图形开发基础（3）-实际例子

实现的功能包含：

1）实现一个椭圆的按钮。可居中显示一行文本。

2）鼠标离开按钮和进入按钮时，按钮边框和背景色需要发生变化。

实现步骤：

1）新增一个用户控件库。

public class UserButton:System.Windows.Forms.UserControl
    {

    }

2）定义控件属性：

private Color _borderColor = Color.Blue;

        /// <summary>
        /// 按钮边框色
        /// </summary>
        [System.ComponentModel.Category("Appearance")]
        [System.ComponentModel.DefaultValue(typeof(Color),"Blue")]
        public Color BorderColor { get { return _borderColor; }
            set { _borderColor = value; }
        }

        private Color _backColor = Color.White;

        /// <summary>
        /// 按钮背景色
        /// </summary>
        [System.ComponentModel.Category("Appearance")]
        [System.ComponentModel.DefaultValue(typeof(Color), "White")]
        public Color BackColor
        {
            get { return _backColor; }
            set { _backColor = value; }
        }

        private Color _hoverBorderColor = Color.Red;

        /// <summary>
        /// 鼠标悬停在按钮上方时的边框色
        /// </summary>
        [System.ComponentModel.Category("Appearance")]
        [System.ComponentModel.DefaultValue(typeof(Color), "Red")]
        public Color HoverBorderColor
        {
            get { return _hoverBorderColor; }
            set { _hoverBorderColor = value; }
        }

        private Color _hoverBackColor = Color.RoyalBlue;

        /// <summary>
        /// 按钮背景色
        /// </summary>
        [System.ComponentModel.Category("Appearance")]
        [System.ComponentModel.DefaultValue(typeof(Color), "RoyalBlue")]
        public Color HoverBackColor
        {
            get { return _hoverBackColor; }
            set { _hoverBackColor = value; }
        }

        private string _caption = string.Empty;

        /// <summary>
        /// 按钮文本
        /// </summary>
        [System.ComponentModel.Category("Appearance")]
        [System.ComponentModel.DefaultValue(null)]
        public string Caption
        {
            get { return _caption; }
            set { _caption = value; }
        }

        /// <summary>
        /// 鼠标悬停标志
        /// </summary>
        private bool bMouseHoverFlag = false;

3）添加相关事件

/// <summary>
        ///
        /// </summary>
        /// <param name="e"></param>
        protected override void OnPaint(System.Windows.Forms.PaintEventArgs e)
        {
            base.OnPaint(e);

            using (System.Drawing.Drawing2D.GraphicsPath path = new System.Drawing.Drawing2D.GraphicsPath())
            {
                path.AddEllipse(0,0,this.ClientSize.Width-1,this.ClientSize.Height-1);
                if (bMouseHoverFlag)
                {
                    //绘制背景
                    using (SolidBrush b = new SolidBrush(this.HoverBackColor))
                    {
                        e.Graphics.FillPath(b, path);
                    }
                    //绘制边框
                    using (Pen p = new Pen(this.HoverBorderColor))
                    {
                        e.Graphics.DrawPath(p, path);
                    }
                }
                else {

                    //绘制背景
                    using (SolidBrush b = new SolidBrush(this.BackColor))
                    {
                        e.Graphics.FillPath(b, path);
                    }
                    //绘制边框
                    using (Pen p = new Pen(this.BorderColor))
                    {
                        e.Graphics.DrawPath(p, path);
                    }
                }
                if (this.Caption != string.Empty)
                {
                    using (StringFormat f = new StringFormat())
                    {
                        f.Alignment = System.Drawing.StringAlignment.Center;
                        f.LineAlignment = System.Drawing.StringAlignment.Center;
                        f.FormatFlags = System.Drawing.StringFormatFlags.NoWrap;
                        using (SolidBrush b = new SolidBrush(this.ForeColor))
                        {
                            e.Graphics.DrawString(this.Caption,this.Font,b,new RectangleF(0,0,this.ClientSize.Width,this.ClientSize.Height),f);
                        }

                    }
                }

            }
        }

4)添加效果：

 private bool CheckMouseHover(int x, int y)
        {
            bool flag = false;
            using (System.Drawing.Drawing2D.GraphicsPath path = new System.Drawing.Drawing2D.GraphicsPath())
            {
                path.AddEllipse(0, 0, this.ClientSize.Width - 1, this.ClientSize.Height - 1);
                flag = path.IsVisible(x,y);
                if (flag != bMouseHoverFlag)
                {
                    bMouseHoverFlag = flag;
                    this.Invalidate();
                }
            }
            return flag;
        }

        protected override void OnMouseMove(System.Windows.Forms.MouseEventArgs e)
        {
            base.OnMouseMove(e);
            this.CheckMouseHover(e.X,e.Y);
        }
        protected override void OnMouseLeave(EventArgs e)
        {
            base.OnMouseLeave(e);
            this.CheckMouseHover(-1, -1);

        }

        protected override void OnClick(EventArgs e)
        {
            Point p = System.Windows.Forms.Control.MousePosition;
            p = base.PointToClient(p);
            if (CheckMouseHover(p.X, p.Y))
            {
                base.OnClick(e);
            }
        }