c# - TouchMove事件在Xamarin iOS中如此快速地结束

我创建了如下的画布视图。当我将其应用于新项目时，它可以正常工作，但是当我将其放入真实项目中时，我无法画出一条实线。它总是虚线（如下面的图片）。第一次，我认为这是一个问题，因为我在此可绘制对象之前推了太多的屏幕。但是，每当我向其中推入新视图时，都试图禁用上一个视图的UserInteraction，但此方法不起作用。请帮忙！

public class CanvasView : UIView
{
    public CanvasView (CGRect frame) : base(frame)
    {
        this.drawPath = new CGPath();
        BackgroundColor = UIColor.White;

    }


    private CGPoint touchLocation;
    private CGPoint previousTouchLocation;
    private CGPath drawPath;
    private bool fingerDraw;
    public override void LayoutSubviews ()
    {
        base.LayoutSubviews ();
        Layer.BorderWidth = 0.5f;
        Layer.BorderColor = UIColor.FromRGB (146, 146, 146).CGColor;
    }
    public override void TouchesBegan (NSSet touches, UIEvent evt)
    {
        base.TouchesBegan (touches, evt);
        UITouch touch = touches.AnyObject as UITouch;
        this.fingerDraw = true;
        this.touchLocation = touch.LocationInView(this);
        this.previousTouchLocation = touch.PreviousLocationInView(this);

        this.SetNeedsDisplay();
    }
    public override void TouchesMoved (NSSet touches, UIEvent evt)
    {
        base.TouchesMoved (touches, evt);
        UITouch touch = touches.AnyObject as UITouch;
        this.touchLocation = touch.LocationInView(this);
        this.previousTouchLocation = touch.PreviousLocationInView(this);

        this.SetNeedsDisplay();
    }

    public override void TouchesEnded (NSSet touches, UIEvent evt)
    {
        base.TouchesEnded (touches, evt);
        var alert = new UIAlertView () {
            Message = "Xui"
        };
        alert.AddButton("OK");
        alert.Show();
    }
    public override void Draw (CGRect rect)
    {
        base.Draw (rect);
        if (this.fingerDraw)
        {
            using (CGContext context = UIGraphics.GetCurrentContext())
            {
                context.SetStrokeColor(UIColor.Black.CGColor);
                context.SetLineWidth(1.5f);
                context.SetLineJoin(CGLineJoin.Round);
                context.SetLineCap(CGLineCap.Round);
                this.drawPath.MoveToPoint(this.previousTouchLocation);
                this.drawPath.AddLineToPoint(this.touchLocation);
                context.AddPath(this.drawPath);
                context.DrawPath(CGPathDrawingMode.Stroke);
            }
        }
    }
}

the screen

最佳答案

我认为问题不在于TouchesMoved，而是您的绘制逻辑。当您呼叫SetNeedsDisplay()时，它并不表示“立即绘制”，而是表示“我有需要绘制的更改，因此，请亲爱的在可能的时候绘制我”。这意味着在处理图形之前会有更多的接触。

您必须保持先前的点不变，直到调用Draw为止，或者必须将这些点放入缓冲区中并同时绘制它们。我会做第一个，因为它比较简单。

关于c# - TouchMove事件在Xamarin iOS中如此快速地结束，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/33781504/