如何从文本输入以在屏幕上绘制形状？

Question

大家好，我正在尝试创建一个程序，该程序接受用户的命令以在屏幕上绘制形状。该程序应具有绘制图形的基本命令和清除屏幕后的清除命令，用户应能够在文本框中键入moveTo，并且笔应将其设置为的坐标移动到该坐标上，然后用户应能够键入他们想要绘制的形状（圆（半径），矩形（宽度，高度），三角形（侧面，侧面，侧面）。我想让它适用于矩形，但是要努力实现其他零件可以任何人的帮助。

public partial class Form1 : Form
{
    String input;
    Bitmap drawOutput;

    String command, command2, command3;
    int x, y;

    public Form1()
    {
        InitializeComponent();

        drawOutput = new Bitmap(OutputBox.Size.Width, OutputBox.Size.Height);
        OutputBox.Image = drawOutput;
    }

    private void Form1_Load(object sender, EventArgs e)
    {
        Graphics g;
        g = Graphics.FromImage(drawOutput);

        Pen mypen = new Pen(Color.Black);
        g.Clear(Color.White);
        g.Dispose();
    }

    private void CMDBox_TextChanged(object sender, EventArgs e)
    {
        input = CMDBox.Text;
    }

    private void ExecuteBtn_Click(object sender, EventArgs e)
    {
        string[] spilt = input.Split(' ');
        foreach (String words in spilt)
        {
            command = spilt[0];
            command2 = spilt[1];
            command3 = spilt[2];

            x = Int32.Parse(command2);
            y = Int32.Parse(command3);

            Graphics g;
            g = Graphics.FromImage(drawOutput);
            Pen pen = new Pen(Color.Black, 5);

            if (command == "circle")
            {
                g.DrawEllipse(pen, 0, 0, x, y);

                setImage(g);

            }
            else if (command == "rectangle")
            {
                g.DrawRectangle(pen, 0, 0, x, y);

                setImage(g);


            }
        }

    }

    public void setImage(Graphics g)
    {
        g = Graphics.FromImage(drawOutput);

        OutputBox.Image = drawOutput;

        g.Dispose();
    }
}

此程序的基本上下文是创建一种真正的基本编程语言，该语言需要用户输入并在屏幕上显示它

Answer 1

您无需声明类级别的位图（drawOutput）或从其创建Graphics对象。您需要在Paint事件处理程序中进行绘制。尝试以下操作：

• 声明形状的枚举，用于保存形状类型，x和y坐标以及形状w和h的大小的类级变量。

enum Shapes
{
    Ellipse,
    Rectangle,
    Line
}

int x, y, w, h;
Shapes shape;

• 在ExecuteBtn click事件中验证用户的输入，分配值，如果输入正确，则调用OutputBox.Invalidate（）。

var cmd = textBox1.Text.Split(' ');
var validCmds = Enum.GetNames(typeof(Shapes));

if (cmd.Length < 5 || !validCmds.Contains(cmd[0], StringComparer.OrdinalIgnoreCase))
{
    MessageBox.Show("Enter a valid command.");
    return;
}

if(!int.TryParse(cmd[1], out x) || 
    !int.TryParse(cmd[2], out y) ||
    !int.TryParse(cmd[3], out w) ||
    !int.TryParse(cmd[4], out h))                    
{
    MessageBox.Show("Enter a valid shape");
    return;
}
shape = (Shapes)validCmds.ToList().FindIndex(a => a.Equals(cmd[0], StringComparison.OrdinalIgnoreCase));
OutputBox.Invalidate();

• 在Paint事件中绘制形状。

private void OutputBox_Paint(object sender, PaintEventArgs e)
{
    if (w > 0 && h > 0)
    {
        e.Graphics.Clear(Color.White);
        e.Graphics.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;

        using (Pen pn = new Pen(Color.Black, 5))
        {
            switch (shape)
            {
                case Shapes.Ellipse:
                    e.Graphics.DrawEllipse(pn, x, y, w, h);
                    break;
                case Shapes.Rectangle:
                    e.Graphics.DrawRectangle(pn, x, y, w, h);
                    break;
                case Shapes.Line:
                    e.Graphics.DrawLine(pn, x, y, w, h);
                    break;
            }
        }
    }
}

---

更好的是，Shape类方法，如下所述。

• 创建Shape类以枚举形状，为其声明属性，并提供一种方法来解析给定的命令字符串并在成功时输出所需的形状：

public class Shape
{
    #region enums.

    public enum Shapes
    {
        Ellipse,
        Rectangle,
        Line
    }
    #endregion

    #region Constructors

    public Shape()
    { }

    public Shape(Shapes shape, int x, int y, int width, int height)
    {
        ThisShape = shape;
        X = x;
        Y = y;
        Width = width;
        Height = height;
    }

    #endregion

    #region Properties

    public Shapes ThisShape { get; set; } = Shapes.Ellipse;
    public int X { get; set; }
    public int Y { get; set; }
    public int Width { get; set; }
    public int Height { get; set; }

    #endregion

    #region Methods

    public static bool TryParse(string input, out Shape result)
    {
        result = null;

        if (string.IsNullOrEmpty(input))
            return false;

        var cmd = input.Split(' ');
        var validCmds = Enum.GetNames(typeof(Shapes));

        if (cmd.Length < 5 || !validCmds.Contains(cmd[0], StringComparer.OrdinalIgnoreCase))
            return false;

        int x, y, w, h;

        if (!int.TryParse(cmd[1], out x) ||
            !int.TryParse(cmd[2], out y) ||
            !int.TryParse(cmd[3], out w) ||
            !int.TryParse(cmd[4], out h))
            return false;

        if (w <= 0 || h <= 0)
            return false;

        var shape = (Shapes)validCmds.ToList().FindIndex(a => a.Equals(cmd[0], StringComparison.OrdinalIgnoreCase));

        result = new Shape(shape, x, y, w, h);
        return true;
    }

    #endregion

}

• 在您的Form中，声明一个形状变量：

Shape shape;

• [ExecuteBtn单击事件：

shape = null;

if (!Shape.TryParse(textBox1.Text, out shape))
{
    MessageBox.Show("Enter a valid command.");
    return;
}
OutputBox.Invalidate();

• 最后，您的绘画活动：

private void OutputBox_Paint(object sender, PaintEventArgs e)
{
    if (shape != null)
    {
        e.Graphics.Clear(Color.White);
        e.Graphics.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;

        using (Pen pn = new Pen(Color.Black, 5))
        {
            switch (shape.ThisShape)
            {
                case Shape.Shapes.Ellipse:
                    e.Graphics.DrawEllipse(pn, shape.X, shape.Y, shape.Width, shape.Height);
                    break;
                case Shape.Shapes.Rectangle:
                    e.Graphics.DrawRectangle(pn, shape.X, shape.Y, shape.Width, shape.Height);
                    break;
                case Shape.Shapes.Line:
                    //Note: the Width and Height properties play here the X2 and Y2 roles.
                    e.Graphics.DrawLine(pn, shape.X, shape.Y, shape.Width, shape.Height);
                    break;
            }
        }
    }
}