前天有一網友問及有關設計模式的適配器模式(Adapter)時，說不太好理解。讓Insus.NET能否舉個簡單的例子來說明一下。下面的動畫是Insus.NET做出來的效果:
上面的演示，兩個燈的規格一樣，要求輸入的電壓為15伏。
Light1是直接使用，而Light2是使用Adapter(電源適配器)。因此Light1只能接收15伏的電壓，小於15伏，會提示電壓過低，如果超過了15伏，Light1肯定被燒壞。
Light2使用了電源適配器，它接收15伏至220的電壓，在這電壓范圍之內，電源適配器會把電壓轉為15的電壓。小於15伏，會提示電壓過低，如果超過了220伏，適配器被燒壞。
好，我們程序開始，先創建一個燈Light的類：
Light.cs
using System; using System.Collections.Generic; using System.Linq; using System.Web; /// <summary> /// Summary description for Light /// </summary> namespace Insus.NET { public class Light { private int _InputVoltage = 15; public int InputVoltage { get { return _InputVoltage; } set { if (value < 15) throw new Exception("電壓過低。"); else if (value > 15) throw new Exception("危險！電壓過大燈燒壞。"); else value = 15; _InputVoltage = value; } } public Light() { // // TODO: Add constructor logic here // } } }
再創建一個燈的電源適配器：
PowerAdapter.cs
using System; using System.Collections.Generic; using System.Linq; using System.Web; /// <summary> /// Summary description for PowerAdapter /// </summary> namespace Insus.NET { public class PowerAdapter : Light { Light _Light; public PowerAdapter(Light light) { this._Light = light; } public int InputVoltage { get { return _Light.InputVoltage; } set { if (value < 15) throw new Exception("電壓過低。"); else if (value > 220) throw new Exception("危險！電壓過大電源適配器燒壞。"); else value = 15; _Light.InputVoltage = value; } } } }
如何測試它們，我們得模擬一個環境，創建一個網頁Default.aspx：
Default.aspx
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %> <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head runat="server"> <title></title> <script type="text/javascript"> function isNumeric(keyCode) { return ((keyCode >= 48 && keyCode <= 57) || keyCode == 8) } </script> </head> <body> <form id="form1" runat="server"> <table> <tr> <td align="right">插座電壓</td> <td colspan="2"> <asp:TextBox ID="TextBox1" runat="server" onkeydown="return isNumeric(event.keyCode);" Text="220"></asp:TextBox></td> </tr> <tr> <td align="right">開關</td> <td colspan="2"> <asp:CheckBox ID="CheckBoxSwitch" runat="server" AutoPostBack="true" OnCheckedChanged="CheckBoxSwitch_CheckedChanged" /></td> </tr> <tr> <td align="right">燈</td> <td> <fieldset style="width: 200px;"> <legend>Light 1 </legend> <asp:Image ID="Image1" runat="server" ImageUrl="Images/Light_C.gif" Width="36" Height="55" /><br /> <asp:Label ID="Label1" runat="server" Text=""></asp:Label> </fieldset> </td> <td> <fieldset style="width: 250px;"> <legend>Light 2 </legend> <asp:Image ID="Image2" runat="server" ImageUrl="Images/Light_C.gif" Width="36" Height="55" /><br /> <asp:Label ID="Label2" runat="server" Text=""></asp:Label> </fieldset> </td> </tr> </table> </form> </body> </html>
接下來，看看開關的事開與關的事件，有詳細的注解：
Default.aspx.cs
using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.UI; using System.Web.UI.WebControls; using Insus.NET; public partial class _Default : System.Web.UI.Page { string offLight = "~/Images/Light_C.gif"; string onLight = "~/Images/Light_O.gif"; protected void Page_Load(object sender, EventArgs e) { } protected void CheckBoxSwitch_CheckedChanged(object sender, EventArgs e) { var cb = (CheckBox)sender; //插座缺少電壓為220伏 int input = Convert.ToInt32(string.IsNullOrEmpty(this.TextBox1.Text.Trim()) ? "220" : this.TextBox1.Text.Trim()); //開關打開 if (cb.Checked) { try { //實例一個電燈 Light light = new Light(); //插入插座，使用插座電壓 light.InputVoltage = input; //電燈被打開 this.Image1.ImageUrl = onLight; //顯示正常輸出電壓 this.Label1.Text = light.InputVoltage.ToString(); } catch (Exception ex) { //如果電壓不正常，電燈打不開或是被燒壞。 this.Image1.ImageUrl = offLight; //顯示異常信息。 this.Label1.Text = ex.Message; } try { Light light = new Light(); //使用電源適配器 PowerAdapter pa = new PowerAdapter(light); pa.InputVoltage = input; this.Image2.ImageUrl = onLight; this.Label2.Text = pa.InputVoltage.ToString(); } catch (Exception ex) { this.Image2.ImageUrl = offLight; this.Label2.Text = ex.Message; } this.TextBox1.Enabled = false; } //開關關閉 else { this.TextBox1.Text = string.Empty; this.TextBox1.Enabled = true; this.Image1.ImageUrl = offLight; this.Image2.ImageUrl = offLight; } } }
11：44分，補充下面內容，有網友問及演示完整代碼(.NET Framework 4.0)
http://download.cnblogs.com/insus/ASPDOTNET/AdapterDemo.rar