Installing ActionListeners

The ActionListener instance to receive ActionEvents in the program example of the previous section is the class WombatEventHandlingExample itself. This is defined during the class declaration by the argument "implements ActionListener". To satisfy the requirements of an ActionListener instance, the method onActionEvent(ActionEvent event) has to be implemented. The following sections were taken from the source code listing and show the relevant segments for successfully installing an ActionListener.

    ...
    16     public class WombatEventHandlingExample
    17                  extends Frame implements ActionListener {
    ...
    31         // add the ActionListener
    32         b1.setActionListener(this);
    33         button_right.setActionListener(this);
    ...
    52       public void onActionEvent(ActionEvent event) {
    ...

For onActionEvents to be triggerd by both Buttons, we pass a pointer to the class instance by using Button.setActionListener(this) and therewith register the ActionListener. A pointer to any other class that implements the interface ActionListener will be acceptable as well.