Question

我有两个Jlist（blockList和layerList），当我点击layerList中的另一个项目时，我正在尝试更新blockList的值。由于某种原因，它无法正常工作。这是我的代码：

  JButton openButton, saveButton;
  JTextArea log;
  JFileChooser fc;
  JList layerList;
  JList blockList;
  DefaultListModel model;
  String[] layers = {"Layer 1", "Layer 2", "Layer 3", "Layer 4", "Layer 5"};
  String[] blocksListMenu1 = {"Block 1", "Block 2", "Block 3", "Block 4", "Block 5"};
  String[] blocksListMenu2 = {"Block 6", "Block 7", "Block 8", "Block 9", "Block 10"};
  String[] blocksListMenu3 = {"Block 11", "Block 12", "Block 13", "Block 14", "Block 15"};
  String[] blocksListMenu4 = {"Block 16", "Block 17", "Block 18", "Block 19", "Block 20"};
  String[] blocksListMenu5 = {"Block 21", "Block 22", "Block 23", "Block 24", "Block 25"};

public MainPage() {
super(new BorderLayout());  

JPanel content = new JPanel(new BorderLayout());

final JPanel layerPanel = new JPanel(new BorderLayout());
layerPanel.setBackground(Color.WHITE);
layerPanel.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));

JLabel layerLabel = new JLabel("Layers:");
layerList = new JList(layers);
layerList.setSelectedIndex(0);
layerList.addListSelectionListener(new ListSelectionListener() {
     @Override
     public void valueChanged(ListSelectionEvent e) {
        blockList = new JList();
        String selectedLayer = layers[layerList.getSelectedIndex()];
        if(selectedLayer.equals("Layer 1"))
             blockList.setListData(blocksListMenu1);
        else if(selectedLayer.equals("Layer 2"))
             blockList.setListData(blocksListMenu2);
        else if(selectedLayer.equals("Layer 3"))
             blockList.setListData(blocksListMenu3);
        else if(selectedLayer.equals("Layer 4"))
             blockList.setListData(blocksListMenu4);
        else if(selectedLayer.equals("Layer 5"))
             blockList.setListData(blocksListMenu5);;
    }
});

layerPanel.add(layerLabel, BorderLayout.PAGE_START);
layerPanel.add(layerList, BorderLayout.CENTER);
layerPanel.setVisible(false);

//--------------------------------------------------------------------------

final JPanel blockPanel = new JPanel(new BorderLayout());
blockPanel.setBackground(Color.WHITE);
blockPanel.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));

JLabel blockLabel = new JLabel("Blcoks:");
blockList = new JList(blocksListMenu1);
blockPanel.add(blockLabel, BorderLayout.PAGE_START);
blockPanel.add(blockList, BorderLayout.CENTER);
blockPanel.setVisible(false);

final JTextField path = new JTextField();
JButton button = new JButton("Select File");
button.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent ae) {
      JFileChooser fileChooser = new JFileChooser();
      FileNameExtensionFilter filter = new FileNameExtensionFilter("DXF Files", "dxf");
      fileChooser.setFileFilter(filter);
      int returnValue = fileChooser.showOpenDialog(null);
      if (returnValue == JFileChooser.APPROVE_OPTION) {
        File selectedFile = fileChooser.getSelectedFile();
        System.out.println(selectedFile.getName());
        path.setText(selectedFile.getPath());
        layerPanel.setVisible(true);
        blockPanel.setVisible(true);
      }
    }
});    

content.add(path, BorderLayout.CENTER);
content.add(button, BorderLayout.LINE_END);
content.setBorder(BorderFactory.createEmptyBorder(7, 7, 7, 7));
add(content, BorderLayout.PAGE_START);
add(layerPanel, BorderLayout.LINE_START);
add(blockPanel, BorderLayout.LINE_END);

}

当我选择文件时，所选的layersList索引为0，这意味着所选项目为“第1层”，并且blockList显示正确的数组。但是，当我按“第2层”项时，它没有更新。

任何想法为什么？提前谢谢！

Answer 1

问题是您正在创建新的JList，并设置该数据：

public void valueChanged(ListSelectionEvent e) {
    blockList = new JList();
    ...

新列表尚未添加到容器中，因此无法在任何位置显示。您只需更改已存在的JList的数据。

Answer 2

@ chikito1990：原因是你在blockList中实例化valueChanged()这就是为什么每次重新实例化时你应该有一个实例化的原因，为此你应该在blockList中实例化public MainPage() { ... blockList = new JList(); ... }构造

{{1}}

试试这个，它会起作用。

如何从另一个JLIst动态更新JList？

2 个答案: