AlarmManager系统服务

package com.lulu.lalarm;

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;

public class MainActivity extends AppCompatActivity {

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

public void startAlarmClick(View view){
//获取系统的闹钟服务
AlarmManager am = (AlarmManager) getSystemService(Context.ALARM_SERVICE);

//触发闹钟的时间, 毫秒为单位
long triggerTime = System.currentTimeMillis() + 2000;
Intent intent = new Intent(this, AlarmReceiver.class);
PendingIntent pendingIntent = PendingIntent.getBroadcast(this, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT);
//只会执行一次的闹钟
//        am.set(AlarmManager.RTC_WAKEUP, triggerTime, pendingIntent);
//指定时间重复执行
am.setRepeating(AlarmManager.RTC, triggerTime,50, pendingIntent);
}

}

package com.lulu.lalarm;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.widget.Toast;

public class AlarmReceiver extends BroadcastReceiver {
public AlarmReceiver() {
}

@Override
public void onReceive(Context context, Intent intent) {
Toast.makeText(context, "起床了", Toast.LENGTH_SHORT).show();
}
}

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.lulu.lalarm.MainActivity">

<Button
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="启动闹钟"
android:onClick="startAlarmClick"
android:id="@+id/button"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true" />
</RelativeLayout>