Visual Basic 6 Black Book:Visual Basic And The Internet: Web Browsing, Email, HTTP, FTP, And DHTML
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Immediate Solutions
Creating A Web Browser
The Testing Department is calling again. They need a new Web browser program right away. What’s wrong with the old one? you ask. They say, it doesn’t display the founder’s picture. Oh, you say.

It’s easy to build a Web browser in Visual Basic—you just use the Microsoft WebBrowser control. In this and the next few topics, we’ll put together the functioning Web browser that you see in Figure 21.1. Our browser will support Back, Next, Home, Stop, and Refresh buttons, as you can see in that figure. In addition, the browser will have all the power of the Microsoft Internet Explorer (largely because it is the Internet Explorer; we use the WebBrowser control, which is the Internet Explorer in a control). To let the user navigate, we’ll include a combo box, as you see in Figure 21.1. When the user types a new URL in the combo box and presses the Enter key, we’ll navigate to that URL (and keep a record of the URLs we’ve been to in the combo box’s drop-down list).

Figure 21.1  Our Web browser.
To create our Web browser, follow these steps:


1.  Create a new standard Visual Basic project.
2.  Select the Project|Components item.
3.  Click the Controls tab in the Components dialog box.
4.  Select the Microsoft Internet Controls and Microsoft Windows Common Controls entries, and click on OK to close the Components dialog box.
5.  Add a WebBrowser control and a toolbar to the form, stretching the WebBrowser control, WebBrowser1, to fill the space under the toolbar.
6.  Add five buttons to the toolbar (right-click the toolbar, select the Properties item, click the Buttons tab, and use the Insert Button button to add the buttons).
7.  Give the buttons the same captions and Key properties: Back, Next, Home, Stop, and Refresh (for example, the button with the caption “Back” will also have its Key property set to Back so we can identify which button in the toolbar was clicked).
8.  Add a combo box, combo1, to the end of the toolbar (draw the combo box in the toolbar to make sure it’s part of the toolbar; don’t double-click to create a combo box and then move it to the toolbar).

That sets up the Web browser—but how do we work with it in code? We’ll take a look at that in the next few topics.

Specifying URLs In A Web Browser
Now that you’ve set up the controls we’ll need in a Web browser (see the previous topic), how do you let the user navigate?

You use the WebBrowser control’s Navigate method. Let’s see this at work. For example, when our Web browser first loads, we can navigate to the Microsoft Web page this way (note that you can specify URLs with or without the “http://” part in the Internet Explorer, and although we omit it here, you can include that prefix if you prefer):


Private Sub Form_Load()
WebBrowser1.Navigate "www.microsoft.com"
...
End Sub


We also want the user to be able to navigate to a new URL, and that’s usually done with a combo box like the one we added to our Web browser in the previous topic, combo1. We start working with combo1 by displaying the present URL and adding it to the combo box’s drop-down list:


Private Sub Form_Load()
WebBrowser1.Navigate "www.microsoft.com"
Combo1.Text = "www.microsoft.com"
Combo1.AddItem Combo1.Text
End Sub


Users can select past URLs from the combo box’s drop-down list. When they do select a URL that way, a Click event is generated, and we can navigate to the newly selected URL this way:


Private Sub Combo1_Click()
WebBrowser1.Navigate Combo1.Text
End Sub


In addition, users can type a new URL into the combo box and press Enter, just as they can in commercial browsers. When they press Enter, we can navigate to the new URL simply by calling the Combo1_Click event handler directly from the KeyPress event handler:


Private Sub Combo1_KeyPress(KeyAscii As Integer)
If KeyAscii = vbKeyReturn Then
Combo1_Click
End If
End Sub


Finally, when the downloading process is complete, the WebBrowser control fires a DownloadComplete event, and we can display the present URL in the browser’s title bar, just as any commercial browser might. To do that, we get the browser’s present URL from its LocationName property:


Private Sub WebBrowser1_DownloadComplete()
Me.Caption = WebBrowser1.LocationName
...
End Sub


In addition, we can add that URL to the top of the combo box’s list this way:



Private Sub WebBrowser1_DownloadComplete()
Me.Caption = WebBrowser1.LocationName
Combo1.AddItem WebBrowser1.LocationURL, 0
End Sub


And that’s it—now the user can navigate around using the combo box. However, we have yet to make all the buttons, such as Back, Forward, and Home, active, and we’ll do that in the next two topics. The code for the browser, browser.frm version 1 (version 2, which is included on the accompanying CD-ROM, will include support for the browser buttons), appears in Listing 21.1.


TIP:  In our example, we made the Web browser navigate to the Microsoft home page when the browser is first opened. However, you can make the browser start with the user’s home page (as recorded by the Internet Explorer) with the browser control’s GoHome method.





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