Implementation of the Content Handler MIDlets

This MIDlet suite includes two MIDlets, TextHandler and AudioHandler. Of these two MIDlets, the deceptively named TextHandler functions as the main MIDlet that can display text content or launch AudioHandler when audio content needs to be invoked.

These MIDlets deal with the following use cases:

• Handle text content in the same MIDlet

  TextHandler MIDlet handles the content type text/plain. When such a file is requested by the MIDlet, the text is displayed right away using the TextViewer class in the MIDlet.

• Invoke audio content in another MIDlet

  TextHandler does not have the ability to handle audio content, but it is set to invoke the AudioHandler MIDlet, when audio/x-wav content type is requested. The AudioHandler is then launched and it handles the audio content.

  

• Invoke native content handlers

  Apart from text/plain and audio/x-wav, this MIDlet suite does not include handlers for any additional content. So when an image file is requested in this MIDlet, the MIDlet invokes the native handler for that content type.

Each one of these use cases is demonstrated by an example. When the TextHandler MIDlet starts, there is a menu that contains three choices, each an example of one use case. The MIDlet works as described in the list above; the text is displayed in the same MIDlet, the audio is played in the invoked AudioHandler instance, and the native handler is used for the image file.

Figure 122: TextHandler main menu

These content type registration is defined in the JAD file, a portion of which is shown below. Notice the MicroEdition-Handler-# parameter that contains the classname of the MIDlet and the content type that the MIDlet is registered to handle. Another important parameter is Nok-Resource-File-Name, which is a custom JAD attribute and defined in ChoiceList class. This parameter contains a link to a text file, links.txt, which in turn contains the links to the content that is displayed in the main menu.

Another MIDlet, AudioHandler, is registered dynamically in the

MIDlet-Permissions: javax.microedition.io.Connector.http,javax.microedition.content.ContentHandler
MIDlet-1: Text Handler,/com/nokia/midp/example/jsr211/res/icon.png,com.nokia.midp.example.jsr211.texthandler.TextHandler
MicroEdition-Handler-1: com.nokia.midp.example.jsr211.texthandler.TextHandler,text/plain
MicroEdition-Handler-1-ID: com.nokia.midp.example.jsr211.texthandler.TextHandler
Nok-Resource-File-Name: /com/nokia/midp/example/jsr211/res/links.txt

The links.txt file is located in the res directory. It contains the following rows:

ReadMe - txt Help.txt (http)~http://localhost/ReadMe.txt
Audio  - wav cock.wav (http)~http://localhost/cock.wav
Image  - img nokia.png (http)~http://localhost/nokia.png

The line preceded by the ~ sign is the text shown to the user in the main menu and the URL after that the link to the actual file. In this example, the files are retrieved from the root of local web server. The server is configured on the same computer as the emulator that runs this example. If you place the files on an external web server, or use your own customized files, you need to edit this file accordingly.