SnapKit 约束 实例

• Constraint 修改约束

效果图.gif

//  ViewController.swift

import UIKit
var TopScaleImg_H: CGFloat = 300

class ViewController: UIViewController {
    
    var topConstraint:Constraint?

    
    lazy var topScaleImgView: UIImageView = {
       let img = UIImageView(image: UIImage(named: "home_block_green_a"))
        img.contentMode = .ScaleAspectFill
        img.backgroundColor = UIColor.orangeColor()
        return img
    }()
    
    lazy var tableView: UITableView = {
       let t = UITableView(frame: CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height), style: .Plain)
        t.contentInset = UIEdgeInsets(top: TopScaleImg_H, left: 0, bottom: 0, right: 0)
        t.delegate = self
        t.dataSource = self
        
        t.registerClass(UITableViewCell.self, forCellReuseIdentifier: "cellID")
        return t
    }()

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        
     self.tableView.backgroundColor = UIColor.clearColor()
        self.view.addSubview(self.tableView)
        self.view.insertSubview(self.topScaleImgView, belowSubview: tableView)
        
        
        self.topScaleImgView.snp_makeConstraints { (make) in
            make.left.equalTo(self.view.snp_left)
            make.right.equalTo(self.view.snp_right)
            make.top.equalTo(self.view.snp_top)
            self.topConstraint = make.height.equalTo(TopScaleImg_H).constraint
        }
    }

    func scrollViewDidScroll(scrollView: UIScrollView) {
        let offsetY = scrollView.contentOffset.y
        if offsetY < 0{
            
            self.topConstraint?.updateOffset(-offsetY)
            
        }else{
            
            self.topConstraint?.updateOffset(offsetY)
        }
    }
}

extension ViewController: UITableViewDelegate, UITableViewDataSource{
    
    func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return 30
    }
    
    func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
        let cell = UITableViewCell(style: .Default, reuseIdentifier: "cellID")
        cell.textLabel?.text = "row  \(indexPath.row)"
        cell.backgroundColor = UIColor.grayColor()
        return cell
    }
}

常用总结：

• 重做约束:

snp_remakeConstraints (先会先清除掉之前所有被SnapKit设置的约束。)

+ 删除约束:  
   - 要实现对现有的约束进行更新或者移除，我们需要先将约束的结果赋值给一个局部变量或一个类属性，然后对这个约束的引用进行操作。

1. 保存 相关约束
   view.snp_makeConstraints { (make) -> Void in
   make.width.height.equalTo(150)
   make.centerX.equalTo(self.view)
   self.topConstraint = make.top.equalTo(self.view).offset(40).constraint
   }
2. 移除约束
   self.topConstraint?.uninstall()

+ 更新修改相关约束

1. 保存 约束 引用
   var topConstraint:Constraint?
   topView.snp_makeConstraints { (make) -> Void in
   make.width.height.equalTo(100)
   make.centerX.equalTo(self.view)
   self.topConstraint = make.top.equalTo(self.view).offset(10).constraint
   }
2. 更新修改约束
   self.topConstraint?.updateOffset(5)

+ 使用snp_updateConstraints更新约束