Question

我创建了以下示例源代码，并且想知道我需要做什么来更新我的JPanel，其中JLabel的信息位于JTable中单击的行中。

我还想注意，这只是一个很好的例子，因为我已经在这里改进了一些SO成员，因此我对示例代码做了很多改进。所以我发布这个简单的例子作为一种学习方式

SwingTesting（主要）

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);
            }
        }        
    }
}

所以我想知道如何从ListSelectionListener访问该JPanel。我应该将面板传递给TablePane类吗？或者有更合适的方法吗？

另外，我的ListSelectionListener由于某种原因打印出两次行信息，我是否搞乱了循环？

修改

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)

}

是否像关闭final一样简单？

Answer 1

您可以将JLabel对象传递给TablePane对象（在TablePane的构造函数中，或者通过提供自定义setLabel()方法）。然后，您可以使用StringBuilder创建需要在标签上显示的文字，并使用setText()对象的内容（通过其StringBuilder调用标签上的toString()法）。

我相信你打印的时间是两次因为valueChanged方法被调用了两次：一次是关于取消选择当前行的通知，一次是关于选择新行的通知。

如何使用其他类的信息更新JPanel？

1 个答案: