我有以下代码发出 HTTP 请求，然后将结果输出到 UITextView:

@IBOutlet var echoLog: UITextView!

@IBAction func sendEcho(sender: AnyObject) {
    let callback = { (textString: String) -> Void in
        self.echoLog.text = textString // App crashes here :(
    }
    HTTPRequest("http://localhost/echo", ["echo": "Echo!"], callback)
}

但是当我调用 sendEcho 时，应用程序崩溃并出现此错误:

2014-07-28 20:58:22.218 AppName[10463:144343] *** Assertion failure in void _UIPerformResizeOfTextViewForTextContainer(NSLayoutManager *, UIView<NSTextContainerView> *, NSTextContainer *, NSUInteger)(), /SourceCache/UIFoundation_Sim/UIFoundation-364/UIFoundation/TextSystem/NSLayoutManager_Private.m:1547
2014-07-28 20:58:22.231 AppName[10463:144343] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Only run on the main thread!'
*** First throw call stack:
(
    0   CoreFoundation                      0x00496ca6 __exceptionPreprocess + 182
    1   libobjc.A.dylib                     0x01df08bf objc_exception_throw + 44
    2   CoreFoundation                      0x00496b3a +[NSException raise:format:arguments:] + 138
    3   Foundation                          0x00904d2e -[NSAssertionHandler handleFailureInFunction:file:lineNumber:description:] + 102
    4   UIFoundation                        0x03344072 -[NSLayoutManager(NSPrivate) _resizeTextViewForTextContainer:] + 418
    5   UIFoundation                        0x03343d6e -[NSLayoutManager(NSPrivate) _recalculateUsageForTextContainerAtIndex:] + 2017
    6   UIFoundation                        0x0337da43 -[NSLayoutManager textStorage:edited:range:changeInLength:invalidatedRange:] + 871
    7   UIFoundation                        0x0337db53 -[NSLayoutManager processEditingForTextStorage:edited:range:changeInLength:invalidatedRange:] + 85
    8   UIFoundation                        0x033a7a7b -[NSTextStorage _notifyEdited:range:changeInLength:invalidatedRange:] + 153
    9   UIFoundation                        0x033a759a -[NSTextStorage processEditing] + 458
    10  UIFoundation                        0x033a7124 -[NSTextStorage endEditing] + 80
    11  UIFoundation                        0x033a71af -[NSTextStorage coordinateEditing:] + 67
    12  UIKit                               0x014938ae -[UITextView setAttributedText:] + 250
    13  UIKit                               0x01499745 -[UITextView setText:] + 149
    14  AppName                            0x00036216 _TFFC8AppName19FirstViewController8sendEchoFS0_FPSs9AnyObject_T_U_FOS_9JSONValueT_ + 1350
    15  AppName                            0x0003525a _TPA__TFFC8AppName19FirstViewController8sendEchoFS0_FPSs9AnyObject_T_U_FOS_9JSONValueT_ + 106
    16  AppName                            0x0001de86 _TFF8AppName11HTTPRequestFTSSGVSs10DictionarySSPSs9AnyObject__FOS_9JSONValueT__T_U_FTGSQCSo6NSData_GSQCSo13NSURLResponse_GSQCSo7NSError__T_ + 1350
    17  AppName                            0x0001d0a4 _TPA__TFF8AppName11HTTPRequestFTSSGVSs10DictionarySSPSs9AnyObject__FOS_9JSONValueT__T_U_FTGSQCSo6NSData_GSQCSo13NSURLResponse_GSQCSo7NSError__T_ + 100
    18  AppName                            0x0001e289 _TTRXFo_oGSQCSo6NSData_oGSQCSo13NSURLResponse_oGSQCSo7NSError__dT__XFo_iTGSQS__GSQS0__GSQS1____iT__ + 41
    19  AppName                            0x0001d15a _TPA__TTRXFo_oGSQCSo6NSData_oGSQCSo13NSURLResponse_oGSQCSo7NSError__dT__XFo_iTGSQS__GSQS0__GSQS1____iT__ + 90
    20  AppName                            0x0001e2d7 _TTRXFo_iTGSQCSo6NSData_GSQCSo13NSURLResponse_GSQCSo7NSError___iT__XFo_oGSQS__oGSQS0__oGSQS1___dT__ + 55
    21  AppName                            0x0001d224 _TPA__TTRXFo_iTGSQCSo6NSData_GSQCSo13NSURLResponse_GSQCSo7NSError___iT__XFo_oGSQS__oGSQS0__oGSQS1___dT__ + 100
    22  AppName                            0x0001e36e _TTRXFo_oGSQCSo6NSData_oGSQCSo13NSURLResponse_oGSQCSo7NSError__dT__XFdCb_dGSQS__dGSQS0__dGSQS1___dT__ + 142
    23  CFNetwork                           0x02c36158 __49-[__NSCFLocalSessionTask _task_onqueue_didFinish]_block_invoke + 181
    24  Foundation                          0x0092da35 __NSBLOCKOPERATION_IS_CALLING_OUT_TO_A_BLOCK__ + 12
    25  Foundation                          0x00854635 -[NSBlockOperation main] + 99
    26  Foundation                          0x00833a97 -[__NSOperationInternal _start:] + 700
    27  Foundation                          0x008337c9 -[NSOperation start] + 83
    28  Foundation                          0x00833613 __NSOQSchedule_f + 237
    29  libdispatch.dylib                   0x022ef3ff _dispatch_client_callout + 14
    30  libdispatch.dylib                   0x022d8578 _dispatch_queue_drain + 1424
    31  libdispatch.dylib                   0x022d7f90 _dispatch_queue_invoke + 142
    32  libdispatch.dylib                   0x022d9e06 _dispatch_root_queue_drain + 312
    33  libdispatch.dylib                   0x022dae67 _dispatch_worker_thread2 + 45
    34  libsystem_pthread.dylib             0x0263fdab _pthread_wqthread + 336
    35  libsystem_pthread.dylib             0x02643cce start_wqthread + 30
)
    libc++abi.dylib: terminating with uncaught exception of type NSException

提前致谢!

最佳答案

看起来你的问题是你不在主线程上，在跟踪的第二行。

由于 HTTPRequest 异步处理数据的性质，您可能仍在后台运行代码……这很好。说完一切后，您只需要进入主线程即可。

这里是可能的修复方法...

@IBAction func sendEcho(sender: AnyObject)
{
    let callback = {(textString: String) in 
        dispatch_sync(dispatch_get_main_queue())
        {
            self.echoLog.text = textString //Yay!
        }
    }
    HTTPRequest("http://localhost/echo", ["echo": "Echo!"], callback)
}

提醒时间 UI 更新应该只在主线程上执行。仅仅是因为这样做为这件事的发生提供了高优先级。通常，当您尝试在后台线程上执行 UI 更新时，您会看到代码执行和看到结果之间的延迟。在这种情况下，断言失败(我喜欢这样)。如果你不知道你是否在主线程上，你可以通过返回 bool 的 NSThread.isMainThread() 来检查它。

警告 如果您在调用 dispatch_sync(dispatch_get_main_queue()) {...} 时已经在主线程上，您的应用将卡住，因此请确保您知道你在哪个线程...

关于Swift - 从内部回调崩溃应用程序编辑 UITextView，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/25007289/