如何在面板上画一条线?它没有出现 [英] How to draw a line on panel? It is not showing up

问题描述

我有一个名为 panel1 的 Panel，我正在尝试使用以下代码在我的 panel1 上画一条线:

I have a Panel called panel1 and I am trying to draw a line on my panel1 using this code:

var g = panel1.CreateGraphics();
var p = new Pen(Color.Black, 3);

var point1 = new Point(234,118);
var point2 = new Point(293,228);

g.DrawLine(p, point1, point2);

但是什么都没有出现.有任何想法吗?这是一个窗口形式.

But nothing is showing up. Any ideas? This is in a windows form.

推荐答案

处理面板的 Paint event 并将其放在那里.发生的事情是它在构造函数中被绘制一次，然后在每次被调用时在 Paint 事件中被绘制.

Handle the Panel's Paint event and put it in there. What's happening is that it's being drawn once in the constructor but then being drawn over in the Paint event everytime it's called.

private void panel1_Paint(object sender, PaintEventArgs e)
{
    base.OnPaint(e);
    using(Graphics g = e.Graphics)
    {
       var p = new Pen(Color.Black, 3);
       var point1 = new Point(234,118);
       var point2 = new Point(293,228);
       g.DrawLine(p, point1, point2);
    }
}

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