package com.loaderman.daynightdemo;import android.os.Bundle;import android.support.v7.app.AppCompatActivity;import android.support.v7.app.AppCompatDelegate;import android.support.v7.widget.Toolbar;import android.view.View;public class MainActivity extends AppCompatActivity implements View.OnClickListener {    {        AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_AUTO);    }    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);        setSupportActionBar(toolbar);        findViewById(R.id.btn_auto).setOnClickListener(this);        findViewById(R.id.btn_day).setOnClickListener(this);        findViewById(R.id.btn_night).setOnClickListener(this);        findViewById(R.id.fab).setOnClickListener(this);    }    @Override    public void onClick(View v) {        switch (v.getId()) {            case R.id.btn_auto: {                getDelegate().setLocalNightMode(AppCompatDelegate.MODE_NIGHT_AUTO);                recreate();                break;            }            case R.id.btn_day: {                getDelegate().setLocalNightMode(AppCompatDelegate.MODE_NIGHT_NO);                recreate();                break;            }            case R.id.btn_night: {                getDelegate().setLocalNightMode(AppCompatDelegate.MODE_NIGHT_YES);                recreate();                break;            }        }    }}

<?xml version="1.0" encoding="utf-8"?><android.support.design.widget.CoordinatorLayout    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:fitsSystemWindows="true"    tools:context="com.yanzhenjie.daynight.MainActivity">    <android.support.design.widget.AppBarLayout        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:theme="@style/AppTheme.AppBarOverlay">        <android.support.v7.widget.Toolbar            android:id="@+id/toolbar"            android:layout_width="match_parent"            android:layout_height="?attr/actionBarSize"            android:background="?attr/colorPrimary"            app:popupTheme="@style/AppTheme.PopupOverlay"/>    </android.support.design.widget.AppBarLayout>    <include layout="@layout/content_main"/>    <android.support.design.widget.FloatingActionButton        android:id="@+id/fab"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_gravity="bottom|end"        android:layout_margin="@dimen/fab_margin"        android:src="http://www.mamicode.com/@android:drawable/ic_dialog_email"/></android.support.design.widget.CoordinatorLayout>

<?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"    android:paddingBottom="@dimen/activity_vertical_margin"    android:paddingLeft="@dimen/activity_horizontal_margin"    android:paddingRight="@dimen/activity_horizontal_margin"    android:paddingTop="@dimen/activity_vertical_margin"    app:layout_behavior="@string/appbar_scrolling_view_behavior"    tools:context="com.yanzhenjie.daynight.MainActivity"    tools:showIn="@layout/activity_main">    <Button        android:id="@+id/btn_auto"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="自动模式" />    <Button        android:id="@+id/btn_day"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="日间模式" />    <Button        android:id="@+id/btn_night"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="夜间模式" /></LinearLayout>

<resources>    <style name="AppTheme" parent="Theme.AppCompat.DayNight.DarkActionBar">        <item name="colorPrimary">@color/colorPrimary</item>        <item name="colorPrimaryDark">@color/colorPrimaryDark</item>        <item name="colorAccent">@color/colorAccent</item>    </style>    <style name="AppTheme.NoActionBar">        <item name="windowActionBar">false</item>        <item name="windowNoTitle">true</item>    </style>    <style name="AppTheme.AppBarOverlay" parent="ThemeOverlay.AppCompat.Dark.ActionBar" />    <style name="AppTheme.PopupOverlay" parent="ThemeOverlay.AppCompat.Light" /></resources>

<?xml version="1.0" encoding="utf-8"?><manifest xmlns:android="http://schemas.android.com/apk/res/android"    package="com.loaderman.daynightdemo">    <application        android:allowBackup="true"        android:icon="@mipmap/ic_launcher"        android:label="@string/app_name"        android:supportsRtl="true"        android:theme="@style/AppTheme">        <activity            android:name=".MainActivity"            android:label="@string/app_name"            android:theme="@style/AppTheme.NoActionBar">            <intent-filter>                <action android:name="android.intent.action.MAIN" />                <category android:name="android.intent.category.LAUNCHER" />            </intent-filter>        </activity>    </application></manifest>