ios - 如何在 iOS 上的 View 之间进行展开/收缩转换？

Question

我正在尝试在 iOS 中制作过渡动画，其中 View 或 View Controller 看起来会扩展以填满整个屏幕，然后在完成后收缩回原来的位置。我不确定这种过渡的正式名称是什么，但您可以在适用于 iPad 的 YouTube 应用程序中看到一个示例。当您点击网格上的其中一个搜索结果缩略图时，它会从缩略图展开，然后在您返回搜索时收缩回缩略图。

我对这两个方面感兴趣:

1. 在一个 View 和另一个 View 之间转换时，您将如何实现这种效果？换句话说，如果 View A 占据了屏幕的某个区域，您将如何将其转换为占据整个屏幕的 View B，反之亦然？

2. 您将如何以这种方式转换到模态视图？换句话说，如果 UIViewController C 当前正在显示并包含占据屏幕一部分的 View D，您如何让它看起来像 View D 正在变成 UIViewController E，它以模态方式呈现在 C 之上？

编辑:我正在添加赏金，看看是否能让这个问题更受欢迎。

编辑:我有一些执行此操作的源代码，Anomie 的想法非常有效，只需进行一些改进。我首先尝试为模态 Controller 的 View (E) 设置动画，但它并没有产生您正在放大屏幕的感觉，因为它没有展开 (C) 中缩略图 View 周围的所有内容。因此，我尝试为原始 Controller 的 View (C) 设置动画，但重新绘制它会导致动画不稳定，并且背景纹理之类的东西无法正确缩放。所以我最后做的是拍摄原始 View Controller (C) 的图像并在模态视图 (E) 内缩放它。这种方法比我原来的方法复杂得多，但看起来确实不错!我认为这也是 iOS 必须如何进行内部转换的方式。不管怎样，这是我在 UIViewController 上作为类别编写的代码。

UIViewController+Transitions.h:

#import <Foundation/Foundation.h>

@interface UIViewController (Transitions)

// make a transition that looks like a modal view 
//  is expanding from a subview
- (void)expandView:(UIView *)sourceView 
        toModalViewController:(UIViewController *)modalViewController;

// make a transition that looks like the current modal view 
//  is shrinking into a subview
- (void)dismissModalViewControllerToView:(UIView *)view;

@end

UIViewController+Transitions.m:

#import "UIViewController+Transitions.h"

@implementation UIViewController (Transitions)

// capture a screen-sized image of the receiver
- (UIImageView *)imageViewFromScreen {
  // make a bitmap copy of the screen
  UIGraphicsBeginImageContextWithOptions(
    [UIScreen mainScreen].bounds.size, YES, 
    [UIScreen mainScreen].scale);
  // get the root layer
  CALayer *layer = self.view.layer;
  while(layer.superlayer) {
    layer = layer.superlayer;
  }
  // render it into the bitmap
  [layer renderInContext:UIGraphicsGetCurrentContext()];
  // get the image
  UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
  // close the context
  UIGraphicsEndImageContext();
  // make a view for the image
  UIImageView *imageView = 
    [[[UIImageView alloc] initWithImage:image]
      autorelease];

  return(imageView);
}

// make a transform that causes the given subview to fill the screen
//  (when applied to an image of the screen)
- (CATransform3D)transformToFillScreenWithSubview:(UIView *)sourceView {
  // get the root view
  UIView *rootView = sourceView;
  while (rootView.superview) rootView = rootView.superview;
  // convert the source view's center and size into the coordinate
  //  system of the root view
  CGRect sourceRect = [sourceView convertRect:sourceView.bounds toView:rootView];
  CGPoint sourceCenter = CGPointMake(
    CGRectGetMidX(sourceRect), CGRectGetMidY(sourceRect));
  CGSize sourceSize = sourceRect.size;
  // get the size and position we're expanding it to
  CGRect screenBounds = [UIScreen mainScreen].bounds;
  CGPoint targetCenter = CGPointMake(
    CGRectGetMidX(screenBounds),
    CGRectGetMidY(screenBounds));
  CGSize targetSize = screenBounds.size;
  // scale so that the view fills the screen
  CATransform3D t = CATransform3DIdentity;
  CGFloat sourceAspect = sourceSize.width / sourceSize.height;
  CGFloat targetAspect = targetSize.width / targetSize.height;
  CGFloat scale = 1.0;
  if (sourceAspect > targetAspect)
    scale = targetSize.width / sourceSize.width;
  else
    scale = targetSize.height / sourceSize.height;
  t = CATransform3DScale(t, scale, scale, 1.0);
  // compensate for the status bar in the screen image
  CGFloat statusBarAdjustment =
    (([UIApplication sharedApplication].statusBarFrame.size.height / 2.0) 
      / scale);
  // transform to center the view
  t = CATransform3DTranslate(t, 
    (targetCenter.x - sourceCenter.x), 
    (targetCenter.y - sourceCenter.y) + statusBarAdjustment, 
    0.0);

  return(t);
}

- (void)expandView:(UIView *)sourceView 
        toModalViewController:(UIViewController *)modalViewController {

  // get an image of the screen
  UIImageView *imageView = [self imageViewFromScreen];

  // insert it into the modal view's hierarchy
  [self presentModalViewController:modalViewController animated:NO];
  UIView *rootView = modalViewController.view;
  while (rootView.superview) rootView = rootView.superview;
  [rootView addSubview:imageView];

  // make a transform that makes the source view fill the screen
  CATransform3D t = [self transformToFillScreenWithSubview:sourceView];

  // animate the transform
  [UIView animateWithDuration:0.4
    animations:^(void) {
      imageView.layer.transform = t;
    } completion:^(BOOL finished) {
      [imageView removeFromSuperview];
    }];
}

- (void)dismissModalViewControllerToView:(UIView *)view {

  // take a snapshot of the current screen
  UIImageView *imageView = [self imageViewFromScreen];

  // insert it into the root view
  UIView *rootView = self.view;
  while (rootView.superview) rootView = rootView.superview;
  [rootView addSubview:imageView];

  // make the subview initially fill the screen
  imageView.layer.transform = [self transformToFillScreenWithSubview:view];
  // remove the modal view
  [self dismissModalViewControllerAnimated:NO];

  // animate the screen shrinking back to normal
  [UIView animateWithDuration:0.4 
    animations:^(void) {
      imageView.layer.transform = CATransform3DIdentity;
    }
    completion:^(BOOL finished) {
      [imageView removeFromSuperview];
    }];
}

@end

您可能会在 UIViewController 子类中使用它:

#import "UIViewController+Transitions.h"

...

- (void)userDidTapThumbnail {

  DetailViewController *detail = 
    [[DetailViewController alloc]
      initWithNibName:nil bundle:nil];

  [self expandView:thumbnailView toModalViewController:detail];

  [detail release];
}

- (void)dismissModalViewControllerAnimated:(BOOL)animated {
  if (([self.modalViewController isKindOfClass:[DetailViewController class]]) &&
      (animated)) {

    [self dismissModalViewControllerToView:thumbnailView];

  }
  else {
    [super dismissModalViewControllerAnimated:animated];
  }
}

编辑:好吧，事实证明它并没有真正处理纵向以外的界面方向。所以我不得不切换到使用 View Controller 在 UIWindow 中动画转换以传递旋转。请参阅下面更复杂的版本:

UIViewController+Transitions.m:

@interface ContainerViewController : UIViewController { }
@end

@implementation ContainerViewController
  - (BOOL)shouldAutorotateToInterfaceOrientation:
          (UIInterfaceOrientation)toInterfaceOrientation {
    return(YES);
  }
@end

...

// get the screen size, compensating for orientation
- (CGSize)screenSize {
  // get the size of the screen (swapping dimensions for other orientations)
  CGSize size = [UIScreen mainScreen].bounds.size;
  if (UIInterfaceOrientationIsLandscape(self.interfaceOrientation)) {
    CGFloat width = size.width;
    size.width = size.height;
    size.height = width;
  }
  return(size);
}

// capture a screen-sized image of the receiver
- (UIImageView *)imageViewFromScreen {

  // get the root layer
  CALayer *layer = self.view.layer;
  while(layer.superlayer) {
    layer = layer.superlayer;
  }
  // get the size of the bitmap
  CGSize size = [self screenSize];
  // make a bitmap to copy the screen into
  UIGraphicsBeginImageContextWithOptions(
    size, YES, 
    [UIScreen mainScreen].scale);
  CGContextRef context = UIGraphicsGetCurrentContext();
  // compensate for orientation
  if (self.interfaceOrientation == UIInterfaceOrientationLandscapeLeft) {
    CGContextTranslateCTM(context, size.width, 0);
    CGContextRotateCTM(context, M_PI_2);
  }
  else if (self.interfaceOrientation == UIInterfaceOrientationLandscapeRight) {
    CGContextTranslateCTM(context, 0, size.height);
    CGContextRotateCTM(context, - M_PI_2);
  }
  else if (self.interfaceOrientation == UIInterfaceOrientationPortraitUpsideDown) {
    CGContextTranslateCTM(context, size.width, size.height);
    CGContextRotateCTM(context, M_PI);
  }
  // render the layer into the bitmap
  [layer renderInContext:context];
  // get the image
  UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
  // close the context
  UIGraphicsEndImageContext();
  // make a view for the image
  UIImageView *imageView = 
    [[[UIImageView alloc] initWithImage:image]
      autorelease];
  // done
  return(imageView);
}

// make a transform that causes the given subview to fill the screen
//  (when applied to an image of the screen)
- (CATransform3D)transformToFillScreenWithSubview:(UIView *)sourceView
                 includeStatusBar:(BOOL)includeStatusBar {
  // get the root view
  UIView *rootView = sourceView;
  while (rootView.superview) rootView = rootView.superview;
  // by default, zoom from the view's bounds
  CGRect sourceRect = sourceView.bounds;
  // convert the source view's center and size into the coordinate
  //  system of the root view
  sourceRect = [sourceView convertRect:sourceRect toView:rootView];
  CGPoint sourceCenter = CGPointMake(
    CGRectGetMidX(sourceRect), CGRectGetMidY(sourceRect));
  CGSize sourceSize = sourceRect.size;
  // get the size and position we're expanding it to
  CGSize targetSize = [self screenSize];
  CGPoint targetCenter = CGPointMake(
    targetSize.width / 2.0,
    targetSize.height / 2.0);

  // scale so that the view fills the screen
  CATransform3D t = CATransform3DIdentity;
  CGFloat sourceAspect = sourceSize.width / sourceSize.height;
  CGFloat targetAspect = targetSize.width / targetSize.height;
  CGFloat scale = 1.0;
  if (sourceAspect > targetAspect)
    scale = targetSize.width / sourceSize.width;
  else
    scale = targetSize.height / sourceSize.height;
  t = CATransform3DScale(t, scale, scale, 1.0);
  // compensate for the status bar in the screen image
  CGFloat statusBarAdjustment = includeStatusBar ?
    (([UIApplication sharedApplication].statusBarFrame.size.height / 2.0) 
      / scale) : 0.0;
  // transform to center the view
  t = CATransform3DTranslate(t, 
    (targetCenter.x - sourceCenter.x), 
    (targetCenter.y - sourceCenter.y) + statusBarAdjustment, 
    0.0);

  return(t);
}

- (void)expandView:(UIView *)sourceView 
        toModalViewController:(UIViewController *)modalViewController {

  // get an image of the screen
  UIImageView *imageView = [self imageViewFromScreen];
  // show the modal view
  [self presentModalViewController:modalViewController animated:NO];
  // make a window to display the transition on top of everything else
  UIWindow *window = 
    [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];
  window.hidden = NO;
  window.backgroundColor = [UIColor blackColor];
  // make a view controller to display the image in
  ContainerViewController *vc = [[ContainerViewController alloc] init];
  vc.wantsFullScreenLayout = YES;
  // show the window
  [window setRootViewController:vc];
  [window makeKeyAndVisible];
  // add the image to the window
  [vc.view addSubview:imageView];

  // make a transform that makes the source view fill the screen
  CATransform3D t = [self 
    transformToFillScreenWithSubview:sourceView
    includeStatusBar:(! modalViewController.wantsFullScreenLayout)];

  // animate the transform
  [UIView animateWithDuration:0.4
    animations:^(void) {
      imageView.layer.transform = t;
    } completion:^(BOOL finished) {
      // we're going to crossfade, so change the background to clear
      window.backgroundColor = [UIColor clearColor];
      // do a little crossfade
      [UIView animateWithDuration:0.25 
        animations:^(void) {
          imageView.alpha = 0.0;
        }
        completion:^(BOOL finished) {
          window.hidden = YES;
          [window release];
          [vc release];
        }];
    }];
}

- (void)dismissModalViewControllerToView:(UIView *)view {

  // temporarily remove the modal dialog so we can get an accurate screenshot 
  //  with orientation applied
  UIViewController *modalViewController = [self.modalViewController retain];
  [self dismissModalViewControllerAnimated:NO];

  // capture the screen
  UIImageView *imageView = [self imageViewFromScreen];
  // put the modal view controller back
  [self presentModalViewController:modalViewController animated:NO];
  [modalViewController release];

  // make a window to display the transition on top of everything else
  UIWindow *window = 
    [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];
  window.hidden = NO;
  window.backgroundColor = [UIColor clearColor];
  // make a view controller to display the image in
  ContainerViewController *vc = [[ContainerViewController alloc] init];
  vc.wantsFullScreenLayout = YES;
  // show the window
  [window setRootViewController:vc];
  [window makeKeyAndVisible];
  // add the image to the window
  [vc.view addSubview:imageView];

  // make the subview initially fill the screen
  imageView.layer.transform = [self 
    transformToFillScreenWithSubview:view
    includeStatusBar:(! self.modalViewController.wantsFullScreenLayout)];

  // animate a little crossfade
  imageView.alpha = 0.0;
  [UIView animateWithDuration:0.15 
    animations:^(void) {
      imageView.alpha = 1.0;
    }
    completion:^(BOOL finished) {
      // remove the modal view
      [self dismissModalViewControllerAnimated:NO];
      // set the background so the real screen won't show through
      window.backgroundColor = [UIColor blackColor];
      // animate the screen shrinking back to normal
      [UIView animateWithDuration:0.4 
        animations:^(void) {
          imageView.layer.transform = CATransform3DIdentity;
        }
        completion:^(BOOL finished) {
          // hide the transition stuff
          window.hidden = YES;
          [window release];
          [vc release];
        }];
    }];

}

哇!但现在它看起来就像没有使用任何受限 API 的 Apple 版本。此外，即使模态视图在前面时方向发生变化，它也能正常工作。

Answer 1

1. 制作效果很简单。您采用全尺寸 View ，初始化其 transform 和 center 以将其定位在缩略图的顶部，将其添加到适当的 super View ，然后在动画 block 中重置transform 和 center 将其定位在最终位置。要关闭 View ，只需执行相反的操作:在动画 block 中设置 transform 和 center 将其定位在缩略图的顶部，然后在完成 block 中将其完全删除.

   请注意，尝试从一个点(即宽度为 0 和高度为 0 的矩形)开始缩放会搞砸。如果您想这样做，请改为从宽度/高度约为 0.00001 的矩形进行缩放。

2. 一种方法是执行与#1 中相同的操作，然后使用动画 NO 调用 presentModalViewController:animated: 以在动画完成时呈现实际的 View Controller (其中，如果操作正确，将不会因 presentModalViewController:animated: 调用而产生可见差异)。和 dismissModalViewControllerAnimated: 后跟与 #1 相同的 NO 以关闭。

   或者您可以像#1 中那样直接操作模态视图 Controller 的 View ，并接受 parentViewController、interfaceOrientation 和其他一些东西将无法正常工作模态视图 Controller ，因为 Apple 不支持我们创建自己的容器 View Controller 。