Google Maps Interface (JavaScript)

Google Maps uses JavaScript and planOfile uses Java. Java and JavaScript can communicate, but different browser/platform combinations give varying success, depending on the approach used. The following paragraphs describe what was found to work.

JavaScript can call a Java applet function without problem as long as it passes primitive types or strings as parameters. Sharing objects between Java and JavaScript doesn't seem to work on all platforms; which turns out not to be required in practice anyway.

Mouse clicks on the Google Map are mostly handled by the Java applet. The JavaScript event handler calls a Java applet function which handles the event. The Java applet function generally returns a string containing the JavaScript commands that are eval'd by the JavaScript after calling the applet function. This is a quite effective way of binding JavaScript events to Java applet functionality.

The web page also run a periodic (half second) poll of the Java applet to obtain the latest positions and other information to be displayed on the Google Map. There are a lot of calculations required to obtain these positions and doing this in Java seems to work quickly and without the memory management issues that you find when using JavaScript. The result of the polled Java applet function is a string which contains JavaScript function calls to be eval'd to update the Google Map to update marker and other positions on the map.

It is possible to use JSObject to eval() JavaScript commands directly from the Java applet. But for the moment, all interaction with Google Maps does not require this and can be handled in response to Google Map and periodic events.