Question

我正在为推荐开发一款iPhone应用程序。它使用Parse来维护用户，联系人和推荐。它还使用Core Data与Parse同步并维护脱机活动。它有一个刷新方法，可以将Parse与Core Data同步。我试图找到一种方法，一旦用户离开应用程序，与Parse的同步在后台完成。我一直在applicationDidEnterBackground中使用简单的解析查询进行测试，但是无法正常工作。这是我使用的代码：

(void)applicationDidEnterBackground:(UIApplication *)application{

   self.backgroundTask = [application beginBackgroundTaskWithName:@"MyTask" expirationHandler:^{
       [application endBackgroundTask:self.backgroundTask];
       self.backgroundTask = UIBackgroundTaskInvalid;
   }];

   dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

       NSString *message = @"begin background task";
       NSDictionary *dict =  @{@"status": message};
       [[NSUserDefaults standardUserDefaults] setObject:dict forKey:kBeginBackgroundTaskWithNameKey];

       PFQuery *query = [PFQuery queryWithClassName:@"Referral"];

       [query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
           if (!error) {
               NSString *message = [NSString stringWithFormat:@"array has %lu objects", (unsigned long)objects.count];
               NSDictionary *dict =  @{@"status": message};
               [[NSUserDefaults standardUserDefaults] setObject:dict forKey:kBeginBackgroundTaskWithNameKey];

               [application endBackgroundTask:self.backgroundTask];
               self.backgroundTask = UIBackgroundTaskInvalid;
           }

       }];    
   });
}

我做错了什么？

Answer 1

我终于找到了解决问题的方法。我使用了Ray Wenderlich教程＆＃34; iOS中的背景模式＆＃34;作为指导http://www.raywenderlich.com/29948/backgrounding-for-ios。这里是AppDelegate的主要变化：

- （无效）parseSync {

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

    // Parse code ....

});


self.backgroundTask = [[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:^{
    NSLog(@"Background handler called. Not running background tasks anymore.");
    [[UIApplication sharedApplication] endBackgroundTask:self.backgroundTask];
    self.backgroundTask = UIBackgroundTaskInvalid;
}];

}

（void）applicationWillResignActive：（UIApplication *）application {

[self parseSync];

}

如何使用parse实现后台进程

1 个答案: