Question

嗨，我想使用鼠标事件在winforms的图片框中画一条直线。我使用鼠标按下，鼠标移动和鼠标向上事件来绘制一条线。但是，当我移动鼠标时，还会绘制其他几条线。

如果有人能提供如何解决这个问题的指南，我真的很感激。

我还附上了我的代码片段供您参考。提前谢谢！

    private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
    {

        mousepress = true;
        x1 = e.Location.X;
        y1= e.Location.Y;
        if (counter>0)
        {
            this.Invalidate();
            pictureBox1.Refresh();
        }
    }

    private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
    {

        Graphics g = pictureBox1.CreateGraphics();
        Pen newpen = new Pen(Color.Blue, 1);



        if (mousepress)
        {
            g.DrawLine(newpen, x1, y1, e.Location.X, e.Location.Y);
            x2 = e.Location.X;
            y2 = e.Location.Y;
            angle = GetAngle(x1, y1, x2, y2);
        }
        Invalidate();


    }

  private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
    {
        mousepress = false;
        double tempX=e.Location.X, tempY=e.Location.Y;

        {
            textBox_coordinates.Text = "Index: " + i + Environment.NewLine + "X: " + x2
         + Environment.NewLine + "Y: " + y2 + Environment.NewLine + "Angle: " + angle;
            i++;

        }

        counter++;
    }

Answer 1

在MouseMove事件中，您还必须刷新PictureBox以清除您在上一次调用中绘制的行。并且永远不要忘记在分配之后处理非托管图形资源，除非你想要一个内存漏洞。

private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
{
    // vvv take care of automatic disposal 
    using (Graphics g = pictureBox1.CreateGraphics())
    using (Pen newpen = new Pen(Color.Blue, 1))
    {
        if (mousepress)
        {
            pictureBox1.Refresh(); // <-- get rid of the previous lines

            g.DrawLine(newpen, x1, y1, e.Location.X, e.Location.Y);
            x2 = e.Location.X;
            y2 = e.Location.Y;
            angle = GetAngle(x1, y1, x2, y2);
        }
        // Invalidate(); // check if necessary!
    }
}

编辑：获得所需内容的另一种方法是拦截绘制事件并在那里进行线条绘制（在继承绘制PictureBox之后）。我想大多数人会认为这是一个更干净的解决方案，因为这正是油漆事件的目的所在。但是如果你只是想快速完成你的狭隘任务，那么上面建议的解决方案就足够了。

Answer 2

类似的东西...

public partial class Form1 : Form
{
    bool mousepressed;
    int x1=0, y1=0,x2=0,y2=0;
    Pen newPen = new Pen(Color.Blue, 2);
    public Form1()
    {
        InitializeComponent();
    }

    private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
    {
        mousepressed = true;
        x1 = e.X;
        y1 = e.Y;
    }

    private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
    {
        if (mousepressed)
        {
            x2 = e.X;
            y2 = e.Y;
            pictureBox1.Refresh();
        }            
    }
    private void pictureBox1_Paint(object sender, PaintEventArgs e)
    {
        e.Graphics.DrawLine(newPen, x1, y1, x2, y2);
    }

    private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
    {
        mousepressed = false;
    }
}

在Winforms中绘制一条没有重复的行

2 个答案: