c# - 自定义控件 - 首先绘制 OK，第二个不

Question

我在某个地方找到了一些自定义分组框的代码，用圆角、渐变背景和阴影绘制。我觉得它看起来很不错，所以我调整它以使用标签控件做同样的事情。

奇怪的是，当我将其中一个控件放到窗体设计器上时，默认属性已设置并且绘制得很好 - 我在窗体上放置了多个副本，它们都很好。

但是，当我尝试在运行时添加多个控件时，实际上只有第一个版本被正确绘制。其他的最终只是空白的白框。

我真的不知道该怎么办。

标签的代码如下(抱歉 - 太长了!)

public class LabelEx : Label
{
    private System.Drawing.Color _BorderColor = Color.FromArgb(141, 178, 227);
    private float _BorderWidth = 1;
    private System.Drawing.Color _BackgroundColor = Color.White;
    private System.Drawing.Color _BackgroundColorGradient = Color.FromArgb(227, 235, 246);
    private ControlGradientMode _BackgroundGradientMode = ControlGradientMode.Vertical;

    private int _CornerRadius = 5;
    private RoundedControlCorners _Corners = RoundedControlCorners.All;
    private int _DropShadowThickness = 3;
    private bool _DropShadowVisible = true;
    private System.Drawing.Color _ShadowColor = Color.FromArgb(50, Color.Black);

    private ControlStyles _LabelStyle = ControlStyles.Extended;

    public enum ControlStyles
    {
        Standard,
        Extended
    }

    public LabelEx()
    {
        //InitializeComponent();
    }

    /// <summary>Gets or sets the radius of the corners of the control.</summary>
    //[Category("Appearance"), Description("This feature will round the corners of the control.")]
    public int CornerRadius
    {
        get { return _CornerRadius; }
        set
        {
            if (value > 35)
            {
                _CornerRadius = 35;
            }
            else
            {
                if (value < 1)
                {
                    _CornerRadius = 1;
                }
                else
                {
                    _CornerRadius = value;
                }
            }
            Invalidate();
        }
    }
    /// <summary>Turns on or off the control shadowing.</summary>
    //[Category("Appearance"), Description("This feature will turn on control shadowing.")]
    public bool DropShadowVisible
    {
        get { return _DropShadowVisible; }
        set
        {
            _DropShadowVisible = value;
            Invalidate();
        }
    }
    /// <summary>Gets or sets the color of the control's border.</summary>
    //[Category("Appearance"), Description("This feature will allow you to change the color of the control's border.")]
    public System.Drawing.Color BorderColor
    {
        get { return _BorderColor; }
        set
        {
            _BorderColor = value;
            Invalidate();
        }
    }
    /// <summary>Gets or Sets the control's border size.</summary>
    //[Category("Appearance"), Description("This feature will allow you to set the control's border size.")]
    public float BorderWidth
    {
        get { return _BorderWidth; }
        set
        {
            if (value > 10)
            {
                _BorderWidth = 10;
            }
            else
            {
                if (value < 1)
                {
                    _BorderWidth = 1;
                }
                else
                {
                    _BorderWidth = value;

                }
            }

            Invalidate();
        }
    }
    /// <summary>Gets or sets the size of the shadow border thickness.</summary>
   // [Category("Appearance"), Description("This feature will change the size of the shadow border.")]
    public int DropShadowThickness
    {
        get { return _DropShadowThickness; }
        set
        {
            if (value > 10)
            {
                _DropShadowThickness = 10;
            }
            else
            {
                if (value < 1)
                {
                    _DropShadowThickness = 1;
                }
                else
                {
                    _DropShadowThickness = value;
                }
            }
            Invalidate();
        }
    }
    /// <summary>Gets or sets the background color to use. This color can also be used in combination with BackgroundColorGradient for a gradient paint.</summary>
    // [Category("Appearance"), Description("This feature will change the group control color. This color can also be used in combination with BackgroundColorGradient for a gradient paint.")]
    public System.Drawing.Color BackgroundColor
    {
        get { return _BackgroundColor; }
        set
        {
            _BackgroundColor = value;
            Invalidate();
        }
    }
    /// <summary>Specifies the second color when using the gradient mode.</summary>
    // [Category("Appearance"), Description("This feature can be used in combination with BackgroundColor to create a gradient background.")]
    public System.Drawing.Color BackgroundColorGradient
    {
        get { return _BackgroundColorGradient; }
        set
        {
            _BackgroundColorGradient = value;
            Invalidate();
        }
    }

    /// <summary>This property secifies the type of gradient to use when painting the background.</summary>
    // [Category("Appearance"), Description("This feature turns on background gradient painting.")]
    public ControlGradientMode BackgroundGradientMode
    {
        get { return _BackgroundGradientMode; }
        set
        {
            _BackgroundGradientMode = value;
            Invalidate();
        }
    }

    /// <summary>Specifies which corners to apply rounding for</summary>
    public RoundedControlCorners Corners
    {
        get { return _Corners; }
        set
        {
            _Corners = value;
            Invalidate();
        }
    }

    /// <summary>Gets or sets the Style for the GroupBox.  Standard duplicates the stock groupbox.  Extended allows the customization ability</summary>
    // [Category("Appearance"), Description("Gets or sets the Style for the GroupBox.  Standard duplicates the stock groupbox.  Extended allows the customization ability")]
    // [DefaultValue(ControlStyles.Extended)]
    public ControlStyles LabelStyle
    {
        get { return _LabelStyle; }
        set
        {
            _LabelStyle = value;
            Invalidate();
        }
    }

    /// <summary>
    /// Function to paint the label as per what we want.
    /// </summary>
    /// <param name="e"></param>
    protected override void OnPaint(PaintEventArgs e)
    {
        //Just use a normal label if the "standard" is set.
        if (_LabelStyle == ControlStyles.Standard)
        {
            base.OnPaint(e);
            return;
        }

        //we must set the smoothing mode to anti alias or high quality(They are the same) in order to get the
        //nice rounded corders on our control

        e.Graphics.SmoothingMode = SmoothingMode.AntiAlias;

        //first lets set the rectangles we will be drawing in.  If the drop shadow is visible then we need to 
        //reduce the size of the main rectangle and create a second one that is offset by the shadow thickness.
        Rectangle shadowRec = default(Rectangle);
        Rectangle frameRec = default(Rectangle);
        if (DropShadowVisible)
        {
            shadowRec = Rectangle.FromLTRB(DropShadowThickness, DropShadowThickness, this.ClientRectangle.Right - 1, this.ClientRectangle.Bottom - 1);
            frameRec = Rectangle.FromLTRB(0, 0, this.ClientRectangle.Right - DropShadowThickness - 2, this.ClientRectangle.Bottom - DropShadowThickness - 2);
        }
        else
        {
            frameRec = Rectangle.FromLTRB(this.ClientRectangle.Left, this.ClientRectangle.Top, this.ClientRectangle.Right - 1, this.ClientRectangle.Bottom - 1);
        }

        if (frameRec.Height <= 0 | frameRec.Width <= 0)
            return;

        //draw the drop shadow using the shadow path rectangle
        if (DropShadowVisible)
        {
            using (GraphicsPath path = GraphicsFunctions.RoundRectangle(shadowRec, _CornerRadius, _Corners))
            {
                using (SolidBrush b = new SolidBrush(_ShadowColor))
                {
                    e.Graphics.FillPath(b, path);
                }
            }
        }

        //draw the rest of the control in the main frame path
        using (GraphicsPath path = GraphicsFunctions.RoundRectangle(frameRec, _CornerRadius, _Corners))
        {
            //paint the background inside the frame
            if (BackgroundGradientMode == ControlGradientMode.None)
            {
                //solid background
                using (SolidBrush b = new SolidBrush(BackgroundColor))
                {
                    e.Graphics.FillPath(b, path);
                }
            }
            else
            {
                //gradient
                if (BackgroundGradientMode == ControlGradientMode.VerticalGlow)
                {
                    using (LinearGradientBrush b = new LinearGradientBrush(new Point(0, frameRec.Top + (frameRec.Height / 2)), new Point(0, frameRec.Bottom - 1), BackgroundColorGradient, BackgroundColor))
                    {

                        b.WrapMode = WrapMode.TileFlipXY;
                        e.Graphics.FillPath(b, path);
                    }
                }
                else if (BackgroundGradientMode == ControlGradientMode.HorizontalGlow)
                {
                    using (LinearGradientBrush b = new LinearGradientBrush(new Point(frameRec.Left + (frameRec.Width / 2), 0), new Point(frameRec.Right - 1, 0), BackgroundColorGradient, BackgroundColor))
                    {

                        b.WrapMode = WrapMode.TileFlipXY;
                        e.Graphics.FillPath(b, path);
                    }
                }
                else
                {
                    using (LinearGradientBrush br = new LinearGradientBrush(frameRec, BackgroundColor, BackgroundColorGradient, (LinearGradientMode)BackgroundGradientMode))
                    {
                        e.Graphics.FillPath(br, path);
                    }
                }

                //
                using (SolidBrush b = new SolidBrush(ForeColor))
                {
                    StringFormat sf = new StringFormat();
                    //Rectangle textRec = default(Rectangle);


                    switch (this.TextAlign)
                    {
                        case ContentAlignment.BottomCenter:
                            sf.Alignment = StringAlignment.Center;
                            sf.LineAlignment = StringAlignment.Far;
                            break;
                        case ContentAlignment.BottomLeft:
                            sf.Alignment = StringAlignment.Near;
                            sf.LineAlignment = StringAlignment.Far;
                            break;
                        case ContentAlignment.BottomRight:
                            sf.Alignment = StringAlignment.Far;
                            sf.LineAlignment = StringAlignment.Far;
                            break;
                        case ContentAlignment.MiddleCenter:
                            sf.Alignment = StringAlignment.Center;
                            sf.LineAlignment = StringAlignment.Center;
                            break;
                        case ContentAlignment.MiddleLeft:
                            sf.Alignment = StringAlignment.Near;
                            sf.LineAlignment = StringAlignment.Center;
                            break;
                        case ContentAlignment.MiddleRight:
                            sf.Alignment = StringAlignment.Far;
                            sf.LineAlignment = StringAlignment.Center;
                            break;
                        case ContentAlignment.TopCenter:
                            sf.Alignment = StringAlignment.Center;
                            sf.LineAlignment = StringAlignment.Near;
                            break;
                        case ContentAlignment.TopLeft:
                            sf.Alignment = StringAlignment.Near;
                            sf.LineAlignment = StringAlignment.Near;
                            break;
                        case ContentAlignment.TopRight:
                            sf.Alignment = StringAlignment.Far;
                            sf.LineAlignment = StringAlignment.Near;
                            break;
                    }


                    sf.Alignment = StringAlignment.Center;
                    e.Graphics.DrawString(this.Text, this.Font, b, (RectangleF)frameRec, sf);
                    Invalidate();
                }
                Invalidate();
            }

            e.Graphics.ResetTransform();
            //draw the border
            using (Pen p = new Pen(BorderColor, BorderWidth))
            {
                e.Graphics.DrawPath(p, path);
            }
        }
    }
}

它依赖于此:

[Flags()]
public enum RoundedControlCorners
{
    None = 0,
    NorthWest = 2,
    NorthEast = 4,
    SouthEast = 8,
    SouthWest = 16,
    All = NorthWest | NorthEast | SouthEast | SouthWest,
    North = NorthWest | NorthEast,
    South = SouthEast | SouthWest,
    East = NorthEast | SouthEast,
    West = NorthWest | SouthWest
}

public enum ControlGradientMode
{
    /// <summary>Specifies no gradient mode.</summary>
    None = 4,

    /// <summary>Specifies a gradient from upper right to lower left.</summary>
    BackwardDiagonal = LinearGradientMode.BackwardDiagonal,

    /// <summary>Specifies a gradient from upper left to lower right.</summary>
    ForwardDiagonal = LinearGradientMode.ForwardDiagonal,

    /// <summary>Specifies a gradient from left to right.</summary>
    Horizontal = LinearGradientMode.Horizontal,

    /// <summary>Specifies a gradient from top to bottom.</summary>
    Vertical = LinearGradientMode.Vertical,

    VerticalGlow = 5,
    HorizontalGlow = 6
}

public static class GraphicsFunctions
{
    public static GraphicsPath RoundRectangle(Rectangle r, int radius, RoundedControlCorners corners)
    {
        GraphicsPath path = new GraphicsPath();
        if (r.Width <= 0 | r.Height <= 0)
            return path;

        int d = radius * 2;

        int nw = ((corners & RoundedControlCorners.NorthWest) == RoundedControlCorners.NorthWest ? d : 0);
        int ne = ((corners & RoundedControlCorners.NorthEast) == RoundedControlCorners.NorthEast ? d : 0);
        int se = ((corners & RoundedControlCorners.SouthEast) == RoundedControlCorners.SouthEast ? d : 0);
        int sw = ((corners & RoundedControlCorners.SouthWest) == RoundedControlCorners.SouthWest ? d : 0);

        //path.AddLine(r.Left + nw, r.Top, r.Right - ne, r.Top);
        path.AddLine(r.Left + nw, r.Top, r.Right - ne, r.Top);

        if (ne > 0)
        {
            path.AddArc(Rectangle.FromLTRB(r.Right - ne, r.Top, r.Right, r.Top + ne), -90, 90);
        }

        path.AddLine(r.Right, r.Top + ne, r.Right, r.Bottom - se);

        if (se > 0)
        {
            path.AddArc(Rectangle.FromLTRB(r.Right - se, r.Bottom - se, r.Right, r.Bottom), 0, 90);
        }

        path.AddLine(r.Right - se, r.Bottom, r.Left + sw, r.Bottom);

        if (sw > 0)
        {
            path.AddArc(Rectangle.FromLTRB(r.Left, r.Bottom - sw, r.Left + sw, r.Bottom), 90, 90);
        }

        path.AddLine(r.Left, r.Bottom - sw, r.Left, r.Top + nw);

        if (nw > 0)
        {
            path.AddArc(Rectangle.FromLTRB(r.Left, r.Top, r.Left + nw, r.Top + nw), 180, 90);
        }

        path.CloseFigure();
        return path;
    }
}

我用来将其添加到表单的代码:

LabelEx oLabel1 = new LabelEx();
LabelEx oLabel2 = new LabelEx();
LabelEx oLabel3 = new LabelEx();

oLabel1.Top = 50;
oLabel2.Top = 100;
oLabel3.Top = 150;

oLabel1.Height = 25;
oLabel2.Height = 25;

oLabel1.Text = "Hello";
oLabel2.Text = "There";

scBase.Panel2.Controls.Add(oLabel1);
scBase.Panel2.Controls.Add(oLabel2);

Answer 1

protected override void OnPaint(PaintEventArgs e)
{
   //...
            Invalidate();
}

对于任何程序员来说，一个好的做法是始终运行任务管理器。我总是将它最小化到通知区域。鸟瞰我的机器上发生的事情，快速点击激活它。

那很快就确定了你的程序出了什么问题，它正在燃烧 100% 的核心。那是因为您在 OnPaint() 方法中调用了 Invalidate()，立即使您绘制的内容无效。这有几个副作用，其中之一是您会看到您的程序永远不会闲置并继续在处理器内核上运行代码。因为 Windows 不断地一遍又一遍地生成绘制事件。

另一方面，只有一个标签控件可以被绘制。第一个，Z 顺序中最低的。因为在完成绘制后，由于 Invalidate() 调用，下一次绘制请求再次针对同一标签。

删除 Invalidate() 调用以解决您的问题，有两个。