如何在android中更改选择器模式背景？

<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:state_pressed="true" android:drawable="@drawable/pressed_background" />
    <item android:state_focused="true" android:drawable="@drawable/focused_background" />
    <item android:drawable="@drawable/default_background" />
</selector>

<!-- pressed_background.xml -->
<shape xmlns:android="http://schemas.android.com/apk/res/android">
    <solid android:color="#FF0000" />
</shape>

<!-- focused_background.xml -->
<shape xmlns:android="http://schemas.android.com/apk/res/android">
    <solid android:color="#00FF00" />
</shape>

<!-- default_background.xml -->
<shape xmlns:android="http://schemas.android.com/apk/res/android">
    <solid android:color="#0000FF" />
</shape>

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:background="@drawable/custom_selector" />