UIImagePickerController 编辑/选取图片时

原因是左侧有一个视图遮挡了取消按钮

解决办法：遵循UINavigationControllerDelegate，实现代理方法

- (void)navigationController:(UINavigationController *)navigationController didShowViewController:(UIViewController *)viewController animated:(BOOL)animated {
    if ([UIDevice currentDevice].systemVersion.floatValue < 11.0) {
        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;
            }
        }];
    }
}