Question

当nsstring获取URL内容时，我的应用程序崩溃了。

website = [NSString stringWithFormat:@"hidden."]; 
contents = [NSString stringWithContentsOfURL:[NSURL URLWithString:website] encoding:NSUTF8StringEncoding error:nil];

崩溃日志是：

void _WebThreadLockFromAnyThread(bool), 0x865cc40: Obtaining the web lock from a thread other than the main thread or the web thread. UIKit should not be called from a secondary thread.
2012-07-10 11:15:17.654 MyApplication[1505:19407] OK // some output
2012-07-10 11:15:17.660 MyApplication[1505:19407] bool _WebTryThreadLock(bool), 0x865cc40: 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   WebThreadLock
2   -[UITextRangeImpl isEmpty]
3   -[UITextRange(UITextSelectionAdditions) _isCaret]
4   -[UITextSelectionView setCaretBlinks:]
5   -[UIKeyboardImpl setCaretBlinks:]
6   -[UIKeyboardImpl setDelegate:force:]
7   -[UIKeyboardImpl setDelegate:]
8   -[UIPeripheralHost(UIKitInternal) _reloadInputViewsForResponder:]
9   -[UIResponder(UIResponderInputViewAdditions) reloadInputViews]
10  -[UIResponder(Internal) _windowBecameKey]
11  -[UITextField _windowBecameKey]
12  -[UIWindow makeKeyWindow]
13  -[UIWindow makeKeyAndVisible]
14  -[MyApplicationAppDelegate checkLogin]
15  -[NSThread main]
16  __NSThread__main__
17  _pthread_start
18  thread_start

使用[self performSelectorInBackground:@selector(checkLogin) withObject:nil];中的IBAction来调用代码。我做错了什么？

（Xcode 4.3，Mac OS X Lion，iPhone模拟器5.1）

Answer 1

根据该错误消息，您尝试从后台线程更新UIKit对象，并且只能从主线程更新UI。

相反，使用self performSelectorOnMainThread回调主线程，使用您的网络电话返回时收到的任何信息更新您的用户界面。

从您的主要帖子：

[self performSelectorInBackground:@selector(checkLogin) withObject:nil];

在后台：

- (void)checkLogin {
    // Do web stuff
    ...

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

- (void)updateUI {
    [statusLabel setText:@"Done!"];
}

Answer 2

尝试使用

      - (id)performSelector:(SEL)aSelector withObject:(id)anObject.

我的应用程序在尝试获取URL的内容时崩溃了

2 个答案: