NSLayoutAnchor 布局锚点
@interface NSLayoutAnchor<AnchorType> : NSObject
// NSLayoutAnchor在macOS 10.12和iOS 10和tvOS 10以及以上的版本上遵循<NSCopying>、<NSCoding>
/// 锚点A ==/>=/<= 锚点B
- (NSLayoutConstraint *)constraintEqualToAnchor:(NSLayoutAnchor<AnchorType> *)anchor __attribute__((warn_unused_result));
- (NSLayoutConstraint *)constraintGreaterThanOrEqualToAnchor:(NSLayoutAnchor<AnchorType> *)anchor __attribute__((warn_unused_result));
- (NSLayoutConstraint *)constraintLessThanOrEqualToAnchor:(NSLayoutAnchor<AnchorType> *)anchor __attribute__((warn_unused_result));
// MARK: 锚点A ==/>=/<= 锚点B + 常数.
- (NSLayoutConstraint *)constraintEqualToAnchor:(NSLayoutAnchor<AnchorType> *)anchor constant:(CGFloat)c __attribute__((warn_unused_result));
- (NSLayoutConstraint *)constraintGreaterThanOrEqualToAnchor:(NSLayoutAnchor<AnchorType> *)anchor constant:(CGFloat)c __attribute__((warn_unused_result));
- (NSLayoutConstraint *)constraintLessThanOrEqualToAnchor:(NSLayoutAnchor<AnchorType> *)anchor constant:(CGFloat)c __attribute__((warn_unused_result));
// MARK: 这些用来调试
@property (readonly, copy) NSString *name API_AVAILABLE(macos(10.12)) API_UNAVAILABLE(ios, watchos, tvos);
@property (readonly, nullable, weak) id item API_AVAILABLE(macos(10.12)) API_UNAVAILABLE(ios, watchos, tvos);
@property (readonly) BOOL hasAmbiguousLayout API_AVAILABLE(macos(10.12)) API_UNAVAILABLE(ios, watchos, tvos);
@property (readonly) NSArray<NSLayoutConstraint *> *constraintsAffectingLayout API_AVAILABLE(macos(10.12)) API_UNAVAILABLE(ios, watchos, tvos);
@end
---
@class NSLayoutXAxisAnchor, NSLayoutYAxisAnchor, NSLayoutDimension;
NSLAYOUTANCHOR_EXTERN API_AVAILABLE(macos(10.11), ios(9.0))
/// NSLayoutAnchor的子类.描述特殊轴的锚点.顶部、底部.前、后.基线等.
@interface NSLayoutXAxisAnchor : NSLayoutAnchor<NSLayoutXAxisAnchor *>
// 创建水平方向锚点相关的布局锚点
- (NSLayoutDimension *)anchorWithOffsetToAnchor:(NSLayoutXAxisAnchor *)otherAnchor API_AVAILABLE(macos(10.12), ios(10.0), tvos(10.0));
@end
---
NSLAYOUTANCHOR_EXTERN API_AVAILABLE(macos(10.11), ios(9.0))
@interface NSLayoutYAxisAnchor : NSLayoutAnchor<NSLayoutYAxisAnchor *>
// 创建垂直方向锚点相关的布局锚点
- (NSLayoutDimension *)anchorWithOffsetToAnchor:(NSLayoutYAxisAnchor *)otherAnchor API_AVAILABLE(macos(10.12), ios(10.0), tvos(10.0));
@end
---
// 这个布局锚点用于宽、高
NSLAYOUTANCHOR_EXTERN API_AVAILABLE(macos(10.11), ios(9.0))
@interface NSLayoutDimension : NSLayoutAnchor<NSLayoutDimension *>
/// 当前变量 = 常数
- (NSLayoutConstraint *)constraintEqualToConstant:(CGFloat)c __attribute__((warn_unused_result));
- (NSLayoutConstraint *)constraintGreaterThanOrEqualToConstant:(CGFloat)c __attribute__((warn_unused_result));
- (NSLayoutConstraint *)constraintLessThanOrEqualToConstant:(CGFloat)c __attribute__((warn_unused_result));
/// 此方法返回inactive的`当前Anchor = anchor * 比例`
- (NSLayoutConstraint *)constraintEqualToAnchor:(NSLayoutDimension *)anchor multiplier:(CGFloat)m __attribute__((warn_unused_result));
- (NSLayoutConstraint *)constraintGreaterThanOrEqualToAnchor:(NSLayoutDimension *)anchor multiplier:(CGFloat)m __attribute__((warn_unused_result));
- (NSLayoutConstraint *)constraintLessThanOrEqualToAnchor:(NSLayoutDimension *)anchor multiplier:(CGFloat)m __attribute__((warn_unused_result));
此方法返回inactive的`当前Anchor = anchor * 比例 + 常数`
- (NSLayoutConstraint *)constraintEqualToAnchor:(NSLayoutDimension *)anchor multiplier:(CGFloat)m constant:(CGFloat)c __attribute__((warn_unused_result));
- (NSLayoutConstraint *)constraintGreaterThanOrEqualToAnchor:(NSLayoutDimension *)anchor multiplier:(CGFloat)m constant:(CGFloat)c __attribute__((warn_unused_result));
- (NSLayoutConstraint *)constraintLessThanOrEqualToAnchor:(NSLayoutDimension *)anchor multiplier:(CGFloat)m constant:(CGFloat)c __attribute__((warn_unused_result));
@end
#endif // NSLAYOUTANCHOR_H
---
@interface NSLayoutXAxisAnchor (UIViewDynamicSystemSpacingSupport)
/// 接收器 [= | ≥ | ≤] '锚点' + '比例' * 系统常量(注意,这里*的是系统常量)
- (NSLayoutConstraint *)constraintEqualToSystemSpacingAfterAnchor:(NSLayoutXAxisAnchor *)anchor multiplier:(CGFloat)multiplier __attribute__((warn_unused_result)) API_AVAILABLE(ios(11.0),tvos(11.0));
- (NSLayoutConstraint *)constraintGreaterThanOrEqualToSystemSpacingAfterAnchor:(NSLayoutXAxisAnchor *)anchor multiplier:(CGFloat)multiplier __attribute__((warn_unused_result)) API_AVAILABLE(ios(11.0),tvos(11.0));
- (NSLayoutConstraint *)constraintLessThanOrEqualToSystemSpacingAfterAnchor:(NSLayoutXAxisAnchor *)anchor multiplier:(CGFloat)multiplier __attribute__((warn_unused_result)) API_AVAILABLE(ios(11.0),tvos(11.0));
@end
---
@interface NSLayoutYAxisAnchor (UIViewDynamicSystemSpacingSupport)
/// 接收器 [= | ≥ | ≤] '锚点' + '比例' * 系统常量(注意,这里*的是系统常量)
- (NSLayoutConstraint *)constraintEqualToSystemSpacingBelowAnchor:(NSLayoutYAxisAnchor *)anchor multiplier:(CGFloat)multiplier __attribute__((warn_unused_result)) API_AVAILABLE(ios(11.0),tvos(11.0));
- (NSLayoutConstraint *)constraintGreaterThanOrEqualToSystemSpacingBelowAnchor:(NSLayoutYAxisAnchor *)anchor multiplier:(CGFloat)multiplier __attribute__((warn_unused_result)) API_AVAILABLE(ios(11.0),tvos(11.0));
- (NSLayoutConstraint *)constraintLessThanOrEqualToSystemSpacingBelowAnchor:(NSLayoutYAxisAnchor *)anchor multiplier:(CGFloat)multiplier __attribute__((warn_unused_result)) API_AVAILABLE(ios(11.0),tvos(11.0));
@end
代码用例
self.viewTest = [UIView new];
self.viewTest.backgroundColor = [UIColor greenColor];
[self.view addSubview:self.viewTest];
self.viewTest.translatesAutoresizingMaskIntoConstraints = NO;
[self.viewTest.leadingAnchor constraintEqualToSystemSpacingAfterAnchor:self.view.leadingAnchor multiplier:0].active = YES;
[self.viewTest.trailingAnchor constraintEqualToSystemSpacingAfterAnchor:self.view.trailingAnchor multiplier:0].active = YES;
[self.viewTest.topAnchor constraintEqualToSystemSpacingBelowAnchor:self.view.topAnchor multiplier:0].active = YES;
[self.viewTest.bottomAnchor constraintEqualToSystemSpacingBelowAnchor:self.view.bottomAnchor multiplier:0].active = YES;
注意代码用例中的multiplier.在这种情况下得传入0.之所以有三个equalTo方法而单单拿这个equalTo方法举例就是因为这个multiplier的特殊性.他是一个系统默认的常数的倍数(8P上测出来的是8PT.其他机型没试)
上面的NSLayoutDimension(宽、高)、NSLayoutXAxisAnchor(水平方向有关)、NSLayoutYAxisAnchor(垂直方向有关).具体可以看下面举的UIView的属性例子
UIView的Anchor例子
@property(nonatomic,readonly,strong) NSLayoutXAxisAnchor *leadingAnchor API_AVAILABLE(ios(9.0));
@property(nonatomic,readonly,strong) NSLayoutXAxisAnchor *trailingAnchor API_AVAILABLE(ios(9.0));
@property(nonatomic,readonly,strong) NSLayoutXAxisAnchor *leftAnchor API_AVAILABLE(ios(9.0));
@property(nonatomic,readonly,strong) NSLayoutXAxisAnchor *rightAnchor API_AVAILABLE(ios(9.0));
@property(nonatomic,readonly,strong) NSLayoutYAxisAnchor *topAnchor API_AVAILABLE(ios(9.0));
@property(nonatomic,readonly,strong) NSLayoutYAxisAnchor *bottomAnchor API_AVAILABLE(ios(9.0));
@property(nonatomic,readonly,strong) NSLayoutDimension *widthAnchor API_AVAILABLE(ios(9.0));
@property(nonatomic,readonly,strong) NSLayoutDimension *heightAnchor API_AVAILABLE(ios(9.0));
@property(nonatomic,readonly,strong) NSLayoutXAxisAnchor *centerXAnchor API_AVAILABLE(ios(9.0));
@property(nonatomic,readonly,strong) NSLayoutYAxisAnchor *centerYAnchor API_AVAILABLE(ios(9.0));
@property(nonatomic,readonly,strong) NSLayoutYAxisAnchor *firstBaselineAnchor API_AVAILABLE(ios(9.0));
@property(nonatomic,readonly,strong) NSLayoutYAxisAnchor *lastBaselineAnchor API_AVAILABLE(ios(9.0));
