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
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
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~
你不是在描述比例匹配;您正在描述方面拟合。(我已经编辑了你的问题。)子视图变得尽可能大，同时保持它的纵横比并完全适合它的父视图。
不管怎样，你可以用自动布局来做这个。你完全可以在Xcode 5.1的IB中完成。让我们从一些视图开始:
浅绿色视图的长宽比为4:1。深绿色视图的长宽比为1:4。我将设置约束，以便蓝色视图填充屏幕的上半部分，粉红色视图填充屏幕的下半部分，每个绿色视图尽可能地扩展，同时保持其纵横比并适合其容器。
首先，我将在蓝色视图的所有四个边创建约束。我将它固定到每条边上最近的邻居，距离为0。我确保关闭了页边距:
注意，我还没有更新框架。我发现在设置约束时在视图之间留出空间更容易，只需手动将常量设置为0(或任何值)。
接下来，我将粉红色视图的左、下、右边缘固定到最近的邻居。我不需要设置上边约束因为它的上边已经被约束到蓝色视图的下边。
我还需要在粉色和蓝色视图之间设置等高约束。这将使它们各自占据屏幕的一半:
如果我告诉Xcode现在更新所有的帧，我得到这个:
所以到目前为止我建立的约束条件是正确的。我撤销它并开始处理浅绿色视图。
对浅绿色视图进行方面拟合需要五个约束:
A required-priority aspect ratio constraint on the light green view. You can create this constraint in a xib or storyboard with Xcode 5.1 or later. A required-priority constraint limiting the width of the light green view to be less than or equal to the width of its container. A high-priority constraint setting the width of the light green view to be equal to the width of its container. A required-priority constraint limiting the height of the light green view to be less than or equal to the height of its container. A high-priority constraint setting the height of the light green view to be equal to the height of its container.
让我们考虑两个宽度约束。小于或等于约束本身不足以确定浅绿色视图的宽度;许多宽度将符合限制。由于存在歧义，自动布局将尝试选择一个解决方案，使其他约束(高优先级但不是必需的)中的错误最小化。最小化误差意味着使宽度尽可能接近容器的宽度，同时不违反所需的小于或等于约束。
同样的事情也发生在高度限制上。由于还需要宽高比约束，它只能沿一个轴最大化子视图的大小(除非容器恰好与子视图具有相同的宽高比)。
首先我创建纵横比约束:
然后我用容器创建等宽和等高的约束:
我需要将这些约束编辑为小于或等于约束:
接下来，我需要用容器创建另一组等宽和高的约束:
我需要让这些新的约束的优先级低于要求的优先级:
最后，你要求子视图在它的容器中居中，所以我将设置这些约束:
现在，为了测试，我将选择视图控制器并让Xcode更新所有的帧。这是我得到的结果:
哦!子视图已经扩展到完全填充它的容器。如果我选择它，我可以看到它保持了它的纵横比，但它在做一个方面填充而不是方面拟合。
问题是，在一个小于或等于的约束上，哪个视图在约束的两端很重要，而Xcode设置的约束与我的期望相反。我可以选择两个约束中的每一个，并反转其第一项和第二项。相反，我将只选择子视图并将约束更改为大于或等于:
Xcode更新布局:
现在我对底部的深绿色视图做同样的事情。我需要确保它的纵横比是1:4 (Xcode以一种奇怪的方式调整了它，因为它没有约束)。我不会再展示步骤了，因为它们是一样的。结果如下:
现在我可以在iPhone 4S模拟器中运行它，它的屏幕大小与IB使用的屏幕大小不同，并测试旋转:
我可以在iPhone 6模拟器中进行测试:
为了方便大家，我上传了我最后的故事板。
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
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 ();
}
}
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);
}];
