c# - 在移动鼠标并按住右键单击按钮的同时绘制一条线

Question

我想在按住右键的同时移动鼠标时在面板上画一条线。这是我到目前为止所尝试的：

private void panel1_MouseDown(object sender, MouseEventArgs e)
{
    Point point = panel1.PointToClient(Cursor.Position);
    Point cordinatedClikedPoint = new Point(xPanelPosition, yPanelPositon);
    DrawPoint((point.X), (point.Y), Color.Navy);                
}

public void DrawPoint(int x, int y, Color color)
{
    Graphics g = this.panel1.CreateGraphics();
    Pen pen = new Pen(color);
    g.DrawRectangle(pen, x, y, 3, 3);
}

Answer 1

另一个……这次使用 ControlPaint.DrawReversibleLine()：

public partial class Form1 : Form
{

    public Form1()
    {
        InitializeComponent();
    }

    private Point StartPoint, EndPoint;

    private void panel1_MouseDown(object sender, MouseEventArgs e)
    {
        if (e.Button == System.Windows.Forms.MouseButtons.Right)
        {
            Point pt = Cursor.Position;
            StartPoint = pt;
            EndPoint = pt;
            ControlPaint.DrawReversibleLine(StartPoint, EndPoint, Color.Black);
        }
    }

    private void panel1_MouseMove(object sender, MouseEventArgs e)
    {
        if (e.Button == System.Windows.Forms.MouseButtons.Right)
        {
            ControlPaint.DrawReversibleLine(StartPoint, EndPoint, Color.Black); // erase previous line
            EndPoint = Cursor.Position;
            ControlPaint.DrawReversibleLine(StartPoint, EndPoint, Color.Black); // draw new line
        }
    }

    private void panel1_MouseUp(object sender, MouseEventArgs e)
    {
        if (e.Button == System.Windows.Forms.MouseButtons.Right)
        {
            ControlPaint.DrawReversibleLine(StartPoint, EndPoint, Color.Black); // erase previous line

            // ... do something with StartPont and EndPoint in here ...

            // possibly add them to a class level structure to use in the Paint() event to make it persistent?

        }
    }

}

Answer 2

只需使用MouseDown和MouseUp事件来设置布尔变量，在MouseMoveEventHandler 中进行绘图。由于您直接调用图形对象，因此面板上的任何无效或重绘操作都会导致它被清除，其他两个答案解决了这个问题。

public partial class Form1 : Form
{
    bool mouseIsDown;
    public Form1()
    {
        InitializeComponent();
    }

    private void panel1_MouseDown(object sender, MouseEventArgs e)
    {
        if (e.Button== System.Windows.Forms.MouseButtons.Right)
            mouseIsDown = true;
    }

    private void panel1_MouseMove(object sender, MouseEventArgs e)
    {
        if (mouseIsDown)
        {
            Point point = panel1.PointToClient(Cursor.Position);
            DrawPoint((point.X), (point.Y), Color.Navy);
        }
    }

    private void panel1_MouseUp(object sender, MouseEventArgs e)
    {
        mouseIsDown = false;
    }

    public void DrawPoint(int x, int y, Color color)
    {
        Graphics g = this.panel1.CreateGraphics();
        Pen pen = new Pen(color);
        g.DrawRectangle(pen, x, y, 3, 3);
    }
}

Answer 3

试试这个，你需要在每次抽奖时使面板无效。

private IList<Point> _pointList = new List<Point>();
private void panel1_MouseMove(object sender, MouseEventArgs e)
{    
    _pointList.Add( e.Location );
    panel1.Invalidate(); //force a repaint
}

private void panel1_Paint( object sender, PaintEventArgs e )
{
    e.Graphics.DrawLines( Pens.Black, _pointList );
}

Answer 4

据我所知，当您按下按钮时，MouseDown 事件会触发一次。每隔几毫秒就会重绘一次 WindowsForms 面板/表单或任何其他内容。因此，您需要将该代码放入OnPaint方法中。

它应该看起来像这样：

//global variable
bool isDragging = false;

private void panel1_MouseDown(object sender, MouseEventArgs e)
{
            isDragging = true;               
}

private void panel1_MouseUp(object sender, MouseEventArgs e)
{
            isDragging = false;               
}

private void form_Paint(object sender, EventArgs e)
{
            if(isDragging)
            {
               Point point = panel1.PointToClient(Cursor.Position);
               Point cordinatedClikedPoint = new Point(xPanelPosition, yPanelPositon);
               DrawPoint((point.X), (point.Y), Color.Navy);
            }
}

Answer 5

我认为这是您尝试做的完整解决方案：

public partial class Form1 : Form
{
    private Graphics g;
    private readonly Pen pen = new Pen(Color.Navy, 7);
    private Point oldCoords;
    private readonly GraphicsPath graphicsPaths = new GraphicsPath();

    public Form1()
    {
        InitializeComponent();
        g = panel1.CreateGraphics();
    }

    private void panel1_MouseMove(object sender, MouseEventArgs e)
    {
        if (e.Button == MouseButtons.Left)
        {
            if (oldCoords.IsEmpty)
                graphicsPaths.StartFigure();
            else
            {
                graphicsPaths.AddLine(oldCoords, new Point(e.X, e.Y));
                g.DrawPath(pen, graphicsPaths);
            }
            oldCoords= new Point(e.X,e.Y);
        }
        else
            oldCoords = Point.Empty;
    }

    private void panel1_Paint(object sender, PaintEventArgs e)
    {
        g.DrawPath(pen, graphicsPaths);
    }
}

干杯:)