解决 iPhone 中分离线程的等待情况？

Question

我正在使用私人 MBProgressHUD

现在我正在使用我正在调用 addrecord 服务的添加按钮上的指示器视图。

UIWindow *window = [UIApplication sharedApplication].keyWindow;
HUD = [[MBProgressHUD alloc] initWithWindow:window];

// Add HUD to screen
[window addSubview:HUD];

// Regisete for HUD callbacks so we can remove it from the window at the right time
HUD.delegate = self;

// Show the HUD while the provided method executes in a new thread
[HUD showWhileExecuting:@selector(addingToFavorites) onTarget:self withObject:nil animated:YES];

添加到收藏夹方法：

NSURL *url = [NSURL URLWithString:urlstring];

NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:url cachePolicy:NSURLRequestReloadIgnoringCacheData timeoutInterval:10.0];
[request setHTTPMethod:@"GET"];
//[request setTimeoutInterval:10];
//NSURLResponse *response = nil;
//      NSError *error = nil;
[[NSURLCache sharedURLCache] setMemoryCapacity:0];
[[NSURLCache sharedURLCache] setDiskCapacity:0];
NSData *data1= [NSURLConnection sendSynchronousRequest:request          
                                     returningResponse:nil error:nil];

if(data1 == nil)
{
    doneFlag = NO;
    UIAlertView *alert = [[UIAlertView alloc]initWithTitle:@"Alert"
                                                   message:@"The network is not available.\n Please check the Internet connection."
                                                  delegate:nil
                                         cancelButtonTitle:@"OK"
                                         otherButtonTitles:nil];
    [alert show];
    [alert release];

}
else
{
    doneFlag = YES;

    UIAlertView *alert = [[UIAlertView alloc]initWithTitle:@"Confirmation"
                                                   message:@"Added To favorites" 
                                                  delegate:nil
                                         cancelButtonTitle:@"OKAY"
                                         otherButtonTitles:nil];
    [alert show];
    alert = nil;
    [alert release];        
}

[request release];

这一切都运行良好，除了仪器泄漏了 uialertview 可能与 mbprogreshud 冲突。

所以我想从调用方法中删除警报并将其放入调用者方法中，如下所示：

现在的调用者方法：

UIWindow *window = [UIApplication sharedApplication].keyWindow;
HUD = [[MBProgressHUD alloc] initWithWindow:window];

// Add HUD to screen
[window addSubview:HUD];

// Regisete for HUD callbacks so we can remove it from the window at the right time
HUD.delegate = self;

// Show the HUD while the provided method executes in a new thread
[HUD showWhileExecuting:@selector(addingToFavorites) onTarget:self withObject:nil animated:YES];
//it should wait for the above line to be executing   ******* then to exexute the be //below condition but how ?

if (doneFlag == NO) {
    UIAlertView *alert = [[UIAlertView alloc]initWithTitle:@"Alert"
                                                   message:@"The network is not available.\n Please check the Internet connection."
                                                  delegate:nil
                                         cancelButtonTitle:@"OK"
                                         otherButtonTitles:nil];
    [alert show];
    [alert release];
} else {
    [favoritesButton setTitle:@"Remove" forState:UIControlStateNormal];
    UIAlertView *alert = [[UIAlertView alloc]initWithTitle:@"Confirmation"
                                                   message:@"Added To favorites" 
                                                  delegate:nil
                                         cancelButtonTitle:@"OKAY"
                                         otherButtonTitles:nil];
    [alert show];
    alert = nil;
    [alert release];        
}

添加到收藏夹方法：

NSURL *url = [NSURL URLWithString:urlstring];

NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:url cachePolicy:NSURLRequestReloadIgnoringCacheData timeoutInterval:10.0];
[request setHTTPMethod:@"GET"];
//[request setTimeoutInterval:10];
//NSURLResponse *response = nil;
//      NSError *error = nil;
[[NSURLCache sharedURLCache] setMemoryCapacity:0];
[[NSURLCache sharedURLCache] setDiskCapacity:0];
NSData *data1= [NSURLConnection sendSynchronousRequest:request          
                                     returningResponse:nil error:nil];

if(data1 == nil)
{
    doneFlag = NO;
}
else
{
    doneFlag = YES;
}

[request release];

在启动 Progresshud 线程时分离类似这样的内容：

[NSThread detachNewThreadSelector:@selector(launchExecution) toTarget:self withObject:nil]

现在我的问题是如果我遵循第一种情况。我怎样才能确保alertview泄漏不会发生

或者如果我遵循第二种情况我怎样才能保证if条件将在完成执行此行后执行：

[HUD showWhileExecuting:@selector(addingToFavorites) onTarget:self withObject:nil animated:YES];

Answer 1

对于第一种情况，从应用程序主线程以外的线程进行 UI 更新通常是一个坏主意。 UIKit 不是线程安全的，执行线程 UI 更新可能会导致各种奇怪的事情发生。现在，我不确定这是否是泄漏的原因，但我会避免在addingToFavorites 中显示 UIAlertView。使用performSelectorOnMainThread 或下面描述的第二种方案。

对于第二种情况，将 showWhileExecuting 调用下方的所有内容移至 hudWasHidden 委托方法。此时您可以确定您的代码已完全执行并且doneFlag已设置。

要使用performSelectorOnMainThread，请定义一个新方法，将代码放入其中，然后调用performSelectorOnMainThread。

即，

- (void)showAlert {
    UIAlertView *alert = [[UIAlertView alloc]initWithTitle:@"Alert" message:@"The network is not available.\n Please check the Internet connection." delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
    [alert show];
    [alert release];
}

打电话，

[self performSelectorOnMainThread:@selector(showAlert) withObject:nil waitUntilDone:NO];

但我会选择第二种情况。

Answer 2

尽管有其他答案，您还是使用以下序列创建了 UIAlertView 泄漏：

[alert show];
alert = nil;
[alert release];

应交换最后两行：

[alert show];
[alert release];
alert = nil;