使用C＃进行双缓冲会产生负面影响

Question

我编写了以下简单程序，它每100毫秒在屏幕上绘制一行（由timer1触发）。 我注意到绘图有点闪烁（也就是说，窗口并不总是完全是蓝色的，但是有些灰色闪耀）。 所以我的想法是使用双缓冲。 但是当我这样做时，情况变得更糟。 现在屏幕几乎总是灰色的，只是偶尔会出现蓝色（由timer2演示，每2000毫秒切换一次DoubleBuffered属性）。

对此有什么解释？

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

namespace WindowsFormsApplication1 {
    public partial class Form1 : Form {
        public Form1() {
            InitializeComponent();
        }

        private void Form1_Paint(object sender, PaintEventArgs e) {
            Graphics g = CreateGraphics();
            Pen pen = new Pen(Color.Blue, 1.0f);
            Random rnd = new Random();
            for (int i = 0; i < Height; i++)
                g.DrawLine(pen, 0, i, Width, i);
        }

        // every 100 ms
        private void timer1_Tick(object sender, EventArgs e) {
            Invalidate();
        }

        // every 2000 ms
        private void timer2_Tick(object sender, EventArgs e) {
            DoubleBuffered = !DoubleBuffered;
            this.Text = DoubleBuffered ? "yes" : "no";
        }
    }
}

Answer 1

我只是将你所有的项目都绘制到你自己的缓冲区中，然后立即将它们全部复制。 我已经在许多应用程序中将它用于图形，并且它对我来说一直很好用：

    public Form1()
    {
        InitializeComponent();
    }
    private void timer1_Tick(object sender, EventArgs e)
    {
        Invalidate();// every 100 ms
    }
    private void Form1_Load(object sender, EventArgs e)
    {
        DoubleBuffered = true;
    }
    private void Form1_Paint(object sender, PaintEventArgs e)
    {
        Bitmap buffer = new Bitmap(Width, Height);
        Graphics g = Graphics.FromImage(buffer);
        Pen pen = new Pen(Color.Blue, 1.0f);
        //Random rnd = new Random();
        for (int i = 0; i < Height; i++)
            g.DrawLine(pen, 0, i, Width, i);
        BackgroundImage = buffer;
    }

编辑：经过进一步调查，看起来你的问题是你将Graphics对象设置为：

Graphics g = CreateGraphics();

需要是：

Graphics g = e.Graphics();

因此，您可以通过创建像我上面所做的手动缓冲区或者只是更改Graphics对象来解决您的问题。 我测试了两者，它们都有效。

Answer 2

在测试时，尝试在构造函数中将double buffered属性设置为true。

您需要使用后台缓冲区。 尝试这个：

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

namespace DoubleBufferTest
{
    public partial class Form1 : Form
    {
        private BufferedGraphicsContext context;
        private BufferedGraphics grafx;

        public Form1()
        {
            InitializeComponent();

            this.Resize += new EventHandler(this.OnResize);
            DoubleBuffered = true;

            // Retrieves the BufferedGraphicsContext for the 
            // current application domain.
            context = BufferedGraphicsManager.Current;

            UpdateBuffer();
        }

        private void timer1_Tick(object sender, EventArgs e)
        {
            this.Refresh();

        }

        private void OnResize(object sender, EventArgs e)
        {
            UpdateBuffer();
            this.Refresh();
        }

        private void UpdateBuffer()
        {
            // Sets the maximum size for the primary graphics buffer
            // of the buffered graphics context for the application
            // domain.  Any allocation requests for a buffer larger 
            // than this will create a temporary buffered graphics 
            // context to host the graphics buffer.
            context.MaximumBuffer = new Size(this.Width + 1, this.Height + 1);

            // Allocates a graphics buffer the size of this form
            // using the pixel format of the Graphics created by 
            // the Form.CreateGraphics() method, which returns a 
            // Graphics object that matches the pixel format of the form.
            grafx = context.Allocate(this.CreateGraphics(),
                 new Rectangle(0, 0, this.Width, this.Height));

            // Draw the first frame to the buffer.
            DrawToBuffer(grafx.Graphics);
        }

        protected override void OnPaint(PaintEventArgs e)
        {
            grafx.Render(e.Graphics);
        }

        private void DrawToBuffer(Graphics g)
        {
            //Graphics g = grafx.Graphics;
            Pen pen = new Pen(Color.Blue, 1.0f);
            //Random rnd = new Random();
            for (int i = 0; i < Height; i++)
                g.DrawLine(pen, 0, i, Width, i);
        }
    }
}

它是MSDN上双缓冲示例的一个有点被黑客攻击的版本。

Answer 3

无需使用多个缓冲区或Bitmap对象或任何东西。

为什么不使用Paint事件提供的Graphics对象？ 像这样：

private void Form1_Paint(object sender, PaintEventArgs e)
{
    Graphics g = e.Graphics;
    Pen pen = new Pen(Color.Blue, 1.0f);
    Random rnd = new Random();
    for (int i = 0; i < Height; i++)
        g.DrawLine(pen, 0, i, Width, i);
}