Question

我有PictureBox作为UserControl。我在主表单上添加了User Control。现在我必须按一个按钮并在用户控件上创建一行。在我的项目中，每次按下此按钮，我都要向用户发送两个PointF（x和y）的控制参数，并绘制一条新线，此外还有现有线。到目前为止，我已加载了图片框的Paint事件。

private void pictureBox1_Paint(object sender, PaintEventArgs e)
{
  Pen graphPen = new Pen(Color.Red, 2);
  PointF pt1D = new PointF();
  PointF pt2D = new PointF();
  pt1D.X = 0;
  pt1D.Y = 10;
  pt2D.X = 10;
  pt2D.Y = 10;

  e.Graphics.DrawLine(graphPen, pt1D, pt2D);
}

Answer 1

假设您想在点击按钮时绘制线条，这是您的代码的修改版本：

List<PointF> points = new List<PointF>();
Pen graphPen = new Pen(Color.Red, 2);

private void btnDrawLines_Click(object sender, EventArgs e)
{
    Graphics g = picBox.CreateGraphics();
    PointF pt1D = new PointF();
    PointF pt2D = new PointF();
    pt1D.X = 0;
    pt1D.Y = 10;
    pt2D.X = 10;
    pt2D.Y = 10;    
    g.DrawLine(graphPen, pt1D, pt2D);
    points.Add(pt1D);
    points.Add(pt2D);
}

private void picBox_Paint(object sender, PaintEventArgs e)
{
    for (int i = 0; i < points.Count; i+=2)
        e.Graphics.DrawLine(graphPen, points[i], points[i + 1]);
}

请注意，您可以通过PictureBox类的CreateGraphics()方法获取Graphics对象，该方法与e.Graphics事件处理程序中的Paint对象相同。

Answer 2

如果要添加要绘制的线条，您可能需要一个小Line类：

public class Line {
  public Point Point1 { get; set; }
  public Point Point2 { get; set; }

  public Line(Point point1, Point point2) {
    this.Point1 = point1;
    this.Point2 = point2;
  }
}

然后你可以将这些“行”添加到列表中：

private List<Line> _Lines = new List<Line>();

并添加它们并告诉控件更新它的绘图：

_Lines.Add(new Line(new Point(10, 10), new Point(42, 42)));
_Lines.Add(new Line(new Point(20, 40), new Point(20, 60)));
pictureBox1.Invalidate()

然后在你的图纸中：

private void pictureBox1_Paint(object sender, PaintEventArgs e) {
  e.Graphics.Clear(Color.White);
  foreach (Line l in _Lines) {
    e.Graphics.DrawLine(Pens.Red, l.Point1, l.Point2);
  }
}

从父级在PictureBox上画一条线

2 个答案: