我正在尝试在iOS中制作过渡动画，其中视图或视图控制器似乎会扩展以填充整个屏幕，然后在完成时收缩回到其原来的位置。我不确定这种类型的过渡是否正式调用，但您可以在YouTube的YouTube应用中看到一个示例。当您点击网格上的某个搜索结果缩略图时，它会从缩略图中展开，然后在您返回搜索时收缩回缩略图。
我对此有两个方面感兴趣：
在一个视图和另一个视图之间进行转换时，如何实现此效果？换句话说，如果视图A占据屏幕的某个区域，您将如何将其转换为占据整个屏幕的视图B，反之亦然？
您如何以这种方式过渡到模态视图？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视图D，那么如何使它看起来像视图D变成UIViewController E，它在C上以模态方式呈现？
< / LI>编辑：我正在添加一笔赏金，看看是否能让这个问题更受关注。
编辑：我有一些源代码可以做到这一点，Anomie的想法就像一个魅力，有一些改进。我首先尝试动画模态控制器的视图（E），但它没有产生感觉像你正在放大屏幕的效果，因为它没有扩展（C）中缩略图视图周围的所有东西。因此，我尝试动画原始控制器的视图（C），但重绘它为一个生涩的动画，像背景纹理之类的东西没有正确缩放。所以我最后做的是拍摄原始视图控制器（C）的图像并在模态视图（E）内部进行缩放。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iOS也必须如何进行内部转换。无论如何，这是我在UIViewController上作为类别编写的代码。
的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
的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
你可以在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：嗯，事实证明，除了肖像之外，它并没有真正处理界面方向。所以我不得不切换到UIWindow中的转换动画，使用视图控制器来传递旋转。请参阅下面更复杂的版本：
的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];
}];
}];
}
呼！但现在它看起来就像Apple的版本没有使用任何受限制的API。此外，即使在模态视图位于前面时方向发生变化，它仍然有效。
答案 0 :(得分：13)
使效果很简单。您可以使用全尺寸视图，初始化其transform和center以将其放置在缩略图顶部，将其添加到相应的超级视图，然后在动画块中重置transform并center将其定位在最终位置。要取消视图，只需执行相反的操作：在动画块集transform和center中将其放置在缩略图顶部，然后在完成块中将其完全删除。
请注意，尝试从一个点（即一个宽度为0，高度为0的矩形）进行缩放会使事情变得棘手。如果您想这样做，请从宽度/高度变为0.00001的矩形进行缩放。
一种方法是在＃1中执行相同的操作，然后使用动画NO调用presentModalViewController:animated:以在动画完成时呈现实际的视图控制器（如果操作正确，将导致由于presentModalViewController:animated:调用没有明显的差异。并且dismissModalViewControllerAnimated:带有NO，后跟＃1中的相同，以消除。
或者您可以像在＃1中一样直接操作模态视图控制器的视图，并接受parentViewController，interfaceOrientation，以及其他一些东西在模态视图控制器中无法正常工作，因为Apple不支持我们创建自己的容器视图控制器。
答案 1 :(得分：9)
观看Youtube iPad动画后，我发现这只是一种幻觉。我们假设搜索结果为SearchViewController，视频本身为DetailViewController，以及视频的其他信息。
DetailViewController有一个类似- (id)initWithFullscreen的方法，它使用视频的全屏空间启动视图控制器。
所以序列如下：
initWithFullscreen创建的，但未显示animated:NO的DetailViewController（如Anomie所述）。似乎youtube应用程序没有做任何更好的事情，赠送的是“放大”动画在放映完整视频之前缩放到黑色方块。