如何使用不同類的信息更新JPanel？

Question

我創建了下面的示例源代碼，並且想知道我需要做什麼來更新我的JPanel，並使用JLabel來更新我的JPanel，該JLabel具有位於JTable中單擊的行中的信息。

我還想指出，這僅僅是一個簡單的例子，因爲我已經通過一些SO成員在這裏改進了示例代碼。所以我張貼這種裸例子，以此來學習

SwingTesting（主）

public class SwingTesting { 

    private final JFrame frame; 
    private final TablePane tablePane; 
    private final JSplitPane splitPane; 
    private final JPanel infoPanel; 
    private final JLabel infoLabel; 

    public SwingTesting() { 
     tablePane = new TablePane(); 
     infoPanel = new JPanel(); 
     frame = new JFrame(); 

     infoLabel = new JLabel(); //this is the panel i want to add the label to 
     infoPanel.add(infoLabel); 

     splitPane = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT, tablePane, infoPanel); 

     frame.add(splitPane); 
     frame.pack(); 
     frame.setVisible(true); 
    } 

    public static void main(String[] args) { 
     SwingUtilities.invokeLater(new Runnable() { 
      public void run() { 
       new SwingTesting(); 
      } 
     }); 
    } 
} 

TablePane

public class TablePane extends JPanel { 

    private final JTable table; 
    private final TableModel tableModel; 
    private final ListSelectionModel listSelectionModel; 

    public TablePane() { 
     table = new JTable(); 
     tableModel = createTableModel(); 
     table.setModel(tableModel); 
     table.setSelectionMode(ListSelectionModel.SINGLE_INTERVAL_SELECTION); 
     table.add(table.getTableHeader(), BorderLayout.PAGE_START); 
     table.setFillsViewportHeight(true); 

     listSelectionModel = table.getSelectionModel(); 
     table.setSelectionModel(listSelectionModel); 
     listSelectionModel.addListSelectionListener(new SharedListSelectionHandler()); 
     table.setSelectionModel(listSelectionModel); 

     this.setLayout(new GridBagLayout()); 

     GridBagConstraints gbc = new GridBagConstraints(); 
     gbc.anchor = GridBagConstraints.NORTHWEST; 
     gbc.fill = GridBagConstraints.BOTH; 
     gbc.gridx = 0; 
     gbc.gridy = 0; 
     gbc.gridheight = 1; 
     gbc.gridwidth = 3; 
     gbc.insets = new Insets(5, 5, 5, 5); 
     gbc.ipadx = 2; 
     gbc.ipady = 2; 
     gbc.weightx = 1; 
     gbc.weighty = 1; 

     this.add(new JScrollPane(table), gbc); 
    } 

    private TableModel createTableModel() { 
     DefaultTableModel model = new DefaultTableModel(
      new Object[] {"Car", "Color", "Year"}, 0 
     ){ 
      @Override public boolean isCellEditable(int row, int column) { 
       return false; 
      } 
     }; 

     addTableData(model); 
     return model; 
    } 

    private void addTableData(DefaultTableModel model) { 
     model.addRow(new Object[] {"Nissan", "Black", "2007"}); 
     model.addRow(new Object[] {"Toyota", "Blue", "2012"}); 
     model.addRow(new Object[] {"Chevrolet", "Red", "2009"}); 
     model.addRow(new Object[] {"Scion", "Silver", "2005"}); 
     model.addRow(new Object[] {"Cadilac", "Grey", "2001"}); 
    } 


    class SharedListSelectionHandler implements ListSelectionListener { 

     //When selection changes i want to add a label to the panel 
     //currently it just prints out the info from the selected row  
     @Override 
     public void valueChanged(ListSelectionEvent e) { 
      ListSelectionModel lsm = (ListSelectionModel) e.getSource(); 
      String contents = ""; 

      if(lsm.isSelectionEmpty()) { 
       System.out.println("<none>"); 
      } else { 
       int minIndex = lsm.getMinSelectionIndex(); 
       int maxIndex = lsm.getMaxSelectionIndex(); 
       for(int i = minIndex; i <= maxIndex; i++) { 
        if(lsm.isSelectedIndex(i)) { 
         for(int j = 0; j < table.getColumnCount(); j++) { 
          contents += table.getValueAt(i, j) + " "; 
         } 
        } 
       } 
       System.out.println(contents); 
      } 
     }   
    } 
} 

所以我不知道如何從ListSelectionListener訪問的JPanel。我應該將面板傳遞給TablePane類嗎？還是有更合適的方法來做到這一點？

另外，由於某種原因，我的ListSelectionListener打印出兩行信息，我搞砸了循環嗎？

編輯

public class TablePane extends JPanel { 

    private final JTable table; 
    private final TableModel tableModel; 
    private final ListSelectionModel listSelectionModel; 

    private final displayPanel; 

    public TablePane() { 
     //removed code for reading purposes 
    } 

    //IDE says issue with thinking displayPanel may have already been initialized 
    public TablePane(JPanel panel) { 
     //this(); 
     //displayPanel = panel; 
    } 


    //ListSelectionListener uses panel.add(jlabel) 

} 

它是那樣簡單採取final了嗎？

Answer 1

可以傳遞JLabel對象到TablePane對象（在TablePane的構造，或者通過提供一個定製setLabel()方法）。然後，您可以使用StringBuilder創建需要放在標籤上的文本，並在StringBuilder對象的標籤上（通過其toString()方法）在標籤上調用setText()。

我相信你打印everytihn兩次，因爲valueChanged方法被調用兩次：一旦關於取消選擇當前行的通知，然後再通知選擇新行。