手势之 shouldReceive touch

Created by 大刘 liuxing8807@126.com

在实际做项目中遇到一个小问题，即往父视图中添加UITapGestureRecognizer，即使点击了子视图，手势也会响应

如上，手势加在红色视图上，绿色视图添加到了红色视图上，点击绿色的子视图，触发了tap方法：

import UIKit

class ViewController: UIViewController {
    var redView: UIView = UIView()
    var greenView: UIView = UIView()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // red view
        redView.frame = self.view.bounds
        redView.backgroundColor = UIColor.red
        let tap: UITapGestureRecognizer = UITapGestureRecognizer.init(target: self, action: #selector(self.tap))
        redView.addGestureRecognizer(tap)
        self.view.addSubview(redView)
        
        // green view on red view
        greenView.frame = CGRect.init(x: 0.0, y: self.view.bounds.size.height/2.0, width: self.view.bounds.size.width, height: self.view.bounds.size.height/2.0)
        greenView.backgroundColor = UIColor.green
        greenView.isUserInteractionEnabled = true
        redView.addSubview(greenView);
    }
    
    @objc
    func tap() {
        print("YES")
    }
}

参考：stackoverflow, 需要实现代理方法 UIGestureRecognizerDelegate：

import UIKit

class ViewController: UIViewController, UIGestureRecognizerDelegate {
    var redView: UIView = UIView()
    var greenView: UIView = UIView()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // red view
        redView.frame = self.view.bounds
        redView.backgroundColor = UIColor.red
        let tap: UITapGestureRecognizer = UITapGestureRecognizer.init(target: self, action: #selector(self.tap))
        tap.delegate = self; // 添加代理方法
        redView.addGestureRecognizer(tap)
        self.view.addSubview(redView)
        
        // green view on red view
        greenView.frame = CGRect.init(x: 0.0, y: self.view.bounds.size.height/2.0, width: self.view.bounds.size.width, height: self.view.bounds.size.height/2.0)
        greenView.backgroundColor = UIColor.green
        redView.addSubview(greenView);
    }
    
    @objc
    func tap() {
        print("YES")
    }
    
    //MARK: -
    //实现代理方法
    func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldReceive touch: UITouch) -> Bool {
        // Prevent subviews of a specific view to send touch events to the view's gesture recognizers.
        if let touchedView = touch.view, let gestureView = gestureRecognizer.view, touchedView.isDescendant(of: gestureView), touchedView !== gestureView {
            // 假如触摸在绿色视图上：
            // touchedView: 触摸的视图，绿色视图
            // gestureView: 添加手势的视图，红色视图
            print("click green view")
            return false
        }
        print("click red view")
        return true
    }
}