Question

我要建立一个支持Control属性的Opcacity派生类这个控件可以同时容纳文本和图像，并且可以将它们淡出并输入。
这是我的代码：

internal class FadeControl : Control
{
    private int opacity = 100;

    public FadeControl()
    {
        SetStyle(ControlStyles.SupportsTransparentBackColor, true);
    }

    public int Opacity
    {
        get
        {
            return opacity;
        }
        set
        {
            if (value > 100) opacity = 100;
            else if (value < 1) opacity = 1;
            else opacity = value;

            if (Parent != null)
                Parent.Invalidate(Bounds, true);
        }
    }

    protected override CreateParams CreateParams
    {
        get
        {
            CreateParams cp = base.CreateParams;
            cp.ExStyle = cp.ExStyle | 0x20;
            return cp;
        }
    }

    protected override void OnPaintBackground(PaintEventArgs e)
    {
        //do nothing
    }

    protected override void OnMove(EventArgs e)
    {
        RecreateHandle();
    }

    protected override void OnPaint(PaintEventArgs e)
    {
        using (Graphics g = e.Graphics)
        {
            Rectangle bounds = new Rectangle(0, 0, Width - 1, Height - 1);
            int alpha = (opacity * 255) / 100;

            using (Brush bckColor = new SolidBrush(Color.FromArgb(alpha, BackColor)))
            {
                if (BackColor != Color.Transparent)
                    g.FillRectangle(bckColor, bounds);
            }

            ColorMatrix colorMatrix = new ColorMatrix();
            colorMatrix.Matrix33 = (float)alpha / 255;
            ImageAttributes imageAttr = new ImageAttributes();
            imageAttr.SetColorMatrix(colorMatrix, ColorMatrixFlag.Default, ColorAdjustType.Bitmap);

            if (BackgroundImage != null)
                g.DrawImage(BackgroundImage, bounds, 0, 0, Width, Height, GraphicsUnit.Pixel, imageAttr);

            if (Text != string.Empty)
            {
                using (Brush txtBrush = new SolidBrush(Color.FromArgb(alpha, ForeColor)))
                {
                    g.DrawString(Text, Font, txtBrush, 5, 5);
                }
            }
        }
    }

    protected override void OnBackColorChanged(EventArgs e)
    {
        if (Parent != null)
            Parent.Invalidate(Bounds, true);

        base.OnBackColorChanged(e);
    }

    protected override void OnParentBackColorChanged(EventArgs e)
    {
        Invalidate();

        base.OnParentBackColorChanged(e);
    }
}

我把控件放在一个有计时器的表格上计时器将控件的不透明度从0设置为100并返回并且工作正常我试图解决的问题是控件在改变其不透明度时会闪烁将控件设置为ControlStyles.DoubleBuffer将使控件在窗体上不可见。

欢迎任何建议。

Answer 1

我无法同时使用双缓冲区和WS_EX_TRANSPARENT（0x20）作为透明背景。所以我决定通过复制父控件的内容来实现透明背景，并使用双缓冲来防止闪烁。

以下是最终的源代码，经过测试和运行：

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

internal class FadeControl : Control
{
    private int opacity = 100;
    private Bitmap backgroundBuffer;
    private bool skipPaint;

    public FadeControl()
    {
        SetStyle(ControlStyles.SupportsTransparentBackColor, true);
        SetStyle(ControlStyles.ResizeRedraw, true);
        SetStyle(ControlStyles.DoubleBuffer |
                 ControlStyles.AllPaintingInWmPaint |
                 ControlStyles.UserPaint, true);
    }

    public int Opacity
    {
        get
        {
            return opacity;
        }
        set
        {
            if (value > 100) opacity = 100;
            else if (value < 1) opacity = 1;
            else opacity = value;

            if (Parent != null)
                Parent.Invalidate(Bounds, true);
        }
    }

    protected override void OnPaintBackground(PaintEventArgs e)
    {
        //do nothig
    }

    protected override void OnMove(EventArgs e)
    {
        RecreateHandle();
    }

    private void CreateBackgroundBuffer(Control parent)
    {
        int offsetX;
        int offsetY;
        GetOffsets(out offsetX, out offsetY, parent);
        backgroundBuffer = new Bitmap(Width + offsetX, Height + offsetY);
    }

    protected override void OnResize(EventArgs e)
    {
        var parent = Parent;
        if (parent != null)
        {
            CreateBackgroundBuffer(parent);
        }
        base.OnResize(e);
    }

    private void GetOffsets(out int offsetX, out int offsetY, Control parent)
    {
        var parentPosition = parent.PointToScreen(Point.Empty);
        offsetY = Top + parentPosition.Y - parent.Top;
        offsetX = Left + parentPosition.X - parent.Left;
    }

    private void UpdateBackgroundBuffer(int offsetX, int offsetY, Control parent)
    {
        if (backgroundBuffer == null)
        {
            CreateBackgroundBuffer(parent);
        }
        Rectangle parentBounds = new Rectangle(0, 0, Width + offsetX, Height + offsetY);
        skipPaint = true;
        parent.DrawToBitmap(backgroundBuffer, parentBounds);
        skipPaint = false;
    }

    private void DrawBackground(Graphics graphics, Rectangle bounds)
    {
        int offsetX;
        int offsetY;
        var parent = Parent;
        GetOffsets(out offsetX, out offsetY, parent);
        UpdateBackgroundBuffer(offsetX, offsetY, parent);
        graphics.DrawImage(backgroundBuffer, bounds, offsetX, offsetY, Width, Height, GraphicsUnit.Pixel);
    }

    private void Draw(Graphics graphics)
    {
        Rectangle bounds = new Rectangle(0, 0, Width, Height);
        DrawBackground(graphics, bounds);

        int alpha = (opacity * 255) / 100;

        using (Brush bckColor = new SolidBrush(Color.FromArgb(alpha, BackColor)))
        {
            if (BackColor != Color.Transparent)
            {
                graphics.FillRectangle(bckColor, bounds);
            }
        }

        ColorMatrix colorMatrix = new ColorMatrix();
        colorMatrix.Matrix33 = (float)alpha / 255;
        ImageAttributes imageAttr = new ImageAttributes();
        imageAttr.SetColorMatrix(colorMatrix, ColorMatrixFlag.Default, ColorAdjustType.Bitmap);

        if (BackgroundImage != null)
        {
            graphics.DrawImage(BackgroundImage, bounds, 0, 0, Width, Height, GraphicsUnit.Pixel, imageAttr);
        }

        if (Text != string.Empty)
        {
            using (Brush txtBrush = new SolidBrush(Color.FromArgb(alpha, ForeColor)))
            {
                graphics.DrawString(Text, Font, txtBrush, 5, 5);
            }
        }
    }

    protected override void OnPaint(PaintEventArgs e)
    {
        if (!skipPaint)
        {
            Graphics graphics = e.Graphics;
            Draw(graphics);
        }
    }

    protected override void OnBackColorChanged(EventArgs e)
    {
        if (Parent != null)
        {
            Parent.Invalidate(Bounds, true);
        }
        base.OnBackColorChanged(e);
    }

    protected override void OnParentBackColorChanged(EventArgs e)
    {
        Invalidate();
        base.OnParentBackColorChanged(e);
    }
}

请注意，方法CreateParams不再存在，我也更改了构造函数。

字段skipPaint是知道何时不绘制，以便能够告诉父母在OnPaint期间将自己绘制到位图而无需无限递归。

backgroundBuffer不是实现双缓冲，而是保留父级内容的副本而不提供控件。每个油漆都会更新，我知道有更高效的解决方案...... *这种方法保持简单，不应该成为瓶颈，除非你在同一个容器上有太多这些控件。

*：更好的解决方案是每次父母无效时更新它。 Futhermore在同一家长的所有FadeControl中共享它。

C＃中的衰落控制

1 个答案: