Android:通过selector改变界面状态

做应用时，可能会需要动态改变控件的背景图片，如果仅仅是简单的点击，选中之类的事件，如果靠程序中写监听的代码就显得太麻烦了，在这种情况下，你可以使用selector动态改变控件背景



1. 在res/drawable目录下建一个mybutton.xml文件，根据需要，不同的状态下建立不同的item，并对应相应的图片



可以设置以下几种触发状态:



android:state_pressed

Boolean . "true" if this item should be used when the object is pressed (such as when a button is touched/clicked); "false" if this item should be used in the default, non-pressed state.

如果是true，当被点击时显示该图片，如果是false没被按下时显示默认。



android:state_focused

Boolean . "true" if this item should be used when the object is focused (such as when a button is highlighted using the trackball/d-pad); "false" if this item should be used in the default, non-focused state.

true，获得焦点时显示；false，没获得焦点显示默认。



android:state_selected

Boolean . "true" if this item should be used when the object is selected (such as when a tab is opened); "false" if this item should be used when the object is not selected.

true，当被选择时显示该图片；false，当未被选择时显示该图片。



android:state_checkable

Boolean . "true" if this item should be used when the object is checkable; "false" if this item should be used when the object is not checkable. (Only useful if the object can transition between a checkable and non-checkable widget.)

true，当CheckBox能使用时显示该图片；false，当CheckBox不能使用时显示该图片。



android:state_checked

Boolean . "true" if this item should be used when the object is checked; "false" if it should be used when the object is un-checked.

true，当CheckBox选中时显示该图片；false，当CheckBox为选中时显示该图片。



android:state_enabled

Boolean . "true" if this item should be used when the object is enabled (capable of receiving touch/click events); "false" if it should be used when the object is disabled.

true，当该组件能使用时显示该图片；false，当该组件不能使用时显示该图片。



android:state_window_focused

Boolean . "true" if this item should be used when the application window has focus (the application is in the foreground), "false" if this item should be used when the application window does not have focus (for example, if the notification shade is pulled down or a dialog appears).

true，当此activity获得焦点在最前面时显示该图片；false，当没在最前面时显示该图片。





<? 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_pressed" /> <!-- pressed -->
    <item android:state_focused = "true"
          android:drawable = "@drawable/button_focused" /> <!-- focused -->
    <item android:drawable = "@drawable/button_normal" /> <!-- default -->
</selector>





范例：

<selector xmlns:android="http://schemas.android.com/apk/res/android">
     <item android:state_pressed="false" android:drawable="@drawable/poker_back" />
     <item android:state_pressed="true" android:drawable="@drawable/poker_a" />
</selector>





对应的button设置：

<ImageButton
     android:id="@+id/imagebutton"
     android:layout_width="wrap_content"
     android:layout_height="wrap_content"
     android:background="@drawable/mybutton"
     />



获得类似Focus的效果，鼠标按下时（非点击），按钮图标改变

如果在监听事件中配合 imageButton.setImageResource(R.drawable.poker_a);  语句

可以达到点击后改变按钮图案的效果，标志图标已被按下