看起来aspect fit
默认情况下将图像与框架底部对齐。有没有办法在保持aspect fit
不变的同时覆盖对齐方式?
**编辑**
此问题早于自动布局。事实上,在WWDC 2012中,自动布局正在被揭示,这个问题被问到的同一周
简而言之,您不能用UIImageView
来做到这一点。
一种解决方案是将包含UIImageView
的UIView
子类化,并根据图像大小更改其帧。例如,您可以在此处找到一个版本。
将UIImageView
的底部布局约束优先级设置为最低(即 250),它将为您处理。
执行此操作的方法是修改 UIImageView 层的 contentRect。 我的项目(UIImageView 的子类)中的以下代码假定 scaleToFill 并偏移图像,使其向上、向下、向左或向右对齐,而不是默认的中心对齐方式。对于aspectFit将是一个类似的解决方案。
typedef NS_OPTIONS(NSUInteger, AHTImageAlignmentMode) {
AHTImageAlignmentModeCenter = 0,
AHTImageAlignmentModeLeft = 1 << 0,
AHTImageAlignmentModeRight = 1 << 1,
AHTImageAlignmentModeTop = 1 << 2,
AHTImageAlignmentModeBottom = 1 << 3,
AHTImageAlignmentModeDefault = AHTImageAlignmentModeCenter,
};
- (void)updateImageViewContentsRect {
CGRect imageViewContentsRect = CGRectMake(0, 0, 1, 1);
if (self.image.size.height > 0 && self.bounds.size.height > 0) {
CGRect imageViewBounds = self.bounds;
CGSize imageSize = self.image.size;
CGFloat imageViewFactor = imageViewBounds.size.width / imageViewBounds.size.height;
CGFloat imageFactor = imageSize.width / imageSize.height;
if (imageFactor > imageViewFactor) {
//Image is wider than the view, so height will match
CGFloat scaledImageWidth = imageViewBounds.size.height * imageFactor;
CGFloat xOffset = 0.0;
if (BM_CONTAINS_BIT(self.alignmentMode, AHTImageAlignmentModeLeft)) {
xOffset = -(scaledImageWidth - imageViewBounds.size.width) / 2;
} else if (BM_CONTAINS_BIT(self.alignmentMode, AHTImageAlignmentModeRight)) {
xOffset = (scaledImageWidth - imageViewBounds.size.width) / 2;
}
imageViewContentsRect.origin.x = (xOffset / scaledImageWidth);
} else if (imageFactor < imageViewFactor) {
CGFloat scaledImageHeight = imageViewBounds.size.width / imageFactor;
CGFloat yOffset = 0.0;
if (BM_CONTAINS_BIT(self.alignmentMode, AHTImageAlignmentModeTop)) {
yOffset = -(scaledImageHeight - imageViewBounds.size.height) / 2;
} else if (BM_CONTAINS_BIT(self.alignmentMode, AHTImageAlignmentModeBottom)) {
yOffset = (scaledImageHeight - imageViewBounds.size.height) / 2;
}
imageViewContentsRect.origin.y = (yOffset / scaledImageHeight);
}
}
self.layer.contentsRect = imageViewContentsRect;
}
迅捷版
///Works perfectly with AspectFill. Note there's no protection for obscure issues like (say) scaledImageWidth is zero.
class AlignmentImageView: UIImageView {
enum HorizontalAlignment { case left, center, right }
enum VerticalAlignment { case top, center, bottom }
var horizontalAlignment: HorizontalAlignment = .center { didSet { updateContentsRect() } }
var verticalAlignment: VerticalAlignment = .center { didSet { updateContentsRect() } }
override var image: UIImage? { didSet { updateContentsRect() } }
override func layoutSubviews() {
super.layoutSubviews()
updateContentsRect()
}
private func updateContentsRect() {
var contentsRect = CGRect(origin: .zero, size: CGSize(width: 1, height: 1))
guard let imageSize = image?.size else {
layer.contentsRect = contentsRect
return
}
let viewBounds = bounds
let imageViewFactor = viewBounds.size.width / viewBounds.size.height
let imageFactor = imageSize.width / imageSize.height
if imageFactor > imageViewFactor {
// Image is wider than the view, so height will match
let scaledImageWidth = viewBounds.size.height * imageFactor
var xOffset: CGFloat = 0.0
if case .left = horizontalAlignment {
xOffset = -(scaledImageWidth - viewBounds.size.width) / 2
}
else if case .right = horizontalAlignment {
xOffset = (scaledImageWidth - viewBounds.size.width) / 2
}
contentsRect.origin.x = xOffset / scaledImageWidth
}
else {
let scaledImageHeight = viewBounds.size.width / imageFactor
var yOffset: CGFloat = 0.0
if case .top = verticalAlignment {
yOffset = -(scaledImageHeight - viewBounds.size.height) / 2
}
else if case .bottom = verticalAlignment {
yOffset = (scaledImageHeight - viewBounds.size.height) / 2
}
contentsRect.origin.y = yOffset / scaledImageHeight
}
layer.contentsRect = contentsRect
}
}
图像填充宽度并仅占据适合图像所需的高度(宽度说话)
斯威夫特 4.2
:let image = UIImage(named: "my_image")!
let ratio = image.size.width / image.size.height
cardImageView.widthAnchor
.constraint(equalTo: cardImageView.heightAnchor, multiplier: ratio).isActive = true
我也有类似的问题。最简单的方法是创建自己的UIImageView子类。我为子类 3 添加了属性,因此现在可以在不知道内部实现的情况下轻松使用它:
@property (nonatomic) LDImageVerticalAlignment imageVerticalAlignment;
@property (nonatomic) LDImageHorizontalAlignment imageHorizontalAlignment;
@property (nonatomic) LDImageContentMode imageContentMode;
你可以在这里查看:https://github.com/LucasssD/LDAlignmentImageView
- 将纵横比约束与图像比例添加。
- 不要将UIImageView固定到底部。
- 如果要动态更改 UIImage,请记住更新纵横比约束。
我在界面生成器中通过对 UIImageView 的高度设置约束来原生解决此问题,因为当图像大于屏幕大小时,图像将始终被"推高"。
更具体地说,我将 UIImageView 设置为与其所在的视图相同的高度(通过高度约束),然后在 IB 中使用间距约束定位 UIImageView。这导致UIImageView具有"方面拟合",该拟合仍然遵循我在IB中设置的顶部间距约束。
如果你能够子类化UIImageView
,那么你就可以覆盖image
var。
override var image: UIImage? {
didSet {
self.sizeToFit()
}
}
在 Objective-C 中,你可以通过覆盖 setter 来做同样的事情。