我们有2个控制器：MainVC和ProfileVC。
从MainVC我们转到ProfileVC，按profileButton按（导航栏上的左项）。
在Profile VC中，导航栏上有2个按钮：返回main（leftItem）并打开alertView（rightItem）。
所以有简单的KIF测试（导航栏上只有永久的左右点击）：
- (void)testProfileButtons
{
[tester waitForAnimationsToFinishWithTimeout:0.3];
while (true)
{
[tester tapScreenAtPoint:CGPointMake(20, 20)];
[tester waitForTimeInterval:0.1];
[tester tapScreenAtPoint:CGPointMake(380, 20)];
[tester waitForTimeInterval:0.1];
[tester tapScreenAtPoint:CGPointMake(20, 20)];
[tester waitForTimeInterval:0.1];
}
}
它崩溃了应用程序错误：
*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Application tried to present modally an active controller <UINavigationController: 0x7fe862ef82d0>.'
*** First throw call stack:
(
0 CoreFoundation 0x0000000110944c65 __exceptionPreprocess + 165
1 libobjc.A.dylib 0x00000001105dabb7 objc_exception_throw + 45
2 UIKit 0x000000010f44b80d -[UIViewController _presentViewController:withAnimationController:completion:] + 3238
3 UIKit 0x000000010f44d6c1 __62-[UIViewController presentViewController:animated:completion:]_block_invoke + 132
4 UIKit 0x000000010fa5e5ae -[_UIViewControllerTransitionCoordinator _applyBlocks:releaseBlocks:] + 217
5 UIKit 0x000000010fa5b8e5 -[_UIViewControllerTransitionContext _runAlongsideCompletions] + 123
6 UIKit 0x000000010fa5b670 -[_UIViewControllerTransitionContext completeTransition:] + 126
7 UIKit 0x000000010f2fe8a6 __53-[_UINavigationParallaxTransition animateTransition:]_block_invoke93 + 687
8 UIKit 0x000000010f387193 -[UIViewAnimationBlockDelegate _didEndBlockAnimation:finished:context:] + 326
9 UIKit 0x000000010f36e0f6 -[UIViewAnimationState sendDelegateAnimationDidStop:finished:] + 209
10 UIKit 0x000000010f36e42c -[UIViewAnimationState animationDidStop:finished:] + 76
11 UIKit 0x000000011daf3fdf -[UIViewAnimationStateAccessibility animationDidStop:finished:] + 48
12 QuartzCore 0x000000010f03e892 _ZN2CA5Layer23run_animation_callbacksEPv + 308
13 libdispatch.dylib 0x0000000111c67964 _dispatch_client_callout + 8
14 libdispatch.dylib 0x0000000111c52a59 _dispatch_main_queue_callback_4CF + 704
15 CoreFoundation 0x00000001108ac1f9 __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 9
16 CoreFoundation 0x000000011086ddcb __CFRunLoopRun + 2043
17 CoreFoundation 0x000000011086d366 CFRunLoopRunSpecific + 470
18 TurboChat UI Tests 0x000000011b73ef69 -[KIFTestActor tryRunningBlock:complete:timeout:error:] + 425
19 TurboChat UI Tests 0x000000011b73f179 -[KIFTestActor runBlock:complete:timeout:] + 137
20 TurboChat UI Tests 0x000000011b73f304 -[KIFTestActor runBlock:timeout:] + 84
21 TurboChat UI Tests 0x000000011b73f73e -[KIFTestActor waitForTimeInterval:] + 174
22 TurboChat UI Tests 0x000000011b73c2ad -[TCProfileButtonsTest testProfileButtons] + 909
23 CoreFoundation 0x000000011083adec __invoking___ + 140
24 CoreFoundation 0x000000011083ac42 -[NSInvocation invoke] + 290
25 XCTest 0x000000011b79217a -[XCTestCase invokeTest] + 253
26 XCTest 0x000000011b792379 -[XCTestCase performTest:] + 150
27 XCTest 0x000000011b79bc35 -[XCTest run] + 260
28 XCTest 0x000000011b79108b -[XCTestSuite performTest:] + 379
29 XCTest 0x000000011b79bc35 -[XCTest run] + 260
30 XCTest 0x000000011b79108b -[XCTestSuite performTest:] + 379
31 XCTest 0x000000011b79bc35 -[XCTest run] + 260
32 XCTest 0x000000011b79108b -[XCTestSuite performTest:] + 379
33 XCTest 0x000000011b79bc35 -[XCTest run] + 260
34 XCTest 0x000000011b78e129 __25-[XCTestDriver _runSuite]_block_invoke + 56
35 XCTest 0x000000011b798edd -[XCTestObservationCenter _observeTestExecutionForBlock:] + 162
36 XCTest 0x000000011b78e060 -[XCTestDriver _runSuite] + 269
37 XCTest 0x000000011b78ea8d -[XCTestDriver _checkForTestManager] + 234
38 XCTest 0x000000011b79eb20 +[XCTestProbe runTests:] + 182
39 Foundation 0x000000010e5f21e5 __NSFireDelayedPerform + 387
40 CoreFoundation 0x00000001108ac174 __CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__ + 20
41 CoreFoundation 0x00000001108abd35 __CFRunLoopDoTimer + 1045
42 CoreFoundation 0x000000011086dd3d __CFRunLoopRun + 1901
43 CoreFoundation 0x000000011086d366 CFRunLoopRunSpecific + 470
44 GraphicsServices 0x00000001123a8a3e GSEventRunModal + 161
45 UIKit 0x000000010f30e8c0 UIApplicationMain + 1282
46 TurboChat 0x000000010cd1e75f main + 111
47 libdyld.dylib 0x0000000111c97145 start + 1
)
我在真实设备上测试时也会得到这个：
Presenting view controllers on detached view controllers is discouraged <TCProfileTableViewController: 0x14f6299c0>.
并将alertView显示在MainVC上，而不是在其下面带有黑色屏幕的ProfileVC。
这就是我们如何在ProfileVC中呈现警报：
- (IBAction)menuButtonPressed:(id)sender
{
[self.navigationController presentViewController:self.menuAlert animated:YES completion:nil];
}
AlertView：
self.menuAlert = [UIAlertController alertControllerWithTitle:[NSString stringWithFormat:@"%@?", NSLocalizedString(@"PROFILE_BTN_MENU", nil)]
message:nil
preferredStyle:UIAlertControllerStyleActionSheet];
有什么建议吗？
答案 0 :(得分：2)
我找到了一种解决方案
- (IBAction)menuButtonPressed:(id)sender
{
[self.parentViewController presentViewController:self.menuAlert animated:YES completion:nil];
}
警报视图有时会出现在menuVC上，但它不会使应用程序崩溃并正常工作。 在那里找到答案：Warning :-Presenting view controllers on detached view controllers is discouraged
答案 1 :(得分：1)
其他开发者可能还有另一种情况：
在按钮触发连接后是否显示目标ViewController？ 如果您有一个所述ViewController的共享实例，用户可能会点击两次，进行两次连接并打开两次相同的ViewController。
通过这样做来防止它：
var didSuccess = false
func success(result: LoginModel.Result) {
if didSuccess {
return
}
didSuccess = true
Answers.logCustomEvent(withName: "Login")
Session.set(token: result.token)
present(MainTabBarController.sharedInstance, animated: true, completion: nil)
}
或在连接期间禁用该按钮。
答案 2 :(得分：0)
您现在要做的就是为问题添加一个计时器。
@IBAction func onBtnMenu(_ sender: UIButton) {
sender.isUserInteractionEnabled = false
Timer.scheduledTimer(withTimeInterval: 1, repeats: false, block: { [weak sender] timer in
sender?.isUserInteractionEnabled = true
})
}
答案 3 :(得分：-2)
防止此异常。只需关闭当前显示的ViewController，返回到您正在解雇的ViewController的调用者：
self.dismiss(animated: true, completion: nil)