To Limit the Number of Choices in TList

We all know that TList in TWaver Java inherits from JList in Swing, so it is quite easy for us to control the selection mode, such as excusive choice, multiple choices and so on. But I will introduce to you in this article how to specify the number of choices available. Life involves choices constantly. Therefore, we have to make choices discreetly, whether the method SelectionModel of TList or way of life.

In actual projects, we often need to limit the number of the choices available in a list. The key may be the simplest one mentioned in our website: the method SelectionModel of DataBox. When the number of choices has surpassed the specified one, the earliest choices will be deleted.

box.getSelectionModel().addDataBoxSelectionListener(new DataBoxSelectionListener() {
    @Override
    public void selectionChanged(DataBoxSelectionEvent e) {
        if (e.getBoxSelectionModel().size() > max)
            e.getBoxSelectionModel().firstElement().setSelected(false);
        }
    }
});

We can set the property max. If max=1, then it becomes an exclusive selection.
In the following, a simple example has been made according to the above way: making a simple order list. There must be some similar scenarios in systems you have made: letting your users choose the specified number of data in list.

package test;

import java.awt.*;
import java.awt.event.*;
import java.util.*;

import javax.swing.*;

import twaver.*;
import twaver.list.*;

public class TestFrame extends JFrame {
    public TestFrame() {
        UIManager.put("Label.font", new Font("Dialog", Font.BOLD, 12));
        UIManager.put("OptionPane.font", new Font("Dialog", Font.BOLD, 12));
        this.setTitle("TWaver's menu orderer");
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.setSize(700, 350);
        TWaverUtil.centerWindow(this);
        JPanel optionPane = new JPanel(new FlowLayout(FlowLayout.CENTER, 0, 120));
        final JComboBox cbMax = new JComboBox();
        for (int i = 1; i < 6; i++) {
            cbMax.addItem(i);
        }
        optionPane.add(new JLabel("At most you could order"));
        optionPane.add(cbMax);
        optionPane.add(new JLabel("dishes.    "));
        optionPane.add(new JLabel("The dishes you have ordered:"));
        final JLabel lbOptions = new JLabel("          ");
        optionPane.add(lbOptions);
        JButton btnOption = new JButton("order");
        optionPane.add(btnOption);
        btnOption.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent arg0) {
                ArrayList<String> options = pickOption((Integer) cbMax.getSelectedItem());
                String text = "";
                for (String option : options) {
                    text += option + "  ";
                }
                lbOptions.setText(text);
            }
        });
        this.getContentPane().add(optionPane, BorderLayout.CENTER);
    }

    private ArrayList<String> pickOption(final int max) {
        String[] options = {
                "double-cooked pork slices",
                "Kung Pao Chicken",
                "Sauteed Shredded Pork with Sweet - Bean Sauce",
                "Braised chicken giblets",
                "Braised large intestine",
                "green pepper and scrambled eggs",
                "stir-fried eggs with tomato",
        };

        TDataBox box = new TDataBox();
        for (String option : options) {
            ResizableNode node = new ResizableNode();
            node.setName(option);
            box.addElement(node);
        }
        box.getSelectionModel().addDataBoxSelectionListener(new DataBoxSelectionListener() {
            @Override
            public void selectionChanged(DataBoxSelectionEvent e) {
                if (e.getBoxSelectionModel().size() > max) {
                    e.getBoxSelectionModel().firstElement().setSelected(false);
                }
            }
        });
        TList list = new TList(box);
        list.setTListSelectionMode(TList.CHECK_SELECTION);
        list.setIconVisible(false);
        JScrollPane scroll = new JScrollPane(list);
        Object[] message = new Object[] { "What would you like? Notice: You could order at most " + max + " dishes", scroll };
        int answer = JOptionPane.showConfirmDialog(this, message, "order", JOptionPane.OK_CANCEL_OPTION);
        ArrayList<String> result = new ArrayList<String>();
        if (answer == JOptionPane.OK_OPTION) {
            Iterator it = box.getSelectionModel().selection();
            while (it.hasNext()) {
                result.add(((Element) it.next()).getName());
            }
        }
        return result;
    }

    public static void main(String[] args) throws Exception {
        UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
        TestFrame ui = new TestFrame();
        ui.setVisible(true);
    }
}