A while back, Mitchell wrote an article about MoreOver.com and their XML news sources (which are free for developers using them for non-profit purposes). Today, Mitchell takes that idea one step further and creates an ActiveX component that uses the MoreOver.com news feeds in a similar way. The component uses the XMLHTTP library and the MSXML parser to retrieve and process the news. This article also acts as a good introduction to ActiveX controls if you have never created one before.
A Real-Time ActiveX News Control - Displaying the link (Page 4 of 6 )
When the user moves their mouse over a label containing a headline, we want to make it look like an actual link. We do this by setting the colour of the links text to blue, underlining it, and setting the cursor to the hand icon.
As mentioned earlier, the hand icon is included with the support material at the end of this article. Our ActiveX control contains a picture control named "picHand". The Picture property of "picHand" is set to the location of the hand cursor file. Then, whenever the MouseMove event is triggered for a label, we set its icon to the hand, like this:
lblLink1.MousePointer = 99
lblLink1.MouseIcon = picHand.Picture
Here's how the hand looks when it is displayed over a label:
When the user actually clicks on a link, the JumpToNews function is called, with the index of the news item clicked:
We create the JumpToNews function as a privately declared sub-routine, like this:
Private Sub JumpToNews(index As Integer)
Our JumpToNews function will actually display a new browser window. The URL of that browser window will be the URL retrieved from the arrLinks array. To actually open a browser window, we use the ShellExecute API call. The ShellExecute function is privately declared in the general declarations section of our ActiveX control, and looks like this:
Private Declare Function ShellExecute Lib "shell32.dll" Alias "ShellExecuteA" (ByVal hwnd As Long, ByVal lpOperation As String, ByVal lpFile As String, ByVal lpParameters As String, ByVal lpDirectory As String, ByVal nShowCmd As Long) As Long
The ShellExecute API call allows us to execute any program (or file) directly from our application. It takes six arguments, and returns a long integer value. Each of these six arguments are described below:
hWnd: Handle to parent window.
lpOperation: String that specifies the operation to perform
lpFile: Filename to execute
lpParameters: String that specifies the executable-file parameters
lpDirectory: String that specifies the default directory
nShowCmd: Specifies how the application is shown when itís opened. Should be zero if lpFile is a document file.
Our call to the ShellExecute API function looks like this:
This will launch a new browser window. The URL of the browser window is retrieved from the arrLinks array, based on which link was clicked.
And that's all there is to it! A couple of controls, some XML objects and an API call. Now that I've talked about the code involved in creating our ActiveX control, I will describe how to compile it and how to use it in both a web page, and a VB application.