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抗压缩(不想变小约束)

setContentCompressionResistancePriority

抗拉伸(不想变大约束)

setContentHuggingPriority

 

约束优先级: 在 Autolayout 中每个约束都有一个优先级, 优先级的范围是1 ~ 1000。创建一个约束,默认的优先级是最高的1000

Content Hugging Priority: 该优先级表示一个控件抗被拉伸的优先级。优先级越高,越不容易被拉伸,默认是250。

Content Compression Resistance Priority: 该优先级和上面那个优先级相对应,表示一个控件抗压缩的优先级。优先级越高,越不容易被压缩,默认是750。

 

UIView 提供了两个方法给我们设置它的这两个约束的优先级:

- (void)setContentHuggingPriority:(UILayoutPriority)priority forAxis:(UILayoutConstraintAxis)axis;
- (void)setContentCompressionResistancePriority:(UILayoutPriority)priority forAxis:(UILayoutConstraintAxis)axis;

其中,第一个参数为优先级,具体有以下几种:

static const UILayoutPriority UILayoutPriorityRequired NS_AVAILABLE_IOS(6_0) = 1000; // A required constraint.  Do not exceed this.
static const UILayoutPriority UILayoutPriorityDefaultHigh NS_AVAILABLE_IOS(6_0) = 750; // This is the priority level with which a button resists compressing its content.
static const UILayoutPriority UILayoutPriorityDefaultLow NS_AVAILABLE_IOS(6_0) = 250; // This is the priority level at which a button hugs its contents horizontally.
static const UILayoutPriority UILayoutPriorityFittingSizeLevel NS_AVAILABLE_IOS(6_0) = 50;

当然,你也可以自己通过数字来设置它们的优先级。
第二个参数代表你要设置约束优先级的方向,分为横向和纵向:

typedef NS_ENUM(NSInteger, UILayoutConstraintAxis) {
    UILayoutConstraintAxisHorizontal = 0,
    UILayoutConstraintAxisVertical = 1
};

UILayoutConstraintAxisHorizontal:横向

UILayoutConstraintAxisVertical:纵向

本文标签: iosContentCompressionResistancePriorityContentHuggingPriority