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I am doing following thing to load my image from server. But problem is that imageview is showing up 5-7 seconds later when alertview is closing.

how to solve this ? 

 - (void)showFullImage :(id) sender
   {    
   // for loading view
  self.loading_alert = [[UIAlertView alloc] initWithTitle:NSLocalizedString(@"LOADING",nil) message:nil delegate:self cancelButtonTitle:nil otherButtonTitles: nil];
  [self.loading_alert show];
  UIActivityIndicatorView *indicator = [[UIActivityIndicatorView alloc] initWithFrame: CGRectMake(125, 65, 30, 30)];
  indicator.activityIndicatorViewStyle = UIActivityIndicatorViewStyleWhiteLarge;

  //indicator.center = CGPointMake(loading_alert.bounds.size.width / 2, loading_alert.bounds.size.height - 50);
  [indicator startAnimating];
  [self.loading_alert addSubview:indicator];      

  self.image_url = [self.question_set valueForKey:@"image_url"];

//--------Asyncronously fetch image----------------------------------------
  NSURL *URL = [NSURL URLWithString:image_url];
  NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:URL cachePolicy:NSURLCacheStorageAllowedInMemoryOnly
                                                   timeoutInterval:60.0];
  [NSURLConnection sendAsynchronousRequest:request queue:[[NSOperationQueue alloc] init] completionHandler:^(NSURLResponse *response, NSData *data, NSError *error){

    NSLog(@"1",nil);
    imgView= [[UIView alloc] initWithFrame:CGRectMake(0,0,320,480) ];

     UIImage* queImage = [UIImage imageWithData:data];

UIImageView *iv = [[UIImageView alloc] initWithFrame:CGRectMake(0,42,320,420)];
iv.image = queImage;

[imgView addSubview:iv];    
[self.view addSubview:imgView];  

    //dismiss alert view on main thread
    dispatch_async(dispatch_get_main_queue(), ^(void) {
        // dismiss alert view...
         NSLog(@"2",nil);
        [self.loading_alert dismissWithClickedButtonIndex:0 animated:YES];
    });

}];    
}

Help will be appreciated.

4

3 に答える 3

1

GCD を忘れて、 NSURLConnection のsendAsynchronousRequest:queue:completionHandler:メソッド[NSOperationQueue mainQueue]のキュー パラメータを渡すことができるので、メイン スレッドとバックグラウンド スレッドについてあまり考える必要はありません。バックグラウンドで呼び出し要求を自動的に処理し、メイン スレッドでデータを返します。

以下は、コードがどのように見えるかです。

NSURL *URL = [NSURL URLWithString:image_url];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:URL cachePolicy:NSURLCacheStorageAllowedInMemoryOnly timeoutInterval:60.0];

// request is called asynchronously and response completion handler will be called on main thread
[NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *error){

    // do your whatever work here as you do normally, because it's in main thread
    NSLog(@"1",nil);
    imgView= [[UIView alloc] initWithFrame:CGRectMake(0,0,320,480) ];

    UIImage* queImage = [UIImage imageWithData:data];

    UIImageView *iv = [[UIImageView alloc] initWithFrame:CGRectMake(0,42,320,420)];
    iv.image = queImage;

    [imgView addSubview:iv];
    [self.view addSubview:imgView];
}
于 2015-07-01T10:10:11.553 に答える
0

バックグラウンド キューで画像をダウンロードし、メイン キューで UI の更新を行う必要があります。

このようにGCDを使用すると、

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), ^{

        NSURL *URL = [NSURL URLWithString:image_url];
  NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:URL cachePolicy:NSURLCacheStorageAllowedInMemoryOnly
                                                   timeoutInterval:60.0];
  [NSURLConnection sendAsynchronousRequest:request queue:[[NSOperationQueue alloc] init] completionHandler:^(NSURLResponse *response, NSData *data, NSError *error){

    NSLog(@"1",nil);


     UIImage* queImage = [UIImage imageWithData:data];

            dispatch_async(dispatch_get_main_queue(), ^{

                imgView= [[UIView alloc] initWithFrame:CGRectMake(0,0,320,480) ];
                if([receivedView isKindOfClass:[UIImageView class]])
                {
UIImageView *iv = [[UIImageView alloc] initWithFrame:CGRectMake(0,42,320,420)];
iv.image = queImage;

[imgView addSubview:iv];    
[self.view addSubview:imgView];  
                }
 // dismiss alert view...
         NSLog(@"2",nil);
        [self.loading_alert dismissWithClickedButtonIndex:0 animated:YES];

            });


        }


    });
于 2013-09-30T12:25:00.297 に答える