Java小程序动作监听器

Question

Can anyone point me in the right direct to this? I want the actionlistener in a applet to display 1 of 3 parameters in a jlabel retreived from the html file, When the appropriate option is selected from a combo box.

Cheers

Answer 1

For a combo box you want to add an ItemListener to your combo box to handle the change. You should create some sort of controller class (just a regular class which implements ItemListener ) and add this as your listener. Then, in the itemStateChanged method, you program your logic. You probably want to give the ItemListener you create a reference to your panel so that it can make the appropriate changes.

One other note. If you're reading the HTML file on the fly when the drop down is selected, the user interface will freeze up until this operation is complete. This is because these events are fired and executed on the Event Dispatch Thread, the main thread for user interaction. To avoid this, you can either parse the HTML file ahead of time into memory or you can spawn a separate thread in the itemStateChanged event to parse the HTML file. Just remember, when you're done, to use SwingUtilities.invokeLater to get another runnable back on the Event Dispatch Thread to update the drop down. All updates to the Swing user interface must be done from within the Event Dispatch Thread.