xcode 中的代码编写自适应布局

(void)viewDidLoad {

[super
viewDidLoad];

UIView *view1=[[UIView
alloc]initWithFrame:CGRectZero];

view1.backgroundColor=[UIColor
blackColor];

//设置其frame还是Autolayout模式

//translatesAutoresizingMaskIntoConstraints的值为no表示Autolayout

//用代码创建一个视图，该值为YES

//如果用IB创建一个视图，该值为NO

view1.translatesAutoresizingMaskIntoConstraints=NO;

[self.view
addSubview:view1];

// 创建一个高度为40的约束

NSLayoutConstraint
*v1=[NSLayoutConstraint
constraintWithItem:view1
attribute:NSLayoutAttributeHeight
relatedBy:NSLayoutRelationEqual
toItem:nil
attribute:NSLayoutAttributeNotAnAttribute
multiplier:0
constant:40];

[self.view
addConstraint:v1];

//创建一个宽度为200的约束

NSLayoutConstraint
*v2=[NSLayoutConstraint
constraintWithItem:view1
attribute:NSLayoutAttributeWidth
relatedBy:NSLayoutRelationEqual
toItem:nil
attribute:NSLayoutAttributeNotAnAttribute
multiplier:0
constant:200];

[self.view
addConstraint:v2];

// 创建一个中心为0的约束

NSLayoutConstraint
*v3=[NSLayoutConstraint
constraintWithItem:view1
attribute:NSLayoutAttributeCenterX
relatedBy:NSLayoutRelationEqual
toItem:self.view
attribute:NSLayoutAttributeCenterX
multiplier:1
constant:0];

[self.view
addConstraint:v3];

NSLayoutConstraint
*v4=[NSLayoutConstraint
constraintWithItem:view1
attribute:
NSLayoutAttributeTop
relatedBy:NSLayoutRelationEqual
toItem:self.view
attribute:NSLayoutAttributeTop
multiplier:1
constant:40];

[self.view
addConstraint:v4];

// Do any additional setup after loading the view, typically from a nib.

}