给自己的程序增加网页浏览功能
有很多文章介绍了怎样在自己的程序中加入浏览网页的功能，我也曾经用VB制作自己的浏览器。大多是利用了SHDOCVW.DLL中的WEBBROWSER控件和INTERNET EXPLORER AUTOMATION。Shdocvw.DLL提供了COM接口，使得程序员可以在自己的程序中使用WEBBROWSER控件和INTERNET EXPLORER AUTOMATION。它还提供了系列的INTERNET API函数，给我们控制INTERNET EXPLORER。
如果大家想了解SHDOCVW.DLL提供了些什么给我们，可以用《高级VISUAL BASIC编程》（中国电力出版社）中TYPE LIBRARY EDITOR工具浏览SHDOCVW.DLL中的内幕。还可以用Exescope这个资源编辑工具看看SHDOCVW.DLL中有什么函数。
IE基本架构（摘自《程序员》专刊）
IEXPLORER.EXE | |||
SHDOCVW.DLL–WEBBROWSER CONTROL AND INTERNET EXPLORER AUTOMATION页面显示 | |||
MSHTML.DLL – MSHTML，处理页面的语法分析，又是一个COM服务器，把HTML中的页面元素定义成对象，给客户端访问 | |||
HTML | |||
ACTIVEX CONTROL | ACTIVEX SCRIPT ENGINE | JAVA APPLET | PLUG IN |
在MSDN中有详细的帮助介绍WEBBROWSER控件和INTERNET EXPLORER AUTOMATION。它们的属性、方法和事件大部分相同，有部分属性和方法WEBBROWSER控件会忽略掉。SHDOCVW.DLL提供一个手段给我们把网页浏览功能加入到我们的程序中，或控制一个INTERNET EXPLORER实例。以下是一些我在应用中使用到的技巧，我以代码加说明的形式给出大家参考。
一、 工具栏
brwWebBrowser是一个WEBBROWSER控件的实例，CommandStateChange事件可以实现工具栏中的前进和后退的是否有效。
Private Sub brwWebBrowser_CommandStateChange(ByVal Command As Long, ByVal Enable As Boolean)
Select Case Command
Case CSC_UPDATECOMMANDS
' Me.tbToolBar.Buttons(1).Enabled = Enable
' Me.tbToolBar.Buttons(2).Enabled = Enable
Case CSC_NAVIGATEFORWARD
‘工具栏的前进按扭的有效状态改变
Me.tbToolBar.Buttons(2).Enabled = Enable
‘工具栏的后退按扭的有效状态改变
Case CSC_NAVIGATEBACK
Me.tbToolBar.Buttons(1).Enabled = Enable
Case Else
End Select
End Sub
利用WEBBROWSER的方法进行导航
Private Sub tbToolBar_ButtonClick(ByVal Button As MSComctlLib.Button)
On Error Resume Next
Select Case Button.Key
Case "Back"
brwWebBrowser.GoBack ‘后退
Case "Forward"
brwWebBrowser.GoForward ‘前进
Case "Refresh"
brwWebBrowser.Refresh ‘刷新
Case "Home"
brwWebBrowser.GoHome ‘到主页
Case "Search"
Me.tbToolBar.Buttons("HtmlClass").Value = tbrUnpressed
Me.tbToolBar.Buttons("History").Value = tbrUnpressed
If Button.Value = tbrPressed Then
Me.brwSearch.Visible = True
Me.brwSearch.GoSearch
m_blnIsSplitter = True
Else
Me.brwSearch.Visible = False
Me.brwSearch.GoSearch
m_blnIsSplitter = False
End If
Me.UCtlHistroy1.Visible = False
Me.UCtlClassUrl1.Visible = False
Call ResizeControls(m_blnIsSplitter, Me.imgSplitter.Left)
Case "Stop"
brwWebBrowser.Stop
Me.Caption = brwWebBrowser.LocationName & " - " & strCurrentUserName
Case "HtmlClass"
' If Button.Value = tbrPressed Then
' Me.tbToolBar.Buttons("History").Value = tbrUnpressed
' Me.tbToolBar.Buttons("Search").Value = tbrUnpressed
'
' m_blnIsSplitter = True
' Me.UCtlClassUrl1.Visible = True
' Me.UCtlHistroy1.Visible = False
'
' Me.UCtlClassUrl1.BuildTree (Normal)
'
' Else
' m_blnIsSplitter = False
' Me.UCtlClassUrl1.Visible = False
' Me.UCtlHistroy1.Visible = False
' End If
' Call ResizeControls(m_blnIsSplitter, Me.imgSplitter.Left)
Call mnuManClass_Click
Case "History"
' If Button.Value = tbrPressed Then
' Me.tbToolBar.Buttons("HtmlClass").Value = tbrUnpressed
' Me.tbToolBar.Buttons("Search").Value = tbrUnpressed
'
' m_blnIsSplitter = True
' Me.UCtlHistroy1.Visible = True
' Me.UCtlClassUrl1.Visible = False
' Me.UCtlHistroy1.BuildTree (0)
' Else
' m_blnIsSplitter = False
' Me.UCtlHistroy1.Visible = False
' Me.UCtlClassUrl1.Visible = False
' Me.UCtlHistroy1.BuildTree (0)
' End If
' Call ResizeControls(m_blnIsSplitter, Me.imgSplitter.Left)
'
Call mnuManHistory_Click
Case "PrintOut"
brwWebBrowser.SetFocus
On Error Resume Next
brwWebBrowser.ExecWB OLECMDID_PRINT, OLECMDEXECOPT_DODEFAULT ‘打印
Case "Status"
' m_blnStatusBarShow = CBool(Button.Value)
Me.tbToolBar.Customize
' Me.tbToolBar.SaveToolbar
Case "Help"
Call mnuHelpAbout_Click
Case "Exit"
Call mnuFileClose_Click
Case Else
Exit Sub
End Select
End Sub
(不好意思以上有很多垃圾代码。)
二、 状态栏
利用了WEBBROWSER控件的ProgressChange事件显示一个进度条；StatusTextChange事件更新状态栏窗格的信息，反映WEBBROWSER控件的的状态。
Private Sub brwWebBrowser_DownloadBegin()
ProgressShow True
End Sub
Sub ProgressShow(Visible As Boolean) ‘显示一个进度条
Me.sbrHtml.Panels(2).Visible = Visible
Progress1.Visible = Visible
If Visible Then Progress1.Move sbrHtml.Panels(2).Left + 10, sbrHtml.Top + (sbrHtml.Height - sbrHtml.Height) / 2 + 10, sbrHtml.Panels(2).Width - 20
End Sub
Private Sub brwWebBrowser_ProgressChange(ByVal Progress As Long, ByVal ProgressMax As Long)
On Error Resume Next
Progress1.Max = ProgressMax
If Progress > 0 Then
Progress1.Value = Progress
Else
Progress1.Value = ProgressMax
End If
End Sub
Private Sub brwWebBrowser_StatusTextChange(ByVal Text As String)
Me.sbrHtml.Panels(1).Text = Text
Me.sbrHtml.Refresh
End Sub
Private Sub brwWebBrowser_DownloadComplete()
On Error Resume Next
Me.Caption = brwWebBrowser.LocationName
Me.cboAddress = Me.brwWebBrowser.LocationURL ‘地址栏的现时地址
ProgressShow False
End Sub
三、 地址栏
Private mbDontNavigateNow As Boolean ‘是否正在在导航状态的变量
Private Sub cboAddress_Click() ‘选中下拉列表中的行
If mbDontNavigateNow Then Exit Sub
brwWebBrowser.Navigate cboAddress.Text ‘导航到下拉列表文本中的地址
End Sub
Private Sub cboAddress_KeyPress(KeyAscii As Integer)
On Error Resume Next
If KeyAscii = vbKeyReturn Then ‘在下拉列表中输入地址完毕
cboAddress_Click
End If
End Sub
NavigateComplete2事件中把导航的地址加入下拉列表中（如果列表中没有的话）。
Private Sub brwWebBrowser_NavigateComplete2(ByVal pDisp As Object, URL As Variant)
' On Error Resume Next
Dim i As Integer
Dim bFound As Boolean
Dim strTemp() As String
Me.Caption = brwWebBrowser.LocationName
查找地址是否已在列表中
For i = 0 To cboAddress.ListCount - 1
If cboAddress.List(i) = brwWebBrowser.LocationURL Then
bFound = True
Exit For
End If
Next i
mbDontNavigateNow = True
If bFound Then ‘找到
cboAddress.RemoveItem I ‘移除
End If
cboAddress.AddItem brwWebBrowser.LocationURL, 0 ‘添加
cboAddress.ListIndex = 0
mbDontNavigateNow = False
End Sub
四、 菜单
WEBBROWSER控件和INTERNET EXPLORER AUTOMATION的EXECWB方法，提供了很多命令给用户执行，命令作用在OLE对象上。但有很多命令执行对WEBBROWSER控件无效，具体的方法参数请看MSDN。
Private Sub mnuEdigCut_Click()
brwWebBrowser.SetFocus
On Error Resume Next
brwWebBrowser.ExecWB OLECMDID_CUT, OLECMDEXECOPT_DODEFAULT
‘剪切
End Sub
Private Sub mnuEditCopy_Click()
On Error Resume Next
brwWebBrowser.SetFocus
brwWebBrowser.ExecWB OLECMDID_COPY, OLECMDEXECOPT_DODEFAULT
‘复制
End Sub
Private Sub mnuEditFind_Click()
On Error Resume Next
brwWebBrowser.SetFocus
brwWebBrowser.ExecWB OLECMDID_FIND, OLECMDEXECOPT_DODEFAULT
‘查找，（无效）
End Sub
Private Sub mnuEditPaste_Click()
On Error Resume Next
brwWebBrowser.SetFocus
brwWebBrowser.ExecWB OLECMDID_PASTE, OLECMDEXECOPT_DODEFAULT
‘粘贴
End Sub
Private Sub mnuEditSelectedAll_Click()
brwWebBrowser.SetFocus
brwWebBrowser.ExecWB OLECMDID_SELECTALL, OLECMDEXECOPT_DODEFAULT
‘全选
End Sub
Private Sub mnuFileAttrib_Click()
Me.brwWebBrowser.SetFocus
On Error Resume Next
brwWebBrowser.ExecWB OLECMDID_PROPERTIES, OLECMDEXECOPT_DODEFAULT
‘显示网页的属性
End Sub
Private Sub mnuFileNew_Click()
Dim frmNew As New frmMainExploer ‘新建窗口
frmNew.Show
Set frmNew = Nothing
End Sub
Private Sub mnuFileOpen_Click()
' brwWebBrowser.SetFocus
' On Error Resume Next
' brwWebBrowser.ExecWB OLECMDID_OPEN, OLECMDEXECOPT_DODEFAULT
‘打开
‘以下是用原始的方式打开
Dim sFile As String
With dlgCommonDialog
.DialogTitle = "打开网页"
.CancelError = False
'ToDo: 设置 common dialog 控件的标志和属性
.Filter = "HTML文件(*.html,*.htm)|*.html;*htm|文本文件(*.txt)|*.txt|Asp文件(*.asp)|*.asp" & _
"|图形文件(*.bmp;*.jpg;*.jpeg;*.gif)|*.bmp;*.jpg;*.jpeg;*.gif|所有文件(*.*)|*.*"
.ShowOpen
If Len(.filename) = 0 Then
Exit Sub
End If
sFile = .filename
End With
'ToDo: 添加处理打开的文件的代码
brwWebBrowser.Navigate sFile
End Sub
Private Sub mnuFilePrint_Click()
brwWebBrowser.SetFocus
On Error Resume Next
brwWebBrowser.ExecWB OLECMDID_PRINT, OLECMDEXECOPT_DODEFAULT
‘打印
End Sub
Private Sub mnuFileSave_Click()
brwWebBrowser.SetFocus
On Error Resume Next
brwWebBrowser.ExecWB OLECMDID_SAVE, OLECMDEXECOPT_DODEFAULT
‘保存
‘以下是用原始的方式保存网页
' Dim sFile As String
'
' With dlgCommonDialog
' .DialogTitle = "保存"
' .Filter = "HTML文件(*.html,*.htm)|*.html;*htm|文本文件(*.txt)|*.txt|Asp文件(*.asp)|*.asp" & _
' "|图形文件(*.bmp;*.jpg;*.jpeg;*.gif)|*.bmp;*.jpg;*.jpeg;*.gif|所有文件(*.*)|*.*"
' .ShowSave
' End With
End Sub
