java - 单击时重复的选定值

Question

我对列表中的 getSelection 值的代码有些怀疑。当我使用鼠标时，得到的值是重复的，当我使用我的键盘时不是：

import javax.swing.BorderFactory;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.JScrollPane;
import javax.swing.ListSelectionModel;

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JPanel;
import javax.swing.event.ListSelectionEvent;
import javax.swing.event.ListSelectionListener;

import br.com.operacao.Paga;

    public class Tela extends JPanel implements ActionListener{

        private static final long serialVersionUID = 1L;
        JLabel image;
      public Tela() {

        this.setLayout(new GridBagLayout());


        GridBagConstraints c = new GridBagConstraints();
        c.fill = GridBagConstraints.BOTH; 
        c.insets = new Insets(5, 5, 5, 5); 


        String labels[] = { "Coca-Cola", "Fanta Laranja", "Fanta-Uva", 
         "Sprite"};
        final JList<String> list = new JList<String>(labels);
        list.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
        list.setBorder(BorderFactory.createEmptyBorder(3, 3, 3, 3));
        list.setSelectedIndex(0);


        JScrollPane pane = new JScrollPane();
        pane.getViewport().add(list);
        JPanel firstpanel = new JPanel();
        firstpanel.add(pane);
        firstpanel.setBackground(Color.BLACK);
        c.gridx = 0;
        c.gridy = 0;
        c.gridwidth = 1;
        c.gridheight = 1;
        c.weightx = c.weighty = 0.0;
        this.add(firstpanel,c);

        image = new JLabel();
        image.setFont(image.getFont().deriveFont(Font.ITALIC));
        image.setHorizontalAlignment(JLabel.CENTER);
        updateLabel(labels[list.getSelectedIndex()]);
        image.setBorder(BorderFactory.createEmptyBorder(10,0,0,0));

        c.gridx = 1;
        c.gridy = 0;
        c.gridwidth = 1;
        c.gridheight = 1;
        c.weightx = c.weighty = 0.0;
        this.add(image, c);

        JScrollPane js = new JScrollPane();
        js.setPreferredSize(new Dimension(110,110));
        c.gridx = 0;
        c.gridy = 2;
        c.gridwidth = 3;
        c.gridheight = 1;
        this.add(js, c);

        final JButton comprar = new JButton("Comprar");
        comprar.setEnabled(false);
        list.addListSelectionListener(new ListSelectionListener() {

            public void valueChanged(ListSelectionEvent e) {
                int selections[] = list.getSelectedIndices();
                //String selectedValue = list.getSelectedValue();
                Object selectionValues[] = list.getSelectedValues();
                for (int i = 0, n = selections.length; i < n; i++) {
                    if (i == 0) {
               System.out.println("Value" + selectionValues[i] );
                    }}
               comprar.setEnabled(true);

            }
        });
        c.gridx = 0;
        c.gridy = 4;
        c.gridwidth = 1;
        c.gridheight = 1;
        this.add(comprar, c);
        comprar.addActionListener(new Paga());

        final JButton confirma = new JButton("Confirmar");
        confirma.setEnabled(false);
        c.gridx = 1;
        c.gridy = 4;
        c.gridwidth = 1;
        c.gridheight = 1;
        this.add(confirma,c);
        /*
        c.gridx = 2;
        c.gridy = 4;
        c.gridwidth = 1;
        c.gridheight = 1;
        this.add(new JButton("Button #6"), c);
        */

      }

    @Override
      public void actionPerformed(ActionEvent e) {

            //String selectedValue = list.getSelectedValue();
            JList<String> jl = (JList<String>)e.getSource(); //some doubt here to display the correct images when selected item from list?
            String refriName = jl.getSelectedValue();
            updateLabel(refriName);
        }
        protected void updateLabel(String name) {
            ImageIcon icon = createImageIcon("assets/" + name + ".jpg");
            image.setIcon(icon);
            //image.setToolTipText("A drawing of a " + name.toLowerCase());
            if (icon != null) {
                image.setText(null);
            } else {
                image.setText("Image not found");
            }
        }

        /** Returns an ImageIcon, or null if the path was invalid.*/
        protected static ImageIcon createImageIcon(String path) {
            java.net.URL imgURL = Tela.class.getResource(path);
            if (imgURL != null) {
                return new ImageIcon(imgURL);
            } else {
                System.err.println("Couldn't find file: " + path);
                return null;
            }
        }

    }

这是我的主要课程：

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;

import javax.swing.JFrame;
import javax.swing.JOptionPane;

import br.com.operacao.Tela;
public class Executa {


    public static void main(String[] args) {
        Tela display = new Tela();

    JFrame f = new JFrame();
    f.addWindowListener(new WindowAdapter() {
      public void windowClosing(WindowEvent e) {
        System.exit(0);
      }
    });

    f.setContentPane(new Tela());
    f.setTitle("Maquina de Refrigerante");
    f.pack();
    f.setDefaultCloseOperation(f.EXIT_ON_CLOSE);
    f.setVisible(true);
    f.setSize(280, 380);
  }
}   

那么，我的 actionListener 有什么问题，而且我的图像也有一些问题，无法显示，但为什么？