轮询请求

开始使用AlarmManager+Service+Thread来实现我们的轮询服务吧！

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IntentIntent 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Servicemanager.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;@Overridepublic IBinder onBind(Intent intent) {return null;}@Overridepublic void onCreate() {initNotifiManager();}@Overridepublic 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Notificationprivate void showNotification() {mNotification.when = System.currentTimeMillis();//Navigator to the new activity when click the notification titleIntent 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 {@Overridepublic 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!");}}}@Overridepublic void onDestroy() {super.onDestroy();System.out.println("Service:onDestroy");}}

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

 

 

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

四、运行效果

运行工程后可以在控制台输出看到，每隔5s就发出一个通知，退出Activity时，轮询服务就停止了，达到了我们事先期望的效果，并且锁屏后很长一段时间也不会停止服务，因为AlarmManager是系统及服务。Demo效果如下图：

 

在手机上我们可以看到弹出的通知信息，点击通知则进到消息界面：

                            

当进入消息详情Activity时，顶部状态栏的消息通知就会取消，使用如下方式也可以取消状态栏顶部的消息通知显示：

 

NotificationManager manager = (NotificationManager)getSystemService(Context.NOTIFICATION_SERVICE);manager.cancelAll();