AlarmManager定时运行没有用

这是一个service的代码：
package com.example.cjlhappiness.servicebestpractice;

import java.util.Date;
import android.app.AlarmManager;
import android.app.PendingIntent;
import android.app.Service;
import android.content.Intent;
import android.os.IBinder;
import android.os.SystemClock;
import android.util.Log;

public class ServiceBestPractice extends Service {

@Override
public IBinder onBind(Intent intent) {
    return null;
}

@Override
public int onStartCommand(Intent intent, int flags, int startId) {
    new Thread(new Runnable() {
        @Override
        public void run() {
            Log.d("LongRunningService", "executed at " + new Date().toString());
        }
    }).start();
    AlarmManager manager = (AlarmManager) getSystemService(ALARM_SERVICE);
    int anHour = 100;
    long triggerAtTime = SystemClock.elapsedRealtime() + anHour;
    Intent i = new Intent(this, AlarmManager.class);
    PendingIntent pi = PendingIntent.getBroadcast(this, 0, i, 0);
    manager.set(AlarmManager.ELAPSED_REALTIME_WAKEUP, triggerAtTime, pi);
    return super.onStartCommand(intent, flags, startId);
}

@Override
public void onDestroy() {
    super.onDestroy();
    Log.d("提示", "onDestroy: ");
}

}

BroadcastReceiver代码：
package com.example.cjlhappiness.servicebestpractice;

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

public class AlarmReceiver extends BroadcastReceiver {

@Override
public void onReceive(Context context, Intent intent) {
    Intent i = new Intent(context, ServiceBestPractice.class);
    context.startService(i);
}

}

通过Activity里的按钮启动service服务。
没有任何报错信息，安卓4.4版本。
在AlarmReceiver加log没有提示，onReceive方法应该是没有调用过，但第哪里出了问题。
使用提供的源代码可以运行，应该是4.1版本的。

权限加了吗，加上权限试试