iOS Autoresizing Autolayout Size classes

Autoresizing:出现最早，仅仅能够针对父控件做约束（注意：要关闭Autolayout&Size classes才能够看到Autoresizing）

代码对应：

UIView.h中的autoresizingMask属性

@property(nonatomic) UIViewAutoresizing autoresizingMask;    // simple resize. default is UIViewAutoresizingNone

typedef NS_OPTIONS(NSUInteger, UIViewAutoresizing) {

    UIViewAutoresizingNone                 = 0,

    UIViewAutoresizingFlexibleLeftMargin   = 1 << 0,

    UIViewAutoresizingFlexibleWidth        = 1 << 1,

    UIViewAutoresizingFlexibleRightMargin  = 1 << 2,

    UIViewAutoresizingFlexibleTopMargin    = 1 << 3,

    UIViewAutoresizingFlexibleHeight       = 1 << 4,

    UIViewAutoresizingFlexibleBottomMargin = 1 << 5

};

Autolayout：不仅仅能够针对父控件约束，而且可以针对同级进行约束，但对不同设备的横竖屏还是有依赖

Size classes：将所有尺寸分为Regular（标准的）compact(紧凑的) any（任意的）三种情况 进行组合，不再依赖于死的尺寸，这就有效解决了Autolayout的弊端

Size classes:

但是我们看到图中的宽度和高度都是Any,Any是什么意思呢？如果weight设为Any，height设置为Regular，那么在该状态下的界面元素在只要height为Regular，无论weight是Regular还是Compact的状态中都会存在。这种关系应该叫做继承关系，具体的四种界面描述与可继承的界面描述如下：

• w:Compact h:Compact 继承 (w:Any h:Compact , w:Compact h:Any , w:Any h:Any)
• w:Regular h:Compact 继承 (w:Any h:Compact , w:Regular h:Any , w:Any h:Any)
• w:Compact h:Regular 继承 (w:Any h:Regular , w:Compact h:Any , w:Any h:Any)
• w:Regular h:Regular 继承 (w:Any h:Regular , w:Regular h:Any , w:Any h:Any)

我们知道了iOS 8下面设备界面可以描述为4种，但是这么多设备(iPhone4S,iPhone5/5s,iPhone6,iPhone6 Plus,iPad,Apple Watch)具体对应什么描述呢？经过查看官方文档和具体实践得知具体对应关系如下:

• iPhone4S,iPhone5/5s,iPhone6
  • 竖屏：(w:Compact h:Regular)
  • 横屏：(w:Compact h:Compact)
• iPhone6 Plus
  • 竖屏：(w:Compact h:Regular)
  • 横屏：(w:Regular h:Compact)
• iPad
  • 竖屏：(w:Regular h:Regular)
  • 横屏：(w:Regular h:Regular)
• Apple Watch(猜测)
  • 竖屏：(w:Compact h:Compact)
  • 横屏：(w:Compact h:Compact)

代码对应：UITraitCollection

UIViewController.h

- (void)willTransitionToTraitCollection:(UITraitCollection *)newCollection withTransitionCoordinator:(id <UIViewControllerTransitionCoordinator>)coordinator NS_AVAILABLE_IOS(8_0);

UITraitCollection.h(普通View)

/*! Trait environments expose a trait collection that describes their environment. */

@protocol UITraitEnvironment <NSObject>

@property (nonatomic, readonly) UITraitCollection *traitCollection;

/*! To be overridden as needed to provide custom behavior when the environment's traits change. */

- (void)traitCollectionDidChange:(UITraitCollection *)previousTraitCollection;

@end

Autolayout:

代码对应： 

NSLayoutConstraint

注意：手码自动布局先关闭UIView的以下属性

1.- (BOOL)translatesAutoresizingMaskIntoConstraints NS_AVAILABLE_IOS(6_0); // Default YES

2.1VFL语言

+ (NSArray *)constraintsWithVisualFormat:(NSString *)format options:(NSLayoutFormatOptions)opts metrics:(NSDictionary *)metrics views:(NSDictionary *)views;

2.2纯粹代码 

+(instancetype)constraintWithItem:(id)view1 attribute:(NSLayoutAttribute)attr1 relatedBy:(NSLayoutRelation)relation toItem:(id)view2 attribute:(NSLayoutAttribute)attr2 multiplier:(CGFloat)multiplier constant:(CGFloat)c;

详情：http://www.cnblogs.com/zhw511006/p/3998534.html