如何在 DragAndDrop 期间在 Main-JTable 上绘制 RowHeader-JTable 的 Dropline？

Posted 2023-05-08

【中文标题】如何在 DragAndDrop 期间在 Main-JTable 上绘制 RowHeader-JTable 的 Dropline？

【英文标题】：How to paint the Dropline of a RowHeader-JTable on the Main-JTable during a DragAndDrop?

【发布时间】：2012-05-29 03:22:29

【问题描述】：

我在 JScrollPane 的视口中使用第二个 JTable 来为主表构建 RowHeader。 主表上的 DragAndDrop 被禁用。在行头表上启用了 DnD。

如果用户启动了对行标题的拖动，我想将绘制的行标题下拉线（图像中的黑线）延伸到主表上（如图像中的绿线）。

有人对我有什么建议吗？ 这是 SSCCE：

import java.awt.Component;
import java.awt.EventQueue;
import java.awt.Font;
import java.awt.datatransfer.StringSelection;
import java.awt.datatransfer.Transferable;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import javax.swing.DropMode;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.JViewport;
import javax.swing.TransferHandler;
import javax.swing.UIManager;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
import javax.swing.table.DefaultTableCellRenderer;
import javax.swing.table.JTableHeader;
import javax.swing.table.TableColumn;


public class DNDLinePainterExampleMain extends JFrame 

  public DNDLinePainterExampleMain() 
    JTable mainTable = new JTable(4, 3);
    mainTable.setAutoResizeMode(JTable.AUTO_RESIZE_OFF);

    JTable rowTable = new RowHeaderTable(mainTable);
    rowTable.setAutoscrolls(true);
    rowTable.setDragEnabled(true);
    rowTable.setTransferHandler(new RowHeaderTransferHandler());
    rowTable.setDropMode(DropMode.INSERT_ROWS);

    JScrollPane scrollPane = new JScrollPane(mainTable);
    scrollPane.setRowHeaderView(rowTable);
    scrollPane.setCorner(JScrollPane.UPPER_LEFT_CORNER,
        rowTable.getTableHeader());
    this.add(scrollPane);
  

  public static void main(String[] args) 
    EventQueue.invokeLater(new Runnable() 
      @Override
      public void run() 
        JFrame f = new DNDLinePainterExampleMain();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.pack();
        f.setVisible(true);
      
    );
  


  /*
   * Use a JTable as a renderer for row numbers of a given main table. This
   * table must be added to the row header of the scrollpane that contains the
   * main table. from:
   * http://tips4java.wordpress.com/2008/11/18/row-number-table/
   */
  public class RowHeaderTable extends JTable implements ChangeListener,
      PropertyChangeListener 

    private final JTable table;

    public RowHeaderTable(JTable table) 
      this.table = table;
      table.addPropertyChangeListener(this);

      setFocusable(false);
      setAutoCreateColumnsFromModel(false);

      updateRowHeight();
      updateModel();
      updateSelectionModel();

      TableColumn column = new TableColumn();
      column.setHeaderValue("");
      addColumn(column);
      column.setCellRenderer(new RowNumberRenderer());

      getColumnModel().getColumn(0).setPreferredWidth(50);
      setPreferredScrollableViewportSize(getPreferredSize());

      getTableHeader().setReorderingAllowed(false);
    

    @Override
    public void addNotify() 
      super.addNotify();
      Component c = getParent();
      // Keep scrolling of the row table in sync with the main table.
      if (c instanceof JViewport) 
        JViewport viewport = (JViewport) c;
        viewport.addChangeListener(this);
      
    

    /*
     * Delegate method to main table
     */
    @Override
    public int getRowCount() 
      return table.getRowCount();
    

    @Override
    public int getRowHeight(int row) 
      return table.getRowHeight(row);
    

    /*
     * This table does not use any data from the main TableModel, so just return
     * a value based on the row parameter.
     */
    @Override
    public Object getValueAt(int row, int column) 
      return Integer.toString(row + 1);
    

    /*
     * Don't edit data in the main TableModel by mistake
     */
    @Override
    public boolean isCellEditable(int row, int column) 
      return false;
    

    // implements ChangeListener
    @Override
    public void stateChanged(ChangeEvent e) 
      // Keep the scrolling of the row table in sync with main table
      JViewport viewport = (JViewport) e.getSource();
      JScrollPane scrollPane = (JScrollPane) viewport.getParent();
      scrollPane.getVerticalScrollBar().setValue(viewport.getViewPosition().y);
    

    // implements PropertyChangeListener
    @Override
    public void propertyChange(PropertyChangeEvent e) 
      // Keep the row table in sync with the main table
      if ("rowHeight".equals(e.getPropertyName()))
        updateRowHeight();

      if ("selectionModel".equals(e.getPropertyName()))
        updateSelectionModel();

      if ("model".equals(e.getPropertyName()))
        updateModel();
    

    private void updateRowHeight() 
      setRowHeight(table.getRowHeight());
    

    private void updateModel() 
      setModel(table.getModel());
    

    private void updateSelectionModel() 
      setSelectionModel(table.getSelectionModel());
    


    /*
     * Borrow the renderer from JDK1.4.2 table header
     */
    private class RowNumberRenderer extends DefaultTableCellRenderer 

      public RowNumberRenderer() 
        setHorizontalAlignment(JLabel.CENTER);
      

      @Override
      public Component getTableCellRendererComponent(JTable table,
          Object value, boolean isSelected, boolean hasFocus, int row,
          int column) 
        if (table != null) 
          JTableHeader header = table.getTableHeader();

          if (header != null) 
            setForeground(header.getForeground());
            setBackground(header.getBackground());
            setFont(header.getFont());
          
        

        if (isSelected) 
          setFont(getFont().deriveFont(Font.BOLD));
        

        setText((value == null) ? "" : value.toString());
        setBorder(UIManager.getBorder("TableHeader.cellBorder"));

        return this;
      
    //class RowNumberRenderer

  //class RowHeaderTable


  public class RowHeaderTransferHandler extends TransferHandler 

    @Override
    public int getSourceActions(JComponent c) 
      return COPY_OR_MOVE;
    

    @Override
    protected Transferable createTransferable(JComponent c) 
      return new StringSelection(c.getName());
    

    @Override
    public boolean canImport(TransferSupport supp) 
      return true;
    
  //class RowHeaderTransferHandler


//class DNDLinePainterExampleMain

【参考方案1】：

感谢 naugler、Xeon 和 Boro 的巨大贡献，我现在结合使用他们的 3 个示例。它看起来像这样：

这是代码：

import java.awt.AlphaComposite;
import java.awt.Color;
import java.awt.Component;
import java.awt.EventQueue;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import java.awt.datatransfer.StringSelection;
import java.awt.datatransfer.Transferable;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import javax.swing.DropMode;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.JTable.DropLocation;
import javax.swing.JViewport;
import javax.swing.RootPaneContainer;
import javax.swing.SwingUtilities;
import javax.swing.TransferHandler;
import javax.swing.UIManager;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
import javax.swing.table.DefaultTableCellRenderer;
import javax.swing.table.JTableHeader;
import javax.swing.table.TableColumn;


public class DNDLinePainterSolutionMain

  public static void main(String[] args)
  
    EventQueue.invokeLater(new Runnable()
    
      @Override
      public void run()
      
        JFrame f = new MainFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.pack();
        f.setVisible(true);
      
    );
  
//public class DNDLinePainterSolutionMain


class MainFrame extends JFrame

  public MainFrame()
  
    JTable mainTable = new JTable(4, 3);
    mainTable.setAutoResizeMode(JTable.AUTO_RESIZE_OFF);

    JTable rowTable = new RowHeaderTable(mainTable);
    rowTable.setAutoscrolls(true);
    rowTable.setDragEnabled(true);
    rowTable.setTransferHandler(new RowHeaderTransferHandler());
    rowTable.setDropMode(DropMode.INSERT_ROWS);

    //install the DropLocation-Extension:
    rowTable.addPropertyChangeListener("dropLocation",
        new DropLocationRepainter(this));

    JScrollPane scrollPane = new JScrollPane(mainTable);
    scrollPane.setRowHeaderView(rowTable);
    scrollPane.setCorner(JScrollPane.UPPER_LEFT_CORNER,
        rowTable.getTableHeader());
    this.add(scrollPane);
  
//class MainFrame


class RowHeaderTransferHandler extends TransferHandler

  @Override
  public int getSourceActions(JComponent c)
  
    return COPY_OR_MOVE;
  

  @Override
  protected Transferable createTransferable(JComponent c)
  
    return new StringSelection(c.getName());
  

  @Override
  public boolean canImport(TransferSupport supp)
  
    return true;
  
//class RowHeaderTransferHandler


/**
 * Listens to a dropLocation-PropertyChange and repaints the DropLine.
 */
class DropLocationRepainter implements PropertyChangeListener

  private static RowHeaderDropLineGlassPane glassPane;
  private final RootPaneContainer           rootPaneContainer;

  public DropLocationRepainter(RootPaneContainer dndLinePainterSolutionMain)
  
    this.rootPaneContainer = dndLinePainterSolutionMain;
  

  @Override
  public void propertyChange(PropertyChangeEvent pce)
  
    String propertyName = pce.getPropertyName();
    if ("dropLocation".equals(propertyName) && pce.getNewValue() != null)
    
      if (glassPane == null)
      
        rootPaneContainer.getRootPane().setGlassPane(
            glassPane = new RowHeaderDropLineGlassPane((RowHeaderTable) pce
                .getSource()));
      
      rootPaneContainer.getRootPane().getGlassPane().setVisible(true);

      repaintDropLocation(((JTable) pce.getSource()).getDropLocation());
    
    else
      if ("dropLocation".equals(propertyName))
        rootPaneContainer.getRootPane().getGlassPane().setVisible(false);
  

  private void repaintDropLocation(DropLocation loc)
  
    Component c = rootPaneContainer.getRootPane().getGlassPane();
    if (c instanceof RowHeaderDropLineGlassPane)
    
      RowHeaderDropLineGlassPane glassPane = (RowHeaderDropLineGlassPane) c;
      glassPane.repaint();
    
  
//class DropLocationRepainter


class RowHeaderDropLineGlassPane extends JPanel

  private RowHeaderTable table;

  public RowHeaderDropLineGlassPane(RowHeaderTable table)
  
    this.table = table;
    setOpaque(false);
  

  @Override
  public void paintComponent(Graphics g)
  
    Graphics2D g2 = (Graphics2D) g;
    g2.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 0.3f));
    Rectangle rect = table.getDropLineRect();
    if (rect != null)
    
      Rectangle r = SwingUtilities.convertRectangle(table, rect, this);
      g2.setColor(new Color(40, 80, 0));
      g2.fill(r);
    
  
//class RowHeaderDropLineGlassPane


/**
 * Use a JTable as a renderer for row numbers of a given main table. This table
 * must be added to the row header of the scrollpane that contains the main
 * table. From: http://tips4java.wordpress.com/2008/11/18/row-number-table/
 * <p>
 * Added @code getDropLineRect() for DropLine extension over the maintable.
 * </p>
 */
class RowHeaderTable extends JTable implements ChangeListener,
    PropertyChangeListener


  private final JTable mainTable;

  public RowHeaderTable(JTable mainTable)
  
    this.mainTable = mainTable;
    mainTable.addPropertyChangeListener(this);

    setFocusable(false);
    setAutoCreateColumnsFromModel(false);

    updateRowHeight();
    updateModel();
    updateSelectionModel();

    TableColumn column = new TableColumn();
    column.setHeaderValue("");
    addColumn(column);
    column.setCellRenderer(new RowNumberRenderer());

    getColumnModel().getColumn(0).setPreferredWidth(50);
    setPreferredScrollableViewportSize(getPreferredSize());

    getTableHeader().setReorderingAllowed(false);
  

  /*
   * called from the class RowHeaderDropLineGlassPane
   */
  public Rectangle getDropLineRect()
  
    DropLocation loc = getDropLocation();
    if (loc == null /* || !loc.isDropable() */)
      return null;

    final Rectangle lineRect = new Rectangle();

    int index = loc.getRow();
    if (index < 0)
    
      lineRect.setRect(0, 0, 0, 0);
      return null;
    

    Rectangle r = getCellRect(index, 0, true);
    if (index == getRowCount())
      r.height = getCellRect(index - 1, 0, true).height;//if the last line is the DropTarget a height of 0 (of a non-existing Cell after the last row) is returned.

    lineRect.setRect(r.x, r.y - (r.height / 4d), getVisibleRect().width
        + mainTable.getWidth(), r.height / 2d - 1);
    return lineRect;
  

  @Override
  public void addNotify()
  
    super.addNotify();
    Component c = getParent();
    // Keep scrolling of the row table in sync with the main table.
    if (c instanceof JViewport)
    
      JViewport viewport = (JViewport) c;
      viewport.addChangeListener(this);
    
  

  /*
   * Delegate method to main table
   */
  @Override
  public int getRowCount()
  
    return mainTable.getRowCount();
  

  @Override
  public int getRowHeight(int row)
  
    return mainTable.getRowHeight(row);
  

  /*
   * This table does not use any data from the main TableModel, so just return a
   * value based on the row parameter.
   */
  @Override
  public Object getValueAt(int row, int column)
  
    return Integer.toString(row + 1);
  

  /*
   * Don't edit data in the main TableModel by mistake
   */
  @Override
  public boolean isCellEditable(int row, int column)
  
    return false;
  

  // implements ChangeListener
  @Override
  public void stateChanged(ChangeEvent e)
  
    // Keep the scrolling of the row table in sync with main table
    JViewport viewport = (JViewport) e.getSource();
    JScrollPane scrollPane = (JScrollPane) viewport.getParent();
    scrollPane.getVerticalScrollBar().setValue(viewport.getViewPosition().y);
  

  // implements PropertyChangeListener
  @Override
  public void propertyChange(PropertyChangeEvent e)
  
    // Keep the row table in sync with the main table
    if ("rowHeight".equals(e.getPropertyName()))
      updateRowHeight();

    if ("selectionModel".equals(e.getPropertyName()))
      updateSelectionModel();

    if ("model".equals(e.getPropertyName()))
      updateModel();
  

  private void updateRowHeight()
  
    setRowHeight(mainTable.getRowHeight());
  

  private void updateModel()
  
    setModel(mainTable.getModel());
  

  private void updateSelectionModel()
  
    setSelectionModel(mainTable.getSelectionModel());
  


  /*
   * Borrow the renderer from JDK1.4.2 table header
   */
  private class RowNumberRenderer extends DefaultTableCellRenderer
  
    public RowNumberRenderer()
    
      setHorizontalAlignment(JLabel.CENTER);
    

    @Override
    public Component getTableCellRendererComponent(JTable table, Object value,
        boolean isSelected, boolean hasFocus, int row, int column)
    
      if (table != null)
      
        JTableHeader header = table.getTableHeader();

        if (header != null)
        
          setForeground(header.getForeground());
          setBackground(header.getBackground());
          setFont(header.getFont());
        
      

      if (isSelected)
        setFont(getFont().deriveFont(Font.BOLD));

      setText((value == null) ? "" : value.toString());
      setBorder(UIManager.getBorder("TableHeader.cellBorder"));

      return this;
    
  //class RowNumberRenderer

//class RowHeaderTable

【讨论】：

感谢您决定在此处发布。我非常喜欢这个解决方案。再次欢呼bobndrew，既然您将其添加为答案...到底是什么... +1 :)

【参考方案2】：

好的。忏悔时间。这是一些粗糙、生硬的仪器代码。对于无法产生更优雅或更干净的解决方案，我深表歉意。我是深邃黑暗的秋千地牢中的 1 级游客。

此自定义代码属于快速而肮脏的类别。它不适用于列，我不确定所有边缘情况，并且我不知道在绘制例程中间窃取另一个组件图形上下文的规则。底线：这是一个示例，而不是完整的解决方案。

因为您使用单独的表格进行拖放（您的 rowTable），所以该表格没有很好的方法可以绘制到 mainTable。应该注意的是，可能有一个光滑而闪亮的路径使用 PropertyChangeListeners 或其他东西来触发 mainTable 的事件，但我没有管理它。这是BasicTableUI的自定义扩展：

public class ExtendedDropLineTableUI extends BasicTableUI 

        private JTable drawTable;
        private Integer oldRow;

        //We give this UI instance a reference to a separate table for drawing
        public ExtendedDropLineTableUI(JTable drawTable) 
            this.drawTable = drawTable;
        

        @Override
        public void paint(Graphics g, JComponent c) 
            super.paint(g, c);
            paintExtendedDropLine();
        

        private void paintExtendedDropLine() 
            JTable.DropLocation loc = table.getDropLocation();
            if (loc == null) 
                drawTable.repaint();
                return;
            

            //get the correct line color. no color? no line!
            Color color = UIManager.getColor("Table.dropLineColor");
            if (color == null) 
                return;
            

            //try to repaint the draw table only if the row changes
            if (oldRow != null && oldRow != loc.getRow()) 
                drawTable.repaint();
            
            oldRow = loc.getRow();
            //get location of cell rectangle
            int row = loc.getRow();
            int col = loc.getColumn();
            if (col >= table.getColumnCount()) 
                col--;
            
            Rectangle rect = table.getCellRect(row, col, true);
            //adjust rectangle to fit between the cells
            if (rect.y == 0) 
                rect.y = -1;
             else 
                rect.y -= 2;
            
            //what's a line but a really thin rectangle?
            rect.height = 3;
            //extend the rectangle to the width of the drawing table
            rect.width = drawTable.getWidth();
            //draw the rectangle
            Graphics g = drawTable.getGraphics();
            g.setColor(color);
            g.fillRect(rect.x, rect.y, rect.width, rect.height);
        
    

您需要将此 UI 提供给您的 rowTable，以便它可以绘制到 mainTable，如下所示：

rowTable.setUI(new ExtendedDropLineTableUI(mainTable));

我非常依赖实际的source code 来劫持绘制下降线，因为涉及这些东西的方法都是私有的。

编辑： 我忘了顺便提一下，我担心您可能试图通过拖动 rowTable 中的单元格来重新排列 mainTable 中的整行。该解决方案也没有考虑到这一点，它只是划清界限。为此，您确实需要一个更优雅的解决方案，或者一个使 mainTable 中的行与 rowTable 保持同步的检查。

【讨论】：

@Xeon 和 naugler 感谢有趣的建议，这些建议在我解决问题时非常有用。 (+1) 给你们。

感谢您的回答！我将为您提供最快，完整的工作示例。它帮助我正确计算了线条画，我很欣赏它是一个“单线和一类”的解决方案。但是...我也认为 BasicTableUI 的扩展太冒险了 ;-) 因此我会接受@Xeon 的回答。

哦，我忘了回答你的编辑：这两个表已经在我们的程序中同步，并且在 DnDropping 之后重新排列行数据已经开始工作了。我只是没能划清界限。

【参考方案3】：

我的解决方案使用了稍微不同的方法，因为我们想在现有组件之上添加一些自定义绘画。因此，我选择使用GlassPane 并在那里进行绘画。通过这种方式，您可以想象到所有亮点，并且它的大小不受单元格大小的限制，因为它可以使用例如单元格渲染器的方法。

要运行此示例，您需要下载 the FinalGlassPane from this site。它是必需的，因为我们使用它来捕获事件（使用常规的GlassPane 将被消耗）。如果您知道在拖动最终结束时捕获事件的不同方法，则可以完全避免。 如果你知道，请分享。 对我来说，这是最好的，而且我喜欢有一个GlassPane，它可以捕获事件并且不会消耗所有事件。

import java.awt.*;
import java.awt.datatransfer.StringSelection;
import java.awt.datatransfer.Transferable;
import java.awt.dnd.*;
import java.awt.event.AWTEventListener;
import java.awt.event.MouseEvent;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import javax.swing.*;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
import javax.swing.table.DefaultTableCellRenderer;
import javax.swing.table.JTableHeader;
import javax.swing.table.TableColumn;

public class DNDLinePainterExampleMain extends JFrame 

    public int x = -1;
    public int y = -1;
    private boolean isDragged = false;
    public FinalGlassPane glassPane;
    private boolean isOutsideTable = false;

    public DNDLinePainterExampleMain() 
        final JTable mainTable = new JTable(4, 3);
        mainTable.setAutoResizeMode(JTable.AUTO_RESIZE_OFF);

        final JTable rowTable = new RowHeaderTable(mainTable);
        rowTable.setAutoscrolls(true);
        rowTable.setDragEnabled(true);
        rowTable.setTransferHandler(new RowHeaderTransferHandler());
        rowTable.setDropMode(DropMode.INSERT_ROWS);
        final JScrollPane scrollPane = new JScrollPane(mainTable);
        scrollPane.setRowHeaderView(rowTable);
        scrollPane.setCorner(JScrollPane.UPPER_LEFT_CORNER,
                rowTable.getTableHeader());

        final JPanel panel = new JPanel();

        DragSourceMotionListener dsml = new DragSourceMotionListener() 

            @Override
            public void dragMouseMoved(DragSourceDragEvent dsde) 
                isDragged = true;
                isOutsideTable = true;
                Component source = dsde.getDragSourceContext().getComponent();
                //the coordinates of the drag event in screen coords
                Point toConvert = new Point(dsde.getX(), dsde.getY());
                //convert to source coords
                SwingUtilities.convertPointFromScreen(toConvert, source);
                int rowMargin = rowTable.getRowMargin();
                Point toTest = new Point(toConvert.x, toConvert.y);
                for (int i = 0; i < rowTable.getRowCount(); i++) 
                    Rectangle bounds = rowTable.getCellRect(i, 0, true);
                    boolean isIn = bounds.contains(toTest);
//                    System.out.println("bounds = "+bounds+";  rowMargin = "+rowMargin+";  i = "+i+";  isIn = "+isIn);
                    if (isIn) 
                        isOutsideTable = false;
                        int hHalf = bounds.height / 2;
                        int hIn = toTest.y - bounds.y;
                        boolean isTop = false;
                        if (hIn < hHalf) 
                            isTop = true;
                        
                        x = bounds.width;
                        y = bounds.y - rowMargin;
                        if (!isTop) 
                            y += bounds.height;
                        
                        //now convert the point to the glass pane coordinates
                        Point c = SwingUtilities.convertPoint(rowTable, x, y, glassPane);
                        x = c.x;
                        y = c.y;
//                        System.out.println("hIn = "+hIn+";  isTop = "+isTop + "");
                    
                
                glassPane.repaint();
            
        ;
        DragSource ds = new DragSource();
        ds.addDragSourceMotionListener(dsml);


        this.setContentPane(panel);
        panel.add(new JButton("Oi for testing"));
        panel.add(scrollPane);


        DragSource dragSource = DragSource.getDefaultDragSource();
        dragSource.addDragSourceMotionListener(dsml);
        glassPane = new FinalGlassPane(this) 

            @Override
            public void eventDispatched(AWTEvent event) 
                super.eventDispatched(event);
                if (event instanceof MouseEvent) 
                    //after drag is relesed we are back here with mouse entered event
                    if (isDragged) 
                        isDragged = false;
                        repaint();
                    
                
            

            @Override
            protected void paintComponent(Graphics g) 
                Graphics2D g2 = (Graphics2D) g;
                if (isDragged && !isOutsideTable) 
                    g2.setPaint(Color.GREEN);
                    g2.drawLine(x + 2, y + 1, x + mainTable.getWidth() - 4, y + 1);
                    g2.drawLine(x, y, x + mainTable.getWidth(), y);
                    g2.drawLine(x + 2, y - 1, x + mainTable.getWidth() - 4, y - 1);
                
            
        ;
        AWTEventListener al = (AWTEventListener) glassPane;
        Toolkit.getDefaultToolkit().addAWTEventListener(al,
                AWTEvent.MOUSE_MOTION_EVENT_MASK | AWTEvent.MOUSE_EVENT_MASK);

        this.setGlassPane(glassPane);
        glassPane.setVisible(true);
    

    public static void main(String[] args) 
        EventQueue.invokeLater(new Runnable() 

            @Override
            public void run() 
                JFrame f = new DNDLinePainterExampleMain();
                f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                f.pack();
                f.setVisible(true);
            
        );
    


    /*
     * Use a JTable as a renderer for row numbers of a given main table. This
     * table must be added to the row header of the scrollpane that contains the
     * main table. from:
     * http://tips4java.wordpress.com/2008/11/18/row-number-table/
     */
    public class RowHeaderTable extends JTable implements ChangeListener,
            PropertyChangeListener 

        private final JTable table;

        public RowHeaderTable(JTable table) 
            this.table = table;
            table.addPropertyChangeListener(this);

            setFocusable(false);
            setAutoCreateColumnsFromModel(false);

            updateRowHeight();
            updateModel();
            updateSelectionModel();

            TableColumn column = new TableColumn();
            column.setHeaderValue("");
            addColumn(column);
            column.setCellRenderer(new RowNumberRenderer());

            getColumnModel().getColumn(0).setPreferredWidth(50);
            setPreferredScrollableViewportSize(getPreferredSize());

            getTableHeader().setReorderingAllowed(false);
        

        @Override
        public void addNotify() 
            super.addNotify();
            Component c = getParent();
            // Keep scrolling of the row table in sync with the main table.
            if (c instanceof JViewport) 
                JViewport viewport = (JViewport) c;
                viewport.addChangeListener(this);
            
        

        /*
         * Delegate method to main table
         */
        @Override
        public int getRowCount() 
            return table.getRowCount();
        

        @Override
        public int getRowHeight(int row) 
            return table.getRowHeight(row);
        

        /*
         * This table does not use any data from the main TableModel, so just
         * return a value based on the row parameter.
         */
        @Override
        public Object getValueAt(int row, int column) 
            return Integer.toString(row + 1);
        
        /*
         * Don't edit data in the main TableModel by mistake
         */

        @Override
        public boolean isCellEditable(int row, int column) 
            return false;
        
        // implements ChangeListener

        @Override
        public void stateChanged(ChangeEvent e) 
            // Keep the scrolling of the row table in sync with main table
            JViewport viewport = (JViewport) e.getSource();
            JScrollPane scrollPane = (JScrollPane) viewport.getParent();
            scrollPane.getVerticalScrollBar().setValue(viewport.getViewPosition().y);
        
        // implements PropertyChangeListener

        @Override
        public void propertyChange(PropertyChangeEvent e) 
            // Keep the row table in sync with the main table
            if ("rowHeight".equals(e.getPropertyName())) 
                updateRowHeight();
            

            if ("selectionModel".equals(e.getPropertyName())) 
                updateSelectionModel();
            

            if ("model".equals(e.getPropertyName())) 
                updateModel();
            
        

        private void updateRowHeight() 
            setRowHeight(table.getRowHeight());
        

        private void updateModel() 
            setModel(table.getModel());
        

        private void updateSelectionModel() 
            setSelectionModel(table.getSelectionModel());
        
        /*
         * Borrow the renderer from JDK1.4.2 table header
         */

        private class RowNumberRenderer extends DefaultTableCellRenderer 

            public RowNumberRenderer() 
                setHorizontalAlignment(JLabel.CENTER);
            

            @Override
            public Component getTableCellRendererComponent(JTable table,
                    Object value, boolean isSelected, boolean hasFocus, int row,
                    int column) 
                if (table != null) 
                    JTableHeader header = table.getTableHeader();

                    if (header != null) 
                        setForeground(header.getForeground());
                        setBackground(header.getBackground());
                        setFont(header.getFont());
                    
                
                if (isSelected) 
                    setFont(getFont().deriveFont(Font.BOLD));
                
                setText((value == null) ? "" : value.toString());
                setBorder(UIManager.getBorder("TableHeader.cellBorder"));
                return this;
            
        //class RowNumberRenderer
    //class RowHeaderTable

    public class RowHeaderTransferHandler extends TransferHandler 

        @Override
        public int getSourceActions(JComponent c) 
            return COPY_OR_MOVE;
        

        @Override
        protected Transferable createTransferable(JComponent c) 
            return new StringSelection(c.getName());
        

        @Override
        public boolean canImport(TransferSupport supp) 
            return true;
        
    //class RowHeaderTransferHandler

【讨论】：

很好的答案，也谢谢你。 +1 使用GlassPane，这样可以在两个表上绘制一个透明的 DropLine。但我不认为它必须是FinalGlassPane，我认为dropLocation 的PropertyChangeListener 更具体。请查看我的答案中的最新代码，以及我在 RowHeader-Table 中使用 getDropLocation() 计算 DropLine-Rectangle 的方式。

@bobndrew 谢谢。你说的对。因此，我想问您是否可以发布您使用的解决方案？例如，将其编辑到您的问题中，在最底部添加标题为 EDIT - SOLUTION 的部分，解决方案将在该部分下。

【参考方案4】：

我建议你这样做（使用 Swing 的拖放功能）：

    RowHeaderTable rowTable = new RowHeaderTable(mainTable);
    rowTable.setAutoscrolls(true);
    rowTable.setDragEnabled(true);
    rowTable.setTransferHandler(new RowHeaderTransferHandler(mainTable));
    rowTable.setDropMode(DropMode.INSERT_ROWS);
    try 
        DropTarget dropTarget = rowTable.getDropTarget();
        dropTarget.addDropTargetListener(rowTable);
    
    catch(TooManyListenersException e) 
        e.printStackTrace();
    

现在你必须实现DropTargetListener:

public class RowHeaderTable extends JTable implements ChangeListener, PropertyChangeListener, DropTargetListener 

您应该对以下 2 种方法感兴趣：

    @Override
    public void dragEnter(DropTargetDragEvent dtde)  shouldPaint = true 

    @Override
    public void dragExit(DropTargetEvent dte)  shouldPaint = false 

现在您应该使用您的 TranserHandler 操作您的 mainTable（绘制这条“绿线”）：

    @Override
    public boolean canImport(TransferSupport supp) 
        DropLocation location = supp.getDropLocation();
        if(location instanceof javax.swing.JTable.DropLocation && shouldPaint) 
            javax.swing.JTable.DropLocation tableLocation = (javax.swing.JTable.DropLocation) location;
            int rowToInsert = tableLocation.getRow();
            //paint somehow the "green line"
            //remember that canImport is invoked when you move your mouse
        
        return true;
    

基本上，您应该实现自己的行渲染器或类似的东西（如@naugler 答案）。您还应该以某种方式向您的 TransferHandler 提供布尔值shouldPaint。但这并不是什么大不了的事情。

希望这会有所帮助。

【讨论】：

很好的答案！我会接受它，因为现在我在我的源代码中使用了与您类似的想法（不是DropTargetListener，而是dropLocation 上的PropertyChangeListener）。为什么你认为在canImport() 的TransferHandler 中进行绘画是个好主意？我正在使用从侦听器可见的 GlassPane。

直接在TransferHandler中作画不是个好主意。我提到了类似的东西：添加组件/更改 L&F UI/使用图层/等。然后重新验证/重新绘制