使用AlarmManager设置闹钟

运行效果：

                           

activity_main.xml:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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"
    tools:context=".MainActivity">

    <TimePicker
        android:id="@+id/time"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>  //时间拾取器

    <Button
        android:id="@+id/set"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/time"
        android:layout_centerHorizontal="true"
        android:text="set"
        />  //设置闹钟按钮

</RelativeLayout>

 MainActivity:

package com.mingrisoft.alarm;

import android.app.AlarmManager;
import android.app.PendingIntent;
import android.content.Context;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TimePicker;
import android.widget.Toast;

import java.util.Calendar;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        final TimePicker timePicker = findViewById(R.id.time);  //时间拾取器
        final Calendar calendar;    //日历对象

        calendar = Calendar.getInstance();  //获取日历对象
        timePicker.setIs24HourView(true);   //设置使用24小时制

        Button button = findViewById(R.id.set); //获取“设置闹钟”按钮
        //为按钮添加时间监听器
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //创建Intent对象
                Intent intent = new Intent(MainActivity.this, AlarmActivity.class);
                //获取显示闹钟的PendingIntent对象
                PendingIntent pendingIntent = PendingIntent.getActivity(MainActivity.this, 0 , intent, 0);
                //获取AlarmManager对象
                AlarmManager alarmManager = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
                //设置闹钟的小时数
                calendar.set(Calendar.HOUR_OF_DAY, timePicker.getCurrentHour());
                //设置闹钟的分钟数
                calendar.set(Calendar.MINUTE, timePicker.getCurrentMinute());
                //设置闹钟的秒数
                calendar.set(Calendar.SECOND, 0);
                //设置一个闹钟
                alarmManager.set(alarmManager.RTC_WAKEUP, calendar.getTimeInMillis(), pendingIntent);
                //显示一个消息提示
                Toast.makeText(MainActivity.this, "闹钟设置成功", Toast.LENGTH_SHORT).show();
            }
        });
    }
}

创建一个AlarmActivity，用于显示闹钟提示的内容。在该Activity中重写onCreate（）方法，在该方法中创建并显示一个带“确定”按钮的对话框，显示闹钟的提示内容：

package com.mingrisoft.alarm;

import android.content.DialogInterface;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;

public class AlarmActivity extends AppCompatActivity {
    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        AlertDialog alert = new AlertDialog.Builder(this).create();
        alert.setIcon(R.drawable.alarm);    //设置对话框的图标
        alert.setTitle("传递正能量");    //设置对话框的标题
        alert.setMessage("hemeiwolong");    //设置要要显示的内容

        alert.setButton(DialogInterface.BUTTON_POSITIVE, "确定", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {

            }
        });
        alert.show();   //显示对话框
    }
}

AndroidManifest.xml:

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

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

        <activity
            android:name=".AlarmActivity"
            android:label="闹钟">
        </activity>
    </application>

</manifest>