服务的最佳实践——后台执行的定时任务

创建一个ServiceBestPractice项目，然后新增一个LongRunningService类，代码如下所示：

package com.example.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 LongRunningService extends Service{

    @Override
    public IBinder onBind(Intent intent) {
        // TODO Auto-generated method stub
        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 = 60 * 60 * 1000;  //这是一小时的毫秒数
        long triggerAtTime = SystemClock.elapsedRealtime() + anHour;
        Intent i = new Intent(this, AlarmReceiver.class);
        PendingIntent pi = PendingIntent.getBroadcast(this, 0, i, 0);
        manager.set(AlarmManager.ELAPSED_REALTIME_WAKEUP, triggerAtTime, pi);
        return super.onStartCommand(intent, flags, startId);
    }

}

新建一个AlarmReceiver类，并让它继承自BroadcastReceiver，代码如下所示：

package com.example.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, LongRunningService.class);
        context.startService(i);
    }

}

接下来我们需要在打开程序的时候启动一次LongRunningService，修改mainActivity中的代码，如下所示：

package com.example.servicebestpractice;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Intent i = new Intent(this, LongRunningService.class);
        startService(i);
    }

}

最后别忘了，我们用到的广播接收器和服务都要在AndroidManifest.xml中注册才行，代码如下所示：

        <service android:name=".LongRunningService">
        </service>
        <receiver android:name=".AlarmReceiver">
        </receiver>