用代码创建约束，实现屏幕适配

//

//  ViewController.m

//  1_AutoLayout(code)

//

//  Created by mac on 16/7/13.

//  Copyright © 2016年 mac. All rights reserved.

//

#import "ViewController.h"

@interface
ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {

    [superviewDidLoad];

    

   
//1.调用创建视图的方法

    [selfcreateView];

}

//创建视图的方法

- (void) createView {

    

    //1.创建视图1（蓝色)

    //a) 创建

    UIView *cyanView = [[UIViewalloc]init];

    //b) 背景颜色

    cyanView.backgroundColor = [UIColorcyanColor];

    //c) 取消默认的Autoresizing自动添加约束，避免冲突

    cyanView.translatesAutoresizingMaskIntoConstraints =NO;

    //d) 添加到视图

    [self.viewaddSubview:cyanView];

    

    //2.创建视图2（绿色)

    //a) 创建

    UIView *greenView = [[UIViewalloc]init];

    //b) 背景颜色

    greenView.backgroundColor = [UIColorgreenColor];

    //c) 取消默认的Autoresizing自动添加约束，避免冲突

    greenView.translatesAutoresizingMaskIntoConstraints =NO;

    //d) 添加到视图

    [self.viewaddSubview:greenView];

    

    //2.创建视图3（红色)

    //a) 创建

    UIView *magentaView = [[UIViewalloc]init];

    //b) 背景颜色

    magentaView.backgroundColor = [UIColormagentaColor];

    //c) 取消默认的Autoresizing自动添加约束，避免冲突

    magentaView.translatesAutoresizingMaskIntoConstraints =NO;

    //d) 添加到视图

    [self.viewaddSubview:magentaView];

    

    //2.编写VFL语句

    //a)cyanView和greenView的水平约束

    NSString *hVFL =@"H:|-Space-[cyanView(==greenView)]-Between-[greenView]-Space-|";

    //b) magentaView的水平约束

    NSString *hBottom =@"H:|-Space-[magentaView]-Space-|";

    //c) cyanView和magentaView的垂直约束

    NSString *vLeft =@"V:|-Space-[cyanView(==magentaView)]-Between-[magentaView]-Space-|";

    //d) greenView和magentaView的垂直约束

    NSString *vRight =@"V:|-Space-[greenView]-Between-[magentaView]-Space-|";

    

   
//e) 将约束条件和视图，放入字典中

    NSDictionary *metrics =@{@"Space":@20,@"Between":@20};

    NSDictionary *views1 =NSDictionaryOfVariableBindings(cyanView,greenView);

    NSDictionary *views2 =NSDictionaryOfVariableBindings(magentaView);

    NSDictionary *views3 =NSDictionaryOfVariableBindings(cyanView,magentaView);

    NSDictionary *views4 =NSDictionaryOfVariableBindings(greenView,magentaView);

    

    //3.创建约束

    //a) 两个水平约束

    NSArray *hVFLContraints = [NSLayoutConstraint constraintsWithVisualFormat:hVFLoptions:NSLayoutFormatDirectionLeadingToTrailingmetrics:metricsviews:views1];

    NSArray *hBottomContraints = [NSLayoutConstraint constraintsWithVisualFormat:hBottomoptions:NSLayoutFormatDirectionLeadingToTrailingmetrics:metricsviews:views2];

    //b) 两个垂直约束

    NSArray *vLeftContraints = [NSLayoutConstraint constraintsWithVisualFormat:vLeftoptions:NSLayoutFormatDirectionLeadingToTrailingmetrics:metricsviews:views3];

    NSArray *vRightContraints = [NSLayoutConstraint constraintsWithVisualFormat:vRightoptions:NSLayoutFormatDirectionLeadingToTrailingmetrics:metricsviews:views4];

    

   
//4.将约束全部添加到父视图

a632
    [self.viewaddConstraints:hVFLContraints];

    [self.viewaddConstraints:hBottomContraints];

    [self.viewaddConstraints:vLeftContraints];

    [self.viewaddConstraints:vRightContraints];

   

}

@end