objective-c - 呈现 UIModalPresentationFormSheet，但显示为 UIModalPresnetationPageSheet

Question

我一直在谷歌搜索这个问题是什么两个多小时无济于事。

我正在尝试做的是将“演练”作为表单呈现在屏幕上。modalPresentationStyle 值在整个层次结构中设置正确，但“演练”显示为页面表。

SYNavigationController 只是将 -shouldAutoRotate 和 -supportedInterfaceOrientation 转发到 topViewController。

有谁知道为什么会发生这种情况？我已经包含了下面的代码。

NSString *storyboardName = @"MainStoryboard_iPhone";
if(UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) storyboardName = @"MainStoryboard_iPad";

UIStoryboard *storyBoard = [UIStoryboard storyboardWithName:storyboardName bundle:nil];

SYNavigationController *walkThrough = [storyBoard instantiateViewControllerWithIdentifier:@"walkthroughNav"];
walkThrough.modalPresentationStyle = UIModalPresentationFormSheet;

WalkThroughViewController *wtvc = (WalkThroughViewController *)walkThrough.topViewController;
wtvc.showSignIn = YES;

[self presentViewController:walkThrough animated:NO completion:nil];