我想使用AutoLayout以一种让人联想到UIImageView的方面适合内容模式的方式来大小和布局视图。
我在接口生成器的容器视图中有一个子视图。子视图有一些固有的纵横比，我希望尊重它。容器视图的大小在运行时之前是未知的。
如果容器视图的纵横比比子视图宽，那么我希望子视图的高度等于父视图的高度。
如果容器视图的纵横比大于子视图，那么我希望子视图的宽度等于父视图的宽度。
在这两种情况下，我希望子视图在容器视图中水平和垂直居中。
在Xcode 6或之前的版本中，是否有一种方法可以使用AutoLayout约束来实现这一点?理想情况下使用Interface Builder，但如果不是，也许可以通过编程方式定义这样的约束。
当前回答
我发现自己想要aspect-fill行为，这样UIImageView就能保持自己的长宽比并完全填充容器视图。令人困惑的是，我的UIImageView打破了高优先级等宽和等高的限制(在Rob的回答中描述了)，并以全分辨率渲染。
解决方案是简单地设置UIImageView的内容压缩阻力优先级低于等宽等高约束的优先级:
其他回答
我找不到任何现成的完全程序化的解决方案，所以这里是我在swift 5中对方面填充扩展到视图的看法:
extension UIView {
public enum FillingMode {
case full(padding:Int = 0)
case aspectFit(ratio:CGFloat)
// case aspectFill ...
}
public func addSubview(_ newView:UIView, withFillingMode fillingMode:FillingMode) {
newView.translatesAutoresizingMaskIntoConstraints = false
addSubview(newView)
switch fillingMode {
case let .full(padding):
let cgPadding = CGFloat(padding)
NSLayoutConstraint.activate([
newView.leadingAnchor.constraint(equalTo: leadingAnchor, constant: cgPadding),
newView.trailingAnchor.constraint(equalTo: trailingAnchor, constant: -cgPadding),
newView.topAnchor.constraint(equalTo: topAnchor, constant: cgPadding),
newView.bottomAnchor.constraint(equalTo: bottomAnchor, constant: -cgPadding)
])
case let .aspectFit(ratio):
guard ratio != 0 else { return }
NSLayoutConstraint.activate([
newView.centerXAnchor.constraint(equalTo: centerXAnchor),
newView.centerYAnchor.constraint(equalTo: centerYAnchor),
newView.leadingAnchor.constraint(greaterThanOrEqualTo: leadingAnchor),
newView.leadingAnchor.constraint(equalTo: leadingAnchor).usingPriority(900),
newView.trailingAnchor.constraint(lessThanOrEqualTo: trailingAnchor),
newView.trailingAnchor.constraint(equalTo: trailingAnchor).usingPriority(900),
newView.topAnchor.constraint(greaterThanOrEqualTo: topAnchor),
newView.topAnchor.constraint(equalTo: topAnchor).usingPriority(900),
newView.bottomAnchor.constraint(lessThanOrEqualTo: bottomAnchor),
newView.bottomAnchor.constraint(equalTo: bottomAnchor).usingPriority(900),
newView.heightAnchor.constraint(equalTo: newView.widthAnchor, multiplier: CGFloat(ratio)),
])
}
}
}
这里是优先级扩展(来自另一个线程，但我“保护它”与1…1000之间的一些模式匹配:
extension NSLayoutConstraint {
/// Returns the constraint sender with the passed priority.
///
/// - Parameter priority: The priority to be set.
/// - Returns: The sended constraint adjusted with the new priority.
func usingPriority(_ priority: Int) -> NSLayoutConstraint {
self.priority = UILayoutPriority( (1...1000 ~= priority) ? Float(priority) : 1000 )
return self
}
}
希望能有所帮助~
我需要一个解决方案从接受的答案，但从代码执行。我发现的最优雅的方式是使用砌体框架。
#import "Masonry.h"
...
[view mas_makeConstraints:^(MASConstraintMaker *make) {
make.width.equalTo(view.mas_height).multipliedBy(aspectRatio);
make.size.lessThanOrEqualTo(superview);
make.size.equalTo(superview).with.priorityHigh();
make.center.equalTo(superview);
}];
这是针对macOS的。
我有问题使用罗伯的方式来实现方面适合OS X应用程序。但我用了另一种方法——我没有使用宽度和高度，而是使用了前导、后导、顶部和底部空间。
基本上，添加两个前导空格，其中一个是>= 0 @1000所需优先级，另一个是= 0 @250低优先级。对尾距、顶部和底部空间做相同的设置。
当然，你需要设置纵横比和中心X和中心Y。
然后工作就完成了!
这是@rob_mayoff对以代码为中心的方法的出色回答的一个端口，使用NSLayoutAnchor对象并移植到Xamarin。对我来说，NSLayoutAnchor和相关类使AutoLayout更容易编程:
public class ContentView : UIView
{
public ContentView (UIColor fillColor)
{
BackgroundColor = fillColor;
}
}
public class MyController : UIViewController
{
public override void ViewDidLoad ()
{
base.ViewDidLoad ();
//Starting point:
var view = new ContentView (UIColor.White);
blueView = new ContentView (UIColor.FromRGB (166, 200, 255));
view.AddSubview (blueView);
lightGreenView = new ContentView (UIColor.FromRGB (200, 255, 220));
lightGreenView.Frame = new CGRect (20, 40, 200, 60);
view.AddSubview (lightGreenView);
pinkView = new ContentView (UIColor.FromRGB (255, 204, 240));
view.AddSubview (pinkView);
greenView = new ContentView (UIColor.Green);
greenView.Frame = new CGRect (80, 20, 40, 200);
pinkView.AddSubview (greenView);
//Now start doing in code the things that @rob_mayoff did in IB
//Make the blue view size up to its parent, but half the height
blueView.TranslatesAutoresizingMaskIntoConstraints = false;
var blueConstraints = new []
{
blueView.LeadingAnchor.ConstraintEqualTo(view.LayoutMarginsGuide.LeadingAnchor),
blueView.TrailingAnchor.ConstraintEqualTo(view.LayoutMarginsGuide.TrailingAnchor),
blueView.TopAnchor.ConstraintEqualTo(view.LayoutMarginsGuide.TopAnchor),
blueView.HeightAnchor.ConstraintEqualTo(view.LayoutMarginsGuide.HeightAnchor, (nfloat) 0.5)
};
NSLayoutConstraint.ActivateConstraints (blueConstraints);
//Make the pink view same size as blue view, and linked to bottom of blue view
pinkView.TranslatesAutoresizingMaskIntoConstraints = false;
var pinkConstraints = new []
{
pinkView.LeadingAnchor.ConstraintEqualTo(blueView.LeadingAnchor),
pinkView.TrailingAnchor.ConstraintEqualTo(blueView.TrailingAnchor),
pinkView.HeightAnchor.ConstraintEqualTo(blueView.HeightAnchor),
pinkView.TopAnchor.ConstraintEqualTo(blueView.BottomAnchor)
};
NSLayoutConstraint.ActivateConstraints (pinkConstraints);
//From here, address the aspect-fitting challenge:
lightGreenView.TranslatesAutoresizingMaskIntoConstraints = false;
//These are the must-fulfill constraints:
var lightGreenConstraints = new []
{
//Aspect ratio of 1 : 5
NSLayoutConstraint.Create(lightGreenView, NSLayoutAttribute.Height, NSLayoutRelation.Equal, lightGreenView, NSLayoutAttribute.Width, (nfloat) 0.20, 0),
//Cannot be larger than parent's width or height
lightGreenView.WidthAnchor.ConstraintLessThanOrEqualTo(blueView.WidthAnchor),
lightGreenView.HeightAnchor.ConstraintLessThanOrEqualTo(blueView.HeightAnchor),
//Center in parent
lightGreenView.CenterYAnchor.ConstraintEqualTo(blueView.CenterYAnchor),
lightGreenView.CenterXAnchor.ConstraintEqualTo(blueView.CenterXAnchor)
};
//Must-fulfill
foreach (var c in lightGreenConstraints)
{
c.Priority = 1000;
}
NSLayoutConstraint.ActivateConstraints (lightGreenConstraints);
//Low priority constraint to attempt to fill parent as much as possible (but lower priority than previous)
var lightGreenLowPriorityConstraints = new []
{
lightGreenView.WidthAnchor.ConstraintEqualTo(blueView.WidthAnchor),
lightGreenView.HeightAnchor.ConstraintEqualTo(blueView.HeightAnchor)
};
//Lower priority
foreach (var c in lightGreenLowPriorityConstraints)
{
c.Priority = 750;
}
NSLayoutConstraint.ActivateConstraints (lightGreenLowPriorityConstraints);
//Aspect-fit on the green view now
greenView.TranslatesAutoresizingMaskIntoConstraints = false;
var greenConstraints = new []
{
//Aspect ratio of 5:1
NSLayoutConstraint.Create(greenView, NSLayoutAttribute.Height, NSLayoutRelation.Equal, greenView, NSLayoutAttribute.Width, (nfloat) 5.0, 0),
//Cannot be larger than parent's width or height
greenView.WidthAnchor.ConstraintLessThanOrEqualTo(pinkView.WidthAnchor),
greenView.HeightAnchor.ConstraintLessThanOrEqualTo(pinkView.HeightAnchor),
//Center in parent
greenView.CenterXAnchor.ConstraintEqualTo(pinkView.CenterXAnchor),
greenView.CenterYAnchor.ConstraintEqualTo(pinkView.CenterYAnchor)
};
//Must fulfill
foreach (var c in greenConstraints)
{
c.Priority = 1000;
}
NSLayoutConstraint.ActivateConstraints (greenConstraints);
//Low priority constraint to attempt to fill parent as much as possible (but lower priority than previous)
var greenLowPriorityConstraints = new []
{
greenView.WidthAnchor.ConstraintEqualTo(pinkView.WidthAnchor),
greenView.HeightAnchor.ConstraintEqualTo(pinkView.HeightAnchor)
};
//Lower-priority than above
foreach (var c in greenLowPriorityConstraints)
{
c.Priority = 750;
}
NSLayoutConstraint.ActivateConstraints (greenLowPriorityConstraints);
this.View = view;
view.LayoutIfNeeded ();
}
}
罗伯，你的答案太棒了! 我也知道这个问题是专门关于实现这一点使用自动布局。但是，作为参考，我想展示如何在代码中实现这一点。像Rob演示的那样，设置顶部和底部视图(蓝色和粉红色)。然后你创建一个自定义的AspectFitView:
AspectFitView.h:
#import <UIKit/UIKit.h>
@interface AspectFitView : UIView
@property (nonatomic, strong) UIView *childView;
@end
AspectFitView.m：
#import "AspectFitView.h"
@implementation AspectFitView
- (void)setChildView:(UIView *)childView
{
if (_childView) {
[_childView removeFromSuperview];
}
_childView = childView;
[self addSubview:childView];
[self setNeedsLayout];
}
- (void)layoutSubviews
{
[super layoutSubviews];
if (_childView) {
CGSize childSize = _childView.frame.size;
CGSize parentSize = self.frame.size;
CGFloat aspectRatioForHeight = childSize.width / childSize.height;
CGFloat aspectRatioForWidth = childSize.height / childSize.width;
if ((parentSize.height * aspectRatioForHeight) > parentSize.height) {
// whole height, adjust width
CGFloat width = parentSize.width * aspectRatioForWidth;
_childView.frame = CGRectMake((parentSize.width - width) / 2.0, 0, width, parentSize.height);
} else {
// whole width, adjust height
CGFloat height = parentSize.height * aspectRatioForHeight;
_childView.frame = CGRectMake(0, (parentSize.height - height) / 2.0, parentSize.width, height);
}
}
}
@end
接下来，您将故事板中蓝色和粉色视图的类更改为AspectFitViews。最后，你设置两个输出到你的视图控制器topAspectFitView和bottomAspectFitView，并在viewDidLoad中设置它们的childViews:
- (void)viewDidLoad {
[super viewDidLoad];
UIView *top = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 500, 100)];
top.backgroundColor = [UIColor lightGrayColor];
UIView *bottom = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 100, 500)];
bottom.backgroundColor = [UIColor greenColor];
_topAspectFitView.childView = top;
_bottomAspectFitView.childView = bottom;
}
所以在代码中做到这一点并不难，它仍然具有很强的适应性，适用于可变大小的视图和不同的纵横比。
2015年7月更新:在这里找到一个演示应用程序:https://github.com/jfahrenkrug/SPWKAspectFitView
