一：配合service一起简单使用，开启一个后台定时任务

思路简单说明：

• 开启一个不重复的定时闹钟任务
• 任务的功能是去开启一个服务
• 服务里面去做一些需要的操作，比如说发送一个网络请求
• 网络请求完毕后，再次开启这个定时闹钟任务
  从而达到一个循环的定时任务效果。

第一步：创建一个service

public class AlarmService extends IntentService {
    public AlarmService() {
        super("AlarmService");
    }

    @Override
    protected void onHandleIntent(Intent intent) {
        try {
            Thread.sleep(1000);//此处模拟发送一个网络请求
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        Log.d("AlarmService", "executed at " + new Date().toString());
        //请求结束后在开启一个闹钟
        AlarmManager.getInstance().startAlarm(this);
    }
}

第二步：创建一个AlarmReceiver

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

    @Override
    public void onReceive(Context context, Intent intent) {
//        收到广播后开启服务
        Intent i = new Intent(context, AlarmService.class);
        context.startService(i);
    }
}

第三步:创建一个开启闹钟的管理者

public class AlarmManager {
    private static AlarmManager manager;

    public static AlarmManager getInstance() {
        if (manager == null) {
            manager = new AlarmManager();
        }
        return manager;
    }

    public void startAlarm(Context context) {
        android.app.AlarmManager manager = (android.app.AlarmManager) context.getSystemService(ALARM_SERVICE);
//        int time = 60 * 60 * 1000;   // 这是一小时的毫秒数
        int time = 5 * 1000;
        long triggerAtTime = SystemClock.elapsedRealtime() + time;
        Intent i = new Intent(context, AlarmReceiver.class);
        PendingIntent pi = PendingIntent.getBroadcast(context, 0, i, 0);
        manager.set(android.app.AlarmManager.ELAPSED_REALTIME_WAKEUP, triggerAtTime, pi);
    }

}

第四步：开启这个定时任务,可以启用这个服务开启，也可以通过调用AlarmManager去开启。

public class AlarmActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_alarm);
        findViewById(R.id.btn).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                AlarmManager.getInstance().startAlarm(AlarmActivity.this);
            }
        });


        findViewById(R.id.btn1).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(AlarmActivity.this, AlarmService.class);
                startService(intent);
            }
        });

    }
}

运行结果

07-13 14:19:50.865 2811-3774/com.tomato.soapplication D/AlarmService: executed at Fri Jul 13 14:19:50 GMT+08:00 2018
07-13 14:19:56.876 2811-3878/com.tomato.soapplication D/AlarmService: executed at Fri Jul 13 14:19:56 GMT+08:00 2018
07-13 14:20:02.887 2811-3931/com.tomato.soapplication D/AlarmService: executed at Fri Jul 13 14:20:02 GMT+08:00 2018
07-13 14:20:08.900 2811-3969/com.tomato.soapplication D/AlarmService: executed at Fri Jul 13 14:20:08 GMT+08:00 2018
07-13 14:20:14.928 2811-3982/com.tomato.soapplication D/AlarmService: executed at Fri Jul 13 14:20:14 GMT+08:00 2018
07-13 14:20:20.962 2811-4001/com.tomato.soapplication D/AlarmService: executed at Fri Jul 13 14:20:20 GMT+08:00 2018
07-13 14:20:26.992 2811-4002/com.tomato.soapplication D/AlarmService: executed at Fri Jul 13 14:20:26 GMT+08:00 2018
07-13 14:20:33.024 2811-4019/com.tomato.soapplication D/AlarmService: executed at Fri Jul 13 14:20:33 GMT+08:00 2018