UIImage 在开始时不适合 UIScrollView

Question

我有一个像这样的图像：

当我将图像加载到 uiimageview 然后作为子视图添加到 uiscrollview 时，开始图像显示如下：

问题是我想在开始时看到所有适合屏幕的图像但它显示已经缩放。有没有办法处理这个问题请帮忙...

我有这样的代码：

[self.view addSubview:scrollView];
UIImageView *tempImageView = 
[[UIImageView alloc] initWithImage:[UIImage imageNamed:@"Tree.jpg"]];
self.imageView = tempImageView;
[tempImageView release];
[scrollView setContentMode:UIViewContentModeScaleAspectFit];
[imageView sizeToFit];
scrollView.backgroundColor=[UIColor blackColor];
scrollView.contentSize = imageView.frame.size;
scrollView.minimumZoomScale = scrollView.frame.size.width / imageView.frame.size.width;
scrollView.maximumZoomScale = 4.0;
[scrollView setZoomScale:1.0];
scrollView.clipsToBounds = YES;
scrollView.delegate = self;
[scrollView addSubview:imageView];

Answer 1

也许您正在寻找这个，

UIImageView *tempImageView = [[[UIImageView alloc] initWithImage:[UIImage imageNamed:@"Watson.jpg"]] autorelease];
tempImageView.frame = scrollView.bounds;
self.imageView = tempImageView;

scrollView.backgroundColor = [UIColor blackColor];
scrollView.minimumZoomScale = 1.0  ;
scrollView.maximumZoomScale = imageView.image.size.width / scrollView.frame.size.width;
scrollView.zoomScale = 1.0;
scrollView.delegate = self;

[scrollView addSubview:imageView];

Answer 2

看一下UIView的contentMode-Property（UIImageView也支持这个）。

imageView.contentMode = UIViewContentModeScaleAspectFit;

这应该有效...

Answer 3

我认为问题出在

UIImageView *tempImageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"Tree.jpg"]];

Apple 的文档中说“此方法调整接收器的框架以匹配指定图像的大小。默认情况下它还会禁用图像视图的用户交互。”

改为使用

UIImageView *tempImageView = [[UIImageView alloc] initWithFrame:CGRectMake(0,0,320,480)];
tempImageView.image = [UIImage imageNamed:@"Tree.jpg"];

Answer 4

请注意，还有 [scrollView ZoomToRect:animated:] 描述 此处

您可以将其设置为图像的外边界，以便它会自动适应您的视图中的图像。但请确保按照上面的 Deepak 解决方案正确设置 MaximumZoomScale。

Answer 5

我使用 Deepak 的解决方案和 Apple 的建议，并将 UIScrollView 子类化，其中包含 UIImageView 。但是，我仅在滚动视图子类的第一个布局上缩放图像，并且仅当帧大小小于图像大小时：

- (void)layoutSubviews
{
[super layoutSubviews];

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

_imageView.frame = frameToCenter;

// If image is bigger than frame, we zoom it on first load (zoom value is smaller than 1.0)
if (_firstLayout) {
    _firstLayout = NO;
    self.zoomScale = (self.frame.size.width < _imageView.image.size.width) ? (self.frame.size.width / _imageView.image.size.width) : 1.0;
}
}

这就是我初始化子类的方式：

- (id)initWithFrame:(CGRect)frame image:(UIImage*)image
{
self = [super initWithFrame:frame];
if (self) {

    _firstLayout = YES;

    _imageView = [[UIImageView alloc] initWithImage:image];
    [self addSubview:_imageView];

    self.backgroundColor = [UIColor blackColor];
    self.minimumZoomScale = 0.1;
    self.maximumZoomScale = 10;


    self.delegate = self;
}
return self;
}