Android 轮询最佳实践 Service + AlarmManager

虽然alarm的意思是闹钟，而且在原生android自带的闹钟应用中AlarmManager也确实非常重要，但并不代表AlarmManager只是用来做闹钟应用的，作为一个一种系统级别的提示服务，肯定应该有着非常重要的地位，实际上android中很多东西都可以利用AlarmManager来实现。

AlarmManager在特定的时刻为我们广播一个指定的Intent。简单的说就是我们设定一个时间，然后在该时间到来时，AlarmManager为我们广播一个我们设定的Intent。这个intent可以指向一个activity，也可以指向一个service。

下面就是使用alarm定时调用service实现轮询的实现方法：

一、新建轮询工具类PollingUtils.java

 

public class PollingUtils {
    //开启轮询服务
    public static void startPollingService(Context context, int seconds, Class<?> cls,String action) {
        //获取AlarmManager系统服务
        AlarmManager manager = (AlarmManager) context
                .getSystemService(Context.ALARM_SERVICE);
                                                                                                                                                                                                                                       
        //包装需要执行Service的Intent
        Intent intent = new Intent(context, cls);
        intent.setAction(action);
        PendingIntent pendingIntent = PendingIntent.getService(context, 0,
                intent, PendingIntent.FLAG_UPDATE_CURRENT);
                                                                                                                                                                                                                                       
        //触发服务的起始时间
        long triggerAtTime = SystemClock.elapsedRealtime();
                                                                                                                                                                                                                                       
        //使用AlarmManger的setRepeating方法设置定期执行的时间间隔（seconds秒）和需要执行的Service
        manager.setRepeating(AlarmManager.ELAPSED_REALTIME, triggerAtTime,
                seconds * 1000, pendingIntent);
    }
    //停止轮询服务
    public static void stopPollingService(Context context, Class<?> cls,String action) {
        AlarmManager manager = (AlarmManager) context
                .getSystemService(Context.ALARM_SERVICE);
        Intent intent = new Intent(context, cls);
        intent.setAction(action);
        PendingIntent pendingIntent = PendingIntent.getService(context, 0,
                intent, PendingIntent.FLAG_UPDATE_CURRENT);
        //取消正在执行的服务
        manager.cancel(pendingIntent);
    }
}

 二、构建轮询任务执行PollingService.java

 

public class PollingService extends Service {
    public static final String ACTION = "com.ryantang.service.PollingService";
                                                                                                                                                                                                                           
    private Notification mNotification;
    private NotificationManager mManager;
    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }
    @Override
    public void onCreate() {
        initNotifiManager();
    }
                                                                                                                                                                                                                           
    @Override
    public void onStart(Intent intent, int startId) {
        new PollingThread().start();
    }
    //初始化通知栏配置
    private void initNotifiManager() {
        mManager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
        int icon = R.drawable.ic_launcher;
        mNotification = new Notification();
        mNotification.icon = icon;
        mNotification.tickerText = "New Message";
        mNotification.defaults |= Notification.DEFAULT_SOUND;
        mNotification.flags = Notification.FLAG_AUTO_CANCEL;
    }
    //弹出Notification
    private void showNotification() {
        mNotification.when = System.currentTimeMillis();
        //Navigator to the new activity when click the notification title
        Intent i = new Intent(this, MessageActivity.class);
        PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, i,
                Intent.FLAG_ACTIVITY_NEW_TASK);
        mNotification.setLatestEventInfo(this,
                getResources().getString(R.string.app_name), "You have new message!", pendingIntent);
        mManager.notify(0, mNotification);
    }
    /**
     * Polling thread
     * 模拟向Server轮询的异步线程
     * @Author Ryan
     * @Create 2013-7-13 上午10:18:34
     */
    int count = 0;
    class PollingThread extends Thread {
        @Override
        public void run() {
            System.out.println("Polling...");
            count ++;
            //当计数能被5整除时弹出通知
            if (count % 5 == 0) {
                showNotification();
                System.out.println("New message!");
            }
        }
    }
                                                                                                                                                                                                                           
    @Override
    public void onDestroy() {
        super.onDestroy();
        System.out.println("Service:onDestroy");
    }
}

 三、AndroidManifest.xml 配置

 

<!--服务配置-->
        <service
            android:name="com.ryantang.service.PollingService"
            android:exported="false">
            <intent-filter>
                <action android:name="com.ryantang.service.PollingService" />
            </intent-filter>
        </service>

 四、在MainActivity.java中开启和停止PollingService

public class MainActivity extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //Start polling service
        System.out.println("Start polling service...");
        PollingUtils.startPollingService(this, 5, PollingService.class, PollingService.ACTION);
    }
                                                                                                                                                                                                                   
    @Override
    protected void onDestroy() {
        super.onDestroy();
        //Stop polling service
        System.out.println("Stop polling service...");
        PollingUtils.stopPollingService(this, PollingService.class, PollingService.ACTION);
    }
}