iphone - 将 UIAppearance 与 UIBarButtonItem 的子类一起使用会导致无法识别的选择器被发送到 UINavigationButton

Question

TL&DR;

使用 UIAppearance 代理设置 UIBarButtonItem 子类的自定义属性会导致“无法识别的选择器”异常，因为 setter 可能由 UIAppearance 转发到 UINavigationButton，而不是栏按钮本身。

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SDK概览

我正在使用 iOS 7 Beta 5 SDK 和 Xcode 5 DP5。但是，请不要告诉我它处于 NDA 之下，因为我不会在这个问题中讨论任何新功能或新类。我通知你我的 SDK，因为可以查出它只是 beta 软件中的一个错误。

我做了什么

我子类化了一个 UIBarButtonItem 并在头文件中创建了一个自定义属性:

@property (nonatomic, strong) NSString *mySubclassedProperty UI_APPEARANCE_SELECTOR;

我的 setter 和 getter 看起来像这样:

- (void)setMySubclassedProperty:(NSString *)mySubclassedProperty {
    _mySubclassedProperty = mySubclassedProperty;
    NSLog(@"%p %s %@", self, __PRETTY_FUNCTION__, mySubclassedProperty);
}

没什么特别的吧？但它根本不适用于 UIAppearance。当我尝试在我的应用程序的委托(delegate)中设置默认外观时，它没有给我任何错误，也没有任何警告。

[[AKBarButtonItem appearance] setMySubclassedProperty:@"GLOBALLY ASSIGNED"];

崩溃

它看起来像一个魅力，除了当我尝试将 AKBarButtonItem 的实例设置为 self.navigationItem.rightBarButtonItem 时它崩溃的事实:

self.navigationItem.rightBarButtonItem = [[AKBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemAction target:nil action:nil];

回溯看起来像这样:

2013-08-13 14:30:08.551 UIBarButtonItem Subclass Demo[1512:a0b] -[UINavigationButton setMySubclassedProperty:]: unrecognized selector sent to instance 0x8c42710
2013-08-13 14:30:08.556 UIBarButtonItem Subclass Demo[1512:a0b] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[UINavigationButton setMySubclassedProperty:]: unrecognized selector sent to instance 0x8c42710'
*** First throw call stack:
(
    0   CoreFoundation                      0x0173b6f4 __exceptionPreprocess + 180
    1   libobjc.A.dylib                     0x014bb8b6 objc_exception_throw + 44
    2   CoreFoundation                      0x017d8983 -[NSObject(NSObject) doesNotRecognizeSelector:] + 275
    3   CoreFoundation                      0x0172ba1b ___forwarding___ + 1019
    4   CoreFoundation                      0x0172b5fe _CF_forwarding_prep_0 + 14
    5   CoreFoundation                      0x0172fe2d __invoking___ + 29
    6   CoreFoundation                      0x0172fd3a -[NSInvocation invoke] + 362
    7   CoreFoundation                      0x0172feba -[NSInvocation invokeWithTarget:] + 74
    8   UIKit                               0x00763255 workaround10030904InvokeWithTarget + 824
    9   UIKit                               0x0075dea8 +[_UIAppearance _applyInvocationsTo:window:matchingSelector:] + 4497
    10  UIKit                               0x0075e299 +[_UIAppearance _applyInvocationsTo:window:] + 55
    11  UIKit                               0x0029ddcb -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 183
    12  libobjc.A.dylib                     0x014cd81f -[NSObject performSelector:withObject:] + 70
    13  QuartzCore                          0x03ac172a -[CALayer layoutSublayers] + 148
    14  QuartzCore                          0x03ab5514 _ZN2CA5Layer16layout_if_neededEPNS_11TransactionE + 380
    15  QuartzCore                          0x03ac3b55 -[CALayer(CALayerPrivate) layoutBelowIfNeeded] + 43
    16  UIKit                               0x00290886 -[UIView(Hierarchy) layoutBelowIfNeeded] + 595
    17  UIKit                               0x0029062d -[UIView(Hierarchy) layoutIfNeeded] + 74
    18  UIKit                               0x0050841e -[UIBarButtonItem(UIStatic) _leftRightImagePaddingForEdgeMarginInNavBarIsMini:] + 574
    19  UIKit                               0x002ea325 -[UINavigationBar _getTitleViewFrame:leftViewFrames:rightViewFrames:forItemAtIndex:returnedIdealWidthOfTextContent:availableLayoutWidthForTextContent:idealBackButtonWidth:] + 3522
    20  UIKit                               0x002ef2da -[UINavigationBar _getTitleViewFrame:leftViewFrames:rightViewFrames:forItemAtIndex:] + 591
    21  UIKit                               0x002ef59a -[UINavigationBar _getTitleViewFrame:leftViewFrames:rightViewFrames:] + 151
    22  UIKit                               0x002dc515 -[UINavigationBar _setLeftViews:rightViews:] + 1894
    23  UIKit                               0x002ca6c5 -[UINavigationItem updateNavigationBarButtonsAnimated:] + 188
    24  UIKit                               0x002cab63 -[UINavigationItem setObject:forLeftRightKeyPath:animated:] + 547
    25  UIKit                               0x002cb1ae -[UINavigationItem setRightBarButtonItem:animated:] + 171
    26  UIKit                               0x002cb0fe -[UINavigationItem setRightBarButtonItem:] + 48
    27  UIBarButtonItem Subclass Demo       0x0000665e -[AKViewController viewDidLoad] + 222
    28  UIKit                               0x00345c18 -[UIViewController loadViewIfRequired] + 696
    29  UIKit                               0x00345eb4 -[UIViewController view] + 35
    30  UIKit                               0x00370369 -[UINavigationController rotatingSnapshotViewForWindow:] + 52
    31  UIKit                               0x00698e10 -[UIClientRotationContext initWithClient:toOrientation:duration:andWindow:] + 420
    32  UIKit                               0x00276ff2 -[UIWindow _setRotatableClient:toOrientation:updateStatusBar:duration:force:isRotating:] + 1495
    33  UIKit                               0x00276a16 -[UIWindow _setRotatableClient:toOrientation:updateStatusBar:duration:force:] + 82
    34  UIKit                               0x002768e8 -[UIWindow _setRotatableViewOrientation:updateStatusBar:duration:force:] + 117
    35  UIKit                               0x00276970 -[UIWindow _setRotatableViewOrientation:duration:force:] + 67
    36  UIKit                               0x00275a0a __57-[UIWindow _updateToInterfaceOrientation:duration:force:]_block_invoke + 120
    37  UIKit                               0x0027596c -[UIWindow _updateToInterfaceOrientation:duration:force:] + 400
    38  UIKit                               0x002766c3 -[UIWindow setAutorotates:forceUpdateInterfaceOrientation:] + 870
    39  UIKit                               0x00279c7e -[UIWindow setDelegate:] + 449
    40  UIKit                               0x0034a037 -[UIViewController _tryBecomeRootViewControllerInWindow:] + 180
    41  UIKit                               0x0026f91c -[UIWindow addRootViewControllerViewIfPossible] + 609
    42  UIKit                               0x00270146 -[UIWindow setRootViewController:] + 960
    43  UIBarButtonItem Subclass Demo       0x00006a07 -[AKAppDelegate application:didFinishLaunchingWithOptions:] + 823
    44  UIKit                               0x0022d525 -[UIApplication _handleDelegateCallbacksWithOptions:isSuspended:restoreState:] + 309
    45  UIKit                               0x0022dd65 -[UIApplication _callInitializationDelegatesForURL:payload:suspended:] + 1536
    46  UIKit                               0x00232578 -[UIApplication _runWithURL:payload:launchOrientation:statusBarStyle:statusBarHidden:] + 824
    47  UIKit                               0x0024657c -[UIApplication handleEvent:withNewEvent:] + 3447
    48  UIKit                               0x00246ae9 -[UIApplication sendEvent:] + 85
    49  UIKit                               0x002341f5 _UIApplicationHandleEvent + 736
    50  GraphicsServices                    0x0365a33b _PurpleEventCallback + 776
    51  GraphicsServices                    0x03659e46 PurpleEventCallback + 46
    52  CoreFoundation                      0x016b6e95 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 53
    53  CoreFoundation                      0x016b6bcb __CFRunLoopDoSource1 + 523
    54  CoreFoundation                      0x016e18ac __CFRunLoopRun + 2156
    55  CoreFoundation                      0x016e0bf3 CFRunLoopRunSpecific + 467
    56  CoreFoundation                      0x016e0a0b CFRunLoopRunInMode + 123
    57  UIKit                               0x00231cad -[UIApplication _run] + 840
    58  UIKit                               0x00233f0b UIApplicationMain + 1225
    59  UIBarButtonItem Subclass Demo       0x00006e9d main + 141
    60  libdyld.dylib                       0x01d77725 start + 0
)
libc++abi.dylib: terminating with uncaught exception of type NSException

经过一些检查，我奇怪地意识到 setMySubclassedProperty: 消息被发送到 UINavigationButton(它是导航中使用的 UIButton 的私有(private)子类栏、工具栏和搜索栏)。我在 26 帧中设置按钮，UIAppearance 魔法在 10 帧中执行。

在 iOS 6 中，问题存在，但向 UINavigationButton 发送了一条不同的消息:

2013-08-13 14:35:58.316 UIBarButtonItem Subclass Demo[1591:c07] -[UINavigationButton _UIAppearance_setMySubclassedProperty:]: unrecognized selector sent to instance 0x810d600
2013-08-13 14:35:58.359 UIBarButtonItem Subclass Demo[1591:c07] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[UINavigationButton _UIAppearance_setMySubclassedProperty:]: unrecognized selector sent to instance 0x810d600'
*** First throw call stack:
(0x12b2012 0x10d7e7e 0x133d4bd 0x12a1bbc 0x12a194e 0x12a61bd 0x12a60d6 0x12a624a 0x68b9e8 0x68769c 0x687a95 0x291884 0x3088ca 0x28cf96 0x2934a4 0x28b89d 0x2cc646 0x2bc076 0x2bc517 0x2bcb66 0x2bcab6 0x665e 0x3261c7 0x326232 0x3264da 0x33d8e5 0x33d9cb 0x33dc76 0x33dd71 0x33e89b 0x33e9b9 0x33ea45 0x44420b 0x2952dd 0x10eb6b0 0x289dfc0 0x289233c 0x289deaf 0x3342bd 0x27cb56 0x27b66f 0x27b589 0x27a7e4 0x27a61e 0x27b3d9 0x27e2d2 0x32899c 0x275574 0x275cc1 0x6a07 0x242157 0x242747 0x24394b 0x254cb5 0x255beb 0x247698 0x24b8df9 0x24b8ad0 0x1227bf5 0x1227962 0x1258bb6 0x1257f44 0x1257e1b 0x24317a 0x244ffc 0x6e9d 0x1ab0725)
libc++abi.dylib: terminate called throwing an exception

演绎

我的第一个想法是:“UIAppearance 将 setter 转发给 AKBarButtonItem，然后它崩溃了”。但是是吗？在 an article by Peter Steinberger我发现 Apple 正在使用 _UIAppearance 的一个特殊子类用于栏目，称为 _UIBarItemAppearance。我想确认这一点并在 -[_UIBarItemAppearance forwardInvocation:] 上设置一个符号断点，并且 lldb 在异常发生之前成功停止。

现在在我看来，Apple 在 -[_UIBarItemAppearance forwardInvocation:] 中做了一些肮脏的逻辑，以实现应该将哪个选择器发送到哪个实例，例如:

• setBackgroundImage:forState: 应该发送到 UINavigationButton
• setBackButtonBackgroundImage:forState:barMetrics: 到 UIBarButtonItem
• ...

他们的代码是这样的:

if (selector == @selector(setBackButtonBackgroundImage:forState:barMetrics:)) {
    // forward to UIBarButtonItem
} else if (selector == @selector(setBackButtonBackgroundVerticalPositionAdjustment:forBarMetrics:)) {
    // forward to UIBarButtonItem
} else if (...) {
    // more forwarding to UIBarButtonItem
} else {
    // forward to UINavigationButton
}

然后，根据我的推论，最后的 else 语句导致 setNiceBarButtonItemAttributes: 选择器被发送到 UINavigationButton，而不是 UIBarButtonItem 。如果这是真的，我们就完蛋了。

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示例代码

您可以在此处下载示例项目:http://cl.ly/241I2A3U0a0y .

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帮助

我只是做错了什么，还是一个错误？或者苹果是故意的？任何帮助将不胜感激。

Answer 1

问题是 UIBarButtonItem 不是 UIView 的子类，它是创建私有(private) UIView 子类的“ Controller ”类。对于条形按钮项目，使用了一个私有(private)外观代理，而不是通常的代理(一些信息 here )。

我可以建议走另一条路吗？您真的需要为您的定制子类化条形按钮项目吗？您不能创建 UINavigationBar 的子类并将其用作您对 appearanceWhenContainedIn: 进行更改的触发器吗？