Draw a circle under the Android status bar

drawable+bg_toolbar.xml

<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
    <item>
        <shape>
            <solid android:color="?attr/colorPrimary"/>
        </shape>
    </item>
    <item android:gravity="right|center_vertical" android:width="200dp" android:height="200dp" android:right="30dp" android:top="-100dp" android:bottom="-100dp">
        <shape android:shape="oval">
            <solid android:color="?attr/colorAccent"/>
        </shape>
    </item>
</layer-list>

layout+activity_main.xml

<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:fitsSystemWindows="true">

    <android.support.design.widget.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:fitsSystemWindows="true"
        android:background="@drawable/bg_toolbar"
        android:theme="@style/AppTheme.AppBarOverlay">

        <!-- AppBarLayout will dispatch applyWindowInsets event to child view, use a FrameLayout to consumes that -->
        <!-- https://github.com/hehonghui/android-tech-frontier/blob/master/issue-35/%E4%B8%BA%E4%BB%80%E4%B9%88%E6%88%91%E4%BB%AC%E8%A6%81%E7%94%A8fitsSystemWindows.md -->
        <FrameLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:fitsSystemWindows="true">

            <android.support.v7.widget.Toolbar
                android:id="@+id/toolbar"
                android:layout_width="match_parent"
                android:layout_height="?attr/actionBarSize"
                app:popupTheme="@style/AppTheme.PopupOverlay"/>

        </FrameLayout>

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

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

values+strings.xml

<resources>
    <string name="app_name">PlayFitSystemWindow</string>
</resources>

values+styles.xml

<resources>

    <!-- Base application theme. -->
    <style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
        <!-- Customize your theme here. -->
        <item name="colorPrimary">#3949AB</item>
        <item name="colorPrimaryDark">#43A047</item>
        <item name="colorAccent">#FF5722</item>
    </style>

    <style name="AppTheme.NoActionBar">
        <item name="windowActionBar">false</item>
        <item name="windowNoTitle">true</item>
    </style>

    <style name="AppTheme.AppBarOverlay" parent="ThemeOverlay.AppCompat.Dark.ActionBar"/>

    <style name="AppTheme.PopupOverlay" parent="ThemeOverlay.AppCompat.Light"/>

</resources>

values-v21+styles.xml

<resources>
    <style name="AppTheme.NoActionBar">
        <item name="windowActionBar">false</item>
        <item name="windowNoTitle">true</item>
        <item name="android:windowDrawsSystemBarBackgrounds">true</item>
        <item name="android:statusBarColor">@android:color/transparent</item>
    </style>
</resources>

Preview

On Android N with split window feature & Android M