transparent Actionbar with AppCompat-v7 21

Solution 1:

<!-- Application theme. -->
<style name="AppTheme" parent="Theme.AppCompat.Light">
    <item name="android:actionBarStyle">@style/MyActionBar</item>

    <!-- Support library compatibility -->
    <item name="actionBarStyle">@style/MyActionBar</item>
</style>

<!-- ACTION BAR STYLES -->
<style name="MyActionBar" parent="@style/Widget.AppCompat.ActionBar">
    <item name="android:background">@drawable/actionbar_background</item>
    <item name="android:windowActionBarOverlay">true</item>

    <!-- Support library compatibility -->
    <item name="background">@drawable/actionbar_background</item>
    <item name="windowActionBarOverlay">true</item>
</style>

Solution 2:

Actually, it's quite easy and simple.

1. Just ensure that you use RelativeLayout to lay Toolbar and the body.
2. Put the Toolbar in the last.
3. Put transparent color for android:background attribute of the Toolbar

This is an example of a working code:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:baselineAligned="false"
    android:orientation="vertical">

    <fragment
        android:id="@+id/fragment_editor"
        android:name="ichsan.myapp.HelloFragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:layout="@layout/fragment_editor" />

    <android.support.v7.widget.Toolbar
        android:id="@+id/my_toolbar"
        android:layout_height="wrap_content"
        android:layout_width="match_parent"
        android:minHeight="?attr/actionBarSize"
        android:background="#10000000"
        app:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
        app:popupTheme="@style/ThemeOverlay.AppCompat.Light"/>

</RelativeLayout>

Hope it answers the question.