[英]issue with using performSelector for activityIndicator while calling web service - IOS
我正在嘗試使performSelector在進行Web服務調用時將活動指示器加載到單獨的線程上。 問題是“返回parsedData;” 未在fetchJSON:中設置。 但是,當我在getData:方法中打印parsedData時,它又恢復正常了。 我假設在performSelector完成獲取數據之前正在執行返回。 有什么方法可以讓fetchJSON:方法在返回parsedData之前等待performSelector完成嗎?
-(void)showActivityIndicator
{
CGRect frame = CGRectMake(0.0, 0.0, 125.0, 125.0);
loading = [[UIActivityIndicatorView alloc] initWithFrame:frame];
[loading setActivityIndicatorViewStyle:UIActivityIndicatorViewStyleWhiteLarge];
[loading hidesWhenStopped];
//loading.center=[self tableView].center;
[loading startAnimating];
[loading sizeToFit];
loading.autoresizingMask = (UIViewAutoresizingFlexibleLeftMargin |
UIViewAutoresizingFlexibleRightMargin |
UIViewAutoresizingFlexibleTopMargin |
UIViewAutoresizingFlexibleBottomMargin);
// initing the bar button
//UIBarButtonItem *loadingView = [[UIBarButtonItem alloc] initWithCustomView:loading];
//loadingView.target = self;
[loadingView addSubview:loading];
}
- (NSDictionary *)fetchJSON:(NSString *)urlString
{
NSMutableString *domain = [[NSMutableString alloc] initWithString:@"http://www.blablabla.com/dev/"];
[domain appendString:urlString];
//NSLog(@"%@", domain);
NSURL *url = [NSURL URLWithString:domain];
NSURLRequest *req = [NSURLRequest requestWithURL:url];
[self showActivityIndicator];
[self performSelector:@selector(getData:) withObject:req afterDelay:0.0];
//[self performSelectorOnMainThread:@selector(getData:) withObject:req waitUntilDone:YES];
return parsedData;
}
-(IBAction)getData:(id)sender
{
NSURLResponse* response = nil;
NSData *data = [NSURLConnection sendSynchronousRequest:sender returningResponse:&response error:nil];
parsedData = [NSJSONSerialization
JSONObjectWithData:data
options:NSJSONReadingMutableLeaves
error:nil];
NSLog(@"GET DATA %@", parsedData);
[loading stopAnimating];
loading = nil;
}
“將活動指示器加載到單獨線程上的performSelector”
??
通常,UIKit不是線程安全的。
在注釋掉的代碼和令人困惑的方法聲明之間(為什么要使用getData:IBAction?是從代碼內部調用還是作為控件的操作調用它?),我確實在這里缺少想要執行的操作的上下文。
您可以先概述一下您要完成的工作以及此代碼如何適應該情況嗎?
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