iPhone/Objective-C的：如何從計時器

修改的UILabel我有以下定時器：iPhone/Objective-C的：如何從計時器

uploadGPS_timer=[NSTimer scheduledTimerWithTimeInterval:5.0 target:self selector:@selector(uploadGPS_tick:) userInfo:nil repeats:YES]; 
[self uploadGPS_tick:nil];

這裏是回調：uploadGPS_tick（）：

-(void)uploadGPS_tick:(NSTimer*)timer{ 
    if(!lat || !lng){ 
     //do nothing 
    }else{ 
     NSString *urlStr=[[NSString alloc] initWithFormat:@"http://www.example.com/ajax/updateCoords.php"]; 
     NSURL *url=[NSURL URLWithString:urlStr]; 

     __block ASIFormDataRequest *request=[[ASIFormDataRequest alloc ]initWithURL:url]; 
     [request setPostValue:lat forKey:@"lat"]; 
     [request setPostValue:lng forKey:@"lng"]; 
     NSLog(@"EOH: %@",lat); 
     [request setDelegate:self]; 
     [request setCompletionBlock:^{ 
      NSString *response=[request responseString]; 
      NSLog(@"%@",response); 

      if([response isEqualToString:@"LO"]){ 
       [self.navigationItem setBackBarButtonItem:nil]; 
       DriverLogin *x= [[DriverLogin alloc] initWithNibName:nil bundle:nil]; 
       [[self navigationController]pushViewController:x animated:NO]; 
      } 

      SBJsonParser *parser=[[SBJsonParser alloc]init]; 
      NSMutableDictionary *obj=[[NSMutableDictionary alloc]init ]; 
      obj=[[parser objectWithString:[request responseString] error:nil]retain]; 

      credits.text=[[obj objectForKey:@"credits"] stringValue]; //this won't show... 
      creditsUsed.text=[[obj objectForKey:@"creditsUsed"] stringValue]; //this won't show... 
      NSInteger timeLeftSecs=[[obj objectForKey:@"creditTimeLeft"] intValue]; 
      NSInteger timeLeftMins=(int)(timeLeftSecs/60); 
      creditTimeLeft.text=[[NSString alloc]initWithFormat:@"%d",timeLeftMins]; //this won't show... 

      NSLog(@"xxx:%@",obj); 

     }]; 
     [request setFailedBlock:^{ 
      NSError *error =[request error]; 
      NSLog(@"%@",error); 
      //do nothing 
     }]; 
     [request startAsynchronous]; 
    } 
}

正如你所看到的，每五秒鐘，一個JSON對象從服務器發送。然後分析此JSON對象，並根據此JSON數據設置三個UILabels。

我遇到的麻煩是UILabels沒有得到他們的文本集！儘管我可以在調試器中清楚地看到NSLog(@"xxx:%@",obj);。 UILabel在.xib中正確連接。

任何幫助非常感謝。

來源

2012-07-23 Eamorr

UI元素只能從主循環更新。你確定你正在UI更新代碼的主循環上運行嗎？ – 2012-07-23 08:43:41

嗯。我不知道。如何檢查這個？非常感謝， – Eamorr 2012-07-23 08:44:26

'ASIHTTPRequest'總是在主線程上回調。 – Lvsti 2012-07-23 08:48:16

你應該從主線程做到這一點。將標籤文本分配替換爲以下代碼：

dispatch_async(dispatch_get_main_queue(), ^{ 
    creditTimeLeft.text=[NSString stringWithFormat:@"%d",timeLeftMins]; 

});

來源

2012-07-23 10:50:07

iPhone/Objective-C的：如何從計時器

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