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| ==Progress Listeners==
| | Moved to [http://developer.mozilla.org/en/docs/Code_snippets:Progress_Listeners MDC]. |
| Progress Listeners allow extensions to be notified of events assosiated with documents loading in the browser and with tab switching events. Progress Listeners implement the [http://www.xulplanet.com/references/xpcomref/ifaces/nsIWebProgressListener.html nsIWebProgressListener] interface.
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| Note that if you just want to execute your code each time a page loads, you can use an [[Dev : Extensions : Example Code : On Tab Load|an easier method]].
| | [[Category:Redirects]] |
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| ==Example==
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| <ol><li>Create an object which implements nsIWebProgressListener:
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| <pre>const STATE_START = Components.interfaces.nsIWebProgressListener.STATE_START;
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| const STATE_STOP = Components.interfaces.nsIWebProgressListener.STATE_STOP;
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| var myListener =
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| {
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| QueryInterface: function(aIID)
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| {
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| if (aIID.equals(Components.interfaces.nsIWebProgressListener) ||
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| aIID.equals(Components.interfaces.nsISupportsWeakReference) ||
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| aIID.equals(Components.interfaces.nsISupports))
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| return this;
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| throw Components.results.NS_NOINTERFACE;
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| },
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| onStateChange: function(aProgress, aRequest, aFlag, aStatus)
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| {
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| if(aFlag & STATE_START)
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| {
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| // This fires when the load event is initiated
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| }
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| if(aFlag & STATE_STOP)
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| {
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| // This fires when the load finishes
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| }
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| return 0;
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| },
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| onLocationChange: function(aProgress, aRequest, aURI)
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| {
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| // This fires when the location bar changes i.e load event is confirmed
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| // or when the user switches tabs
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| return 0;
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| },
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| // For definitions of the remaining functions see XulPlanet.com
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| onProgressChange: function() {return 0;},
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| onStatusChange: function() {return 0;},
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| onSecurityChange: function() {return 0;},
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| onLinkIconAvailable: function() {return 0;}
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| }</pre>
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| </li>
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| <li>Attach the progress listener to a <browser> or a <tabbrowser> element, e.g. for Firefox put the following code in a ''load'' listener of a main window:
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| <pre>const NOTIFY_STATE_DOCUMENT = Components.interfaces.nsIWebProgress.NOTIFY_STATE_DOCUMENT;
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| window.getBrowser().addProgressListener(myListener, NOTIFY_STATE_DOCUMENT);</pre>
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| The second argument is a [http://www.xulplanet.com/references/xpcomref/comps/c_appshellcomponentbrowserstatusfilter1.html status filter] which determines the type of events that will be recieved.
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| </li>
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| </ol>
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| Remember to change ''myListener'' to an [[Dev : Javascript coding guidelines|unique identifier]].
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