问题描述

我希望我的 UIImageView 根据它所显示的实际图像的大小来增长或缩小.但我希望它保持垂直居中，距离超级视图的前沿 10 点.

I want my UIImageView to grow or shrink depending on the size of what the actual image it's displaying is. But I want it to stay vertically centered and 10pts from the leading edge of the superview.

但是，如果我设置了这两个约束，它会抱怨我没有设置足够的约束来满足自动布局.对我来说，它似乎完美地描述了我想要的东西.我错过了什么?

However, if I set these two constraints it complains I haven't set up enough constraints to satisfy Auto Layout. To me it seems to perfectly describe what I want. What am I missing?

推荐答案

图像视图的固有大小已经取决于图像的大小.您的假设(和约束是正确的).

The image view's intrinsic size is already dependent on the size of the image. Your assumptions (and constraints are correct).

但是，如果您在界面构建器中设置了图像视图并且没有为它提供图像，那么布局系统(界面构建器)将不知道您的图像视图在编译时应该有多大.您的布局不明确，因为您的图像视图可能有多种尺寸.这就是引发错误的原因.

However, if you've set up your image view in interface builder and have not provided it with an image, then the layout system (interface builder) won't know how big your image view is supposed to be at compile time. Your layout is ambiguous because your image view could be many sizes. This is what throws the errors.

一旦您设置了图像视图的图像属性，图像视图的固有大小就由图像的大小定义.如果您在运行时设置视图，那么您可以完全按照 Anna 提到的操作，并在图像视图的属性检查器中为界面构建器提供占位符"内在大小.这告诉界面生成器，暂时使用这个尺寸，稍后我会给你一个真实的尺寸".占位符约束在运行时被忽略.

Once you set your image view's image property, then the image view's intrinsic size is defined by the size of the image. If you're setting the view at runtime, then you can do exactly what Anna mentioned and provide interface builder with a "placeholder" intrinsic size in the property inspector of the image view. This tells interface builder, "use this size for now, I'll give you a real size later". The placeholder constraints are ignored at runtime.

您的另一个选择是直接将图像分配给界面构建器中的图像视图(但我假设您的图像是动态的，所以这对您不起作用).

Your other option is to assign the image to the image view in interface builder directly (but I assume your images are dynamic, so this won't work for you).

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