UIAlertView需要时间显示

我想在按下按钮时显示警报视图。显示它，但在屏幕上显示需要很长时间。这里要说的是，我在按下按钮调用该函数：UIAlertView需要时间显示

-(void)saveAndClose:(id)sender 
{ 
    waitForOCR=[[UIAlertView alloc] initWithTitle:@"Processing..." message:@"Please wait." delegate:self cancelButtonTitle:@"Cancel" otherButtonTitles:nil, nil]; 
    waitForOCR.delegate=self; 
    [waitForOCR show]; 
    if(!isCancelled){ 
    NSMutableArray *dateSaved=[[NSMutableArray alloc] initWithArray:[[NSUserDefaults standardUserDefaults] arrayForKey:@"dateCaptured"]]; 
    NSDateFormatter *dateText=[[NSDateFormatter alloc] init]; 
    [dateText setDateFormat:@"yyyy-MM-dd"]; 
    NSDate *now=[NSDate date]; 
    NSString *dateValue=[dateText stringFromDate:now]; 
    [dateSaved addObject:dateValue]; 
    NSMutableArray *timeSaved=[[NSMutableArray alloc] initWithArray:[[NSUserDefaults standardUserDefaults] arrayForKey:@"timeCaptured"]]; 
    NSDateFormatter *timeText=[[NSDateFormatter alloc] init]; 
    [timeText setDateFormat:@"HH:mm:ss"]; 
    NSString *timeValue=[timeText stringFromDate:now]; 
    [timeSaved addObject:timeValue]; 
    [[NSUserDefaults standardUserDefaults] setObject:dateSaved forKey:@"dateCaptured"]; 
    [[NSUserDefaults standardUserDefaults] setObject:timeSaved forKey:@"timeCaptured"]; 
    [dateSaved release]; 
    dateSaved=nil; 
    [timeSaved release]; 
    timeSaved=nil; 
    int counter = [[NSUserDefaults standardUserDefaults] integerForKey:@"LaunchesCounter"]; 
    counter++; 
    [[NSUserDefaults standardUserDefaults] setInteger:counter forKey:@"LaunchesCounter"]; 
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); 
    NSString *documentsDirectory = [paths objectAtIndex:0]; 
    NSString *localFilePath = [documentsDirectory stringByAppendingPathComponent:[NSString stringWithFormat:@"image%d.png",counter]]; 
    NSData *thedata = [[NSData alloc] initWithData:UIImagePNGRepresentation(imageToCrop)]; 
    [thedata writeToFile:localFilePath atomically:YES]; 
    [thedata release]; 

    [NSThread detachNewThreadSelector:@selector(processOcrAt:) toTarget:self withObject:[self.imageCropper getCroppedImage]]; 
    } 
    else{ 
     isCancelled=FALSE; 
    } 

}

正如你可以看到，我在函数开始显示UIAlerView。但显示时间过长。任何建议来解决这个问题？感谢问候 Idrees

来源

2012-10-02 Idrees Ashraf

当然，因为你正在写在主线程'[海图将writeToFile：localFilePath原子：YES]到文件;' – Nekto

但写入文件之前，我显示UIAlertView中。它显示，但过了一段时间。 –

警报只会在当前运行循环的末尾显示出来，所以你所做的一切之后“显示”，会实际发生之前。请注意，将代码移到背景中会是一个好主意，因为否则它会阻止主线程并使应用程序无法响应。

来源

2012-10-02 06:40:14 Eiko

100％正确答案:)非常感谢你 –

将[alertview show];移动到主队列中。如果您打算显示来自异步回调的警报，这很有用。

dispatch_async(dispatch_get_main_queue(), ^{ 
    [alertview show]; 
});

来源

2014-07-16 17:39:51

嘿谢谢！这只是解决了我的问题。 –

UIAlertView需要时间显示

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