按钮没有得到焦点

我想提出一个应用程序有4个按钮它。我希望得到他们的重点只要鼠标或通过them.But一些指针移动我不能够做that.Please告诉我是什么问题。按钮的编码如下

i am making an application with 4 buttons in it.I want to get them the focus whenever the mouse or some pointer moves over them.But i am not able to do that.Please tell me what is the problem. The coding of buttons is as follows.

            m_NextButton.requestFocus();
    m_PrevButton.requestFocus();
    m_SubmitButton.requestFocus();
    m_SkipButton.requestFocus();

中的XML编码如下：

The xml coding is as follows:

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

</selector>

先谢谢了。