这是其中一种实现模式，也是比较麻烦的一种，首先写布局，不多说上代码

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context="com.example.day_night_demo2.MainActivity"><Button
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:onClick="onClick"
android:text="?attr/textContent"/><TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="100dp"
android:text="Hello World!"
android:textColor="?attr/textColorValue" /><TextView
android:textColor="?attr/textColorValue"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="20dp"
android:text="Hello World!" /><TextView
android:textColor="?attr/textColorValue"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="20dp"
android:text="Hello World!" />
</LinearLayout>-------------------------------------------------------------------------------------------------------

res资源文件夹下values文件夹下创建attrs.xml资源文件

<?xml version="1.0" encoding="utf-8"?>
<resources><attr name="textColorValue" format="color"></attr><attr name="textContent" format="string"></attr>
</resources>

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colors.xml

<color name="background">#252a2e</color>
<color name="unablebtn">#dcdcdc</color>
<color name="dark_bg">#505050</color>
<color name="light">#ECECEC</color>
<color name="white">#FFFFFF</color>
<color name="black">#000000</color>
<color name="green">#05D992</color>
<color name="zise">#E5004F</color>
<color name="dark_bg1">#414141</color>
<color name="pink">#FF5877</color>
<color name="yellow">#FFFF00</color>

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Strings.xml

<string name="changge_to_night">切换成夜间模式</string>
<string name="changge_to_day">切换成日间模式</string>

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styles.xml

<!-- Base application theme. 白天的模式 -->
<style name="day_theme" parent="Theme.AppCompat.Light.DarkActionBar"><!-- Customize your theme here. -->
<item name="colorPrimary">@color/colorPrimary</item><item name="colorPrimaryDark">@color/colorPrimaryDark</item><item name="colorAccent">@color/colorAccent</item><item name="android:windowBackground">@color/white</item><!--日间模式对应的字体颜色 和日间模式对应的文本内容-->
<item name="textColorValue">@color/black</item><item name="textContent">@string/changge_to_night</item></style><!-- Base application theme. 夜晚的模式 -->
<style name="night_theme" parent="Theme.AppCompat.Light.DarkActionBar"><!-- Customize your theme here. -->
<item name="colorPrimary">@color/dark_bg</item><item name="colorPrimaryDark">@color/dark_bg</item><item name="colorAccent">@color/dark_bg</item><item name="android:windowBackground">@color/dark_bg</item><!--夜间模式对应的字体颜色 和夜间模式对应的文本内容-->
<item name="textColorValue">@color/white</item><item name="textContent">@string/changge_to_day</item>
</style>

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在res文件夹下创建anim文件夹用来存放动画，为了使模式切换更自然，使用补间动画

sliding_in.xml

<?xml version="1.0" encoding="utf-8"?>
<alphaxmlns:android="http://schemas.android.com/apk/res/android"
android:duration="1000"
android:fromAlpha="0.0"
android:toAlpha="1.0"></alpha>

sliding_out.xml

<?xml version="1.0" encoding="utf-8"?>
<alpha xmlns:android="http://schemas.android.com/apk/res/android"
android:duration="1000"
android:toAlpha="0.0"
android:fromAlpha="1.0"></alpha>

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下面就是具体实现代码了

package com.example.day_night_demo2;import android.app.Activity;
import android.content.Intent;/**
 * Created by lenovo on 2017/9/5.
 */
public class ThemeUtil {//我当前的主题
private static int theme = 0;//日间模式主题
private static final int DAY_THEME = 0;//夜间模式主题
private static final int NIGHT_THEME = 1;public static void onActivityCreatedSetTheme(Activity activity) {switch (theme) {case DAY_THEME:activity.setTheme(R.style.day_theme);break;case NIGHT_THEME:activity.setTheme(R.style.night_theme);break;}}//点击按钮改变对应的主题
public static void ChangeCurrentTheme(Activity activity) {//改变当前主题的theme变量
switch (theme) {case DAY_THEME:theme = NIGHT_THEME;break;case NIGHT_THEME:theme = DAY_THEME;break;}//重启这个activity
activity.finish();activity.overridePendingTransition(R.anim.sliding_in,R.anim.sliding_out);activity.startActivity(new Intent(activity,activity.getClass()));}
}

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package com.example.day_night_demo2;import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;public class MainActivity extends AppCompatActivity {@Override
protected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);//设置对应的主题 ，在ui创建好之后设置主题无效，所以要放到setContentView（）方法前面setTheme()
ThemeUtil.onActivityCreatedSetTheme(this);setContentView(R.layout.activity_main);}public void onClick(View v){ThemeUtil.ChangeCurrentTheme(this);}
}