20

在我的应用程序中，我想向用户展示一个全屏照片查看器，就像在照片应用程序中使用的那样。这仅适用于单张照片，因此应该非常简单。我只希望用户能够查看这张具有缩放和平移功能的照片。

我有大部分工作。而且，如果我不将我的 UIImageView 居中，一切都会完美运行。但是，当图像充分缩小时，我真的希望 UIImageView 在屏幕上居中。我不希望它粘在滚动视图的左上角。

一旦我试图使这个视图居中，我的垂直可滚动区域似乎比它应该的要大。因此，一旦我放大一点，我就可以滚动超过图像顶部约 100 像素。我究竟做错了什么？

@interface MyPhotoViewController : UIViewController <UIScrollViewDelegate>
{
    UIImage* photo;
    UIImageView *imageView;
}
- (id)initWithPhoto:(UIImage *)aPhoto;
@end

@implementation MyPhotoViewController

- (id)initWithPhoto:(UIImage *)aPhoto
{
    if (self = [super init])
    {
        photo = [aPhoto retain];

        // Some 3.0 SDK code here to ensure this view has a full-screen
        // layout.
    }

    return self;
}

- (void)dealloc
{
    [photo release];
    [imageView release];
    [super dealloc];
}

- (void)loadView
{
    // Set the main view of this UIViewController to be a UIScrollView.
    UIScrollView *scrollView = [[UIScrollView alloc] init];
    [self setView:scrollView];
    [scrollView release];
}

- (void)viewDidLoad
{
    [super viewDidLoad];

    // Initialize the scroll view.
    CGSize photoSize = [photo size];
    UIScrollView *scrollView = (UIScrollView *)[self view];
    [scrollView setDelegate:self];
    [scrollView setBackgroundColor:[UIColor blackColor]];

    // Create the image view. We push the origin to (0, -44) to ensure
    // that this view displays behind the navigation bar.
    imageView = [[UIImageView alloc] initWithFrame:CGRectMake(0.0, -44.0,
        photoSize.width, photoSize.height)];
    [imageView setImage:photo];
    [scrollView addSubview:imageView];

    // Configure zooming.
    CGSize screenSize = [[UIScreen mainScreen] bounds].size;
    CGFloat widthRatio = screenSize.width / photoSize.width;
    CGFloat heightRatio = screenSize.height / photoSize.height;
    CGFloat initialZoom = (widthRatio > heightRatio) ? heightRatio : widthRatio;
    [scrollView setMaximumZoomScale:3.0];
    [scrollView setMinimumZoomScale:initialZoom];
    [scrollView setZoomScale:initialZoom];
    [scrollView setBouncesZoom:YES];
    [scrollView setContentSize:CGSizeMake(photoSize.width * initialZoom,
        photoSize.height * initialZoom)];

    // Center the photo. Again we push the center point up by 44 pixels
    // to account for the translucent navigation bar.
    CGPoint scrollCenter = [scrollView center];
    [imageView setCenter:CGPointMake(scrollCenter.x,
        scrollCenter.y - 44.0)];
}

- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];
    [[[self navigationController] navigationBar] setBarStyle:UIBarStyleBlackTranslucent];
    [[UIApplication sharedApplication] setStatusBarStyle:UIStatusBarStyleBlackTranslucent animated:YES];
}

- (void)viewWillDisappear:(BOOL)animated
{
    [super viewWillDisappear:animated];
    [[[self navigationController] navigationBar] setBarStyle:UIBarStyleDefault];
    [[UIApplication sharedApplication] setStatusBarStyle:UIStatusBarStyleDefault animated:YES];
}

- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView
{
    return imageView;
}

@end
4

5 回答 5

28

这段代码应该可以在大多数版本的 iOS 上运行（并且已经过测试可以在 3.1 以上版本上运行）。

它基于PhotoScroller 的 Apple WWDC 代码。

将以下内容添加到您的子类中UIScrollView，并替换tileContainerView为包含您的图像或图块的视图：

- (void)layoutSubviews {
    [super layoutSubviews];

    // center the image as it becomes smaller than the size of the screen
    CGSize boundsSize = self.bounds.size;
    CGRect frameToCenter = tileContainerView.frame;

    // center horizontally
    if (frameToCenter.size.width < boundsSize.width)
        frameToCenter.origin.x = (boundsSize.width - frameToCenter.size.width) / 2;
    else
        frameToCenter.origin.x = 0;

    // center vertically
    if (frameToCenter.size.height < boundsSize.height)
        frameToCenter.origin.y = (boundsSize.height - frameToCenter.size.height) / 2;
    else
        frameToCenter.origin.y = 0;

    tileContainerView.frame = frameToCenter;
}
于 2010-08-13T17:00:00.993 回答
2

你检查过 UIViewAutoresizing 选项吗？

（来自文档）

UIViewAutoresizing
Specifies how a view is automatically resized.

enum {
   UIViewAutoresizingNone                 = 0,
   UIViewAutoresizingFlexibleLeftMargin   = 1 << 0,
   UIViewAutoresizingFlexibleWidth        = 1 << 1,
   UIViewAutoresizingFlexibleRightMargin  = 1 << 2,
   UIViewAutoresizingFlexibleTopMargin    = 1 << 3,
   UIViewAutoresizingFlexibleHeight       = 1 << 4,
   UIViewAutoresizingFlexibleBottomMargin = 1 << 5
};
typedef NSUInteger UIViewAutoresizing;
于 2010-01-29T21:24:55.003 回答
1

您是否使用 IB 添加滚动视图？将滚动视图的自动调整大小选项更改为附加图像。 替代文字

于 2009-04-28T04:35:29.757 回答
0

我认为其背后的原因是因为 zoomScale 适用于整个 contentSize，而不管 scrollView 内的子视图的实际大小（在你的情况下它是一个 imageView）。contentSize 高度似乎总是等于或大于 scrollView 框架的高度，但永远不会更小。因此，当对其应用缩放时，contentSize 的高度也会乘以 zoomScale 因子，这就是为什么您会获得额外的 100 像素左右的垂直滚动。

于 2009-08-04T19:22:32.593 回答
-1

您可能希望设置滚动视图的边界 = 图像视图的边界，然后将滚动视图置于其包含视图的中心。如果您将视图放置在滚动视图中与顶部偏移的位置，您将获得其上方的空白空间。

于 2009-04-27T21:29:43.993 回答