如何创建半透明模态UIViewController？

Question

我想创建一个可重用的UIViewController子类,它可以显示为任何其他视图控制器上的模态视图控制器.这个可重用的VC需要做的第一件事就是弹出一个UIActionSheet.为此,我在VC中创建一个默认(空白)视图以显示来自的操作表.

但是,这看起来很糟糕,因为当弹出模态vc时,隐藏了父vc.因此,看起来动作表漂浮在空白背景上.如果动作表可能看起来弹出原始(父)vc会更好.

有没有办法实现这个目标？简单地抓住父vc的视图并从中激活UIActionSheet是否安全？

Answer 1

在您的模态视图动画后,它的大小将调整为与其父视图相等.你可以做的是在viewDidAppear:中,拍摄parentController的视图,然后在你自己的视图的子视图列表后面插入一个包含父图片的UIImageView:

#pragma mark -
#pragma mark Sneaky Background Image
- (void)viewDidAppear:(BOOL)animated {
    [super viewDidAppear:animated];

    // grab an image of our parent view
    UIView *parentView = self.parentViewController.view;

    // For iOS 5 you need to use presentingViewController:
    // UIView *parentView = self.presentingViewController.view;

    UIGraphicsBeginImageContext(parentView.bounds.size);
    [parentView.layer renderInContext:UIGraphicsGetCurrentContext()];
    UIImage *parentViewImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    // insert an image view with a picture of the parent view at the back of our view's subview stack...
    UIImageView *imageView = [[UIImageView alloc] initWithFrame:self.view.bounds];
    imageView.image = parentViewImage;
    [self.view insertSubview:imageView atIndex:0];
    [imageView release];
}

- (void)viewWillDisappear:(BOOL)animated {
    [super viewWillDisappear:animated];

    // remove our image view containing a picture of the parent view at the back of our view's subview stack...
    [[self.view.subviews objectAtIndex:0] removeFromSuperview];
}

Answer 2

您可以通过在父视图中插入视图来简单地将其显示在父视图控制器上。

像这样的东西：

PseudoModalVC *vc = ...//initialization
vc.view.backgroundColor = [UIColor clearColor]; // like in previous comment, although you can do this in Interface Builder
vc.view.center = CGPointMake(160, -vc.view.bounds.size.height/2);
[parentVC.view addSubView:vc.view];

// animation for pop up from screen bottom
[UIView beginAnimation:nil context:nil];
vc.view.center = CGPointMake(160, vc.view.bounds.size.height/2);
[UIView commitAnimation];