<resources>
    <!-- Base application theme. -->
    <style name="AppTheme" parent="Theme.AppCompat.Light">
        <!-- Customize your theme here. -->
        <item name="android:actionBarStyle">@style/MyStyle</item>
    </style>
    <style name="MyStyle" parent="Widget.AppCompat.Light.Spinner.DropDown.ActionBar">
        <item name="android:background">@drawable/bar</item>
    </style>
</resources>

 <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme">
        <activity
            android:name=".MainActivity"
            android:label="@string/app_name"
            android:logo="@mipmap/ic_launcher">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>