如何创建一条线作为可拖动对象？答案

【问题标题】：How to create a line to be draggable object?如何创建一条线作为可拖动对象？
【发布时间】：2021-07-04 12:07:05
【问题描述】：

我通过保持起点和终点创建了一条线。目前，如果我想移动起点或终点，我必须点击某个点才能移动一个点。

但有时我不想改变起点和终点的距离。所以我想点击两点之间的一条线来移动一条线并移动线的位置。

如何使一条线成为对象？用户点击该行如何处理？

【问题讨论】：

【解决方案1】：

这是一个画线的类：

using System;
using System.Collections.Generic;
using System.Text;
using System.Windows.Forms;
using System.Drawing;
using System.ComponentModel;

namespace BaseClasses
{
    public class MyLine : Control
    {
        private int _lineSize = 1;
        [DefaultValue(typeof(int), "1")]
        public int LineSize
        {
            get
            {
                return _lineSize;
            }

            set
            {
                if (value != _lineSize)
                {
                    _lineSize = value;
                    MinimumSize = new Size(_lineSize, _lineSize);
                    if (Parent != null)
                        Invalidate();
                }
            }
        }

        private LineOrientation _orientation = LineOrientation.Diag1;
        [DefaultValue(typeof(LineOrientation), "Diag1")]
        public LineOrientation Orientation
        {
            get
            {
                return _orientation;
            }
            set
            {
                if (value != _orientation)
                {
                    _orientation = value;
                    if (Parent != null)
                        Invalidate();
                }
            }
        }

        private Color _lineColor = Color.Black;
        [DefaultValue(typeof(Color), "Black")]
        public Color LineColor
        {
            get
            {
                return _lineColor;
            }

            set
            {
                if (value != _lineColor)
                {
                    _lineColor = value;
                    if (Parent != null)
                        Invalidate();
                }
            }
        }

        public MyLine()
        {
            TabStop = false;
        }

        protected override void OnParentChanged(EventArgs e)
        {
            base.OnParentChanged(e);
            if (Parent != null)
                this.BackColor = this.Parent.BackColor;
        }

        protected override void OnParentBackColorChanged(EventArgs e)
        {
            base.OnParentBackColorChanged(e);
            this.BackColor = this.Parent.BackColor;
        }

        protected override void OnPaint(PaintEventArgs e)
        {
            base.OnPaint(e);
            using (Pen pen = new Pen(_lineColor, _lineSize))
            {
                if (_orientation == LineOrientation.Diag1)
                    e.Graphics.DrawLine(pen, _lineSize - 1, _lineSize - 1, Width - _lineSize, Height - _lineSize);
                else if (_orientation == LineOrientation.Diag2)
                    e.Graphics.DrawLine(pen, _lineSize - 1, Height - _lineSize, Width - _lineSize, _lineSize - 1);
                else if (_orientation == LineOrientation.Horiz)
                    e.Graphics.DrawLine(pen, _lineSize - 1, (Height - _lineSize) / 2, Width - _lineSize, (Height - _lineSize) / 2);
                else if (_orientation == LineOrientation.Vert)
                    e.Graphics.DrawLine(pen, (Width - _lineSize) / 2, Height - _lineSize, (Width - _lineSize) / 2, _lineSize - 1);
            }
        }

        protected override void OnResize(EventArgs e)
        {
            base.OnResize(e);
            Invalidate();
        }

    }

    public enum LineOrientation { Diag1, Diag2, Vert, Horiz }
}

应在基类级别（Control）处理单击事件，并确定单击是在线上还是其他地方发生。

【讨论】：