android selector介绍

android selector是android的资源选择器，如按钮的多种状态对应多种显示模式，选择框的选择与未选择状态等等。

在res/drawable.../下使用xml来定义显示，有两种写法，

1.android:drawable

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">

    <item android:state_xxx1="xxx"

               android:state_xxx2="xxx"

               android:drawable="@drawable/btn_check_on_dis"/>
    <item ...... />

</selector>

2.shape

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">

    <item android:state_xxx1="xxx"

               android:state_xxx2="xxx">

              <shape ...... />

    </item>

    <item ...... />

</selector>

Selector支持的属性如下，很多都不知道啥意思，慢慢学习吧。

android:state_checked=""

android:state_enabled=""
android:state_focused=""
android:state_pressed=""
android:state_selected=""

android:state_active=""
android:state_activated=""
android:state_checkable=""
android:state_single="true"
android:state_window_focused=""
android:state_accelerated=""
android:state_hoverred=""
android:state_drag_can_accept=""
android:state_hovered=""
android:state_accessibility_focused=""

android:state_first=""
android:state_middle=""

android:state_last=""

如下是一些常见用法

    <CheckBox
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:button="@drawable/selector_check"
        android:checked="true"
        android:text="Checked" />

selector_check.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">

    <item android:drawable="@drawable/btn_check_on_dis" android:state_checked="true" android:state_enabled="false"/>
    <item android:drawable="@drawable/btn_check_on" android:state_checked="true"/>
    <item android:drawable="@drawable/btn_check_off_dis" android:state_enabled="false"/>
    <item android:drawable="@drawable/btn_check_off"/>

</selector>

        <Button
            android:id="@+id/button1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_margin="@dimen/content_margin"
            android:background="@drawable/selector_press"
            android:padding="8dp"
            android:text="Pressed" />

selector_press.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <!-- 禁用时的图片背景 -->
    <item android:state_enabled="false">
        <shape>
            <solid android:color="@color/btn_green_disable" />
            <corners android:radius="2dp" />
        </shape>
    </item>

    <!-- 点击时的图片背景 -->
    <item android:state_pressed="true">
        <shape>
            <solid android:color="@color/btn_green_selected" />
            <corners android:radius="2dp" />
        </shape>
    </item>

    <!-- 默认时的背景图片 -->
    <item>
        <shape>
            <solid android:color="@color/btn_green_normal" />
            <corners android:radius="2dp" />
        </shape>
    </item>

</selector>

        <EditText
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_margin="@dimen/content_margin"
            android:layout_weight="1"
            android:background="@drawable/selector_focus"
            android:padding="8dp"
            android:text="Normal" />

selector_focus.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">

    <!-- 获取焦点状态 -->
    <item android:state_focused="true">
        <shape>
            <stroke android:width="2dp" android:color="@color/btn_green_normal" />
            <corners android:radius="2dp" />
        </shape>
    </item>

    <!-- 不可用状态 -->
    <item android:state_enabled="false">
        <shape>
            <stroke android:width="1sp" android:color="#DDDDDD" />
            <corners android:radius="2dp" />
        </shape>
    </item>

    <!-- 普通状态 -->
    <item>
        <shape>
            <stroke android:width="1sp" android:color="@color/btn_green_normal" />
            <corners android:radius="2dp" />
        </shape>
    </item>

</selector>

    <GridView
        android:id="@+id/gridView"
        android:layout_width="match_parent"
        android:layout_height="70dp"
        android:cacheColorHint="@android:color/transparent"
        android:listSelector="@drawable/selector_select"
        android:numColumns="3" />

selector_select.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">

    <item android:state_selected="true">
        <shape>
            <solid android:color="#ff0000" />
        </shape>
    </item>
    <item android:state_pressed="true" android:state_selected="false">
        <shape>
            <solid android:color="@color/btn_green_selected" />
        </shape>
    </item>

</selector>