UI ceation discussion with a personal example

[Ekhard Aldric]

I was used to create 90% of the UI dynamically, removing and rebuilding everything inside the frame as needed on the fly, but recently people have advised me to not do it like that. So, on my current project I am trying to have everything already created as the program launches.
The following method is called inside initcomponents() to create one of the panels inside my frame. As you can see, the panel has a JList referencing custom objects; an area with CardLayout storing a card with components for each item from the JList; and a JButton.
I tried to make the code short, but probably failed, sorry.

private void criaInterfaceH(Object o) {
        JPanel areaLista = new JPanel();
        JPanel geral2 = new JPanel();
         JPanel areaBotoes = new JPanel();
         JPanel areaHistorico = new JPanel();
          JPanel areaParaScrollH = new JPanel();
          JPanel subAreaEntradas = new JPanel();
        
        GridLayout gridLay = new GridLayout(0, 2, 5, 10);
        
        geral2.setLayout(new BorderLayout());
        areaBotoes.setLayout(gridLay);
        areaHistorico.setLayout(new BorderLayout());
        areaLista.setLayout(new BorderLayout());
        subAreaEntradas.setLayout(new CardLayout());
        areaParaScrollH.setLayout(new BorderLayout());
        
        historicoCli.setLayout(new GridLayout(2, 0, 5, 10));                 //this is a jpanel, it stores all components created by this method
        
        DefaultListModel listModel = new DefaultListModel();               //setting the list...
        if(o.getClass() == new Cliente().getClass()) {
            if(sg2s.getC()!=null) {
                for(Cliente c : sg2s.getC()) {                                       //Cliente is a custom class
                    listModel.addElement(c);
                }
            }
        }
        
        final JList list = new JList(listModel);                                     //still setting the list...
        
        list.setLayoutOrientation(JList.VERTICAL);
        list.setVisible(true);
        list.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
        JScrollPane scroll = new JScrollPane(list);
                                                                                                        //setting the panels...
        historicoCli.add(areaLista);
        historicoCli.add(geral2);

        areaLista.add(scroll, BorderLayout.CENTER);
        
        geral2.add(areaBotoes, BorderLayout.NORTH);
        geral2.add(areaHistorico, BorderLayout.CENTER);
        
        novo = new JButton("Novo");

        final List jt = new ArrayList<>();
        
        subAreaEntradas.add(new JPanel(), "0");                    //adding an empty panel to be the initial card
        
        //the next block creates jlabels and jtextareas with data from custom objects and put them on cards
        ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////
        if(o.getClass() == new Cliente().getClass()) {
            for (Cliente c : sg2s.getC()) {
                JPanel p = new JPanel();
                p.setLayout(new GridLayout(0, 2));
                for(Historico h : c.getHistorico()) {
                    DateFormat date = new SimpleDateFormat("dd/MM/yyyy - HH:mm:ss");
                    p.add(new JLabel(date.format(h.getData())));
                    JTextArea jta = new JTextArea(h.getTexto());
                    Border b = BorderFactory.createLineBorder(Color.BLACK);
                    jta.setBorder(b);
                    jta.setLineWrap(true);
                    jta.setEditable(false);
                    jta.setBackground(Color.LIGHT_GRAY);
                    p.add(jta);
                }
                subAreaEntradas.add(p, c.getCnpj());
            }
        }
        //the next block swaps cards to reflect the item selected on the jlist
        /////////////////////////////////////////////////////////////////////////////
        CardLayout card = (CardLayout) subAreaEntradas.getLayout();
        list.addListSelectionListener(new ListSelectionListener() {
            @Override
            public void valueChanged(ListSelectionEvent lse) {
                int i = list.getSelectedIndex();
                if (i != -1) {
                    card.show(subAreaEntradas, sg2s.getC().get(i).getCnpj());
                    subAreaEntradas.revalidate();
                    indexxx = i;                                                                      //just a reference
                }
            }
        });
        //just final settings
        novo.setName("novoHCli");
        novo.addActionListener(this);

        areaBotoes.add(novo);

        JScrollPane scrollHist = new JScrollPane(subAreaEntradas);

        areaHistorico.add(new JLabel("Historico:"), BorderLayout.NORTH);
        areaParaScrollH.add(scrollHist, BorderLayout.CENTER);
        areaHistorico.add(paraParaScrollH, BorderLayout.CENTER);
        list.setCellRenderer(new CellRenderer());
        areaDados.setName(o.getClass().toString());
    }

Next is the JButton actionlistener.

@Override
    public void actionPerformed(ActionEvent e) {
        JButton jb = (JButton) e.getSource();
        switch(jb.getName()) {
            case "novoHCli": {
                textANovo = new JTextArea();
                int resposta = JOptionPane.showConfirmDialog(historicoCli, textANovo, "Novo Historico", JOptionPane.OK_CANCEL_OPTION, JOptionPane.PLAIN_MESSAGE);
                
                if(resposta == JOptionPane.OK_OPTION) {
                    Historico hist = new Historico(textANovo.getText());
                    sg2s.getC().get(indexxx).setHistorico(hist);

                   //the following 4 lines will be discussed next
                   //////////////////////////////////////////////////
                    historicoCli.removeAll();
                    criaInterfaceH(new Cliente());
                    historicoCli.revalidate();
                    historicoCli.repaint();
                }
            }
        }
    }

As you can see, an optionPane gets input from the user and puts it inside an object, then I immediatly update the UI to show the respective card with the new components for the recently acquired input.
At first I tried to call just revalidate and repaint on the parent panel hoping that it would work, but nothing changed. What did work was also calling removeAll and the entire method to dynamically recreate the whole thing, which is exactly what I was advised against.
Was the advice wrong? Is it just this particular case? Was there another way of solving my problem?

[Rob Camick]

Not really sure I understand the question.

But generally what I think people are suggestion is that you create a panel to display the detail information of a client. For example maybe you have data like firstName, lastName, address etc. Then when you prompt for a client you get the client number and then just refresh the data on the panel. So you do something like:

firstName.setText(...);
lastName.setText(...);

So there is no need to recreate a panel just because you change the client you want to display information for.

Maybe there are times when you have data in a JList or JTable and you need to change the data. Again, there is no need to recreate the panel of the component. Instead you change the model of the component:

list.setModel(...);
table.setModel(...);

So there is no need to remove or create new components.

The other part of your question deals with the CardLayout. A CardLayout is used to display different panels in any order. So again the panels are created with components at design time. Then at run time you just populate the data as required. The Swing tutorial on How to Use Card Layout shows how to initially create panels and then swap tem as required.

There is no need for methods like removeAll().

Of course there are times when you need to dynamically create components so you have to look at each situation and decide which is the best approach to use.