监控网页中元素的事件

对编写脚本熟悉的读者都知道页面中可以添加脚本响应元素的事件，例如超链接的OnClick事件，图片的OnMouseMove事件，我们也可以使VB程序响应这些事件。下面是一个VB响应页面中按钮的Click事件的代码：
首先建立一个新工程，在Form1中加入一个Webbrowser控件，然后在Form1中加入以下代码：

Option Explicit

Public Sub Some_Procedure()
MsgBox "你点击了按钮."
End Sub

Private Sub Form_Load()
'下载空页面
WebBrowser1.Navigate2 "about:blank"
End Sub

Private Sub WebBrowser1_DocumentComplete(ByVal pDisp As Object, URL As Variant)
'建立事件响应类
Dim cfForward As clsForward

'定义在浏览器中显示的HTML代码，其中包含一个按钮btnMyButton
Dim sHTML As String
sHTML = "<P>This is some text.</P>"
sHTML = sHTML & "<P>And here is a button.</P>"
sHTML = sHTML & "<BUTTON ID=btnMyButton>"
sHTML = sHTML & "Click this button.</BUTTON>"

'将HTML代码写入浏览器
WebBrowser1.Document.body.innerHTML = sHTML

'将事件响应类连接到页面的按钮btnMyButton上
Set cfForward = New clsForward
cfForward.Set_Destination Me, "Some_Procedure"
WebBrowser1.Document.All("btnMyButton").onclick = cfForward
End Sub

向工程中添加一个Class Module，Class Module的Name属性设定为clsForward，在clsForward中添加以下代码：

Option Explicit

Dim oObject As Object
Dim sMethod As String
Dim bInstantiated As Boolean

Private Sub Class_Initialize()
bInstantiated = False
End Sub

Public Sub Set_Destination(oInObject As Object, sInMethod As String)
Set oObject = oInObject
sMethod = sInMethod
bInstantiated = True
End Sub

Public Sub My_Default_Method()
If bInstantiated Then
CallByName oObject, sMethod, VbMethod
End If
End Sub

在运行前，你需要吧My_Default_Method设置为默认过程，方法是：在clsForward模块的代码窗口中将光标定位到My_Default_Method中，然后选择菜单 Tools | Procedure Attributes。然后在弹出窗口中点击advanced按钮，然后在procedure id下拉框中选择[Default]

运行程序，点击Webbrowser中的“Click this button”按钮。程序就会弹出消息框提示“你点击了按钮.”