Pushing the ActionBar to the Next Level

activity_home.xml

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

    <ImageView
        android:id="@+id/image_header"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:scaleType="centerCrop"
        android:src="@drawable/daft_punk"/>

    <View
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@drawable/gradient"/>

</FrameLayout>

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.cyrilmottier.android.translucentactionbar"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="14"
        android:targetSdkVersion="17" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/Theme.TranslucentActionBar">
        <activity
                android:name=".HomeActivity"
                android:theme="@style/Theme.TranslucentActionBar.ActionBar.Overlay">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>
</manifest>

gradient.xml

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
       android:shape="rectangle">

    <size android:height="100dp"/>

    <gradient
        android:angle="270"
        android:startColor="#8000"
        android:endColor="#0000"/>

</shape>

HomeActivity.java

...
if (Build.VERSION.SDK_INT < Build.VERSION_CODES.JELLY_BEAN_MR1) {
    mActionBarBackgroundDrawable.setCallback(mDrawableCallback);
}
...

private Drawable.Callback mDrawableCallback = new Drawable.Callback() {
    @Override
    public void invalidateDrawable(Drawable who) {
        getActionBar().setBackgroundDrawable(who);
    }

    @Override
    public void scheduleDrawable(Drawable who, Runnable what, long when) {
    }

    @Override
    public void unscheduleDrawable(Drawable who, Runnable what) {
    }
};

NotifyingScrollView.java

private boolean mIsOverScrollEnabled = true;

public void setOverScrollEnabled(boolean enabled) {
    mIsOverScrollEnabled = enabled;
}

public boolean isOverScrollEnabled() {
    return mIsOverScrollEnabled;
}

@Override
protected boolean overScrollBy(int deltaX, int deltaY, int scrollX, int scrollY, int scrollRangeX, int scrollRangeY,
                               int maxOverScrollX, int maxOverScrollY, boolean isTouchEvent) {
    return super.overScrollBy(
            deltaX,
            deltaY,
            scrollX,
            scrollY,
            scrollRangeX,
            scrollRangeY,
            mIsOverScrollEnabled ? maxOverScrollX : 0,
            mIsOverScrollEnabled ? maxOverScrollY : 0,
            isTouchEvent);
}

styles.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <style name="Widget.ActionBar" parent="@android:style/Widget.Holo.Light.ActionBar.Solid.Inverse">
        <item name="android:background">@drawable/ab_background</item>
    </style>

    <style name="Widget.ActionBar.Transparent">
        <item name="android:background">@android:color/transparent</item>
    </style>
</resources>

themes.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <style name="Theme.TranslucentActionBar" parent="@android:style/Theme.Holo.Light.DarkActionBar">
        <item name="android:actionBarStyle">@style/Widget.ActionBar</item>
    </style>

    <style name="Theme.TranslucentActionBar.ActionBar" />

    <style name="Theme.TranslucentActionBar.ActionBar.Overlay">
        <item name="android:actionBarStyle">@style/Widget.ActionBar.Transparent</item>
        <item name="android:windowActionBarOverlay">true</item>
    </style>
</resources>