c#鼠标悬停时在控件周围绘制矩形答案

【问题标题】：c# Draw rectangle around control when hoveredc#鼠标悬停时在控件周围绘制矩形
【发布时间】：2016-02-09 13:53:23
【问题描述】：

我正在重写 Control 类的 OnPaint 方法来创建表情符号。表情符号已创建。但是当它悬停时，我要在它周围添加一个矩形。

public class EmoticonControl : Control
{
    public EmoticonControl(string unicode, Image image)
    {
        this.unicode = unicode;
        this.image = image;
    }

    protected override void OnPaint(PaintEventArgs e)
    {
        Graphics graphics = e.Graphics;
        Rectangle clipRectangle = e.ClipRectangle;
        graphics.DrawImage(this.image, 0, 0, this.Size.Width, this.Size.Height);

        // When hovered
        Brush brush = new SolidBrush(this.selectedColor);
        graphics.FillRectangle(new SolidBrush(selectionColor), clipRectangle);
        graphics.DrawRectangle(new Pen(selectionBorderColor), clipRectangle.X, clipRectangle.Y, clipRectangle.Width - 1, clipRectangle.Height - 1);
        //
    }
    private string unicode;
    private Image image;

    private Color selectedColor = SystemColors.Highlight;
    private Color selectionColor = Color.FromArgb(50, 0, 0, 150);
    private Color selectionBorderColor = SystemColors.Highlight;
}

【问题讨论】：

我看不懂这段代码。画笔在哪里使用（在“悬停时”评论之后）？

标签： c# winforms

【解决方案1】：

您可以使用UIElement.IsMouseOver 属性来了解您的控件是否悬停。

protected override void OnPaint(PaintEventArgs e)
{
    Graphics graphics = e.Graphics;
    Rectangle clipRectangle = e.ClipRectangle;
    graphics.DrawImage(this.image, 0, 0, this.Size.Width, this.Size.Height);

    // When hovered
    if (IsMouseOver)
    {
        Brush brush = new SolidBrush(this.selectedColor);
        graphics.FillRectangle(new SolidBrush(selectionColor), clipRectangle);
        graphics.DrawRectangle(new Pen(selectionBorderColor), clipRectangle.X, clipRectangle.Y, clipRectangle.Width - 1, clipRectangle.Height - 1);
    }
}

【讨论】：

【解决方案2】：

原版

这应该适合你：

public class EmoticonControl : Control
{
    public EmoticonControl(string unicode, Image image)
    {
        this.unicode = unicode;
        this.image = image;
    }

    // Set hover, request invalidation:
    protected override void OnMouseEnter(EventArgs e)
    {
        base.OnMouseEnter(e);
        hover = true;
        this.Invalidate();
    }

    // Unset hover, request invalidation:
    protected override void OnMouseLeave(EventArgs e)
    {
        base.OnMouseLeave(e);
        hover = false;
        this.Invalidate();
    }

    protected override void OnPaint(PaintEventArgs e)
    {
        Graphics graphics = e.Graphics;
        Rectangle clipRectangle = e.ClipRectangle;
        graphics.DrawImage(this.image, 0, 0, this.Size.Width, this.Size.Height);

        // Only do this when hovering:
        if (hover)
        {
            Brush brush = new SolidBrush(this.selectedColor);
            graphics.FillRectangle(new SolidBrush(selectionColor), clipRectangle);
            graphics.DrawRectangle(new Pen(selectionBorderColor), clipRectangle.X, clipRectangle.Y, clipRectangle.Width - 1, clipRectangle.Height - 1);
        }
    }

    // Added flag to track hover status:
    private bool hover = false;

    private string unicode;
    private Image image;

    private Color selectedColor = SystemColors.Highlight;
    private Color selectionColor = Color.FromArgb(50, 0, 0, 150);
    private Color selectionBorderColor = SystemColors.Highlight;
}

更新版本：

（包括对原始代码的一些“最佳实践”修复）

public class EmoticonControl : Control
{       
    public EmoticonControl(string unicode, Image image)
    {
        this.unicode = unicode;
        this.image = image;
    }

    protected override void OnMouseEnter(EventArgs e)
    {
        base.OnMouseEnter(e);
        hover = true;
        this.Invalidate();
    }

    protected override void OnMouseLeave(EventArgs e)
    {
        base.OnMouseLeave(e);
        hover = false;
        this.Invalidate();
    }

    protected override void OnPaint(PaintEventArgs e)
    {
        DrawImage(e.Graphics);
        DrawSelectionRectangle(e.Graphics);
    }

    private void DrawSelectionRectangle(Graphics graphics)
    {
        if (hover)
        {
            using (var brush = new SolidBrush(selectionColor))
            {
                graphics.FillRectangle(brush, this.ClientRectangle);
            }
            using (var pen = new Pen(selectionBorderColor))
            {
                graphics.DrawRectangle(pen,
                    new Rectangle()
                    {
                        Width = (this.Width - 1),
                        Height = (this.Height - 1)
                    });
            }
        }
    }

    private void DrawImage(Graphics graphics)
    {
        if (image != null) graphics.DrawImage(
            this.image, 0, 0, this.Size.Width, this.Size.Height);
    }

    private bool hover = false;
    private Image image;
    private string unicode;

    private Color selectionColor = Color.FromArgb(50, 0, 0, 150);
    private Color selectionBorderColor = SystemColors.Highlight;
}

【讨论】：

我已经尝试过这一步，但没有成功。 this.Invalidate(); 使代码完美。谢谢！
没问题。我还注意到您的代码中还有其他一些小问题，例如在绘制图像时缺少null 检查，在图形对象上缺少using 语句......你介意我发布更新吗？很少有更正/建议？

【解决方案3】：

您可能需要在鼠标离开和输入事件中设置一个标志，然后检查绘图事件中的标志，如下所示：

If(hover)
{
    ControlPaint.DrawBorder(e.Graphics,this.DisplayRectangle,Color.Red,ButtonBorderStyle.Solid)
}

【讨论】：