将按钮添加到滚动视图中的按钮数组

Question

我想在 ui 按钮数组中添加另一个 Uibbuton。当在滚动视图上调用 func 时，它不会被添加。正如您在下面的 gif 中看到的，当按下添加按钮时，没有添加任何内容。我想做的是当按下添加按钮时添加按钮标题 Button 10。由于按钮已在视图中初始化并加载，我想不出该怎么做？

import UIKit
class SwipeableUIScrollView: UIScrollView {

    
    override func touchesShouldCancel(in view: UIView) -> Bool {
        
        if view is UIButton || view is UILabel{
            return true
        }
        
        return touchesShouldCancel(in: view)
    }
    
}
class ViewController: UIViewController {

    var scrollView:SwipeableUIScrollView!
    var greenView:UIView!

    var addMore:UIButton!
    var counter = 10
    
    var scrollViewHeightConstraint:NSLayoutConstraint!
    
  
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        scrollView = SwipeableUIScrollView.init(frame: CGRect.zero)
        scrollView.translatesAutoresizingMaskIntoConstraints = false
        
        greenView = UIView.init(frame: CGRect.zero)
        greenView.translatesAutoresizingMaskIntoConstraints = false
        greenView.backgroundColor = UIColor.green
        
   
        
        addMore = UIButton.init(frame: CGRect.zero)
        addMore.translatesAutoresizingMaskIntoConstraints = false
        addMore.backgroundColor = UIColor.orange
        addMore.setTitle("add", for: .normal)
        

        self.view.addSubview(scrollView)
        self.view.addSubview(greenView)
        
        
        self.view.addSubview(addMore)
        
        
        addMore.addTarget(self, action: #selector(increaseC), for: .touchDown)
        
        scrollViewHeightConstraint = NSLayoutConstraint.init(item: scrollView, attribute: .height, relatedBy: NSLayoutConstraint.Relation.equal, toItem: nil, attribute: .notAnAttribute, multiplier: 1.0, constant: 50.0)
        
        NSLayoutConstraint.activate([

            addMore.topAnchor.constraint(equalTo: self.view.topAnchor, constant: 50.0),
            addMore.trailingAnchor.constraint(equalTo: self.view.trailingAnchor, constant: -15.0),
            addMore.heightAnchor.constraint(equalToConstant: 25.0),
            addMore.widthAnchor.constraint(equalToConstant: 100.0),
            
            scrollView.topAnchor.constraint(equalTo: self.addMore.bottomAnchor, constant: 10.0),
            scrollView.leadingAnchor.constraint(equalTo: self.view.leadingAnchor),
            scrollView.trailingAnchor.constraint(equalTo: self.view.trailingAnchor),
            scrollViewHeightConstraint,
            
            greenView.leadingAnchor.constraint(equalTo: self.view.leadingAnchor),
            greenView.trailingAnchor.constraint(equalTo: self.view.trailingAnchor),
            greenView.topAnchor.constraint(equalTo: self.scrollView.bottomAnchor),
            greenView.bottomAnchor.constraint(equalTo: self.view.bottomAnchor)
            
        ])
       
        var leadingAnchor = self.scrollView!.leadingAnchor
       
        for i in 0..<counter{
           
            let t_button = UIButton.init(frame: CGRect.zero)
            t_button.translatesAutoresizingMaskIntoConstraints = false
           
            
            t_button.backgroundColor = UIColor.blue
            scrollView.addSubview(t_button)
           
            NSLayoutConstraint.activate([
                t_button.leadingAnchor.constraint(equalTo: leadingAnchor, constant:5.0),
                t_button.centerYAnchor.constraint(equalTo: scrollView.centerYAnchor),
                t_button.heightAnchor.constraint(equalToConstant: 20),
                t_button.widthAnchor.constraint(equalToConstant: 75.0)
            ])
           
            leadingAnchor = t_button.trailingAnchor
            
            t_button.setTitle("Button \(i)", for: .normal)

           
        }
           
        self.scrollView.trailingAnchor.constraint(equalTo: leadingAnchor).isActive = true
              
    }

    

    
    

    
    @objc func increaseC(){
        counter += 1
    
    }
}

Answer 1

你可以使用Property Observer。属性观察器允许我们在使用属性时，当我们希望某个属性发生变化时，执行某些操作。也就是一些小代码块，可以在 willSet 之前运行，或者在属性值改变之后 didSet 可以运行。创建属性观察者，在属性后面加上花括号（类似计算属性的做法） 就像这样：

class PropertyObserverExmple {
    var number: Int = 0 {
        willSet(newNumber) {
            print("About to change to \(newNumber)")
        }
        didSet(oldNumber) {
            print("Just changed from \(oldNumber) to \(self.number)")
        }
    }
}

var observer = PropertyObserverExmple()
observer.number = 4
// About to change to 4 ,Just changed from 0 to 4

所以你的例子可以修改成这样

import UIKit
class SwipeableUIScrollView: UIScrollView {

    
    override func touchesShouldCancel(in view: UIView) -> Bool {
        
        if view is UIButton || view is UILabel{
            return true
        }
        
        return touchesShouldCancel(in: view)
    }
    
}
class ViewController: UIViewController {

    var scrollView:SwipeableUIScrollView!
    var greenView:UIView!

    var addMore:UIButton!
    var leadingAnchor: NSLayoutXAxisAnchor!
    var counter: Int? {
        didSet {
            for i in (oldValue ?? 0)..<(counter ?? 0){
               
                let t_button = UIButton.init(frame: CGRect.zero)
                t_button.translatesAutoresizingMaskIntoConstraints = false
               
                
                t_button.backgroundColor = UIColor.blue
                scrollView.addSubview(t_button)
               
                NSLayoutConstraint.activate([
                    t_button.leadingAnchor.constraint(equalTo: leadingAnchor, constant:5.0),
                    t_button.centerYAnchor.constraint(equalTo: scrollView.centerYAnchor),
                    t_button.heightAnchor.constraint(equalToConstant: 20),
                    t_button.widthAnchor.constraint(equalToConstant: 75.0)
                ])
               
                leadingAnchor = t_button.trailingAnchor
                
                t_button.setTitle("Button \(i)", for: .normal)

               
            }
        }
    }
    
    var scrollViewHeightConstraint:NSLayoutConstraint!
    
  
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        scrollView = SwipeableUIScrollView.init(frame: CGRect.zero)
        scrollView.translatesAutoresizingMaskIntoConstraints = false
        
        greenView = UIView.init(frame: CGRect.zero)
        greenView.translatesAutoresizingMaskIntoConstraints = false
        greenView.backgroundColor = UIColor.green
        
   
        
        addMore = UIButton.init(frame: CGRect.zero)
        addMore.translatesAutoresizingMaskIntoConstraints = false
        addMore.backgroundColor = UIColor.orange
        addMore.setTitle("add", for: .normal)
        

        self.view.addSubview(scrollView)
        self.view.addSubview(greenView)
        
        
        self.view.addSubview(addMore)
        
        
        addMore.addTarget(self, action: #selector(increaseC), for: .touchDown)
        
        scrollViewHeightConstraint = NSLayoutConstraint.init(item: scrollView, attribute: .height, relatedBy: NSLayoutConstraint.Relation.equal, toItem: nil, attribute: .notAnAttribute, multiplier: 1.0, constant: 50.0)
        
        NSLayoutConstraint.activate([

            addMore.topAnchor.constraint(equalTo: self.view.topAnchor, constant: 50.0),
            addMore.trailingAnchor.constraint(equalTo: self.view.trailingAnchor, constant: -15.0),
            addMore.heightAnchor.constraint(equalToConstant: 25.0),
            addMore.widthAnchor.constraint(equalToConstant: 100.0),
            
            scrollView.topAnchor.constraint(equalTo: self.addMore.bottomAnchor, constant: 10.0),
            scrollView.leadingAnchor.constraint(equalTo: self.view.leadingAnchor),
            scrollView.trailingAnchor.constraint(equalTo: self.view.trailingAnchor),
            scrollViewHeightConstraint,
            
            greenView.leadingAnchor.constraint(equalTo: self.view.leadingAnchor),
            greenView.trailingAnchor.constraint(equalTo: self.view.trailingAnchor),
            greenView.topAnchor.constraint(equalTo: self.scrollView.bottomAnchor),
            greenView.bottomAnchor.constraint(equalTo: self.view.bottomAnchor)
            
        ])
       
        leadingAnchor  = self.scrollView!.leadingAnchor
       
        counter = 10
           
        self.scrollView.trailingAnchor.constraint(equalTo: leadingAnchor).isActive = true
              
    }

    

    
    

    
    @objc func increaseC(){
        counter! += 1
    
    }
}