按下效果怎么在LinearLayout中怎么不起作用

[nbaqqqq]

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical"
    android:background="@drawable/discount_back" >

    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="@string/hello" />
	<Button android:layout_width="wrap_content"
	    android:layout_height="wrap_content"
	    android:background="@drawable/discount_back"/>
</LinearLayout>

discount_back.xml

<?xml version="1.0" encoding="UTF-8"?>
<selector
  xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:state_focused="true" android:drawable="@drawable/jt_1" />
    <item android:state_selected="true" android:drawable="@drawable/jt_1" />    
    <item android:state_pressed="true" android:drawable="@drawable/jt_1" />
    <item android:drawable="@drawable/jt" />
</selector>

按钮的按下效果起作用，但LinearLayout中按下效果就没用，不知道为什么，求解，thanks

[danielinbiti]

LinearLayout中加上
android:clickable="true"
android:focusable="true"

[nbaqqqq]

有作用，非常感谢！