图片框绘制事件处理程序的执行变得越来越慢

Question

请原谅我的英语不好。我试图通过在计时器滴答处理函数中设置 Paint 事件处理程序来在图片框上绘制旋转线：

private void timer1_Tick(object sender, EventArgs e)
    {
        pictureBox1.Invalidate();
        pictureBox1.Paint += new PaintEventHandler(Draw);//1
        foreach (Line line in lines)//array "lines" contains just 16 objects
        {
            //calculating new coordinates ...
        }
    }

标记为“1”的行随着时间的推移执行得越来越慢。下面是 "Draw" 函数代码：

void Draw(object sender, PaintEventArgs e)
    {
        foreach (Line line in lines)
        {
            e.Graphics.DrawLine(new Pen(Brushes.Black, 5f), line.P1, line.P2);
            e.Graphics.FillEllipse(Brushes.Red, line.P1.X - 2.5f, line.P1.Y - 2.5f, 5, 5);
            e.Graphics.FillEllipse(Brushes.Red, line.P2.X - 2.5f, line.P2.Y - 2.5f, 5, 5);
            e.Graphics.DrawEllipse(new Pen(Brushes.Red, 5f), line.P1.X, line.P1.Y, 1, 1);
            e.Graphics.DrawEllipse(new Pen(Brushes.Red, 5f), line.P2.X, line.P2.Y, 1, 1);
        }
    }

你们能告诉我，我该如何解决这个问题？谢谢！

Answer 1

看起来你的问题是 pictureBox1.Paint += new PaintEventHandler(Draw); 所以当 paint 事件触发第一个 tick 时它在第二个 tick 上不做任何事情它在第 500 个 tick 上重绘一次它重绘 499 次

你需要做的是

private void configure()
{
    pictureBox1.Paint += new PaintEventHandler(pictureBox1_OnPaint);
}
private void timer1_Tick(object sender, EventArgs e)
{
    pictureBox1.Invalidate();
}
private void pictureBox1_OnPaint(object sender, PaintEventArgs e)
{
    foreach (Line line in lines)//array "lines" contains just 16 objects
    {
        //calculating new coordinates ...
        e.Graphics.DrawLine(new Pen(Brushes.Black, 5f), line.P1, line.P2);
        e.Graphics.FillEllipse(Brushes.Red, line.P1.X - 2.5f, line.P1.Y - 2.5f, 5, 5);
        e.Graphics.FillEllipse(Brushes.Red, line.P2.X - 2.5f, line.P2.Y - 2.5f, 5, 5);
        e.Graphics.DrawEllipse(new Pen(Brushes.Red, 5f), line.P1.X, line.P1.Y, 1, 1);
        e.Graphics.DrawEllipse(new Pen(Brushes.Red, 5f), line.P2.X, line.P2.Y, 1, 1);
    }
}

更详细一点，因为您显然不了解事件处理程序的工作原理

pictureBox1.Paint += new PaintEventHandler(pictureBox1_OnPaint);

读作当绘画事件发生时，我希望你调用 pictureBox1_OnPaint 每次你调用该命令时，你都会向你的程序添加该方法调用的一个额外实例，所以

pictureBox1.Paint += new PaintEventHandler(pictureBox1_OnPaint);
pictureBox1.Paint += new PaintEventHandler(pictureBox1_OnPaint);

说当 Paint 发生时你想调用 pictureBox1_OnPaint 两次。它永远不会触发事件，调用 Invalidate() 会触发事件。

所以你需要做的是当表单被初始化时（这可能是构造函数，一个像（Form.Load）这样的初始化事件或类似的地方告诉表单你想要它做什么当

发生时绘制事件

pictureBox1.Paint += new PaintEventHandler( action );

但只做一次

然后在你的计时器上调用 Invalidate 以触发事件

由于每次绘制事件触发时都会发生刻度逻辑，因此您最好将其添加到处理程序操作中，而不是两次遍历行集合

Answer 2

不要执行 pictureBox1.Paint += new PaintEventHandler(Draw);//1 in timer1_Tick。在您的表单加载中执行一次。否则它会在每个 Paint 事件中多次调用 Draw() 并且调用次数会增加。

Answer 3

试试这个

private void timer1_Tick(object sender, EventArgs e)
    {
        Graphics g = pictureBox1.CreateGraphics();
        foreach (Point line in lines)
        {
            g.DrawLine(new Pen(Brushes.Black, 5f), line.P1, line.P2);
            g.FillEllipse(Brushes.Red, line.P1.X - 2.5f, line.P1.Y - 2.5f, 5, 5);
            g.FillEllipse(Brushes.Red, line.P2.X - 2.5f, line.P2.Y - 2.5f, 5, 5);
            g.DrawEllipse(new Pen(Brushes.Red, 5f), line.P1.X, line.P1.Y, 1, 1);
            g.DrawEllipse(new Pen(Brushes.Red, 5f), line.P2.X, line.P2.Y, 1, 1);
        }
    }

如果它不会显示效果，则在循环后添加以下行

pictureBox1.Invalidate();

Answer 4

除了解决其他答案中已经指出的事件处理程序问题之外，我还会更改您的代码中的一些内容。

首先，您为什么要创建这么多 Pen？将他们从循环中解救出来：

void Draw(object sender, PaintEventArgs e)
{
    var blackPen = new Pen(Brushes.Black, 5f);
    var redPen = new Pen(Brushes.Red, 5f);

    foreach (Line line in lines)
    {
        e.Graphics.DrawLine(blackPen, line.P1, line.P2);
        e.Graphics.FillEllipse(Brushes.Red, line.P1.X - 2.5f, line.P1.Y - 2.5f, 5, 5);
        e.Graphics.FillEllipse(Brushes.Red, line.P2.X - 2.5f, line.P2.Y - 2.5f, 5, 5);
        e.Graphics.DrawEllipse(redPen, line.P1.X, line.P1.Y, 1, 1);
        e.Graphics.DrawEllipse(redPen, line.P2.X, line.P2.Y, 1, 1);
    }
}

嗯，现在，请注意 Pen 实现了 IDisposable。养成处理完这些类型的物品的习惯；这样，您将以非终端方式释放底层非托管资源，而不是在 GC 决定：

时

void Draw(object sender, PaintEventArgs e)
{
    using (var blackPen = new Pen(Brushes.Black, 5f))
    using (var redPen = new Pen(Brushes.Red, 5f))
    {
        foreach (Line line in lines)
        {
            e.Graphics.DrawLine(blackPen, line.P1, line.P2);
            e.Graphics.FillEllipse(Brushes.Red, line.P1.X - 2.5f, line.P1.Y - 2.5f, 5, 5);
            e.Graphics.FillEllipse(Brushes.Red, line.P2.X - 2.5f, line.P2.Y - 2.5f, 5, 5);
            e.Graphics.DrawEllipse(redPen, line.P1.X, line.P1.Y, 1, 1);
            e.Graphics.DrawEllipse(redPen, line.P2.X, line.P2.Y, 1, 1);
        }
    }
}

此外，您甚至可以考虑将 Pen 缓存为实例变量；

class MyControl: ..., IDisposable
{
     private readonly Pen blackPen = new Pen(Brushes.Black, 5f));
     private readonly Pen redPen = new Pen(Brushes.Red, 5f));

     void Draw(object sender, PaintEventArgs e)
     {
         foreach (Line line in lines)
         {
            e.Graphics.DrawLine(blackPen, line.P1, line.P2);
            e.Graphics.FillEllipse(Brushes.Red, line.P1.X - 2.5f, line.P1.Y - 2.5f, 5, 5);
            e.Graphics.FillEllipse(Brushes.Red, line.P2.X - 2.5f, line.P2.Y - 2.5f, 5, 5);
            e.Graphics.DrawEllipse(redPen, line.P1.X, line.P1.Y, 1, 1);
            e.Graphics.DrawEllipse(redPen, line.P2.X, line.P2.Y, 1, 1);
        }
    }

    private void Dispose(bool disposing)
    {
         ....
         if (disposing)
         {
             ....
             blackPen.Dispose(;)
             redPen.Dispose();
         }
    }
}

图片框绘制事件处理程序的执行变得越来越慢

Executing of picture box paint event handler becomes slower and slower

c#

performance

gdi