title: How to customize ActionBar background image?
body: <p>I want to use an image as a background of my ActionBar, like this (shown by red rectangle):
  <a href="https://i.stack.imgur.com/fVnRW.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/fVnRW.jpg" alt="enter image description here"></a>, </p>
  
  <p>so I modified some files like these.</p>
  
  <p><strong>styles.xml</strong></p>
  
  <pre><code>&lt;style name="AppTheme.CustomActionBar"&gt;
      &lt;item name="windowActionBar"&gt;true&lt;/item&gt;
      &lt;item name="windowNoTitle"&gt;false&lt;/item&gt;
      &lt;item name="android:actionBarStyle"&gt;@style/MyActionBar&lt;/item&gt;
  &lt;/style&gt;
  
  &lt;style name="MyActionBar"
      parent="@android:style/Widget.Holo.Light.ActionBar.Solid.Inverse"&gt;
      &lt;item name="android:background"&gt;@drawable/ab_img&lt;/item&gt;
  &lt;/style&gt;
  </code></pre>
  
  <p><strong>AndroidManifest.xml</strong></p>
  
  <pre><code> &lt;application
              android:allowBackup="true"
              android:icon="@mipmap/ic_launcher"
              android:label="@string/app_name"
              android:roundIcon="@mipmap/ic_launcher_round"
              android:supportsRtl="true"
              android:theme="@style/AppTheme"&gt;
              &lt;activity
                  android:name=".MainActivity"
                  android:label="@string/app_name"
                  android:theme="@style/AppTheme.CustomActionBar"&gt;
                  &lt;intent-filter&gt;
                      &lt;action android:name="android.intent.action.MAIN" /&gt;
  
                      &lt;category android:name="android.intent.category.LAUNCHER" /&gt;
                  &lt;/intent-filter&gt;
              &lt;/activity&gt;
      &lt;/application&gt;
  </code></pre>
  
  <p>On Android 4.4.2, I don't see any background image. Just the standard ActionBar. How to properly customize its image?</p>