AppBar layout; How it looks before collapsing

however, when CollapsingToolbarLayout is totally collapsed the Toolbar covers the image. How it looks after collapsing

my xml code

 <android.support.design.widget.AppBarLayout android:id="@+id/app_bar" android:layout_width="match_parent" android:layout_height="185dp" android:fitsSystemWindows="true" android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"> <android.support.design.widget.CollapsingToolbarLayout android:id="@+id/collapse_toolbar_layout" android:layout_width="match_parent" android:layout_height="match_parent" android:fitsSystemWindows="true" app:contentScrim="?attr/colorPrimary" app:layout_scrollFlags="scroll|exitUntilCollapsed" app:toolbarId="@+id/toolbar"> <ImageView android:layout_width="match_parent" android:layout_height="match_parent" android:layout_gravity="fill" android:fitsSystemWindows="true" android:scaleType="center" android:src="@drawable/bgg" /> <android.support.v7.widget.Toolbar android:id="@+id/about_toolbar" android:layout_width="match_parent" android:layout_height="?attr/actionBarSize" android:theme="@style/MyTheme1" app:layout_collapseMode="pin" app:layout_scrollFlags="scroll|enterAlways" app:popupTheme="@style/AppTheme.PopupOverlay" /> </android.support.design.widget.CollapsingToolbarLayout> </android.support.design.widget.AppBarLayout> <android.support.v4.widget.NestedScrollView android:id="@+id/item_detail_container" android:layout_width="match_parent" android:layout_height="match_parent" app:layout_behavior="@string/appbar_scrolling_view_behavior"> ..... </android.support.v4.widget.NestedScrollView> <ImageView android:id="@+id/event_logo" android:layout_width="65dp" android:layout_height="65dp" android:layout_alignParentTop="true" android:layout_centerHorizontal="true" android:layout_gravity="center_vertical|left" android:layout_margin="@dimen/fab_margin" android:src="@drawable/barcode_scanner" android:layout_marginTop="120dp" android:contentDescription="event_logo" app:layout_anchor="@+id/app_bar" app:layout_anchorGravity="bottom|right" /> 

Tested on Android 6.0

Any Idea why is this the case?

Answer 1

For future readers to this question...The trick to solve this issue is to set elevation to 20dp

Simply add elevation attribute to the anchored image

 <ImageView android:id="@+id/event_logo" android:layout_width="65dp" android:layout_height="65dp" android:layout_margin="@dimen/fab_margin" android:contentDescription="event_logo" android:elevation="20dp" android:scaleType="fitXY" app:layout_anchor="@+id/app_bar" app:layout_anchorGravity="bottom|right" tools:targetApi="lollipop" /> 

note: attribute elevation is used only for API 21 and higher, that's why it's necessary to add targetApi lollipop