简介

本文将详细介绍如何使用C#和GDI+技术实现一个自定义的温度计控件。这个控件具有以下特点：

• 可视化温度显示
• 可自定义最大最小温度值
• 支持动态更新温度
• 具有平滑的动画效果
• 支持自定义颜色主题

实现代码

首先，创建一个继承自Control的自定义控件类：

C#
using System;
using System.Collections.Generic;
using System.Drawing.Drawing2D;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace AppControls
{
    public class ThermometerControl : Control
    {
        // 温度相关属性  
        private float _currentTemperature = 0;
        private float _minTemperature = -20;
        private float _maxTemperature = 50;

        // 尺寸相关属性  
        private int _bulbRadius = 20;

        // 颜色设置  
        private Color _mercuryColor = Color.Red;
        private Color _backgroundColor = Color.White;
        private Color _borderColor = Color.Black;

        // 控件尺寸常量  
        private const int TUBE_WIDTH = 10;
        private const int SCALE_LENGTH = 5;
        private const int LEFT_MARGIN = 15;
        private const int BOTTOM_MARGIN = 25;


        // 球形底部半径属性  
        public int BulbRadius
        {
            get => _bulbRadius;
            set
            {
                if (value != _bulbRadius && value >= 10 && value <= 50) // 设置合理的范围限制  
                {
                    _bulbRadius = value;
                    UpdateControlSize();
                    Invalidate();
                }
            }
        }

        // 温度相关属性  
        public float CurrentTemperature
        {
            get => _currentTemperature;
            set
            {
                if (value != _currentTemperature)
                {
                    _currentTemperature = Math.Max(_minTemperature, Math.Min(_maxTemperature, value));
                    Invalidate();
                }
            }
        }

        public float MinTemperature
        {
            get => _minTemperature;
            set
            {
                if (value != _minTemperature)
                {
                    _minTemperature = value;
                    Invalidate();
                }
            }
        }

        public float MaxTemperature
        {
            get => _maxTemperature;
            set
            {
                if (value != _maxTemperature)
                {
                    _maxTemperature = value;
                    Invalidate();
                }
            }
        }

        // 颜色属性  
        public Color MercuryColor
        {
            get => _mercuryColor;
            set
            {
                if (value != _mercuryColor)
                {
                    _mercuryColor = value;
                    Invalidate();
                }
            }
        }

        public Color BackgroundColor
        {
            get => _backgroundColor;
            set
            {
                if (value != _backgroundColor)
                {
                    _backgroundColor = value;
                    Invalidate();
                }
            }
        }

        public Color BorderColor
        {
            get => _borderColor;
            set
            {
                if (value != _borderColor)
                {
                    _borderColor = value;
                    Invalidate();
                }
            }
        }

        public ThermometerControl()
        {
            SetStyle(ControlStyles.DoubleBuffer |
                    ControlStyles.AllPaintingInWmPaint |
                    ControlStyles.UserPaint |
                    ControlStyles.ResizeRedraw, true);

            UpdateControlSize();
        }

        // 更新控件尺寸  
        private void UpdateControlSize()
        {
            // 根据球形底部半径计算合适的控件尺寸  
            int minWidth = LEFT_MARGIN + _bulbRadius * 2 + SCALE_LENGTH + 35; // 35为刻度文本预留空间  
            int minHeight = _bulbRadius * 4 + BOTTOM_MARGIN; // 确保有足够空间显示温度计管体  

            MinimumSize = new Size(minWidth, minHeight);
            if (Width < minWidth) Width = minWidth;
            if (Height < minHeight) Height = minHeight;
        }

        protected override void OnPaint(PaintEventArgs e)
        {
            base.OnPaint(e);

            Graphics g = e.Graphics;
            g.SmoothingMode = SmoothingMode.AntiAlias;

            // 计算关键尺寸  
            int bulbCenterX = LEFT_MARGIN + _bulbRadius;
            int bulbCenterY = Height - BOTTOM_MARGIN - _bulbRadius;
            int tubeHeight = Height - 2 * _bulbRadius - BOTTOM_MARGIN;
            int tubeTop = _bulbRadius;

            // 绘制温度计外壳  
            DrawThermometerBody(g, bulbCenterX, bulbCenterY, tubeHeight);

            // 绘制水银柱  
            DrawMercury(g, bulbCenterX, bulbCenterY, tubeHeight);

            // 绘制刻度  
            DrawScale(g, bulbCenterX, tubeTop, tubeHeight);
        }

        private void DrawThermometerBody(Graphics g, int bulbCenterX, int bulbCenterY, int tubeHeight)
        {
            using (Pen borderPen = new Pen(_borderColor, 2))
            {
                // 绘制管子  
                g.DrawLine(borderPen,
                    bulbCenterX - TUBE_WIDTH / 2, _bulbRadius,
                    bulbCenterX - TUBE_WIDTH / 2, bulbCenterY);
                g.DrawLine(borderPen,
                    bulbCenterX + TUBE_WIDTH / 2, _bulbRadius,
                    bulbCenterX + TUBE_WIDTH / 2, bulbCenterY);

                // 绘制球形底部  
                g.DrawEllipse(borderPen,
                    bulbCenterX - _bulbRadius,
                    bulbCenterY - _bulbRadius,
                    _bulbRadius * 2,
                    _bulbRadius * 2);
            }

            // 填充球形底部背景  
            using (SolidBrush bulbBrush = new SolidBrush(_backgroundColor))
            {
                g.FillEllipse(bulbBrush,
                    bulbCenterX - _bulbRadius + 1,
                    bulbCenterY - _bulbRadius + 1,
                    (_bulbRadius - 1) * 2,
                    (_bulbRadius - 1) * 2);
            }
        }

        private void DrawMercury(Graphics g, int bulbCenterX, int bulbCenterY, int tubeHeight)
        {
            float temperatureRange = _maxTemperature - _minTemperature;
            float temperatureHeight = (_currentTemperature - _minTemperature) / temperatureRange;
            int mercuryHeight = (int)(tubeHeight * temperatureHeight);

            using (SolidBrush mercuryBrush = new SolidBrush(_mercuryColor))
            {
                // 填充管中的水银  
                g.FillRectangle(mercuryBrush,
                    bulbCenterX - TUBE_WIDTH / 2 + 2,
                    bulbCenterY - mercuryHeight,
                    TUBE_WIDTH - 3,
                    mercuryHeight);

                // 填充球部的水银  
                g.FillEllipse(mercuryBrush,
                    bulbCenterX - _bulbRadius + 2,
                    bulbCenterY - _bulbRadius + 2,
                    (_bulbRadius - 2) * 2,
                    (_bulbRadius - 2) * 2);
            }
        }

        private void DrawScale(Graphics g, int centerX, int topY, int height)
        {
            using (Pen scalePen = new Pen(_borderColor, 1))
            using (Font scaleFont = new Font("Arial", 8))
            using (StringFormat sf = new StringFormat { Alignment = StringAlignment.Near })
            {
                int scaleCount = 10;
                float temperatureStep = (_maxTemperature - _minTemperature) / scaleCount;
                float pixelStep = height / (float)scaleCount;

                for (int i = 0; i <= scaleCount; i++)
                {
                    int y = topY + (int)(i * pixelStep);

                    // 绘制刻度线  
                    g.DrawLine(scalePen,
                        centerX + TUBE_WIDTH / 2,
                        y,
                        centerX + TUBE_WIDTH / 2 + SCALE_LENGTH,
                        y);

                    // 绘制温度值  
                    float temperature = _maxTemperature - i * temperatureStep;
                    g.DrawString(
                        temperature.ToString("F0") + "°",
                        scaleFont,
                        Brushes.Black,
                        new RectangleF(
                            centerX + TUBE_WIDTH / 2 + SCALE_LENGTH + 2,
                            y - 6,
                            30,
                            12),
                        sf);
                }
            }
        }
    }
}

核心属性设计：

• 温度相关属性：当前温度(_currentTemperature)、最小温度(_minTemperature)、最大温度(_maxTemperature)
• 外观属性：球部半径(_bulbRadius)、水银颜色(_mercuryColor)、背景色(_backgroundColor)、边框色(_borderColor)
• 控件尺寸常量：管宽(TUBE_WIDTH)、刻度长度(SCALE_LENGTH)等

主要绘制逻辑(OnPaint方法)分为三个部分

C#
DrawThermometerBody() // 绘制温度计外壳
DrawMercury()        // 绘制水银柱
DrawScale()          // 绘制刻度

总结

这个温度计控件实现了基本的温度显示功能，具有良好的可扩展性和自定义性。通过GDI+绘图技术，我们实现了平滑的显示效果和专业的外观。该控件可以用于各种需要温度显示的应用场景，如天气站、工业控制等领域。