MFMailComposeViewController由于iOS6上的全局外观属性而崩溃

问题描述

当我出示 MFMailComposeViewController 时，我收到以下崩溃：

I am getting the following crash when I present a MFMailComposeViewController:

2013-11-08 11:04:05.963 <redacted>[7108:1603] *** Assertion failure in NSDictionary *_UIRecordArgumentOfInvocationAtIndex(NSInvocation *, NSUInteger, BOOL)(), /SourceCache/UIKit/UIKit-2380.17/UIAppearance.m:1118
2013-11-08 11:04:06.032 <redacted>[7108:1603] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Unknown key, "NSColor" in title text attributes dictionary'

我已将其跟踪到AppDelegate中的以下外观设置 application：didFinishLaunchingWithOptions： method：

I've tracked it down to the following appearance setting in my AppDelegate's application:didFinishLaunchingWithOptions: method:

        [[UINavigationBar appearance] setTitleTextAttributes:
            @{NSForegroundColorAttributeName : [UIColor whiteColor]}];

评论该线路确实有效，但是遗留了应用程序的其余部分，所以我试着专门设置titleTextAttributes为 MFMailComposeViewController的空字典：

Commenting that line out does the trick, but ruins the rest of the app, so I tried specifically setting the titleTextAttributes to an empty dictionary for the MFMailComposeViewController:

尝试＃1

        [[UINavigationBar appearanceWhenContainedIn:
            NSClassFromString(@"MFMailComposeViewController"), nil]
            setTitleTextAttributes:@{ }];

导致同样的崩溃。并且

        [[UINavigationBar appearanceWhenContainedIn:
            NSClassFromString(@"MFMailComposeViewController"), nil]
            setTitleTextAttributes:nil];

也导致同样的崩溃。

尝试＃2

我注意到 MFMailComposeViewController 是 UINavigationController ，因此全局外观设置可能已本地化为UIVavigationController内的 UIVavigationController 。我整理了一些代码来确定MFMailComposeViewController中的视图控制器：

I noticed that MFMailComposeViewController is a UINavigationController, so maybe the global appearance settings are localized to UIViewControllers inside a UINavigationController. I put together some code to figure out what view controllers are inside the MFMailComposeViewController:

        for (UIViewController *viewController in mailViewController.viewControllers) {
            NSLog(@"%@", NSStringFromClass([viewController class]));
        }

导致输出结果：

2013-11-08 11:04:05.936 <redacted>[7108:907] MFMailComposeInternalViewController

所以我尝试了（尽管依靠Apple的私人视图控制器是不好的做法）：

        [[UINavigationBar appearanceWhenContainedIn:
            NSClassFromString(@"MFMailComposeViewController"), nil]
            setTitleTextAttributes:@{ }];

和

        [[UINavigationBar appearanceWhenContainedIn:
            NSClassFromString(@"MFMailComposeViewController"), nil]
            setTitleTextAttributes:nil];

但这仍然导致同样的崩溃！

But that still results in the same crash!

尝试＃3

        // right before instantiating the MFMailComposeViewController
        [[UINavigationBar appearance] setTitleTextAttributes:@{ }];

和

        [[UINavigationBar appearance] setTitleTextAttributes:nil];

然后在的完成块中恢复全局外观属性dismissViewController：animated：完成：

然而，这种方法也不起作用。有没有人知道如何在全局 UINavigationBar 外观上设置titleTextAttributes而不会崩溃MFMailComposeViewController？

However, this approach didn't work either. Does anyone know how to set titleTextAttributes on the global UINavigationBar appearance without crashing MFMailComposeViewController?

推荐答案

尝试使用 UITextAttributeTextColor 而不是 NSForegroundColorAttributeName 。

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