攀升·Uranus


Something Different,Something New
数据加载中……

iOS 4后台多任务

今天调查了下IOS 4.0 支持的多任务的事宜,系统是4.2 初步结果如下:

 

Ios 4.0 多任务不是传统意义上的多任务。只是把程序的状态保存起来,程序挂起。因为Apple还没准备好多任务同时运行,

主要是因为batterymemory这两个问题还没有解决。

 

现在IOS 4多任务支持的类型(官网):  

§  Background audio

§  Voice over IP

§  Background location 

§  Push notifications

§  Local notifications

§  Task finishing - If your app is in mid-task when your customer leaves it, the app can now keep running to finish the task.

§  Fast app switching - All developers should take advantage of fast app switching, which allows users to leave your app and come right back to where they were when they left - no more having to reload the app.

 

我使用的是Task finishing 既当用户挂起程序时,如果还有task没完成,可以把改task完成。

 

但这个是有限制的,时间的限制,就是说你的后台程序不能执行超过某个时间。

我刚才打log看了,系统返回500s,既是8分钟,8分钟如果还没执行完,就会自动把我们程序结束。


代码如下

#pragma mark -

#pragma mark Background Task Handle

- (void)applicationDidEnterBackground:(UIApplication *)application {


// Request permission to run in the background. Provide an 

// expiration handler in case the task runs long.

NSAssert(self->bgTask == UIBackgroundTaskInvalid, nil);

self->bgTask = [application beginBackgroundTaskWithExpirationHandler: ^{

// Synchronize the cleanup call on the main thread in case

// the task catully finished at around the same time.

dispatch_async(dispatch_get_main_queue(), ^{

if (UIBackgroundTaskInvalid != self->bgTask) {

[application endBackgroundTask:self->bgTask];

self->bgTask = UIBackgroundTaskInvalid;

}

});

}];

// Start the long-running task and return immediately.

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), 

  ^{

  // Do the work assoicated with the task.

  for(int i = 0; i  < 1000; i++) {

                                                  //request network.

                                                  NSLog(@"hahah %d, Time Remain = %f", i, [application backgroundTimeRemaining]);

                                           }

  // Synchronize the cleanup all on the main thread in case

  // the task catully finished at around the same time. 

  dispatch_async(dispatch_get_main_queue(), ^{

  

  if (UIBackgroundTaskInvalid != self->bgTask) {


  [application endBackgroundTask:self->bgTask];

  self->bgTask = UIBackgroundTaskInvalid;

  }

  });

  });

}

#pragma mark -

#pragma mark Local Notifications

- (void)scheduleAlarmForDate:(NSDate *)theDate {

UIApplication *app = [UIApplication sharedApplication];

NSArray *oldNotifications = [app scheduledLocalNotifications];

// Clear out the old notification before scheduling a new one.

if (0 < [oldNotifications count]) {

[app cancelAllLocalNotifications];

}

// Create a new notification

UILocalNotification *alarm = [[UILocalNotification alloc] init];

if (alarm) {


alarm.fireDate = theDate;

alarm.timeZone = [NSTimeZone defaultTimeZone];

alarm.repeatInterval = 0;

alarm.soundName = @"ping.caf";//@"default";

alarm.alertBody = [NSString stringWithFormat:@"Time to wake up!Now is\n[%@]", 

  [NSDate dateWithTimeIntervalSinceNow:10]];

[app scheduleLocalNotification:alarm];

[alarm release];

}

有问题留言,或者微博:http://t.sina.com.cn/passionuranus

posted on 2011-01-06 11:58 攀升 阅读(993) 评论(0)  编辑 收藏 引用 所属分类: iOS


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