.NET Compact Framework上的双重缓冲

Question

我想知道是否有人可以向我解释如何在.net紧凑框架中双缓冲完整表单。 我已经找到了双缓冲的例子，但是我似乎无法使它们工作。

我们创建了具有多种形式的应用程序。 其中一些表格确实需要很长时间才能在屏幕上绘制，从而导致闪烁。 为了让您对我们的应用程序有一些了解，我将解释其中一种形式。 该表单包含一个usercontrol，一些面板，文本框和按钮。 用户控件的面板具有自定义绘图（在屏幕上绘制文本和图像（具有透明性））。 甚至这些面板中的某些面板都包含其他做相同事情的面板。 这些面板也具有自定义绘制，因为我们在屏幕上绘制带有某些效果等的文本。每个面板都需要花费一定的绘制时间，这意味着如果我们在3x3网格中有9个面板，它们将被绘制并以随机顺序显示，而不是发出蜂鸣声同时显示所有内容。 文本绘图等也一样。我们希望同时显示表单上的所有内容。

所以我的问题是，我可以创建一个执行双缓冲的“超级”类吗，图形是否存储在完整表格中？

我可以从中扩展当前的表格，而无需更改控件，面板，图像的绘制等吗？

谢谢

Answer 1

我不确定所有控件上的确切形式的复杂性，但是我已经实现了基本的DoubleBufferableControl类，您可以从中扩展该类以创建具有双缓冲的自定义控件。 我用自定义图形创建了许多控件，这些控件均以此为基类。

您可以使用此类作为控件的基类，这些控件具有自定义绘画功能，以防止闪烁。 在子类中，请确保在构造函数中将DoubleBuffered设置为true。

    /// <summary>
/// Implements the functionality for a control that can be double buffered
/// </summary>
public class DoubleBufferableControl : ScrollableControl
{
    public event BufferedPaintEventHandler BufferedPaint;
    private bool doubleBuffered;
    private Bitmap backBuffer;
    private Size oldSize;

    /// <summary>
    /// Gets or sets whether this control will use double buffering
    /// </summary>
    public bool DoubleBuffered
    {
        get
        {
            return doubleBuffered;
        }
        set
        {
            if (value && !doubleBuffered && Width > 0 && Height > 0)
            {
                backBuffer = new Bitmap(Width, Height);
            }
            else if(!value && doubleBuffered)
            {
                backBuffer.Dispose();
                backBuffer = null;
            }

            doubleBuffered = value;
        }
    }

    /// <summary>
    /// Gets the off screen image used for double buffering
    /// </summary>
    public Bitmap BackBuffer
    {
        get
        {
            return backBuffer;
        }
    }

    /// <summary>
    /// Initializes a new instance of the <see cref="DoubleBufferableControl"/> class.
    /// </summary>
    public DoubleBufferableControl()
    {
        AutoScroll = false;
        doubleBuffered = DefaultDoubleBuffered;
        oldSize = Size;
    }

    #region Designer
    private bool DefaultDoubleBuffered = false;
    protected virtual bool ShouldSerializeDoubleBuffered()
    {
        return !this.doubleBuffered.Equals(DefaultDoubleBuffered);
    }
    protected void ResetDoubleBuffered()
    {
        DoubleBuffered = DefaultDoubleBuffered;
    }
    #endregion

    /// <summary>
    /// Raises the Paint event
    /// </summary>
    /// <param name="e">A PaintEventArgs that represents event data</param>
    protected override sealed void OnPaint(PaintEventArgs e)
    {
        if (doubleBuffered)
        {
            DoubleBufferedPaintEventArgs pe = new DoubleBufferedPaintEventArgs(CreateGraphics(), e.ClipRectangle);
            OnPaint(pe);
            pe.Graphics.Dispose();
            e.Graphics.DrawImage(backBuffer, e.ClipRectangle, e.ClipRectangle, GraphicsUnit.Pixel);
            base.OnPaint(e);
        }
        else
        {
            DoubleBufferedPaintEventArgs pe = new DoubleBufferedPaintEventArgs(e.Graphics, e.ClipRectangle);
            OnPaint(pe);
            base.OnPaint(e);
        }
    }

    /// <summary>
    /// Raises the Paint event for child classes that are to be double buffered
    /// </summary>
    /// <param name="e"></param>
    protected virtual void OnPaint(DoubleBufferedPaintEventArgs e)
    {
        if (BufferedPaint != null)
            BufferedPaint(this, e);
    }

    /// <summary>
    /// Paints the background of the control
    /// </summary>
    /// <param name="e">A PaintEventArgs object that contains event data</param>
    protected override void OnPaintBackground(PaintEventArgs e)
    {
        // do not use arg, because can't control back/screen
        Graphics gfx = CreateGraphics();
        gfx.Clear(BackColor);
        gfx.Dispose();
    }

    /// <summary>
    /// Raises the Resize event
    /// </summary>
    /// <param name="e">An EventArgs that represents event data</param>
    protected override void OnResize(System.EventArgs e)
    {
        if (Size != oldSize) // Stupid control gets resized when like anything happens to the parent form
        {
            if (doubleBuffered)
            {
                if (backBuffer != null)
                    backBuffer.Dispose();

                backBuffer = new Bitmap(Width != 0 ? Width : 1, Height != 0 ? Height : 1);
            }
        }
        oldSize = Size;

        base.OnResize(e);
    }

    /// <summary>
    /// Creates the Graphics for the control
    /// </summary>
    /// <param name="backBuffer">True to bypass the buffer and get the control graphics</param>
    /// <returns></returns>
    public virtual Graphics CreateGraphics(bool bypass)
    {
        if(bypass || !doubleBuffered)
            return base.CreateGraphics();
        else
            return Graphics.FromImage(backBuffer);
    }
    public virtual new Graphics CreateGraphics()
    {
        return CreateGraphics(false);
    }
}

并且您将需要这些：

/// <summary>
/// Provides data for the DoubleBufferedControl.Paint event
/// </summary>
public class DoubleBufferedPaintEventArgs : PaintEventArgs
{
    /// <summary>
    /// Initializes a DoubleBufferedPaintEventArgs
    /// </summary>
    /// <param name="g">The Graphics object to paint to;  If the control is double buffered, the graphics object is for the buffer otherwise the screens graphics is used</param>
    /// <param name="clip">The region in which to paint</param>
    public DoubleBufferedPaintEventArgs(Graphics g, Rectangle clip) : base(g, clip) { }
}
public delegate void BufferedPaintEventHandler(object sender, DoubleBufferedPaintEventArgs args);

我通常从此类继承，重写OnPaintBackground方法，并将其实现保留为空白。 然后，我在OnPaint方法中实现所有自定义绘图。