Question

So I am trying to get my GUI to work. When I run the code below, it does nothing, and I’m sure I’m probably just doing something dumb, but I am completely stuck…

public void actionPerformed(ActionEvent e){
    UI.getInstance().sS++;

    if((UI.getInstance().sS %2) != 0){
        UI.getInstance().startStop.setName("STOP");
        UI.getInstance().change.setEnabled(false);
    }else if(UI.getInstance().sS%2 == 0){
        UI.getInstance().startStop.setName("START");
        UI.getInstance().change.setEnabled(true);
    }


}

public void setStartListener(StartHandler e){
    this.startStop.addActionListener(e);
}

sS is an int that increments every time the button startStop is clicked. change is also a button.

Answer 1

Here’s an example that shows a different approach to managing a Start/Stop button. It uses an instance of javax.swing.Timer to pace updates. Encapsulating the control button and display label may simplify maintenance. This variation illustrates adding a third command to pause updates.

private static final String Start = "Start";
private static final String Stop = "Stop";
…
private static void create() {
    …
    final JButton button = new JButton(Stop);
    button.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            String cmd = e.getActionCommand();
            if (Stop.equals(cmd)) {
                jtl.stop();
                button.setText(Start);
            } else {
                jtl.start();
                button.setText(Stop);
            }

        }
    });
    …
}

More generally, use Action to encapsulate functionality for use elsewhere in your program. This example "exports several actions that make it easy to use them in a control panel."