Swift 纯代码布局框架 SnapKit 基本用法

本文就简单介绍一下SnapKit基本的使用。就说明一下视每种视图之间关系的情况下，怎么建立约束，从而见见了解SnapKit。都是一些基本用法 。
以前使用过Masonry、SDAutoLayout会容易比较容易上手的

第一种情况 、父视图包含子视图，子视图在父视图中的布局(常用的有3种写法)

写法一

    func testDemo(){
        let bgView = UIView()
        bgView.backgroundColor = UIColor.yellow
        self.view.addSubview(bgView)
 
        let box1 = UIView()
        box1.backgroundColor = UIColor.blue
        bgView.addSubview(box1)

        //父视图
        bgView.snp.makeConstraints { (make) in
            make.center.equalToSuperview()
            make.size.equalTo(350)
        }
        //第一个子视图 --- 重点在这里
        box1.snp.makeConstraints { (make) in
            make.center.equalToSuperview() //设置中心点，为父视图的中心点
            make.width.height.equalTo(200)//设置大小为200*200 等价make.size.equalTo(200)
        }

        let label = UILabel()
        label.text = "第一种"
        self.view.addSubview(label)
        label.snp.makeConstraints { (make) in
            make.center.equalToSuperview()
        }
    }

IMG_1479.PNG

写法二

    func testDemo(){
        let bgView = UIView()
        bgView.backgroundColor = UIColor.yellow
        self.view.addSubview(bgView)
 
        let box1 = UIView()
        box1.backgroundColor = UIColor.blue
        bgView.addSubview(box1)

        //父视图
        bgView.snp.makeConstraints { (make) in
            make.center.equalToSuperview()
            make.size.equalTo(350)
        }
        //第一个子视图 --- 重点在这里
        box1.snp.makeConstraints { (make) in
            make.centerY.equalToSuperview()  //设置中心点的Y点，为父视图的Y轴中点
            make.left.equalToSuperview().offset(10) //设置左边距离父视图为10 ）
            make.right.equalToSuperview().offset(-10) //设置有边距离父视图为10 （这句代码是右边距离父视图的宽度为参照 -10 就是往左减少10。10就是向右增加10）
            make.height.equalTo(100) //设置高度为100
        }

        let label = UILabel()
        label.text = "第二种"
        self.view.addSubview(label)
        label.snp.makeConstraints { (make) in
            make.center.equalToSuperview()
        }
    }

IMG_1480.PNG

写法三

    func testDemo(){
        let bgView = UIView()
        bgView.backgroundColor = UIColor.yellow
        self.view.addSubview(bgView)
 
        let box1 = UIView()
        box1.backgroundColor = UIColor.blue
        bgView.addSubview(box1)

        //父视图
        bgView.snp.makeConstraints { (make) in
            make.center.equalToSuperview()
            make.size.equalTo(350)
        }
        //第一个子视图 --- 重点在这里
        box1.snp.makeConstraints { (make) in
          //这个是最简单的，就是距离父视图的上下左右的距离
            make.edges.equalToSuperview().inset(UIEdgeInsets(top: 100, left: 10, bottom: 10, right: 10))
        }

        let label = UILabel()
        label.text = "第三种"
        self.view.addSubview(label)
        label.snp.makeConstraints { (make) in
            make.center.equalToSuperview()
        }
    }

IMG_1481.PNG

第二种情况 、两个子视图之间的关系进行布局(这个变化就多了，大家多多意会，我只写当前的给大家参考)

    func testDemo(){
        let bgView = UIView()
        bgView.backgroundColor = UIColor.yellow
        self.view.addSubview(bgView)
 
        let box1 = UIView()
        box1.backgroundColor = UIColor.blue
        bgView.addSubview(box1)
        
        let box2 = UIView()
        box2.backgroundColor = UIColor.red
        bgView.addSubview(box2)
        //父视图
        bgView.snp.makeConstraints { (make) in
            make.center.equalToSuperview()
            make.size.equalTo(350)
        }
        //第一个子视图
        box1.snp.makeConstraints { (make) in
            make.top.equalToSuperview().offset(50)
            make.left.equalToSuperview().offset(0)
            make.width.equalTo(150)
            make.height.equalTo(100)
        }
        //第二个子视图  -- 重点在这里
         box2.snp.makeConstraints { (make) in
            make.top.equalTo(box1.snp.top).offset(20) //top等于box1.top，再向下偏离20
            make.left.equalTo(box1.snp.right).offset(10)//let等于box1.right 在向右偏离 10
            make.size.equalTo(box1.snp.height) //他的宽高都等于 box1.height
        }
    }

IMG_1482.PNG

关键字 multipliedBy,dividedBy 也比较常用

func testDemo(){
    let bgView = UIView()
    bgView.backgroundColor = UIColor.yellow
    self.view.addSubview(bgView)

    let box1 = UIView()
    box1.backgroundColor = UIColor.blue
    bgView.addSubview(box1)
    
    let box2 = UIView()
    box2.backgroundColor = UIColor.red
    bgView.addSubview(box2)
    //父视图
    bgView.snp.makeConstraints { (make) in
        make.center.equalToSuperview()
        make.size.equalTo(350)
    }
    //第一个子视图
    box1.snp.makeConstraints { (make) in
        make.top.equalToSuperview().offset(50)
        make.left.equalToSuperview().offset(10)
        make.width.height.equalTo(100)

    
    }
    //第二个子视图  -- 重点在这里
     box2.snp.makeConstraints { (make) in
        make.top.equalTo(box1.snp.top).dividedBy(2) //顶部的距离等于box1.top*2
        make.right.equalToSuperview().offset(-10)
        make.height.equalTo(box1.snp.height).multipliedBy(0.5) //他的宽高都等于 box1.height*0.5
        make.left.equalTo(box1.snp.left).dividedBy(0.5) //left等于box1.left➗0.5
     }
}

关键字 multipliedBy,dividedBy

priority 优先级用法 ，SnapKit一共提供了4种优先级，优先级顺序是：required > high > medium > low。

    func testDemo(){
        let bgView = UIView()
        bgView.backgroundColor = UIColor.yellow
        self.view.addSubview(bgView)
 
        let box1 = UIView()
        box1.backgroundColor = UIColor.blue
        bgView.addSubview(box1)

        //父视图
        bgView.snp.makeConstraints { (make) in
            make.center.equalToSuperview()
            make.size.equalTo(350)
        }
        //第一个子视图
        box1.snp.makeConstraints { (make) in
    
            make.center.equalToSuperview().priority(.medium)
            make.right.equalToSuperview().offset(-10).priority(.high) //高于center ，肯定靠左
            make.top.equalToSuperview().offset(10).priority(.low) //低于center，肯定居中
            // size 和center 的优先级没啥冲突，不考虑 。但是自身的优先级还是要考虑的
            make.size.equalTo(100).priority(.medium) //优先级高 size = 100*100
            make.size.equalTo(200).priority(.low)
        }

    }

priority 优先级用法