Gestione di eventi di documento in un'applicazione Visual Basic .NET

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Per la versione di questo articolo relativa a Microsoft Visual C# .NET, vedere 312777.

CONTENUTO DELL'ATTIVITÀ

Sommario
In questo articolo viene dimostrato come intercettare eventi di documento per il controllo WebBrowser in Visual Basic .NET.

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Requisiti

Nell'elenco che segue sono indicati l'hardware, il software, l'infrastruttura di rete e i service pack necessari:
  • Microsoft Visual Studio .NET
  • Microsoft Internet Explorer 5.5 Service Pack 2 (SP2) o versione successiva
In questo articolo si presume la conoscenza dei seguenti argomenti:
  • Visual Studio .NET
  • Internet Explorer
  • Controllo WebBrowser
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Descrizione della tecnica

Il controllo WebBrowser è un controllo facile da utilizzare sia in Visual Studio .NET che nelle versioni precedenti di Microsoft Visual Studio. In Visual Studio .NET, tuttavia, la gestione degli eventi di un controllo WebBrowser presenta maggiori difficoltà.

La seguente interfaccia eventi espone la maggior parte degli eventi di documento gestiti in un'applicazione:
Mshtml.HTMLDocumentEvents2_Event				
Per gestire l'evento, è necessario creare una procedura o funzione Sub che può essere chiamata quando si verifica l'evento. È necessario far corrispondere la firma dell'evento generato. La seguente procedura Sub, ad esempio, gestisce l'evento MouseOver del documento:
Private Sub document_onmouseover(ByVal e As mshtml.IHTMLEventObj)				
Dopo aver aggiunto il gestore eventi, è necessario associare l'evento. È possibile associarlo in qualsiasi momento dopo che viene generato l'evento DocumentComplete nel controllo WebBrowser. Di seguito è riportata la sintassi dell'hook:
AddHandler CType(document, _mshtml.HTMLDocumentEvents2_Event).onmouseover, _AddressOf Me.document_onmouseover				
Questo codice chiama l'istruzione AddHandler e utilizza la funzione CType per passare l'evento. La funzione CType esegue il cast dell'oggetto documento sul tipo appropriato (mshtml.HTMLDocumentEvents2_Event), quindi da questo viene passato l'evento OnMouseOver. La procedura Me.document_onmouseoverSub viene passata al secondo parametro, l'istruzione AddressOf, che fornisce l'indirizzo al gestore.

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Creazione del progetto e aggiunta del codice

Nell'esempio riportato di seguito il controllo WebBrowser accede a http://www.microsoft.com/italy. Dopo il caricamento della pagina, vengono associati gli eventi OnMouseOver e OnClick. Viene quindi aggiunto testo alla casella di riepilogo ogni volta che vengono generati gli eventi.
  1. Avviare Visual Studio .NET.
  2. Creare un nuovo progetto Applicazione Windows di Visual Basic .NET.
  3. Aggiungere al progetto un riferimento a Microsoft.mshtml.
  4. Nella casella degli strumenti fare clic su Generale.
  5. Fare clic con il pulsante destro del mouse sul pannello aperto, quindi scegliere Personalizza casella degli strumenti.
  6. Selezionare la casella di controllo Microsoft Web Browser, quindi scegliere OK.
  7. Nella casella degli strumenti fare doppio clic su Esplora risorse.
  8. Nella casella degli strumenti fare clic su Windows Forms, quindi fare doppio clic sul controllo ListBox.
  9. Disporre i controlli in modo che siano ben visibili nel form.
  10. Aggiungere il codice seguente all'inizio di AssemblyInfo.vb, sostituire le frasi Import esistenti
    Imports SystemImports System.DrawingImports System.CollectionsImports System.ComponentModelImports System.Windows.FormsImports System.DataImports System.ReflectionImports System.Runtime.InteropServicesImports System.ThreadingImports System.Diagnostics
  11. Aggiungere il codice seguente tra Codice generato da Progettazione Windows Form ed End Class nella visualizzazione codice di Form1.vb Public
    Shared dwCookie2 As Integer    Public Sub add_list(ByVal a As Object)        ListBox1.Items.Insert(0, a)    End Sub    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load        AxWebBrowser1.Navigate2("http://www.microsoft.com")        Dim x As IEEvents = New IEEvents(AxWebBrowser1)        x.fm = Me    End Sub    Private Sub AxWebBrowser1_Enter(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles AxWebBrowser1.Enter    End Sub    Private Sub AxWebBrowser1_DocumentComplete(ByVal sender As Object, ByVal e As AxSHDocVw.DWebBrowserEvents2_DocumentCompleteEvent) Handles AxWebBrowser1.DocumentComplete        Dim doc As mshtml.HTMLDocument        doc = AxWebBrowser1.Document        AddHandler CType(doc, _            mshtml.HTMLDocumentEvents2_Event).onclick, AddressOf Document_onclick        AddHandler CType(doc, _     mshtml.HTMLDocumentEvents2_Event).onmouseover, AddressOf Document_onmouseover    End Sub    Private Sub AxWebBrowser1_BeforeNavigate2(ByVal sender As Object, ByVal e As AxSHDocVw.DWebBrowserEvents2_BeforeNavigate2Event) Handles AxWebBrowser1.BeforeNavigate2        Dim doc As mshtml.HTMLDocument        doc = AxWebBrowser1.Document        RemoveHandler CType(doc, _            mshtml.HTMLDocumentEvents2_Event).onclick, _            AddressOf Document_onclick        RemoveHandler CType(doc, _            mshtml.HTMLDocumentEvents2_Event).onmouseover, _            AddressOf Document_onmouseover    End Sub    Private Sub Document_onmouseover(ByVal e As mshtml.IHTMLEventObj)        ListBox1.Items.Insert(0, "onMouseOver: " & _            e.srcElement.tagName.ToString())    End Sub    Private Function Document_onclick(ByVal e As mshtml.IHTMLEventObj) _            As Boolean        ListBox1.Items.Insert(0, "onClick: " & _            e.srcElement.tagName.ToString())        Return True    End Function
  12. Aggiungere il codice seguente dopo End Class
    Public Class IEHTMLDocumentEvents    Implements mshtml.HTMLDocumentEvents2    Public Sub onactivate(ByVal pEvtObj As mshtml.IHTMLEventObj) Implements mshtml.HTMLDocumentEvents2.onactivate    End Sub    Public Sub onafterupdate(ByVal pEvtObj As mshtml.IHTMLEventObj) Implements mshtml.HTMLDocumentEvents2.onafterupdate    End Sub    Public Function onbeforeactivate(ByVal pEvtObj As mshtml.IHTMLEventObj) As Boolean Implements mshtml.HTMLDocumentEvents2.onbeforeactivate        Return True    End Function    Public Function onbeforedeactivate(ByVal pEvtObj As mshtml.IHTMLEventObj) As Boolean Implements mshtml.HTMLDocumentEvents2.onbeforedeactivate        Return True    End Function    Public Sub onbeforeeditfocus(ByVal pEvtObj As mshtml.IHTMLEventObj) Implements mshtml.HTMLDocumentEvents2.onbeforeeditfocus    End Sub    Public Function onbeforeupdate(ByVal pEvtObj As mshtml.IHTMLEventObj) As Boolean Implements mshtml.HTMLDocumentEvents2.onbeforeupdate        Return True    End Function    Public Sub oncellchange(ByVal pEvtObj As mshtml.IHTMLEventObj) Implements mshtml.HTMLDocumentEvents2.oncellchange    End Sub    Public Function onclick(ByVal pEvtObj As mshtml.IHTMLEventObj) As Boolean Implements mshtml.HTMLDocumentEvents2.onclick        Return True    End Function    Public Function oncontextmenu(ByVal pEvtObj As mshtml.IHTMLEventObj) As Boolean Implements mshtml.HTMLDocumentEvents2.oncontextmenu        Return True    End Function    Public Function oncontrolselect(ByVal pEvtObj As mshtml.IHTMLEventObj) As Boolean Implements mshtml.HTMLDocumentEvents2.oncontrolselect        Return True    End Function    Public Sub ondataavailable(ByVal pEvtObj As mshtml.IHTMLEventObj) Implements mshtml.HTMLDocumentEvents2.ondataavailable    End Sub    Public Sub ondatasetchanged(ByVal pEvtObj As mshtml.IHTMLEventObj) Implements mshtml.HTMLDocumentEvents2.ondatasetchanged    End Sub    Public Sub ondatasetcomplete(ByVal pEvtObj As mshtml.IHTMLEventObj) Implements mshtml.HTMLDocumentEvents2.ondatasetcomplete    End Sub    Public Function ondblclick(ByVal pEvtObj As mshtml.IHTMLEventObj) As Boolean Implements mshtml.HTMLDocumentEvents2.ondblclick        Return True    End Function    Public Sub ondeactivate(ByVal pEvtObj As mshtml.IHTMLEventObj) Implements mshtml.HTMLDocumentEvents2.ondeactivate    End Sub    Public Function ondragstart(ByVal pEvtObj As mshtml.IHTMLEventObj) As Boolean Implements mshtml.HTMLDocumentEvents2.ondragstart        Return True    End Function    Public Function onerrorupdate(ByVal pEvtObj As mshtml.IHTMLEventObj) As Boolean Implements mshtml.HTMLDocumentEvents2.onerrorupdate        Return True    End Function    Public Sub onfocusin(ByVal pEvtObj As mshtml.IHTMLEventObj) Implements mshtml.HTMLDocumentEvents2.onfocusin    End Sub    Public Sub onfocusout(ByVal pEvtObj As mshtml.IHTMLEventObj) Implements mshtml.HTMLDocumentEvents2.onfocusout    End Sub    Public Function onhelp(ByVal pEvtObj As mshtml.IHTMLEventObj) As Boolean Implements mshtml.HTMLDocumentEvents2.onhelp        Return True    End Function    Public Sub onkeydown(ByVal pEvtObj As mshtml.IHTMLEventObj) Implements mshtml.HTMLDocumentEvents2.onkeydown    End Sub    Public Function onkeypress(ByVal pEvtObj As mshtml.IHTMLEventObj) As Boolean Implements mshtml.HTMLDocumentEvents2.onkeypress        Return True    End Function    Public Sub onkeyup(ByVal pEvtObj As mshtml.IHTMLEventObj) Implements mshtml.HTMLDocumentEvents2.onkeyup    End Sub    Public Sub onmousedown(ByVal pEvtObj As mshtml.IHTMLEventObj) Implements mshtml.HTMLDocumentEvents2.onmousedown    End Sub    Public Sub onmousemove(ByVal pEvtObj As mshtml.IHTMLEventObj) Implements mshtml.HTMLDocumentEvents2.onmousemove    End Sub    Public Sub onmouseout(ByVal pEvtObj As mshtml.IHTMLEventObj) Implements mshtml.HTMLDocumentEvents2.onmouseout    End Sub    Public Sub onmouseover(ByVal pEvtObj As mshtml.IHTMLEventObj) Implements mshtml.HTMLDocumentEvents2.onmouseover    End Sub    Public Sub onmouseup(ByVal pEvtObj As mshtml.IHTMLEventObj) Implements mshtml.HTMLDocumentEvents2.onmouseup    End Sub    Public Function onmousewheel(ByVal pEvtObj As mshtml.IHTMLEventObj) As Boolean Implements mshtml.HTMLDocumentEvents2.onmousewheel        Return True    End Function    Public Sub onpropertychange(ByVal pEvtObj As mshtml.IHTMLEventObj) Implements mshtml.HTMLDocumentEvents2.onpropertychange    End Sub    Public Sub onreadystatechange(ByVal pEvtObj As mshtml.IHTMLEventObj) Implements mshtml.HTMLDocumentEvents2.onreadystatechange    End Sub    Public Sub onrowenter(ByVal pEvtObj As mshtml.IHTMLEventObj) Implements mshtml.HTMLDocumentEvents2.onrowenter    End Sub    Public Function onrowexit(ByVal pEvtObj As mshtml.IHTMLEventObj) As Boolean Implements mshtml.HTMLDocumentEvents2.onrowexit        Return True    End Function    Public Sub onrowsdelete(ByVal pEvtObj As mshtml.IHTMLEventObj) Implements mshtml.HTMLDocumentEvents2.onrowsdelete    End Sub    Public Sub onrowsinserted(ByVal pEvtObj As mshtml.IHTMLEventObj) Implements mshtml.HTMLDocumentEvents2.onrowsinserted    End Sub    Public Sub onselectionchange(ByVal pEvtObj As mshtml.IHTMLEventObj) Implements mshtml.HTMLDocumentEvents2.onselectionchange    End Sub    Public Function onselectstart(ByVal pEvtObj As mshtml.IHTMLEventObj) As Boolean Implements mshtml.HTMLDocumentEvents2.onselectstart        Return True    End Function    Public Function onstop(ByVal pEvtObj As mshtml.IHTMLEventObj) As Boolean Implements mshtml.HTMLDocumentEvents2.onstop        Return True    End FunctionEnd ClassPublic Class IEEvents    Implements SHDocVw.DWebBrowserEvents2    Public fm As Form1    Private icp As System.Runtime.InteropServices.UCOMIConnectionPoint    Private cookie As Integer = -1    Private m_ie As AxSHDocVw.AxWebBrowser    Public Sub New(ByRef ie As AxSHDocVw.AxWebBrowser)        ' Call QueryInterface for IConnectionPointContainer        m_ie = ie        Dim icpc As System.Runtime.InteropServices.UCOMIConnectionPointContainer = CType(ie.GetOcx(), System.Runtime.InteropServices.UCOMIConnectionPointContainer)        ' Find the connection point for the        ' DWebBrowserEvents2 source interface        Dim g As Guid = GetType(SHDocVw.DWebBrowserEvents2).GUID        icpc.FindConnectionPoint(g, icp)        'Pass a pointer to the host to the connection point        icp.Advise(Me, cookie)        ' Show the browser        ie.Visible = True        Dim oURL As Object = "http://www.microsoft.com"        Dim oEmpty As Object = ""        ie.Navigate2(oURL, oEmpty, oEmpty, oEmpty, oEmpty)    End Sub    Public Sub BeforeNavigate2(ByVal pDisp As Object, ByRef URL As Object, ByRef Flags As Object, ByRef TargetFrameName As Object, ByRef PostData As Object, ByRef Headers As Object, ByRef Cancel As Boolean) Implements SHDocVw.DWebBrowserEvents2.BeforeNavigate2    End Sub    Public Sub ClientToHostWindow(ByRef CX As Integer, ByRef CY As Integer) Implements SHDocVw.DWebBrowserEvents2.ClientToHostWindow    End Sub    Public Sub CommandStateChange(ByVal Command As Integer, ByVal Enable As Boolean) Implements SHDocVw.DWebBrowserEvents2.CommandStateChange    End Sub    Public Sub DocumentComplete(ByVal pDisp As Object, ByRef URL As Object) Implements SHDocVw.DWebBrowserEvents2.DocumentComplete        Dim doc As mshtml.HTMLDocument = CType(CType(pDisp, SHDocVw.IWebBrowser2).Document, mshtml.HTMLDocument)        Dim pConPtCon As System.Runtime.InteropServices.UCOMIConnectionPointContainer = CType(doc, System.Runtime.InteropServices.UCOMIConnectionPointContainer)        Dim guid As Guid = System.Type.GetType("mshtml.HTMLDocumentEvents2").GUID        Dim pConPt As System.Runtime.InteropServices.UCOMIConnectionPoint        pConPtCon.FindConnectionPoint(guid, pConPt)        Dim d As IEHTMLDocumentEvents = New IEHTMLDocumentEvents        pConPt.Advise(d, Form1.dwCookie2)        Dim iEvent As mshtml.HTMLDocumentEvents2_Event        iEvent = CType(doc, mshtml.HTMLDocumentEvents2_Event)        AddHandler iEvent.onclick, AddressOf ClickEventHandler        AddHandler iEvent.onmouseover, AddressOf MouseOverEventHandler    End Sub    Private Function ClickEventHandler(ByVal e As mshtml.IHTMLEventObj) As Boolean        fm.add_list(e.type + ":" + e.srcElement.tagName)        Return True    End Function    Private Sub MouseOverEventHandler(ByVal e As mshtml.IHTMLEventObj)        fm.add_list(e.type + ":" + e.srcElement.tagName)    End Sub    Public Sub DownloadBegin() Implements SHDocVw.DWebBrowserEvents2.DownloadBegin    End Sub    Public Sub DownloadComplete() Implements SHDocVw.DWebBrowserEvents2.DownloadComplete    End Sub    Public Sub FileDownload(ByRef Cancel As Boolean) Implements SHDocVw.DWebBrowserEvents2.FileDownload    End Sub    Public Sub NavigateComplete2(ByVal pDisp As Object, ByRef URL As Object) Implements SHDocVw.DWebBrowserEvents2.NavigateComplete2    End Sub    Public Sub NavigateError(ByVal pDisp As Object, ByRef URL As Object, ByRef Frame As Object, ByRef StatusCode As Object, ByRef Cancel As Boolean) Implements SHDocVw.DWebBrowserEvents2.NavigateError    End Sub    Public Sub NewWindow2(ByRef ppDisp As Object, ByRef Cancel As Boolean) Implements SHDocVw.DWebBrowserEvents2.NewWindow2    End Sub    Public Sub OnFullScreen(ByVal FullScreen As Boolean) Implements SHDocVw.DWebBrowserEvents2.OnFullScreen    End Sub    Public Sub OnMenuBar(ByVal MenuBar As Boolean) Implements SHDocVw.DWebBrowserEvents2.OnMenuBar    End Sub    Public Sub OnQuit() Implements SHDocVw.DWebBrowserEvents2.OnQuit    End Sub    Public Sub OnStatusBar(ByVal StatusBar As Boolean) Implements SHDocVw.DWebBrowserEvents2.OnStatusBar    End Sub    Public Sub OnTheaterMode(ByVal TheaterMode As Boolean) Implements SHDocVw.DWebBrowserEvents2.OnTheaterMode    End Sub    Public Sub OnToolBar(ByVal ToolBar As Boolean) Implements SHDocVw.DWebBrowserEvents2.OnToolBar    End Sub    Public Sub OnVisible(ByVal Visible As Boolean) Implements SHDocVw.DWebBrowserEvents2.OnVisible    End Sub    Public Sub PrintTemplateInstantiation(ByVal pDisp As Object) Implements SHDocVw.DWebBrowserEvents2.PrintTemplateInstantiation    End Sub    Public Sub PrintTemplateTeardown(ByVal pDisp As Object) Implements SHDocVw.DWebBrowserEvents2.PrintTemplateTeardown    End Sub    Public Sub PrivacyImpactedStateChange(ByVal bImpacted As Boolean) Implements SHDocVw.DWebBrowserEvents2.PrivacyImpactedStateChange    End Sub    Public Sub ProgressChange(ByVal Progress As Integer, ByVal ProgressMax As Integer) Implements SHDocVw.DWebBrowserEvents2.ProgressChange    End Sub    Public Sub PropertyChange(ByVal szProperty As String) Implements SHDocVw.DWebBrowserEvents2.PropertyChange    End Sub    Public Sub SetSecureLockIcon(ByVal SecureLockIcon As Integer) Implements SHDocVw.DWebBrowserEvents2.SetSecureLockIcon    End Sub    Public Sub StatusTextChange(ByVal Text As String) Implements SHDocVw.DWebBrowserEvents2.StatusTextChange    End Sub    Public Sub TitleChange(ByVal Text As String) Implements SHDocVw.DWebBrowserEvents2.TitleChange    End Sub    Public Sub UpdatePageStatus(ByVal pDisp As Object, ByRef nPage As Object, ByRef fDone As Object) Implements SHDocVw.DWebBrowserEvents2.UpdatePageStatus    End Sub    Public Sub WindowClosing(ByVal IsChildWindow As Boolean, ByRef Cancel As Boolean) Implements SHDocVw.DWebBrowserEvents2.WindowClosing    End Sub    Public Sub WindowSetHeight(ByVal Height As Integer) Implements SHDocVw.DWebBrowserEvents2.WindowSetHeight    End Sub    Public Sub WindowSetLeft(ByVal Left As Integer) Implements SHDocVw.DWebBrowserEvents2.WindowSetLeft    End Sub    Public Sub WindowSetResizable(ByVal Resizable As Boolean) Implements SHDocVw.DWebBrowserEvents2.WindowSetResizable    End Sub    Public Sub WindowSetTop(ByVal Top As Integer) Implements SHDocVw.DWebBrowserEvents2.WindowSetTop    End Sub    Public Sub WindowSetWidth(ByVal Width As Integer) Implements SHDocVw.DWebBrowserEvents2.WindowSetWidth    End SubEnd Class
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Note aggiuntive

  • Il processo è identico se si automatizza Internet Explorer. Sostituire AxWebBrowser1 con il nome della variabile locale per Internet Explorer.
  • L'esempio non considera eventuali pagine con frame. Quando si accede a un pagina con frame, è possibile che non si verifichino eventi nell'applicazione. Se richiesto dall'applicazione, aggiungere il codice per gestire eventuali pagine con frame.
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Riferimenti
Per ulteriori informazioni sul controllo WebBrowser, nonché su metodi, proprietà ed eventi esposti dal controllo WebBrowser, vedere la seguente documentazione MSDN (informazioni in lingua inglese): Per ulteriori informazioni sullo sviluppo di soluzioni basate sul Web per Microsoft Internet Explorer, visitare i seguenti siti Web Microsoft (informazioni in lingua inglese):Torna all'inizio
web browser
Proprietà

ID articolo: 311284 - Ultima revisione: 12/07/2015 08:05:17 - Revisione: 3.1

Microsoft Visual Basic .NET 2002 Standard Edition, Microsoft Visual Basic .NET 2003 Standard Edition

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