Android: Toolbar elevation / Shadow

Question

I would like to know why this toolbar cast a shadow only if NestedScrollView is there (I've got this example from the internet)

<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.v4.widget.NestedScrollView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_behavior="@string/appbar_scrolling_view_behavior">

        <!-- Your scrolling content -->

    </android.support.v4.widget.NestedScrollView>

    <android.support.design.widget.AppBarLayout
        android:layout_height="wrap_content"
        android:layout_width="match_parent">

        <android.support.v7.widget.Toolbar
            xmlns:android="http://schemas.android.com/apk/res/android"
            xmlns:local="http://schemas.android.com/apk/res-auto"
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:minHeight="?attr/actionBarSize"
            android:background="?attr/colorPrimary"
            local:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
            local:popupTheme="@style/ThemeOverlay.AppCompat.Light"
            />
    </android.support.design.widget.AppBarLayout>

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

This toolbar (without the NestedScrollView) don't cast any shadow:

<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:layout_height="wrap_content"
        android:layout_width="match_parent">

        <android.support.v7.widget.Toolbar
            xmlns:android="http://schemas.android.com/apk/res/android"
            xmlns:local="http://schemas.android.com/apk/res-auto"
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:minHeight="?attr/actionBarSize"
            android:background="?attr/colorPrimary"
            local:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
            local:popupTheme="@style/ThemeOverlay.AppCompat.Light"
            />
    </android.support.design.widget.AppBarLayout>

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

I can post pictures, if needed, but I have no clue why this happen. This is what I've tried so far:

• Setting clipToPadding="false" on the parent Linear Layout
• Manually set elevation (my device is not Pre-Lollipop)
• Seting outlineProvider="bounds" on the view
• Setting android:hardwareAccelerated="true" on the AndroidManifest.xml

Edit: I've solved it by using the tag. Check my answer with the code.

Answer 1

Researching a little bit more, I found out that the merge tag will do the trick. This tag can merge the toolbar.xml in the parent layout that will take care of the z-ordering and place the Toolbar where I intended.

<merge xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto">
<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:layout_height="wrap_content"
        android:layout_width="match_parent">

        <android.support.v7.widget.Toolbar
            xmlns:android="http://schemas.android.com/apk/res/android"
            xmlns:local="http://schemas.android.com/apk/res-auto"
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:minHeight="?attr/actionBarSize"
            android:background="?attr/colorPrimary"
            local:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
            local:popupTheme="@style/ThemeOverlay.AppCompat.Light"
            />
    </android.support.design.widget.AppBarLayout>

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

And no, asking here was not the first thing I did, It was just luck to find this tag in less than an hour after I post here. Anyway, here is my solution.