WinForm(三)揭开可视化控件的面纱

WinForm所见即所得的UI设计框架,开发效率确实有所提升,同时降低了编程门槛,让WinForm更普及。拖拖拽拽就能设计出一个界面,那么我们拖拽的这些东西是什么?它们是什么原理?。.

WinForm我觉得很好的一点是,把所有东西都对像化(毕竟C#是面向对象的语言),包括可视化的窗体,控件等,当然有的控件在运行时是能看见的,比如按钮,文本框,下拉列表框等等,还有一类是在运时看不见的,比如Timers,FileSystemWatcher等。这些全都构建成了对象,那么看得见的控件是怎么看得见的呢?答案是绘制出来的,画出来才能看得见。是用GDI+技术画出来的。

为了能够让大家更深入的理解,我们现在画一个Switch控件,Switch是苹果体系里的控件,在WinForm中,系统控件是没有的。Switch的作用非常像CheckBox,所以我们就参照CheckBoxRenderer来画,只不过画的形状不一样,具体代码如下:

using System;using System.Collections.Generic;using System.Drawing.Drawing2D;using System.Linq;using System.Text;using System.Threading.Tasks;using System.Windows.Forms.VisualStyles;
namespace WinFormDemo02{    public class Switch : Control    {        private Rectangle textRectangleValue = new Rectangle();        private CheckBoxState state = CheckBoxState.UncheckedNormal;        public Switch(): base()        {            this.Location = new Point(50, 50);            this.Size = new Size(50, 25);            this.Font = SystemFonts.IconTitleFont;            DoubleBuffered = true;            SetStyle(ControlStyles.OptimizedDoubleBuffer |                        ControlStyles.ResizeRedraw |                        ControlStyles.AllPaintingInWmPaint, true);        }        public bool Checked        {            get; set;        } = false;
        void DrawSwitch(Graphics g)        {            var x = 0;            var y = 0;            var width = 25;            g.SmoothingMode = SmoothingMode.HighQuality;            g.PixelOffsetMode = PixelOffsetMode.HighQuality;            g.InterpolationMode = InterpolationMode.High;            g.CompositingQuality = CompositingQuality.HighQuality;            SolidBrush brush;            if (Checked)            {                brush = new SolidBrush(Color.MediumSeaGreen);            }            else            {                brush = new SolidBrush(Color.DarkRed);            }            g.FillPie(brush, new Rectangle(x, y, width, width), 90, 180);            g.FillRectangle(brush, new Rectangle(x + width / 2 - 1, y, width, width));            g.FillPie(brush, new Rectangle(x + width - 2, y, width, width), -90, 180);            if (Checked)            {                var selectBrush = new SolidBrush(Color.White);                g.FillEllipse(selectBrush, new Rectangle(x + 2, y + 2, width - 4, width - 4));            }            else            {                var selectBrush = new SolidBrush(Color.White);                g.FillEllipse(selectBrush, new Rectangle(x + width, y + 2, width - 4, width - 4));            }        }
        public Rectangle TextRectangle        {            get            {                using (Graphics g = this.CreateGraphics())                {                    textRectangleValue.X = ClientRectangle.X +                        CheckBoxRenderer.GetGlyphSize(g,                        CheckBoxState.UncheckedNormal).Width;                    textRectangleValue.Y = ClientRectangle.Y;                    textRectangleValue.Width = ClientRectangle.Width -                        CheckBoxRenderer.GetGlyphSize(g,                        CheckBoxState.UncheckedNormal).Width;                    textRectangleValue.Height = ClientRectangle.Height;                }                return textRectangleValue;            }        }
        protected override void OnPaint(PaintEventArgs e)        {            DrawSwitch(e.Graphics);            base.OnPaint(e);        }        public event EventHandler CheckedChanged;        protected override void OnMouseDown(MouseEventArgs e)        {            base.OnMouseDown(e);            if (!Checked)            {                Checked = true;                state = CheckBoxState.CheckedPressed;                Invalidate();            }            else            {                Checked = false;                state = CheckBoxState.UncheckedNormal;                Invalidate();            }            CheckedChanged(this,new EventArgs());        }        protected override void OnMouseHover(EventArgs e)        {            base.OnMouseHover(e);            state = Checked ? CheckBoxState.CheckedHot :                CheckBoxState.UncheckedHot;            Invalidate();        }        protected override void OnMouseUp(MouseEventArgs e)        {            base.OnMouseUp(e);            this.OnMouseHover(e);        }        protected override void OnMouseLeave(EventArgs e)        {            base.OnMouseLeave(e);            state = Checked ? CheckBoxState.CheckedNormal :                CheckBoxState.UncheckedNormal;            Invalidate();        }    }}

我只是简单的实现了一下,重点在DrawSwitch这个方法,就是画两个半圆,中间是一个正方形,然后在上面画一个白圆,根据Checked属性,最上面的白圆在两边切换,仅此而以。

通过上面例子,不知你是否了解了可视化控件的实现方式。如果你是初学者,完整的思路不太通,没关系,理解到控件是画出来的就够了,后面应该会说到GDI+的详细技术点。如果你是WinForm老手,可以自己实现一套自己的专用控件,把Window上的应用Run出Mac的感觉,甚至IOS的感觉。