Question

I want to display program flow to the user in form of comments in a JTextField. Only the last message (“complete”) is shown. How can I make each message appear when I call setText()?

private class CalculateButtonHandler implements ActionListener {
    public void actionPerformed(ActionEvent e) {            
        String keyValue = keywordTF.getText();
        currentTF.setText("calling 1");
        methodCall1();
        currentTF.setText("calling 2");
        methodCall2();
        currentTF.setText("calling 3");
        methodCall3();
        currentTF.setText("complete");
    }
}

Answer 1

The reason is that the EDT has no time to repaint the text field since your methodCall* method is running on the EDT.

If you want to show progress of a heavy task you should perform the heavy work on a worker thread and update the UI on the EDT. Typically this is achieved by using a SwingWorker or using SwingUtilities#invokeLater from the worker thread.

The ‘Concurrency in Swing’ tutorial contains more information