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Build Your Own Windows Mobile RSS Reader : Page 2

Phones using the Windows Mobile 6 Standard do not have touch screens, which poses certain challenges when developing applications to run on them. Learn how to develop with these challenges in mind as you build a useful RSS Reader application for these devices.


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Creating the Helper Methods
When RSS feeds are being downloaded, you would display a message on the screen so that users know that the application is busy (see Figure 4).

Figure 4. Operation Status: The device displays a message informing the user of the operation's status.

For this purpose, you can improvise with the aid of the Panel and Label controls.



Define the CreatePanel() function so that you can dynamically create the message panel using a couple of Panel controls and a Label control, as shown in Listing 1.

Next, define the IsConnected() function to test whether the user is connected to the Internet:

'---check whether you are connected to the Internet--- Private Function IsConnected() As Boolean Try Dim hostName As String = Dns.GetHostName() Dim curhost As IPHostEntry = Dns.GetHostEntry(hostName) Return curhost.AddressList(0).ToString() <> _ IPAddress.Loopback.ToString() Catch ex As Exception Return False End Try End Function

Basically, you compare the IP address of the device with that of localhost (127.0.0.1). As long as the device's IP address is not 127.0.0.1, it is assumed that there is Internet connectivity (as shown in Listing 2).

Each post title and its description are separated by the ASCII character 3 and each posting is separated with the ASCII character 12. Notice that after the XML feed for an URL is downloaded, it is saved onto storage. This is to ensure that the application continues to work in offline mode (i.e. when user disconnects from the Internet). The URL of the feed is used as the filename, minus all the special characters inside within the URL, with the ".xml" extension appended. To strip off all the special characters in the URL, define the RemoveSpecialChars() function as follows:

Figure 5. Adding Posts: Adding each post to the TreeView control.

'---removes special chars from an URL string--- Private Function RemoveSpecialChars(ByVal str As String) As String Dim NewString As String = String.Empty Dim reg As Regex = New Regex("[A-Z]|[a-z]") Dim coll As MatchCollection = reg.Matches(str) For i As Integer = 0 To coll.Count - 1 NewString = NewString + coll(i).Value Next Return NewString End Function

Next, define the SubscribeFeed() function to subscribe to a feed and then add each individual post to the TreeView control (see Figure 5).

Next, for each node representing a feed, the Text property is set to the feed's title and its URL is stored in the Tag property of the node. For each node representing a posting, the Text property is set to the posting's title and its description is stored in the Tag property (see Listing 3).



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