本文以一个用户控件【User Control】实现温度计的小例子，简述用户控件的相关知识，以供学习分享使用，如有不足之处，还请指正。
概述
一般而言，用户控件【User Control】，是在Visual Studio提供的默认控件不能满足实际的工作需要，才需要在现有控件的基础之上进行新的扩展，来实现自己的功能。用户控件有自己特有的属性，事件，方法来支撑特定的功能。用户控件封装实现的细节，可以进行方便的复用。
用户控件分类
用户控件主要有以下三种分类，本例采用的是第三种。
- 复合控件（Composite Controls）：将现有的各种控件组合起来，形成一个新的控件，来满足用户的需求。
- 扩展控件（Extended Controls）：就是在现有的控件基础上，派生出一个新的控件，增加新的功能，或者修改原有功能，来满足用户需求。
- 自定义控件（Custom Controls）：就是直接从UserControl类派生，也就是说完全由自己来设计、实现一个全新的控件，这是最灵活、最强大的方法。
涉及知识点
本例中主要涉及以下知识点：
- UserControl ： 提供一个可用来创建其他控件的空控件。用户创建一个用户控件，会默认继承这个类。
- OnPaint ：控件重绘方法，是protected修饰符，本例中需要重写此方法。
- Graphics ： 密封类，不可被继承，用于绘制图形（包括矩形，扇形，直线等）。
- ToolTip ： 表示一个长方形的小弹出窗口，该窗口在用户将指针悬停在一个控件上时显示有关该控件用途的简短说明。
- 鼠标事件函数：OnMouseHover 鼠标悬停时触发函数，OnMouseLeave鼠标离开时触发函数。
- DataGridView：在可自定义的网格中显示数据。
示例效果图
本例中示例效果图如下所示：
关键代码
本例中的关键代码如下：
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Drawing;
using System.Data;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms; namespace DemoThermometer
{
public partial class Thermometer : UserControl
{
#region 属性与构造函数 private int interval = ; /// <summary>
/// 刻度间隔
/// </summary>
public int Interval
{
get { return interval; } set { interval = value; }
} private int minValue = -; /// <summary>
/// 最低温度
/// </summary>
public int MinValue
{
get { return minValue; } set { minValue = value; }
} private int maxValue = ; /// <summary>
/// 最高温度
/// </summary>
public int MaxValue
{
get { return maxValue; } set { maxValue = value; }
} private float curValue = ; /// <summary>
/// 当前温度
/// </summary>
public float CurValue
{
get { return curValue; } set { curValue = value; }
} private Color thermoColor = Color.Red; /// <summary>
/// 温度条颜色
/// </summary>
public Color ThermoColor
{
get { return thermoColor; } set { thermoColor = value; }
} private Color backGroundColor = Color.SkyBlue; /// <summary>
/// 温度计背景色
/// </summary>
public Color BackGroundColor
{
get { return backGroundColor; } set { backGroundColor = value; }
} private Font thermoFont=new Font("宋体",,FontStyle.Regular); /// <summary>
/// 温度计上字体
/// </summary>
public Font ThermoFont
{
get { return thermoFont; } set { thermoFont = value; }
} private string thermoTitle = "温度计"; /// <summary>
/// 标题
/// </summary>
public string ThermoTitle
{
get { return this.thermoTitle; }
set { this.thermoTitle = value; }
} private bool showTip = false; /// <summary>
/// 是否显示提示
/// </summary>
public bool ShowTip
{
get { return showTip; } set { showTip = value; }
} private ToolTip tip=new ToolTip(); public Thermometer()
{
InitializeComponent();
} #endregion protected override void OnPaint(PaintEventArgs e)
{ //base.OnPaint(e);
//this.BackColor = this.backGroundColor;
int width = this.Width;
int height = this.Height - ;
Graphics g = e.Graphics;
int c_x = width / ;
int c_y = height / ;
int padding = this.Padding.All;//空白
int r = (width - * padding)/;//半径
int d = * r;//直径
int dis = ;//两个半圆之间的间隔
int dis2 = * dis;//填充与边框之间的距离
int startAngle1 = -;
int startAngle2 = ;
int sweepAngle1 = ;
//首先画顶端一个半圆
g.DrawPie(Pens.Black, new Rectangle(padding, padding, d, d),startAngle1, sweepAngle1);
g.DrawPie(Pens.Black, new Rectangle(padding+ dis, padding+ dis, d-* dis, d-* dis), startAngle1, sweepAngle1);
//填充背景色
g.FillPie(new SolidBrush(this.backGroundColor), new Rectangle(padding + dis2, padding + dis2, d - *dis2, d - *dis2), startAngle1, sweepAngle1);
//画底端一个半圆
g.DrawPie(Pens.Black, new Rectangle(padding, height-d-padding, d, d), startAngle2, sweepAngle1);
g.DrawPie(Pens.Black, new Rectangle(padding + dis, height-d-padding + dis, d - *dis, d - *dis), startAngle2, sweepAngle1);
g.FillPie(new SolidBrush(this.backGroundColor), new Rectangle(padding + dis2, height - d - padding+dis2, d - *dis2, d - *dis2), startAngle2, sweepAngle1);
//画一个矩形
g.DrawRectangle(Pens.Black, new Rectangle(padding, padding + r, d, height - d - * padding));
g.DrawRectangle(Pens.Black, new Rectangle(padding+dis, padding + r+dis, d-*dis, height - d - * padding-*dis));
//背景色填充，去掉边界线
g.FillRectangle(new SolidBrush(this.backGroundColor), new Rectangle(padding+, padding + r-, * r-, ));
g.FillRectangle(new SolidBrush(this.backGroundColor), new Rectangle(padding + , height-r-padding-, * r - , ));
//背景色填充中间部分
g.FillRectangle(new SolidBrush(this.backGroundColor), new Rectangle(padding + dis2, padding + r + dis2, d - *dis2, height -d - * padding - *dis2));
//画刻度
int s_s_x_1 = padding + r - ;
int s_s_x_2 = width-padding - r + ;
int s_s_y = padding + r+;
int total = this.maxValue - this.minValue;
int scale_width = ;//刻度宽度
int scale = total / this.interval;
int pscale = (height - * r - * padding) / this.interval;//像素间隔 //竖线
g.DrawLine(Pens.Black, new Point(s_s_x_1, s_s_y ), new Point(s_s_x_1, s_s_y + this.interval* pscale));
g.DrawLine(Pens.Black, new Point(s_s_x_2, s_s_y), new Point(s_s_x_2, s_s_y + this.interval * pscale));
for (int i = ; i <= this.interval; i++) {
//横线刻度
g.DrawLine(Pens.Black, new Point(s_s_x_1- scale_width, s_s_y + i * pscale), new Point(s_s_x_1, s_s_y + i * pscale));
g.DrawLine(Pens.Black, new Point(s_s_x_2, s_s_y + i * pscale), new Point(s_s_x_2 + scale_width, s_s_y + i * pscale));
//画刻度数字 g.DrawString((this.maxValue - (scale * i)).ToString(), this.thermoFont, new SolidBrush( this.ForeColor), new Point(s_s_x_1-, s_s_y + i * pscale-));
g.DrawString((this.maxValue - (scale * i)).ToString(), this.thermoFont, new SolidBrush(this.ForeColor), new Point(s_s_x_2 + , s_s_y + i * pscale-));
}
int white_width = ;//中间白色线宽度
//画条白色细线
g.FillRectangle(Brushes.White, new Rectangle(c_x- white_width, r/, white_width*, height-r));
//在底部画一个圆球
g.FillPie(new SolidBrush(this.thermoColor), new Rectangle(c_x-r/+, height - r - padding, r-, r-), , );
//根据当前温度画红色线
int red_width = ;//红色温度线宽度
float ii = ( this.curValue-this.minValue) / this.interval;
g.FillRectangle(new SolidBrush(this.thermoColor), new RectangleF(c_x - red_width, height - r - padding- (ii * pscale)-, * red_width, ii * pscale+));//此处有一像素的误差
//画标志字符单℃位
g.DrawString("℃", this.thermoFont, new SolidBrush(this.ForeColor), new Point(c_x - , r / - ));
Font titleFont = new Font("宋体", , FontStyle.Bold);
//绘制标题
SizeF tsize = g.MeasureString(this.thermoTitle, titleFont);
g.DrawString(this.thermoTitle, titleFont, new SolidBrush(this.ForeColor), new PointF(c_x- (tsize.Width/), height + ));
string cur = string.Format("当前温度：{0}℃", this.curValue);
SizeF tsize2 = g.MeasureString(cur, this.thermoFont);
g.DrawString(cur, this.thermoFont, new SolidBrush(this.thermoColor), new PointF(c_x - (tsize2.Width / ), height + +tsize.Height));
} /// <summary>
/// 当鼠标覆盖进去时
/// </summary>
/// <param name="e"></param>
protected override void OnMouseHover(EventArgs e)
{
this.showTip = true;
//需要显示的内容
int x = this.Width / ;
int y = (this.Height-) / ;
StringBuilder sbTips = new StringBuilder();
//sbTips.AppendLine(this.ThermoTitle);
sbTips.AppendLine(string.Format("当前温度：{0}", this.curValue));
sbTips.AppendLine("单位：℃");
tip.ToolTipTitle = this.ThermoTitle;
tip.IsBalloon = true;
tip.UseFading = true;
//t.SetToolTip(this, sbTips.ToString());
tip.Show(sbTips.ToString(), this, x, y);
} protected override void OnMouseLeave(EventArgs e)
{
this.showTip = false;
tip.Hide(this);
}
}
}
关于页面调用控件刷新代码如下：
private void dgDetail_SelectionChanged(object sender, EventArgs e)
{
foreach (DataGridViewRow row in this.dgDetail.Rows)
{
if (row.Selected)
{
DataRowView drv = row.DataBoundItem as DataRowView;
DataRow dr = drv.Row;
this.t1.CurValue = int.Parse(dr["Morning"].ToString());
this.t1.ThermoTitle = string.Format("{0}温度",dgDetail.Columns["colMorning"].HeaderText);
this.t1.Refresh();
this.t2.CurValue = int.Parse(dr["Middle"].ToString());
this.t2.ThermoTitle = string.Format("{0}温度", dgDetail.Columns["colMiddle"].HeaderText);
this.t2.Refresh();
this.t3.CurValue = int.Parse(dr["After"].ToString());
this.t3.ThermoTitle = string.Format("{0}温度", dgDetail.Columns["colAfter"].HeaderText);
this.t3.Refresh();
this.t4.CurValue = int.Parse(dr["Night"].ToString());
this.t4.ThermoTitle = string.Format("{0}温度", dgDetail.Columns["colNight"].HeaderText);
this.t4.Refresh();
}
}
}
圆角Panel
关于要实现圆角Panel【扩展控件】，需要以下几个步骤
- 定义一个用户控件，继承于Panel，主要是为了继承Panel的其他容器特性。
- 重写Panel的OnPaint方法，进行绘制四个圆角。
圆角Panel效果图如下：
圆角Panel核心代码如下
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Drawing;
using System.Data;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms; namespace DemoThermometer
{
public partial class UPanelControl : Panel
{
private int radius = ;//弧度半径 public int Radius
{
get { return radius; } set { radius = value; }
} private Color borderColor = Color.Red; public Color BorderColor
{
get { return borderColor; }
set { borderColor = value; }
} public UPanelControl()
{
InitializeComponent();
} protected override void OnPaint(PaintEventArgs e)
{
base.OnPaint(e);
Graphics g = e.Graphics;
int width = this.Width;
int height = this.Height;
int d = * radius;
int p = ;//偏移量
Pen borderPen = new Pen(borderColor,);
Brush brush= new SolidBrush(this.BackColor);
//左上
g.DrawPie(borderPen, new Rectangle(, , d, d), , );
g.FillPie(brush, new Rectangle(p, p, d, d), , ); //左下
g.DrawPie(borderPen, new Rectangle(, height-d, d, d), , );
g.FillPie(brush, new Rectangle(p, height-d-p, d , d ), , );
//右上
g.DrawPie(borderPen, new Rectangle(width-d, , d, d), , );
g.FillPie(brush, new Rectangle(width-d-p, p, d, d), , );
//右下
g.DrawPie(borderPen, new Rectangle(width - d, height - d, d, d), , );
g.FillPie(brush, new Rectangle(width - d - p, height-d-p, d, d), , );
//左边竖线
g.DrawLine(borderPen, , radius, , height - radius); //上边竖线
g.DrawLine(borderPen, radius, , width-radius, ); //右边竖线
g.DrawLine(borderPen, width-, radius-, width-, height - radius+); //下边竖线
g.DrawLine(borderPen, radius-, height-, width - radius+, height-);
}
}
}