如何使用 Paint 事件在鼠标坐标处绘制形状 [英] How to use the Paint event to draw shapes at mouse coordinates

问题描述

我最近显然开始使用 C# 编程，并试图做一个简单的 WinForms 应用程序，该应用程序采用鼠标坐标并根据坐标缩放矩形.

我面临的问题是我不知道如何调用使用更多参数的方法(在这种情况下是 x、y 和 PaintEventArgs).或者，我知道如何处理 PaintEvent.

这是整个代码，因为它非常短而且相当简单:

使用系统；使用 System.Drawing；使用 System.Windows.Forms;公共部分类 Form1 :表单{public void Form1_MouseMove(对象发送者，MouseEventArgs e){int x = e.X;int y = e.Y;字符串数据 = (x.ToString() + " " + y.ToString());DrawRect(Something, x, y);}PaintEventArgs pEventArgs;private void Form1_Paint(对象发送者，PaintEventArgs e){}public void DrawRect(PaintEventArgs e, int rey, int rex){图形 gr = e.Graphics;Pen pen = new Pen(Color.Azure, 4);矩形 rect = new Rectangle(0, 0, rex, rey);gr.DrawRectangle(pen, rect);}}

我正在尝试调用 DrawRect() 方法来根据鼠标坐标绘制具有 width 和 height 的矩形.

那么我怎样才能用坐标和PaintEventArgs调用DrawRect()?

解决方案

PaintEventArgs 允许您访问 Graphics 对象，您需要该对象来绘制一些东西.

如果您不想使用PaintEventArgs，我建议您调用Form 的CreateGraphics() 方法，然后它将允许您绘制矩形.

为了提高性能，我建议您使用 using(...){ } 键来处理 Graphics 对象和 Pen 对象.>

您需要包含 System.Drawing 才能使用 Graphics 和 Pen.

你的代码看起来像这样:

使用 System.Drawing;使用 System.Text;使用 System.Threading.Tasks;使用 System.Windows.Forms;命名空间 WindowsFormsApp2{公共部分类 Form1 :表单{点_坐标；公共 Form1(){this._coordinates = new Point();this.InitializeComponent();}private void Form1_Load(对象发送者，EventArgs e){}public void Form1_MouseMove(对象发送者，MouseEventArgs e){this._coordinates = new Point(e.X, e.Y);this.Invalidate();}private void Form1_Paint(对象发送者，PaintEventArgs e){//不要在第一个 Paint 事件上绘制if(this._coordinates.X != 0 && this._coordinates.Y != 0){this.DrawRect(e);}}public void DrawRect(PaintEventArgs e){使用 (Pen pen = new Pen(Color.Azure, 4)){矩形 rect = new Rectangle(0, 0, this._coordinates.X, this._coordinates.Y);e.Graphics.DrawRectangle(pen, rect);}}}}

I recently started programming in C# obviously and was trying to do a simple WinForms app that takes mouse coordinates and scales a Rectangle according to the coordinates.

The issue I am facing is that I don't know how to call a method that uses more arguments (in this case is x, y and PaintEventArgs). Or, I do know what to do with the PaintEvent.

Here is the whole code, since its pretty short and rather simple:

using System;
using System.Drawing;
using System.Windows.Forms;

public partial class Form1 : Form
{
    public void Form1_MouseMove(object sender, MouseEventArgs e)
    {
        int x = e.X; 
        int y = e.Y;
        String data = (x.ToString() + " " + y.ToString());
        DrawRect(Something, x, y);
    }

    PaintEventArgs pEventArgs;
    private void Form1_Paint(object sender, PaintEventArgs e)
    {

    }

    public void DrawRect(PaintEventArgs e, int rey, int rex)
    {
        Graphics gr = e.Graphics;
        Pen pen = new Pen(Color.Azure, 4);
        Rectangle rect = new Rectangle(0, 0, rex, rey);
        gr.DrawRectangle(pen, rect);
    }
}

I'm trying to call the DrawRect() method to draw the Rectangle with width and height according to the mouse coordinates.

So how can I call the DrawRect() with coordinates and PaintEventArgs?

解决方案

The PaintEventArgs allows you to access to the Graphics object, you need that one to draw something.

If you don't want to use the PaintEventArgs, i suggest that you call the CreateGraphics() method of your Form, and it will allow you to draw the rectangle.

To improve performance, i suggest that you use the using(...){ } keywork in order to dispose the Graphics object and the Pen object.

You need to include System.Drawing in order to use Graphics and Pen.

You're code will look like that :

using System.Drawing;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WindowsFormsApp2
{
    public partial class Form1 : Form
    {
        Point _coordinates;

        public Form1()
        {
            this._coordinates = new Point();
            this.InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
        }

        public void Form1_MouseMove(object sender, MouseEventArgs e)
        {
            this._coordinates = new Point(e.X, e.Y);
            this.Invalidate();
        }

        private void Form1_Paint(object sender, PaintEventArgs e)
        {
            // Don't draw on first Paint event
            if(this._coordinates.X != 0 && this._coordinates.Y != 0)
            {
                this.DrawRect(e);
            }
        }

        public void DrawRect(PaintEventArgs e)
        {
            using (Pen pen = new Pen(Color.Azure, 4))
            {
                Rectangle rect = new Rectangle(0, 0, this._coordinates.X, this._coordinates.Y);
                e.Graphics.DrawRectangle(pen, rect);
            }
        }
    }
}

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