I want to change the background of the Alert dialog. I have tried following code piece to do so:

```
 <style name="Theme.AlertDialog" parent="@android:style/Theme.Holo.Light.Dialog">
        <item name="android:background">@android:color/transparent</item>
        <item name="android:textColor">#659F26</item>
        <item name="android:windowTitleStyle">@style/Theme.AlertDialog.Title</item>
    </style>

    <style name="Theme.AlertDialog.Title" parent="@android:style/TextAppearance.DialogWindowTitle">
        <item name="android:background">@drawable/cab_background_top_example</item>
    </style>

```

Java Code:

```
ContextThemeWrapper ctw = new ContextThemeWrapper( this, R.style.Theme_AlertDialog);
final AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(ctw);

alertDialogBuilder.setTitle(getResources().getString(R.string.confirmation));   
alertDialogBuilder.setMessage(getResources().getString(R.string.msg));       
alertDialogBuilder.show();

```

My app is showing dialog like this:

![enter image description here](https://i.stack.imgur.com/U2Dfb.png)

while i want it to look like:

![enter image description here](https://i.stack.imgur.com/GvBhR.png)

Please suggest, what i am doing wrong.