我正在使用
SnapKit
用于在我的iOS应用程序中自动布局。
我需要在屏幕的最顶部显示图像视图。它将具有动态高度和宽度的图像。我需要它的顶部边缘与视图的顶部对齐。我需要它水平居中。我需要它与屏幕的左右边距大于或等于10。我需要它的高度根据内容动态变化,最大高度等于300。我需要它保持其纵横比,并根据需要使用自动布局自动减小其宽度或高度。
我认为下面的代码应该能完成这项工作:
let padding = 10.0
let preview = UIImageView()
preview.setContentHuggingPriority(.required, for: .vertical)
preview.setContentHuggingPriority(.required, for: .horizontal)
preview.backgroundColor = .red
preview.contentMode = .scaleAspectFit
let image = UIImage(named: "demo3")!
preview.image = image
preview.clipsToBounds = true
view.addSubview(preview)
preview.snp.makeConstraints { make in
make.top.equalTo(view.safeAreaLayoutGuide.snp.top)
make.centerX.equalToSuperview()
make.left.right.greaterThanOrEqualToSuperview().inset(padding).priority(.required)
make.height.lessThanOrEqualTo(300).priority(.required)
make.width.equalTo(preview.snp.height).multipliedBy(image.size.width / image.size.height).priority(.required)
}
这似乎适用于风景图像(宽度大于高度),但在肖像图像中会中断:
在风景图像中工作:
肖像图像失败。注意高度不再是
lessThanOrEqualTo(300)
:
这是由于Xcode打印了一条警告,指出它无法满足约束,必须打破高度约束:
Unable to simultaneously satisfy constraints.
Probably at least one of the constraints in the following list is one you don't want.
Try this:
(1) look at each constraint and try to figure out which you don't expect;
(2) find the code that added the unwanted constraint or constraints and fix it.
(
"<SnapKit.LayoutConstraint:[email protected]#54 UIImageView:0x7f81b19101e0.centerX == UIView:0x7f81b183dc30.centerX>",
"<SnapKit.LayoutConstraint:[email protected]#55 UIImageView:0x7f81b19101e0.right >= UIView:0x7f81b183dc30.right - 12.0>",
"<SnapKit.LayoutConstraint:[email protected]#56 UIImageView:0x7f81b19101e0.height <= 300.0>",
"<SnapKit.LayoutConstraint:[email protected]#57 UIImageView:0x7f81b19101e0.width == UIImageView:0x7f81b19101e0.height * 0.666748046875>",
"<NSLayoutConstraint:0x600003e37a20 'UIView-Encapsulated-Layout-Width' UIView:0x7f81b183dc30.width == 430 (active)>"
)
Will attempt to recover by breaking constraint
<SnapKit.LayoutConstraint:[email protected]#56 UIImageView:0x7f81b19101e0.height <= 300.0>
我原本预计它会在保持纵横比以满足条件的同时减小宽度。但事实并非如此。
