??很多初学c#的朋友对于事件与接口感到迷惑不解,不明白它们之间的关系,下面我就用实例来简单的分析讲解一下。
??事件,用event修饰符来代表一个事件,我们要创建一个C#事件必须按以下顺序来扫行:
??1,创建或标识一个代表。比如下例中的
??public delegate void dele(); //声明代表,delegate 关键字通知编译器 dele 是一个委托类型
??2,创建一个包含事件处理代表,调用事件处理代表的方法的类,如下例
??public class EventClass1 : IEvents //IEvents,是下面我们要讲一接口
??{
??public event dele event1;//定义事件成员event1
??public void FireEvent() //当事件发生时
??{
??event1(); //调用事件处理
??}
??}
??EventClass1继承接口IEvents,以下后面的EventClass2~4,都是一样。
??3,定义一个或多个把方法连接到事件的类
??4,使用事件
??4.1 定义事件响应方法,如下例中的
??IEvents id1 = new EventClass1();
??4.2 使用所定义的构造函数创建一个包含事件的对象,如下例中的
??id1.event1 += new dele(EventFired1);
??4.3 触发事件,如下例中的
??id1.FireEvent();
??下面我们来看看接口,我们必须用interface来声明一个接口。接口声明可以声明零个或多个成员。接口的成员必须是方法、属性、事件或索引器。接口不能包含常数、字段、运算符、实例构造函数、析构函数或类型,也不能包含任何种类的静态成员。
??所有接口成员都隐式地具有 public 访问权限。接口成员声明包含任何修饰符属于编译时错误。具体地说,接口成员包含下列任何修饰符属于编译时错误:abstract、public、protected、internal、private、virtual、override 或 static。更多的信息请看msdn help://MS.VSCC/MS.MSDNVS.2052/csspec/html/vclrfcsharpspec_13_1.htm
??在下面的例子中,我们声明IEvents接口,一个方法FireEvent和一个事件event1
??public interface IEvents
??{
??event dele event1; //定义事件
??void FireEvent();//定义接口
??}
??在后面的EventClass1~4类是继承了接口IEvent,因此在这几个类中必须实现上述一个方法和一个事件。下面的实例可以帮助大家更好的理解。
??这是一个简单的windows Forms,包含一个textbox,几个labels和一个button,在程序启动时焦点在textbox,捕捉键盘按下事件,除方向键外,我能过接口来触事方向键按下事件。
??下面的代码是一个网上常见的例程,大家可以拷贝下来,保存为.cs文件,用CSC编译就行
??代码如下:
??using System;
??using System.Drawing;
??using System.Collections;
??using System.ComponentModel;
??using System.Windows.Forms;
??using System.Data;
??namespace Events_Interfaces
??{
??public delegate void dele();//声明代表 delegate 关键字通知编译器 dele 是一个委托类型
??public interface IEvents //定义接口IEvents,包含方法FireEvent事件event1
??{
??event dele event1;
??void FireEvent();
??}
??public class Form1 : System.Windows.Forms.Form
??{
??private System.Windows.Forms.Label label1;
??private System.Windows.Forms.TextBox textBox1;
??private System.Windows.Forms.Label label2;
??private System.Windows.Forms.Button button1;
??private System.Windows.Forms.Label label3;
??private System.ComponentModel.Container components =null;
??public Form1()
??{
??InitializeComponent();
??}
??protected override void Dispose( bool disposing )
??{
??if( disposing )
??{
??if (components != null)
??{
??components.Dispose();
??}
??}
??base.Dispose( disposing );
??}
??#region Windows Form Designer generated code
??private void InitializeComponent()
??{
??this.textBox1 = new System.Windows.Forms.TextBox();
??this.label1 = new System.Windows.Forms.Label();
??this.button1 = new System.Windows.Forms.Button();
??this.label2 = new System.Windows.Forms.Label();
??this.label3 = new System.Windows.Forms.Label();
??this.SuspendLayout();
??this.textBox1.Location = new System.Drawing.Point(8, 80);
??this.textBox1.Name = "textBox1";
??this.textBox1.Size = new System.Drawing.Size(56,23);
??this.textBox1.TabIndex = 1;
??this.textBox1.Text = "";
??this.textBox1.KeyDown += new System.Windows.Forms.KeyEventHandler(this.Key_Press);
??this.label1.Location = new System.Drawing.Point(16, 16);
??this.label1.Name = "label1";
??this.label1.Size = new System.Drawing.Size(256,64);
??this.label1.TabIndex = 0;
??this.label1.Text = "Whenever you use the arrow keys inside the text box, Corresponding events will be" +"fired to display the label appropriately. Have a try!!";
??this.button1.Location = new System.Drawing.Point(240, 112);
??this.button1.Name = "button1";
??this.button1.Size = new System.Drawing.Size(48,23);
??this.button1.TabIndex = 3;
??this.button1.Text = "Exit";
??this.button1.Click += new System.EventHandler(this.button1_Click);
??//
??// label2
??//
??this.label2.Location = new System.Drawing.Point(88, 80);
??this.label2.Name = "label2";
??this.label2.Size = new System.Drawing.Size(184,23);
??this.label2.TabIndex = 2;
??this.label2.TextAlign =System.Drawing.ContentAlignment.MiddleCenter;
??//
??// label3
??//
??this.label3.Location = new System.Drawing.Point(8, 104);
??this.label3.Name = "label3";
??this.label3.Size = new System.Drawing.Size(64,23);
??this.label3.TabIndex = 4;
??this.label3.TextAlign =System.Drawing.ContentAlignment.MiddleCenter;
??//
??// Form1
??//
??this.AutoScaleBaseSize = new System.Drawing.Size(6, 16);
??this.ClientSize = new System.Drawing.Size(292,141);
??this.Controls.AddRange(new System.Windows.Forms.Control[]{this.label3,this.button1,this.label2,this.textBox1,this.label1});
??this.Font= new System.Drawing.Font("Comic?SansMS",8.25F,System.Drawing.FontStyle.Regular,
??System.Drawing.GraphicsUnit.Point,((System.Byte)(0)));
??this.Name = "Form1";
??this.Text = "Events";
??this.ResumeLayout(false);
??}
??#endregion
??static void Main()
??{
??Application.Run(new Form1());
??}
??private void Key_Press(object sender,
??System.Windows.Forms.KeyEventArgs e)
??{
??textBox1.Text = "";
??label2.Text = "";
??string keyId = e.KeyCode.ToString();
??switch (keyId)//判断是否按下方向键
??{
??case "Right":
??label3.Text = "";
??IEvents id1 = new EventClass1(); //实例化一个接口
??id1.event1 += new dele(EventFired1);//定义EventClass1中的事件响应方法
??id1.FireEvent();//调用EventClass1中的FireEvent方法,触发event1 事件,事件调用EventFired1方法
??break;
??case "Left":
??label3.Text = "";
??IEvents id2 = new EventClass2();
??id2.event1 += new
??dele(EventFired2);
??id2.FireEvent();
??break;
??case "Down":
??label3.Text = "";
??IEvents id3 = new EventClass3();
??id3.event1 += new
??dele(EventFired3);
??id3.FireEvent();
??break;
??case "Up":
??label3.Text = "";
??IEvents id4 = new EventClass4();
??id4.event1 += new
??dele(EventFired4);
??id4.FireEvent();
??break;
??default:
??label3.Text = keyId;
??break;
??}
??}
??//EventFired1方法
??public void EventFired1()
??{
??label2.Text = "";
??label2.Text = "You pressed RIGHT arrow key";
??}
??public void EventFired2()
??{
??label2.Text = "";
??label2.Text = "You pressed LEFT arrow key";
??}
??public void EventFired3()
??{
??label2.Text = "";
??label2.Text = "You pressed DOWN arrow key";
??}
??public void EventFired4()
??{
??label2.Text = "";
??label2.Text = "You pressed UP arrow key";
??}
??private void button1_Click(object sender,
??System.EventArgs e)
??{
??Application.Exit();
??}
??}
??public class EventClass1 : IEvents
??{
??public event dele event1;
??public void FireEvent()
??{
??event1();
??}
??}
??public class EventClass2 : IEvents
??{
??public event dele event1;
??public void FireEvent()
??{
??event1();
??}
??}
??public class EventClass3 : IEvents
??{
??public event dele event1;
??public void FireEvent()
??{
??event1();
??}
??}
??public class EventClass4 : IEvents//EventClass1继承接口IEvents
??{
??public event dele event1;//定义事件成员event1
??//当事件发生时
??public void FireEvent()
??{
??event1();//调用事件处理
??}
??}
??}