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

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);    }}

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