问题：在 iOS 11 下，如果给 UIImagePickerController 设置 allowsEditing = YES，然后在编辑图片的时候，却发现左下角的那个 取消 按键怎么也没法点击到

image.png

解决办法：

///oc版本
- (void)navigationController:(UINavigationController *)navigationController didShowViewController:(UIViewController *)viewController animated:(BOOL)animated {
    if ([UIDevice currentDevice].systemVersion.floatValue < 11) {
        return;
    }
    if ([viewController isKindOfClass:NSClassFromString(@"PUPhotoPickerHostViewController")]) {
        [viewController.view.subviews enumerateObjectsUsingBlock:^(__kindof UIView * _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
            if (obj.frame.size.width < 42) {
                [viewController.view sendSubviewToBack:obj];
                *stop = YES;
            }
        }];
    }
}

///swift版本
/// iOS11 解决图片编辑时左下角cancel按钮很难点击的问题
    func navigationController(_ navigationController: UINavigationController, didShow viewController: UIViewController, animated: Bool) {
        if Double(UIDevice.current.systemVersion)! < 11.0 {
            return
        }
        if viewController.isKind(of: NSClassFromString("PUPhotoPickerHostViewController")!) {
            for item in viewController.view.subviews {
                if item.frame.size.width < 42 {
                    viewController.view.sendSubview(toBack: item)
                    return
                }
            }
        }
    }