8.2. Periodic Refresh in XHTML MP

HTTP refresh can be used in XHTML MP to instruct the WAP browser to refresh the current page periodically. This is a very useful function for mobile Internet browsing applications that provide real-time information. In the following XHTML MP code, the page is refreshed automatically every 15 seconds. Note that <meta http-equiv="Cache-Control" content="no-cache"/> is required in this XHTML MP example. If it is not included, the WAP browser will just display the copy of the document in the cache without connecting to the server for each refresh.


(metadataEg4.xhtml)

<?xml version="1.0"?>
<!DOCTYPE html PUBLIC "-//WAPFORUM//DTD XHTML Mobile 1.0//EN" "http://www.wapforum.org/DTD/xhtml-mobile10.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">
  <head>
    <title>XHTML MP Tutorial</title>
    <meta http-equiv="Cache-Control" content="no-cache"/>
    <meta http-equiv="refresh" content="15"/>
  </head>

  <body>
    <p>This XHTML MP page will be refreshed automatically every 15 seconds.</p>
  </body>
</html>


HTTP refresh can also be used to instruct the WAP browser to go to another URL after a certain period of time. You can make use of such feature to redirect the user to another XHTML MP page or create a slide show. The following XHTML MP example demonstrates how to redirect the user to "helloWorldEg1.xhtml" after 15 seconds.


(metadataEg5.xhtml)

<?xml version="1.0"?>
<!DOCTYPE html PUBLIC "-//WAPFORUM//DTD XHTML Mobile 1.0//EN" "http://www.wapforum.org/DTD/xhtml-mobile10.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">
  <head>
    <title>XHTML MP Tutorial</title>
    <meta http-equiv="refresh" content="15;URL=helloWorldEg1.xhtml"/>
  </head>

  <body>
    <p>Hello, you will be redirected to another XHTML MP page after 15 seconds.</p>
  </body>
</html>


Note that HTTP refresh is not supported on some WAP browsers. For example, HTTP refresh works well on Openwave Mobile Browser 6.2.2, but not on Nokia Mobile Browser 4.0, Sony Ericsson T610 and T68i mobile phone emulators.


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