iOS的ViewController默认backgroundColor是clearColor，如果不设置背景颜色，会导致新界面的背景是透明色，还会导致跳转动画卡顿。
但是每创建一个ViewController就要设置一次backgroundColor。那么有没有什么办法可以简化呢？
最近在复习runtime中Method swizzling的知识，于是决定用runtime的知识来处理下这个问题：
+ (void)load {
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
Class class = [self class];
SEL originalSelector = @selector(viewDidLoad);
SEL swizzledSelector = @selector(ghh_viewDidLoad);
Method originalMethod = class_getInstanceMethod(class, originalSelector);
Method swizzledMethod = class_getInstanceMethod(class, swizzledSelector);
BOOL didAddMethod =
class_addMethod(class,
originalSelector,
method_getImplementation(swizzledMethod),
method_getTypeEncoding(swizzledMethod));
if (didAddMethod) {
class_replaceMethod(class,
swizzledSelector,
method_getImplementation(originalMethod),
method_getTypeEncoding(originalMethod));
} else {
method_exchangeImplementations(originalMethod, swizzledMethod);
}
});
}
- (void)ghh_viewDidLoad {
self.view.backgroundColor = [UIColor lightGrayColor];
[self ghh_viewDidLoad];
NSLog(@"%@ method did changed!", self);
}
没一会儿就写完了，调试运行结果。没有问题！
但是在滑动返回的时候，整个界面变成灰色了！
同时控制台打印结果：
2017-04-17 19:47:53.411627+0800 ThugLife[9251:4390465] <UINavigationController: 0x100816000> method did changed!
2017-04-17 19:47:53.434202+0800 ThugLife[9251:4390465] <ViewController: 0x1004095c0> method did changed!
2017-04-17 19:47:54.785103+0800 ThugLife[9251:4390465] <UINavigationController: 0x100810c00> method did changed!
2017-04-17 19:47:54.788516+0800 ThugLife[9251:4390465] <GHHPhotoViewController: 0x10042e190> method did changed!
2017-04-17 19:47:54.899452+0800 ThugLife[9251:4390465] <GHHGridViewController: 0x10043cd60> method did changed!
2017-04-17 19:47:58.734195+0800 ThugLife[9251:4390465] <GHHPhotoEditingViewController: 0x100440a70> method did changed!
2017-04-17 19:47:59.991616+0800 ThugLife[9251:4390465] <UIInputWindowController: 0x100906200> method did changed!
打开UI调试，看页面层级关系图貌似也没问题：
但是除了正常的UIWindow之外，还有一个UITextEffectsWindow，查看这个window，发现页面什么都没有。在此找到了罪魁祸首，就是这个东西挡在了UI前面导致显示失败
原因
iOS 8 inserts a new “UITextEffectsWindow” above your application’s main UIWindow that currently intercepts clicks when selecting items in the Reveal canvas. To work around this you can either Command-Click to select through the UITextEffectsWindow or double-click on your app’s UIWindow in Reveal’s outline view to focus on the application window.
在Google了相关资料后发现，这是一个iOS8以后新加入的私有window，根据网上说法是用来控制键盘的专属window，后面查证，当vc存在于navigationVC下 此时不管是否弹出键盘 [UIApplication shareappliation] windows 都会包含UITextEffectsWindow
所以当滑动popViewController的时候，这个window被加在UIWindow上，挡住了整个UI视图。
而且这种方法还会对iOS8以后的UIAlertController同样染色。
所以这种黑科技证明是不行的，只能另想办法。
