从ViewController为View中按钮添加点击事件无响应问题排查

问题描述 #

尝试从ViewController为自定义View中创建的按钮添加target时，按钮点击无任何响应；但直接在ViewController中创建该按钮，点击功能可正常工作。

相关代码 #

class ViewController: UIViewController {
    
    var mainView = MainView()
    var counter:Int = 0
    
    @objc func buttonAction(sender:UIButton!)
    {
        counter += 1
        print("Button was predded:\(counter)")
        mainView.lable1.text = "Button was predded:\(counter)"
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        view.addSubview(mainView)
        mainView.buttno1.addTarget(self, action: #selector(buttonAction), for: UIControl.Event.touchUpInside)
    }
    
}


class MainView : UIView {
    
    var background: UIView = {
        return background
    }()
    
    lazy var buttno1: UIButton = {
        var btn = UIButton()
        ....
        
        return btn
    }()
    
    
    func createButton1(){
        print("Main view btn created")
        background.addSubview(buttno1)

    }
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        self.addSubview(background)
        createButton1()
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}

可能的原因及解决方法 #

• background属性初始化循环引用，直接导致崩溃
  你的background初始化代码存在严重错误：闭包里直接返回未初始化的background属性，会触发循环引用初始化崩溃，程序运行到这一步就会卡死，后续的按钮创建、Target绑定逻辑根本不会执行。
  修正方法：正确初始化background视图：

  var background: UIView = {
      let view = UIView()
      view.backgroundColor = .white // 可根据需求设置属性
      view.translatesAutoresizingMaskIntoConstraints = false
      return view
  }()
  

• 视图未设置有效布局，按钮不在可视区域
  如果mainView、background或buttno1（注意拼写错误，建议改为button1）没有设置正确的frame或Auto Layout约束，可能导致按钮处于屏幕外，或者父视图尺寸为CGRect.zero，点击事件无法被触发。
  修正方法：

  1. 给mainView添加铺满父视图的约束：

     override func viewDidLoad() {
         super.viewDidLoad()
         view.addSubview(mainView)
         mainView.translatesAutoresizingMaskIntoConstraints = false
         NSLayoutConstraint.activate([
             mainView.topAnchor.constraint(equalTo: view.topAnchor),
             mainView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
             mainView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
             mainView.bottomAnchor.constraint(equalTo: view.bottomAnchor)
         ])
         mainView.buttno1.addTarget(self, action: #selector(buttonAction), for: .touchUpInside)
     }
     

  2. 给background和按钮也添加合适的约束，确保按钮处于屏幕可视区域内。

• 按钮交互被禁用
  检查按钮的isUserInteractionEnabled属性是否被设置为false，如果是则无法响应点击。默认该属性为true，但如果初始化时被修改过，需要重新开启：

  lazy var buttno1: UIButton = {
      var btn = UIButton()
      btn.isUserInteractionEnabled = true
      // 其他属性设置
      return btn
  }()
  

• 变量名拼写错误（潜在隐患）
  你的按钮变量名是buttno1（正确应为button1），虽然当前代码内拼写一致，但后续修改时容易出现不匹配，建议修正变量名避免潜在问题。

修正后的完整代码示例 #

class ViewController: UIViewController {
    
    var mainView = MainView()
    var counter: Int = 0
    
    @objc func buttonAction(sender: UIButton!) {
        counter += 1
        print("Button was pressed:\(counter)")
        // 若存在label1，需确保其正确初始化并添加约束
        // mainView.label1.text = "Button was pressed:\(counter)"
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        view.addSubview(mainView)
        // 设置mainView约束
        mainView.translatesAutoresizingMaskIntoConstraints = false
        NSLayoutConstraint.activate([
            mainView.topAnchor.constraint(equalTo: view.topAnchor),
            mainView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
            mainView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
            mainView.bottomAnchor.constraint(equalTo: view.bottomAnchor)
        ])
        mainView.button1.addTarget(self, action: #selector(buttonAction), for: .touchUpInside)
    }
}

class MainView : UIView {
    
    var background: UIView = {
        let view = UIView()
        view.backgroundColor = .white
        view.translatesAutoresizingMaskIntoConstraints = false
        return view
    }()
    
    lazy var button1: UIButton = {
        let btn = UIButton(type: .system)
        btn.setTitle("Click Me", for: .normal)
        btn.translatesAutoresizingMaskIntoConstraints = false
        return btn
    }()
    
    func createButton1(){
        print("Main view btn created")
        background.addSubview(button1)
        // 设置按钮约束
        NSLayoutConstraint.activate([
            button1.centerXAnchor.constraint(equalTo: background.centerXAnchor),
            button1.centerYAnchor.constraint(equalTo: background.centerYAnchor),
            button1.widthAnchor.constraint(equalToConstant: 120),
            button1.heightAnchor.constraint(equalToConstant: 40)
        ])
    }
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        self.addSubview(background)
        // 设置background约束
        NSLayoutConstraint.activate([
            background.topAnchor.constraint(equalTo: self.topAnchor),
            background.leadingAnchor.constraint(equalTo: self.leadingAnchor),
            background.trailingAnchor.constraint(equalTo: self.trailingAnchor),
            background.bottomAnchor.constraint(equalTo: self.bottomAnchor)
        ])
        createButton1()
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}

内容的提问来源于stack exchange，提问作者ALEX