C# get form to invalidate when form is resized?

我刚刚接受了一个挑战，创建一个64个相同矩形或正方形的颜色交替的棋盘，从技术上来说，我已经完成了这个挑战；但是出于好奇，我注意到当用户调整窗体的大小并拖动它时，窗体会一直重绘自己，这几乎就像是一个断断续续的图像。我在想我写的代码，也许可以加入一些代码，让它只在用户完成尺寸调整后才会失效？

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

namespace CodeProjectDemo
{
    public class checkerboard : Form
    {
        public checkerboard()
        {
            Size = new Size(400, 400);
            Text = "CheckerBoard";
            BackColor = Color.Red;
        }

        protected override void OnPaint(PaintEventArgs e)
        {
            Graphics g = e.Graphics;

            int h = DisplayRectangle.Height;
            int w = DisplayRectangle.Width;

            for (int i = 0; i < 8; i = i + 2)

                for (int j = 0; j < 8; j = j + 2)
                {
                    Color Black = Color.Black;
                    Brush brush = new SolidBrush(Black);
                    g.FillRectangle(brush, i * w / 8, j * h / 8, w / 8, h / 8);
                }


            for (int i = 1; i < 8; i = i + 2)
                for (int j = 0; j < 8; j = j + 2)
                {
                    Color White = Color.White;
                    Brush brush = new SolidBrush(White);
                    g.FillRectangle(brush, i * w / 8, j * h / 8, w / 8, h / 8);
                }
            for (int i = 1; i < 8; i = i + 2)

                for (int j = 1; j < 8; j = j + 2)
                {
                    Color Black = Color.Black;
                    Brush brush = new SolidBrush(Black);
                    g.FillRectangle(brush, i * w / 8, j * h / 8, w / 8, h / 8);
                }
            for (int i = 0; i < 8; i = i + 2)
                for (int j = 1; j < 8; j = j + 2)
                {
                    Color White = Color.White;
                    Brush brush = new SolidBrush(White);
                    g.FillRectangle(brush, i * w / 8, j * h / 8, w / 8, h / 8);
                }
            base.OnPaint(e);

        }

        static void Main()
        {
            Application.Run(new checkerboard());
        }
    }
}

 

 注：拖动的时候会有叠影

Jibesh：

based on his drawing code he must call the invalidate. situation is when he resizes the forms it takes a new DisplayRectangle and starts drawing the graphics for the new size.

Jibesh：

根据他的绘图代码，他必须调用invalidate。情况是，当他调整Form尺寸大小时，窗体采用新的DisplayRectangle并开始为新的尺寸绘制图形。

---------------------------------------------------------------------------------------------------------------------------

Solution 3

You can call Invalidate method inside the Form Resize handler. In addition to this move your code from OnPaint to OnPainBackground to avoid flickering. Check the code modifications.

可以在Form Resize事件处理程序中调用Invalidate函数，除此之外，将你的代码从OnPaint移至OnPaintBackground中以避免闪烁。下面是修改的代码

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

namespace CodeProjectDemo
{
    public class checkerboard : Form
    {
        static void Main()
        {
            Application.Run(new checkerboard());
        }

        public checkerboard()
        {
            Size = new Size(400, 400);
            Text = "CheckerBoard";
            BackColor = Color.Red;
            DoubleBuffered = true;
            Resize += new System.EventHandler(this.Form1_Resize);
        }

        protected override void OnPaintBackground(PaintEventArgs e)
        {
            Graphics g = e.Graphics;

            int h = DisplayRectangle.Height;
            int w = DisplayRectangle.Width;

            for (int i = 0; i < 8; i = i + 2)
                for (int j = 0; j < 8; j = j + 2)
                {
                    Color Black = Color.Black;
                    Brush brush = new SolidBrush(Black);
                    g.FillRectangle(brush, i * w / 8, j * h / 8, w / 8, h / 8);
                    brush.Dispose(); // added this line to clear object else this will produce resource leak
                }


            for (int i = 1; i < 8; i = i + 2)
                for (int j = 0; j < 8; j = j + 2)
                {
                    Color White = Color.White;
                    Brush brush = new SolidBrush(White);
                    g.FillRectangle(brush, i * w / 8, j * h / 8, w / 8, h / 8);
                    brush.Dispose(); // added this line to clear object else this will produce resource leak
                }
            for (int i = 1; i < 8; i = i + 2)

                for (int j = 1; j < 8; j = j + 2)
                {
                    Color Black = Color.Black;
                    Brush brush = new SolidBrush(Black);
                    g.FillRectangle(brush, i * w / 8, j * h / 8, w / 8, h / 8);
                    brush.Dispose(); // added this line to clear object else this will produce resource leak
                }
            for (int i = 0; i < 8; i = i + 2)
                for (int j = 1; j < 8; j = j + 2)
                {
                    Color White = Color.White;
                    Brush brush = new SolidBrush(White);
                    g.FillRectangle(brush, i * w / 8, j * h / 8, w / 8, h / 8);
                    brush.Dispose();
                }
        }
        private void Form1_Resize(object sender, EventArgs e)
        {
            this.Invalidate();
        } 

    }
}

 引用：https://www.codeproject.com/Questions/525585/answer