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在父视图控制器上显示它。

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];

Answer 3

是的。 将其添加到当前视图控制器的视图（或作为窗口的子视图）并在屏幕上为其设置动画，就像Valerii所说。

要用动画删除它，请执行此操作（我假设模态视图为320 x 460，它将从屏幕滑下）：

- (void)dismissModal
{
    // animate off-screen
    [UIView beginAnimations:nil context:nil];
    [UIView setAnimationCurve:UIViewAnimationCurveEaseOut];
    [UIView setAnimationDuration:0.50];
    [UIView setAnimationDelegate:self];
    [UIView setAnimationDidStopSelector:@selector(animationDidStop:finished:context:)];

    self.view.frame = CGRectMake( 0, 480, 320, 460 );

    [UIView commitAnimations];
}

- (void)animationDidStop:(NSString *)animationID finished:(NSNumber *)finished context:(void *)context
{
    // don't remove until animation is complete. otherwise, the view will simply disappear
    [self.view removeFromSuperview];
}