Question

我在我的项目中使用MBPogressHUD，并且我已正确设置了所有库，导入等。但是，我遇到的崩溃似乎与选择器方法有关。我有一个名为“getInfo”的方法，它基本上连接到服务器。按下按钮即可触发HUD。在对崩溃进行一些研究后，人们说将初始化放在viewWillAppear中，因为一些初始化时间占用了实际执行任务并显示HUD所需的时间。

    -(void)viewWillAppear:(BOOL)animated {
    connectionHUD = [[MBProgressHUD alloc]initWithView:self.view];
    [self.view addSubview:connectionHUD];
    connectionHUD.labelText = @"Connecting";
    connectionHUD.mode = MBProgressHUDModeAnnularDeterminate;    
}

-(IBAction)connectButton:(id)sender {


    [connectionHUD showWhileExecuting:@selector(getInfo) onTarget:self withObject:nil animated:YES];
}

崩溃：

Tried to obtain the web lock from a thread other than the main thread or the web thread. This may be a result of calling to UIKit from a secondary thread. Crashing now...



-(void)getInfo {

NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
UserPi *newPi = [[UserPi alloc]init];
newPi.passWord = self.passTextField.text;
[defaults setObject:self.passTextField.text forKey:@"password"];
newPi.userName = self.userTextField.text;
[defaults setObject:self.userTextField.text forKey:@"username"];
newPi.ipAddress = self.ipTextField.text;
[defaults setObject:self.ipTextField.text forKey:@"ip"];
[newPi connectToServer];
NSString* newAddress = [newPi returnIP];
self.connected = newPi.connected;
[self.delegate sendIP:newAddress];
[self.delegate isConnected:self.connected];
[defaults synchronize];
[self.navigationController popToRootViewControllerAnimated:YES];


}

完整错误：

bool _WebTryThreadLock(bool), 0x7327740: Tried to obtain the web lock from a thread other than the main thread or the web thread. This may be a result of calling to UIKit from a secondary thread. Crashing now...
1   0x3a1ffe9 WebThreadLock
2   0x4ec8ff -[UITextRangeImpl isEmpty]
3   0x4ec4db -[UITextRange(UITextInputAdditions) _isCaret]
4   0x48e7b6 -[UITextSelectionView setCaretBlinks:]
5   0x328f79 -[UIKeyboardImpl setCaretBlinks:]
6   0x3185bc -[UIKeyboardImpl setDelegate:force:]
7   0x3184ae -[UIKeyboardImpl setDelegate:]
8   0x53ff65 -[UIPeripheralHost(UIKitInternal) _reloadInputViewsForResponder:]
9   0x29215b -[UINavigationController navigationTransitionView:didStartTransition:]
10  0x418961 -[UINavigationTransitionView transition:fromView:toView:]
11  0x418658 -[UINavigationTransitionView transition:toView:]
12  0x294651 -[UINavigationController _startTransition:fromViewController:toViewController:]
13  0x29489b -[UINavigationController _startDeferredTransitionIfNeeded:]
14  0x295dc6 _popViewControllerNormal
15  0x296065 -[UINavigationController _popViewControllerWithTransition:allowPoppingLast:]
16  0xe6124b0 -[UINavigationControllerAccessibility(SafeCategory) _popViewControllerWithTransition:allowPoppingLast:]
17  0x2961a8 -[UINavigationController popViewControllerWithTransition:]
18  0x2965b9 -[UINavigationController popToViewController:transition:]
19  0x296257 -[UINavigationController popToRootViewControllerWithTransition:]
20  0x2961de -[UINavigationController popToRootViewControllerAnimated:]
21  0x4868 -[ConnectionViewController getInfo]
22  0x126a6b0 -[NSObject performSelector:withObject:]
23  0x8657 -[MBProgressHUD launchExecution]
24  0xca1805 -[NSThread main]
25  0xca1764 __NSThread__main__
26  0x95108ed9 _pthread_start
27  0x9510c6de thread_start

Answer 1

大多数UIKit框架方法都不是线程安全的，必须始终在主线程上调用。在您的情况下，getInfo正在从后台线程调用UIKit API，-[UINavigationController popToRootViewControllerAnimated:]

MBProgressHUD会导致您在后台线程上调用getInfo。请参阅方法showWhileExecuting:onTarget:withObject:animated:。

尝试使用GCD在主线程上调度UIKit方法：

-(void)getInfo {    
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    UserPi *newPi = [[UserPi alloc]init];
    newPi.passWord = self.passTextField.text;
    [defaults setObject:self.passTextField.text forKey:@"password"];
    newPi.userName = self.userTextField.text;
    [defaults setObject:self.userTextField.text forKey:@"username"];
    newPi.ipAddress = self.ipTextField.text;
    [defaults setObject:self.ipTextField.text forKey:@"ip"];
    [newPi connectToServer];
    NSString* newAddress = [newPi returnIP];
    self.connected = newPi.connected;     
    // **NOTE**   
    // PS: self.delegate methods should not call UIKit methods
    // if they do, then move them into the main thread callback block
    [self.delegate sendIP:newAddress];
    [self.delegate isConnected:self.connected];
    [defaults synchronize];

    // Do UI work on main thread.
    dispatch_async(dispatch_get_main_queue(), ^{
        [self.navigationController popToRootViewControllerAnimated:YES];    
    });
}

Answer 2

您是否在主线程上调用-getInfo？必须在主线程上调用[self.navigationController popToRootViewControllerAnimated:YES];。

Answer 3

问题是您的getInfo方法会调用UI，如下所示：

[self.navigationController popToRootViewControllerAnimated:YES];

...但你是在后台线程上运行它。

-showWhileExecuting: onTarget: withObject: animated:的重点是它会在后台线程中自动运行您的代码。

因此，您需要以与在后台线程中手动运行时相同的方式保护事物。

因此，您的方法中的任何UI代码都需要使用performSelectorOnMainThread:和朋友，或dispatch_async或其他方法来执行相同操作。

在这种特殊情况下，您希望调度一个采用原始（BOOL）参数的方法，这意味着您不能只使用-performSelectorOnMainThread: withObject:。但是你也可能想要等到它完成，这意味着你不能只使用dispatch_async。

你可以编写一个不带参数的包装器方法：

- (void)popNavigationControllerToRoot {
    [self.navigationController popToRootViewControllerAnimated:YES];
}

......然后：

[self performSelectorOnMainThread:@selector(popNavigationControllerToRoot)
                    waitUntilDone:YES];

或者您可以使用NSInvocation周围的包装，就像那些here：

[[self.navigationController dd_invokeOnMainThreadAndWaitUntilDone:YES] 
 popToRootViewControllerAnimated:YES];

尝试使用MBProgressHud后可怕的崩溃

3 个答案: