app切换夜间模式

1. 在res新建attrs.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>

    <attr name="mainBackground" format="color" />
    <attr name="mainTextColor" format="reference|color" />
    <attr name="btnColor" format="color" />
    <attr name="nightMode" format="string" />

</resources>

2. 然后在styles.xml分两种

<resources xmlns:android="http://schemas.android.com/apk/res/android">

    <!--
        Base application theme, dependent on API level. This theme is replaced
        by AppBaseTheme from res/values-vXX/styles.xml on newer devices.
    -->
    <style name="AppBaseTheme" parent="android:Theme.Light">
        <!--
            Theme customizations available in newer API levels can go in
            res/values-vXX/styles.xml, while customizations related to
            backward-compatibility can go here.
        -->
        <item name="mainBackground">#ffffff</item>
        <item name="mainTextColor">#000000</item>
        <item name="btnColor">#00ff00</item>
        <item name="nightMode">夜间模式</item>
    </style>
    
    <style name="NightTheme" parent="android:Theme.Black">
        <item name="mainTextColor">#ffffff</item>
        <item name="mainBackground">#000000</item>
        <item name="btnColor">#0000ff</item>
         <item name="nightMode">日间模式</item>
    </style>

    <!-- Application theme. -->
    <style name="AppTheme" parent="AppBaseTheme">
        <!-- All customizations that are NOT specific to a particular API-level can go here. -->
    </style>

</resources>

3. 在layout的xml这样用：（就是加个?在前面）

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:background="?mainBackground"
    android:orientation="vertical">

    <TextView
        android:id="@+id/pageNum"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="?mainTextColor" />

4. 在java中onCreate可以，当然可以加个boolean来日夜切换：

super.onCreate(savedInstanceState);  
this.setTheme(R.style.NightTheme);  
setContentView(R.layout.main);