如何從其他JLIst動態更新JList？

我有兩個Jlist（blockList和layerList），我試圖更新blockList的值，當我點擊layerList中的一個不同的項目。由於某種原因，它不起作用。這是我的代碼：如何從其他JLIst動態更新JList？

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);

}

當我選擇文件layersList的選定索引是0，這意味着所選擇的項目爲「層1」和塊列表被顯示正確的數組。但是當我按下項目「Layer 2」時，它不會更新。

任何想法爲什麼？提前謝謝！

來源

2014-02-24 chikito1990

的問題是，你正在創建一個新的JList，並設定了數據：

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

新的名單還沒有被添加到容器，所以它是不可見的任何地方。您應該簡單地更改已有的JList的數據。

來源

2014-02-24 09:28:02 kiheru

謝謝！我現在覺得很愚蠢，因爲它很明顯:)謝謝你的幫助！ – chikito1990

@ chikito1990不客氣。有時很難發現明顯的錯誤，因爲作爲我們對他們是盲目的。 – kiheru

@ chikito1990：原因是你在valueChanged()實例blockList這就是爲什麼每一個將其重新實例化，而你應該有一個實例化和那個時候你應該在構造函數實例blockList。

public MainPage() { 
... 

blockList = new JList(); 

... 

}

試試這個，它會工作。

來源

2014-02-24 09:37:51

如何從其他JLIst動態更新JList？

回答

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