画线时触摸结束时线不一致

Posted 2023-02-24

【中文标题】画线时触摸结束时线不一致

【英文标题】：line disagreeing when touch end when drawing line

【发布时间】：2020-12-02 05:49:49

【问题描述】：

我的快速代码目标是在图像视图上画线。现在，当您从图像视图中拿起手时，绘图就会消失。当你的手被按下时，它就在你的手或点被释放时工作，没有任何东西被保存。我不知道我的代码中缺少什么来解决这个问题，它可能只是一行。

import UIKit
class ViewController: UIViewController 
    
    var statPoint = CGPoint.zero
    var swipe = false
    var pic = UIImageView()
    
    
    override func viewDidLoad() 
        super.viewDidLoad()
        
        pic.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(pic)
        pic.backgroundColor = .brown
        view.backgroundColor = .cyan
        pic.frame = CGRect(x: 100, y: 100, width: 100, height: 100)
    
    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) 
        guard let touch = touches.first else 
            return
        
        swipe = false
        statPoint = touch.location(in: view)
    
    
    func drawLine(from fromPoint: CGPoint, to toPoint : CGPoint)  
        UIGraphicsBeginImageContext( view.frame.size)
        
        guard let context = UIGraphicsGetCurrentContext() else 
            return
        
        
        pic.image?.draw(in: view.bounds)
        context.move(to: fromPoint)
        context.addLine(to: toPoint)
        context.setLineCap(.round)
        context.setLineWidth(5)
        context.setBlendMode(.normal)
        context.setStrokeColor(UIColor.black.cgColor)
        context.strokePath()
        pic.image = UIGraphicsGetImageFromCurrentImageContext()
        pic.alpha = 1
        
        UIGraphicsEndImageContext()
        
        
        
    
    override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) 
        guard let touch = touches.first else 
            return
            
        
        swipe = true
        let currentPoint = touch.location(in: view)
        drawLine(from: statPoint, to: currentPoint)
        statPoint = currentPoint
    
    
    
    
    override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) 
        if !swipe 
            drawLine(from: statPoint, to: statPoint)
        
        
        UIGraphicsBeginImageContext(pic.frame.size)
        pic.image?.draw(in: view.bounds, blendMode: .normal, alpha: 1)
        pic.image = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
    

【参考方案1】：

我已经检查了您的代码。我认为问题在于您在 touchEnded 中使用的 frame。

用下面的代码替换你的touchedEnded

override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) 
   if !swipe 
       drawLine(from: statPoint, to: statPoint)
   
       
   UIGraphicsBeginImageContext(view.frame.size)
   pic.image?.draw(in: view.bounds, blendMode: .normal, alpha: 1)
   pic.image = UIGraphicsGetImageFromCurrentImageContext()
   UIGraphicsEndImageContext()