本文以一個用戶控件【User Control】實現溫度計的小例子，簡述用戶控件的相關知識，以供學習分享使用，如有不足之處，還請指正。
概述
一般而言，用戶控件【User Control】，是在Visual Studio提供的默認控件不能滿足實際的工作需要，才需要在現有控件的基礎之上進行新的擴展，來實現自己的功能。用戶控件有自己特有的屬性，事件，方法來支撐特定的功能。用戶控件封裝實現的細節，可以進行方便的復用。
用戶控件分類
用戶控件主要有以下三種分類，本例采用的是第三種。
涉及知識點
本例中主要涉及以下知識點：
示例效果圖
本例中示例效果圖如下所示：
關鍵代碼
本例中的關鍵代碼如下：
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 屬性與構造函數 private int interval = 10; /// <summary> /// 刻度間隔 /// </summary> public int Interval { get { return interval; } set { interval = value; } } private int minValue = -50; /// <summary> /// 最低溫度 /// </summary> public int MinValue { get { return minValue; } set { minValue = value; } } private int maxValue = 50; /// <summary> /// 最高溫度 /// </summary> public int MaxValue { get { return maxValue; } set { maxValue = value; } } private float curValue = 0; /// <summary> /// 當前溫度 /// </summary> public float CurValue { get { return curValue; } set { curValue = value; } } private Color thermoColor = Color.Red; /// <summary> /// 溫度條顏色 /// </summary> public Color ThermoColor { get { return thermoColor; } set { thermoColor = value; } } private Color backGroundColor = Color.SkyBlue; /// <summary> /// 溫度計背景色 /// </summary> public Color BackGroundColor { get { return backGroundColor; } set { backGroundColor = value; } } private Font thermoFont=new Font("宋體",10,FontStyle.Regular); /// <summary> /// 溫度計上字體 /// </summary> public Font ThermoFont { get { return thermoFont; } set { thermoFont = value; } } private string thermoTitle = "溫度計"; /// <summary> /// 標題 /// </summary> public string ThermoTitle { get { return this.thermoTitle; } set { this.thermoTitle = value; } } private bool showTip = false; /// <summary> /// 是否顯示提示 /// </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 - 50 ; Graphics g = e.Graphics; int c_x = width / 2; int c_y = height / 2; int padding = this.Padding.All;//空白 int r = (width - 2 * padding)/2;//半徑 int d = 2 * r;//直徑 int dis = 2;//兩個半圓之間的間隔 int dis2 = 2 * dis;//填充與邊框之間的距離 int startAngle1 = -180; int startAngle2 = 0; int sweepAngle1 = 180; //首先畫頂端一個半圓 g.DrawPie(Pens.Black, new Rectangle(padding, padding, d, d),startAngle1, sweepAngle1); g.DrawPie(Pens.Black, new Rectangle(padding+ dis, padding+ dis, d-2* dis, d-2* dis), startAngle1, sweepAngle1); //填充背景色 g.FillPie(new SolidBrush(this.backGroundColor), new Rectangle(padding + dis2, padding + dis2, d - 2*dis2, d - 2*dis2), startAngle1, sweepAngle1); //畫底端一個半圓 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 - 2*dis, d - 2*dis), startAngle2, sweepAngle1); g.FillPie(new SolidBrush(this.backGroundColor), new Rectangle(padding + dis2, height - d - padding+dis2, d - 2*dis2, d - 2*dis2), startAngle2, sweepAngle1); //畫一個矩形 g.DrawRectangle(Pens.Black, new Rectangle(padding, padding + r, d, height - d - 2 * padding)); g.DrawRectangle(Pens.Black, new Rectangle(padding+dis, padding + r+dis, d-2*dis, height - d - 2 * padding-2*dis)); //背景色填充，去掉邊界線 g.FillRectangle(new SolidBrush(this.backGroundColor), new Rectangle(padding+3, padding + r-2, 2 * r-6, 6)); g.FillRectangle(new SolidBrush(this.backGroundColor), new Rectangle(padding + 3, height-r-padding-4, 2 * r - 6, 8)); //背景色填充中間部分 g.FillRectangle(new SolidBrush(this.backGroundColor), new Rectangle(padding + dis2, padding + r + dis2, d - 2*dis2, height -d - 2 * padding - 2*dis2)); //畫刻度 int s_s_x_1 = padding + r - 20; int s_s_x_2 = width-padding - r + 20; int s_s_y = padding + r+4; int total = this.maxValue - this.minValue; int scale_width = 5;//刻度寬度 int scale = total / this.interval; int pscale = (height - 2 * r - 2 * padding) / this.interval;//像素間隔 //豎線 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 = 0; i <= this.interval; i++) { //橫線刻度 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)); //畫刻度數字 g.DrawString((this.maxValue - (scale * i)).ToString(), this.thermoFont, new SolidBrush( this.ForeColor), new Point(s_s_x_1-35, s_s_y + i * pscale-10)); g.DrawString((this.maxValue - (scale * i)).ToString(), this.thermoFont, new SolidBrush(this.ForeColor), new Point(s_s_x_2 + 10, s_s_y + i * pscale-10)); } int white_width = 3;//中間白色線寬度 //畫條白色細線 g.FillRectangle(Brushes.White, new Rectangle(c_x- white_width, r/2, white_width*2, height-r)); //在底部畫一個圓球 g.FillPie(new SolidBrush(this.thermoColor), new Rectangle(c_x-r/2+5, height - r - padding, r-10, r-10), 0, 360); //根據當前溫度畫紅色線 int red_width = 5;//紅色溫度線寬度 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)-4, 2* red_width, ii * pscale+5));//此處有一像素的誤差 //畫標志字符單℃位 g.DrawString("℃", this.thermoFont, new SolidBrush(this.ForeColor), new Point(c_x - 30, r / 2 - 10)); Font titleFont = new Font("宋體", 13, FontStyle.Bold); //繪制標題 SizeF tsize = g.MeasureString(this.thermoTitle, titleFont); g.DrawString(this.thermoTitle, titleFont, new SolidBrush(this.ForeColor), new PointF(c_x- (tsize.Width/2), height + 5)); string cur = string.Format("當前溫度：{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 / 2), height + 10+tsize.Height)); } /// <summary> /// 當鼠標覆蓋進去時 /// </summary> /// <param name="e"></param> protected override void OnMouseHover(EventArgs e) { this.showTip = true; //需要顯示的內容 int x = this.Width / 2; int y = (this.Height-50) / 2; StringBuilder sbTips = new StringBuilder(); //sbTips.AppendLine(this.ThermoTitle); sbTips.AppendLine(string.Format("當前溫度：{0}", this.curValue)); sbTips.AppendLine("單位：℃"); 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); } }}以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支持VEVB武林網。
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