¿Cómo implementar una pestaña que se puede arrastrar usando Java Swing?

Question

¿Cómo implemento una pestaña que se puede arrastrar usando Java Swing?En lugar del JTabbedPane estático, me gustaría arrastrar y soltar una pestaña en una posición diferente para reorganizar las pestañas.

EDITAR: Los tutoriales de Java: arrastrar y soltar y transferencia de datos.

Answer 1

me gustó DnDTabbedPane de Terai Atsuhiro san, pero quería más de él.La implementación original de Terai transfirió pestañas dentro de TabbedPane, pero sería mejor si pudiera arrastrar de un TabbedPane a otro.

Inspirado por @TomásGracias al esfuerzo, decidí modificar el código yo mismo.Hay algunos detalles que agregué.Por ejemplo, la pestaña fantasma ahora se desliza a lo largo del panel de pestañas en lugar de moverse junto con el mouse.

setAcceptor(TabAcceptor a_acceptor) debería permitir que el código del consumidor decida si permite que una pestaña se transfiera de un panel con pestañas a otro.El aceptador predeterminado siempre regresa true.

/** Modified DnDTabbedPane.java
 * http://java-swing-tips.blogspot.com/2008/04/drag-and-drop-tabs-in-jtabbedpane.html
 * originally written by Terai Atsuhiro.
 * so that tabs can be transfered from one pane to another.
 * eed3si9n.
 */

import java.awt.*;
import java.awt.datatransfer.*;
import java.awt.dnd.*;
import java.awt.geom.*;
import java.awt.image.*;
import javax.swing.*;

public class DnDTabbedPane extends JTabbedPane {
    public static final long serialVersionUID = 1L;
    private static final int LINEWIDTH = 3;
    private static final String NAME = "TabTransferData";
    private final DataFlavor FLAVOR = new DataFlavor(
            DataFlavor.javaJVMLocalObjectMimeType, NAME);
    private static GhostGlassPane s_glassPane = new GhostGlassPane();

    private boolean m_isDrawRect = false;
    private final Rectangle2D m_lineRect = new Rectangle2D.Double();

    private final Color m_lineColor = new Color(0, 100, 255);
    private TabAcceptor m_acceptor = null;

    public DnDTabbedPane() {
        super();
        final DragSourceListener dsl = new DragSourceListener() {
            public void dragEnter(DragSourceDragEvent e) {
                e.getDragSourceContext().setCursor(DragSource.DefaultMoveDrop);
            }

            public void dragExit(DragSourceEvent e) {
                e.getDragSourceContext()
                        .setCursor(DragSource.DefaultMoveNoDrop);
                m_lineRect.setRect(0, 0, 0, 0);
                m_isDrawRect = false;
                s_glassPane.setPoint(new Point(-1000, -1000));
                s_glassPane.repaint();
            }

            public void dragOver(DragSourceDragEvent e) {
                //e.getLocation()
                //This method returns a Point indicating the cursor location in screen coordinates at the moment

                TabTransferData data = getTabTransferData(e);
                if (data == null) {
                    e.getDragSourceContext().setCursor(
                            DragSource.DefaultMoveNoDrop);
                    return;
                } // if

                /*
                Point tabPt = e.getLocation();
                SwingUtilities.convertPointFromScreen(tabPt, DnDTabbedPane.this);
                if (DnDTabbedPane.this.contains(tabPt)) {
                    int targetIdx = getTargetTabIndex(tabPt);
                    int sourceIndex = data.getTabIndex();
                    if (getTabAreaBound().contains(tabPt)
                            && (targetIdx >= 0)
                            && (targetIdx != sourceIndex)
                            && (targetIdx != sourceIndex + 1)) {
                        e.getDragSourceContext().setCursor(
                                DragSource.DefaultMoveDrop);

                        return;
                    } // if

                    e.getDragSourceContext().setCursor(
                            DragSource.DefaultMoveNoDrop);
                    return;
                } // if
                */

                e.getDragSourceContext().setCursor(
                        DragSource.DefaultMoveDrop);
            }

            public void dragDropEnd(DragSourceDropEvent e) {
                m_isDrawRect = false;
                m_lineRect.setRect(0, 0, 0, 0);
                // m_dragTabIndex = -1;

                if (hasGhost()) {
                    s_glassPane.setVisible(false);
                    s_glassPane.setImage(null);
                }
            }

            public void dropActionChanged(DragSourceDragEvent e) {
            }
        };

        final DragGestureListener dgl = new DragGestureListener() {
            public void dragGestureRecognized(DragGestureEvent e) {
                // System.out.println("dragGestureRecognized");

                Point tabPt = e.getDragOrigin();
                int dragTabIndex = indexAtLocation(tabPt.x, tabPt.y);
                if (dragTabIndex < 0) {
                    return;
                } // if

                initGlassPane(e.getComponent(), e.getDragOrigin(), dragTabIndex);
                try {
                    e.startDrag(DragSource.DefaultMoveDrop, 
                            new TabTransferable(DnDTabbedPane.this, dragTabIndex), dsl);
                } catch (InvalidDnDOperationException idoe) {
                    idoe.printStackTrace();
                }
            }
        };

        //dropTarget =
        new DropTarget(this, DnDConstants.ACTION_COPY_OR_MOVE,
                new CDropTargetListener(), true);
        new DragSource().createDefaultDragGestureRecognizer(this,
                DnDConstants.ACTION_COPY_OR_MOVE, dgl);
        m_acceptor = new TabAcceptor() {
            public boolean isDropAcceptable(DnDTabbedPane a_component, int a_index) {
                return true;
            }
        };
    }

    public TabAcceptor getAcceptor() {
        return m_acceptor;
    }

    public void setAcceptor(TabAcceptor a_value) {
        m_acceptor = a_value;
    }

    private TabTransferData getTabTransferData(DropTargetDropEvent a_event) {       
        try {
            TabTransferData data = (TabTransferData) a_event.getTransferable().getTransferData(FLAVOR);             
            return data;
        } catch (Exception e) {
            e.printStackTrace();
        }

        return null;
    }

    private TabTransferData getTabTransferData(DropTargetDragEvent a_event) {
        try {
            TabTransferData data = (TabTransferData) a_event.getTransferable().getTransferData(FLAVOR);             
            return data;
        } catch (Exception e) {
            e.printStackTrace();
        }

        return null;
    }

    private TabTransferData getTabTransferData(DragSourceDragEvent a_event) {
        try {
            TabTransferData data = (TabTransferData) a_event.getDragSourceContext()
                .getTransferable().getTransferData(FLAVOR);             
            return data;
        } catch (Exception e) {
            e.printStackTrace();
        }

        return null;        
    }

    class TabTransferable implements Transferable {
        private TabTransferData m_data = null;

        public TabTransferable(DnDTabbedPane a_tabbedPane, int a_tabIndex) {
            m_data = new TabTransferData(DnDTabbedPane.this, a_tabIndex);
        }

        public Object getTransferData(DataFlavor flavor) {
            return m_data;
            // return DnDTabbedPane.this;
        }

        public DataFlavor[] getTransferDataFlavors() {
            DataFlavor[] f = new DataFlavor[1];
            f[0] = FLAVOR;
            return f;
        }

        public boolean isDataFlavorSupported(DataFlavor flavor) {
            return flavor.getHumanPresentableName().equals(NAME);
        }       
    }

    class TabTransferData {
        private DnDTabbedPane m_tabbedPane = null;
        private int m_tabIndex = -1;

        public TabTransferData() {
        }

        public TabTransferData(DnDTabbedPane a_tabbedPane, int a_tabIndex) {
            m_tabbedPane = a_tabbedPane;
            m_tabIndex = a_tabIndex;
        }

        public DnDTabbedPane getTabbedPane() {
            return m_tabbedPane;
        }

        public void setTabbedPane(DnDTabbedPane pane) {
            m_tabbedPane = pane;
        }

        public int getTabIndex() {
            return m_tabIndex;
        }

        public void setTabIndex(int index) {
            m_tabIndex = index;
        }
    }

    private Point buildGhostLocation(Point a_location) {
        Point retval = new Point(a_location);

        switch (getTabPlacement()) {
            case JTabbedPane.TOP: {
                retval.y = 1;
                retval.x -= s_glassPane.getGhostWidth() / 2;
            } break;

            case JTabbedPane.BOTTOM: {
                retval.y = getHeight() - 1 - s_glassPane.getGhostHeight();
                retval.x -= s_glassPane.getGhostWidth() / 2;
            } break;

            case JTabbedPane.LEFT: {
                retval.x = 1;
                retval.y -= s_glassPane.getGhostHeight() / 2;
            } break;

            case JTabbedPane.RIGHT: {
                retval.x = getWidth() - 1 - s_glassPane.getGhostWidth();
                retval.y -= s_glassPane.getGhostHeight() / 2;
            } break;
        } // switch

        retval = SwingUtilities.convertPoint(DnDTabbedPane.this,
                retval, s_glassPane);
        return retval;
    }

    class CDropTargetListener implements DropTargetListener {
        public void dragEnter(DropTargetDragEvent e) {
            // System.out.println("DropTarget.dragEnter: " + DnDTabbedPane.this);

            if (isDragAcceptable(e)) {
                e.acceptDrag(e.getDropAction());
            } else {
                e.rejectDrag();
            } // if
        }

        public void dragExit(DropTargetEvent e) {
            // System.out.println("DropTarget.dragExit: " + DnDTabbedPane.this);
            m_isDrawRect = false;
        }

        public void dropActionChanged(DropTargetDragEvent e) {
        }

        public void dragOver(final DropTargetDragEvent e) {
            TabTransferData data = getTabTransferData(e);

            if (getTabPlacement() == JTabbedPane.TOP
                    || getTabPlacement() == JTabbedPane.BOTTOM) {
                initTargetLeftRightLine(getTargetTabIndex(e.getLocation()), data);
            } else {
                initTargetTopBottomLine(getTargetTabIndex(e.getLocation()), data);
            } // if-else

            repaint();
            if (hasGhost()) {
                s_glassPane.setPoint(buildGhostLocation(e.getLocation()));
                s_glassPane.repaint();
            }
        }

        public void drop(DropTargetDropEvent a_event) {
            // System.out.println("DropTarget.drop: " + DnDTabbedPane.this);

            if (isDropAcceptable(a_event)) {
                convertTab(getTabTransferData(a_event),
                    getTargetTabIndex(a_event.getLocation()));
                a_event.dropComplete(true);
            } else {
                a_event.dropComplete(false);
            } // if-else

            m_isDrawRect = false;
            repaint();
        }

        public boolean isDragAcceptable(DropTargetDragEvent e) {
            Transferable t = e.getTransferable();
            if (t == null) {
                return false;
            } // if

            DataFlavor[] flavor = e.getCurrentDataFlavors();
            if (!t.isDataFlavorSupported(flavor[0])) {
                return false;
            } // if

            TabTransferData data = getTabTransferData(e);

            if (DnDTabbedPane.this == data.getTabbedPane()
                    && data.getTabIndex() >= 0) {
                return true;
            } // if

            if (DnDTabbedPane.this != data.getTabbedPane()) {
                if (m_acceptor != null) {
                    return m_acceptor.isDropAcceptable(data.getTabbedPane(), data.getTabIndex());
                } // if
            } // if

            return false;
        }

        public boolean isDropAcceptable(DropTargetDropEvent e) {
            Transferable t = e.getTransferable();
            if (t == null) {
                return false;
            } // if

            DataFlavor[] flavor = e.getCurrentDataFlavors();
            if (!t.isDataFlavorSupported(flavor[0])) {
                return false;
            } // if

            TabTransferData data = getTabTransferData(e);

            if (DnDTabbedPane.this == data.getTabbedPane()
                    && data.getTabIndex() >= 0) {
                return true;
            } // if

            if (DnDTabbedPane.this != data.getTabbedPane()) {
                if (m_acceptor != null) {
                    return m_acceptor.isDropAcceptable(data.getTabbedPane(), data.getTabIndex());
                } // if
            } // if

            return false;
        }
    }

    private boolean m_hasGhost = true;

    public void setPaintGhost(boolean flag) {
        m_hasGhost = flag;
    }

    public boolean hasGhost() {
        return m_hasGhost;
    }

    /**
     * returns potential index for drop.
     * @param a_point point given in the drop site component's coordinate
     * @return returns potential index for drop.
     */
    private int getTargetTabIndex(Point a_point) {
        boolean isTopOrBottom = getTabPlacement() == JTabbedPane.TOP
                || getTabPlacement() == JTabbedPane.BOTTOM;

        // if the pane is empty, the target index is always zero.
        if (getTabCount() == 0) {
            return 0;
        } // if

        for (int i = 0; i < getTabCount(); i++) {
            Rectangle r = getBoundsAt(i);
            if (isTopOrBottom) {
                r.setRect(r.x - r.width / 2, r.y, r.width, r.height);
            } else {
                r.setRect(r.x, r.y - r.height / 2, r.width, r.height);
            } // if-else

            if (r.contains(a_point)) {
                return i;
            } // if
        } // for

        Rectangle r = getBoundsAt(getTabCount() - 1);
        if (isTopOrBottom) {
            int x = r.x + r.width / 2;
            r.setRect(x, r.y, getWidth() - x, r.height);
        } else {
            int y = r.y + r.height / 2;
            r.setRect(r.x, y, r.width, getHeight() - y);
        } // if-else

        return r.contains(a_point) ? getTabCount() : -1;
    }

    private void convertTab(TabTransferData a_data, int a_targetIndex) {
        DnDTabbedPane source = a_data.getTabbedPane();
        int sourceIndex = a_data.getTabIndex();
        if (sourceIndex < 0) {
            return;
        } // if

        Component cmp = source.getComponentAt(sourceIndex);
        String str = source.getTitleAt(sourceIndex);
        if (this != source) {
            source.remove(sourceIndex);

            if (a_targetIndex == getTabCount()) {
                addTab(str, cmp);
            } else {
                if (a_targetIndex < 0) {
                    a_targetIndex = 0;
                } // if

                insertTab(str, null, cmp, null, a_targetIndex);

            } // if

            setSelectedComponent(cmp);
            // System.out.println("press="+sourceIndex+" next="+a_targetIndex);
            return;
        } // if

        if (a_targetIndex < 0 || sourceIndex == a_targetIndex) {
            //System.out.println("press="+prev+" next="+next);
            return;
        } // if

        if (a_targetIndex == getTabCount()) {
            //System.out.println("last: press="+prev+" next="+next);
            source.remove(sourceIndex);
            addTab(str, cmp);
            setSelectedIndex(getTabCount() - 1);
        } else if (sourceIndex > a_targetIndex) {
            //System.out.println("   >: press="+prev+" next="+next);
            source.remove(sourceIndex);
            insertTab(str, null, cmp, null, a_targetIndex);
            setSelectedIndex(a_targetIndex);
        } else {
            //System.out.println("   <: press="+prev+" next="+next);
            source.remove(sourceIndex);
            insertTab(str, null, cmp, null, a_targetIndex - 1);
            setSelectedIndex(a_targetIndex - 1);
        }
    }

    private void initTargetLeftRightLine(int next, TabTransferData a_data) {        
        if (next < 0) {
            m_lineRect.setRect(0, 0, 0, 0);
            m_isDrawRect = false;
            return;
        } // if

        if ((a_data.getTabbedPane() == this)
                && (a_data.getTabIndex() == next
                || next - a_data.getTabIndex() == 1)) {
            m_lineRect.setRect(0, 0, 0, 0);
            m_isDrawRect = false;
        } else if (getTabCount() == 0) {
            m_lineRect.setRect(0, 0, 0, 0);
            m_isDrawRect = false;
            return;
        } else if (next == 0) {
            Rectangle rect = getBoundsAt(0);
            m_lineRect.setRect(-LINEWIDTH / 2, rect.y, LINEWIDTH, rect.height);
            m_isDrawRect = true;
        } else if (next == getTabCount()) {
            Rectangle rect = getBoundsAt(getTabCount() - 1);
            m_lineRect.setRect(rect.x + rect.width - LINEWIDTH / 2, rect.y,
                    LINEWIDTH, rect.height);
            m_isDrawRect = true;
        } else {
            Rectangle rect = getBoundsAt(next - 1);
            m_lineRect.setRect(rect.x + rect.width - LINEWIDTH / 2, rect.y,
                    LINEWIDTH, rect.height);
            m_isDrawRect = true;
        }
    }

    private void initTargetTopBottomLine(int next, TabTransferData a_data) {
        if (next < 0) {
            m_lineRect.setRect(0, 0, 0, 0);
            m_isDrawRect = false;
            return;
        } // if

        if ((a_data.getTabbedPane() == this)
                && (a_data.getTabIndex() == next
                || next - a_data.getTabIndex() == 1)) {
            m_lineRect.setRect(0, 0, 0, 0);
            m_isDrawRect = false;
        } else if (getTabCount() == 0) {
            m_lineRect.setRect(0, 0, 0, 0);
            m_isDrawRect = false;
            return;
        } else if (next == getTabCount()) {
            Rectangle rect = getBoundsAt(getTabCount() - 1);
            m_lineRect.setRect(rect.x, rect.y + rect.height - LINEWIDTH / 2,
                    rect.width, LINEWIDTH);
            m_isDrawRect = true;
        } else if (next == 0) {
            Rectangle rect = getBoundsAt(0);
            m_lineRect.setRect(rect.x, -LINEWIDTH / 2, rect.width, LINEWIDTH);
            m_isDrawRect = true;
        } else {
            Rectangle rect = getBoundsAt(next - 1);
            m_lineRect.setRect(rect.x, rect.y + rect.height - LINEWIDTH / 2,
                    rect.width, LINEWIDTH);
            m_isDrawRect = true;
        }
    }

    private void initGlassPane(Component c, Point tabPt, int a_tabIndex) {
        //Point p = (Point) pt.clone();
        getRootPane().setGlassPane(s_glassPane);
        if (hasGhost()) {
            Rectangle rect = getBoundsAt(a_tabIndex);
            BufferedImage image = new BufferedImage(c.getWidth(),
                    c.getHeight(), BufferedImage.TYPE_INT_ARGB);
            Graphics g = image.getGraphics();
            c.paint(g);
            image = image.getSubimage(rect.x, rect.y, rect.width, rect.height);
            s_glassPane.setImage(image);            
        } // if

        s_glassPane.setPoint(buildGhostLocation(tabPt));
        s_glassPane.setVisible(true);
    }

    private Rectangle getTabAreaBound() {
        Rectangle lastTab = getUI().getTabBounds(this, getTabCount() - 1);
        return new Rectangle(0, 0, getWidth(), lastTab.y + lastTab.height);
    }

    public void paintComponent(Graphics g) {
        super.paintComponent(g);

        if (m_isDrawRect) {
            Graphics2D g2 = (Graphics2D) g;
            g2.setPaint(m_lineColor);
            g2.fill(m_lineRect);
        } // if
    }

    public interface TabAcceptor {
        boolean isDropAcceptable(DnDTabbedPane a_component, int a_index);
    }
}

class GhostGlassPane extends JPanel {
    public static final long serialVersionUID = 1L;
    private final AlphaComposite m_composite;

    private Point m_location = new Point(0, 0);

    private BufferedImage m_draggingGhost = null;

    public GhostGlassPane() {
        setOpaque(false);
        m_composite = AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 0.7f);
    }

    public void setImage(BufferedImage draggingGhost) {
        m_draggingGhost = draggingGhost;
    }

    public void setPoint(Point a_location) {
        m_location.x = a_location.x;
        m_location.y = a_location.y;
    }

    public int getGhostWidth() {
        if (m_draggingGhost == null) {
            return 0;
        } // if

        return m_draggingGhost.getWidth(this);
    }

    public int getGhostHeight() {
        if (m_draggingGhost == null) {
            return 0;
        } // if

        return m_draggingGhost.getHeight(this);
    }

    public void paintComponent(Graphics g) {
        if (m_draggingGhost == null) {
            return;
        } // if 

        Graphics2D g2 = (Graphics2D) g;
        g2.setComposite(m_composite);

        g2.drawImage(m_draggingGhost, (int) m_location.getX(), (int) m_location.getY(), null);
    }
}

Answer 2

¡Maldiciones!Superado por una búsqueda en Google.Desafortunadamente, es cierto que no existe una manera fácil de crear paneles de pestañas arrastrables (o cualquier otro componente) en Swing.Entonces, aunque el ejemplo anterior está completo, este que acabo de escribir es un poco más simple.Por lo tanto, es de esperar que demuestre un poco más claramente las técnicas más avanzadas involucradas.Los pasos son:

1. Detectar que se ha producido un arrastre
2. Dibuja la pestaña arrastrada a un búfer fuera de la pantalla
3. Realice un seguimiento de la posición del mouse mientras se arrastra
4. Dibuja la pestaña en el búfer encima del componente.

El ejemplo anterior le dará lo que desea, pero si realmente desea comprender las técnicas aplicadas aquí, podría ser un mejor ejercicio redondear los bordes de este ejemplo y agregarle las características adicionales demostradas anteriormente.

O tal vez simplemente estoy decepcionado porque pasé tiempo escribiendo esta solución cuando ya existía una :p

import java.awt.Component;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionAdapter;
import java.awt.image.BufferedImage;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JTabbedPane;


public class DraggableTabbedPane extends JTabbedPane {

  private boolean dragging = false;
  private Image tabImage = null;
  private Point currentMouseLocation = null;
  private int draggedTabIndex = 0;

  public DraggableTabbedPane() {
    super();
    addMouseMotionListener(new MouseMotionAdapter() {
      public void mouseDragged(MouseEvent e) {

        if(!dragging) {
          // Gets the tab index based on the mouse position
          int tabNumber = getUI().tabForCoordinate(DraggableTabbedPane.this, e.getX(), e.getY());

          if(tabNumber >= 0) {
            draggedTabIndex = tabNumber;
            Rectangle bounds = getUI().getTabBounds(DraggableTabbedPane.this, tabNumber);


            // Paint the tabbed pane to a buffer
            Image totalImage = new BufferedImage(getWidth(), getHeight(), BufferedImage.TYPE_INT_ARGB);
            Graphics totalGraphics = totalImage.getGraphics();
            totalGraphics.setClip(bounds);
            // Don't be double buffered when painting to a static image.
            setDoubleBuffered(false);
            paintComponent(totalGraphics);

            // Paint just the dragged tab to the buffer
            tabImage = new BufferedImage(bounds.width, bounds.height, BufferedImage.TYPE_INT_ARGB);
            Graphics graphics = tabImage.getGraphics();
            graphics.drawImage(totalImage, 0, 0, bounds.width, bounds.height, bounds.x, bounds.y, bounds.x + bounds.width, bounds.y+bounds.height, DraggableTabbedPane.this);

            dragging = true;
            repaint();
          }
        } else {
          currentMouseLocation = e.getPoint();

          // Need to repaint
          repaint();
        }

        super.mouseDragged(e);
      }
    });

    addMouseListener(new MouseAdapter() {
      public void mouseReleased(MouseEvent e) {

        if(dragging) {
          int tabNumber = getUI().tabForCoordinate(DraggableTabbedPane.this, e.getX(), 10);

          if(tabNumber >= 0) {
            Component comp = getComponentAt(draggedTabIndex);
            String title = getTitleAt(draggedTabIndex);
            removeTabAt(draggedTabIndex);
            insertTab(title, null, comp, null, tabNumber);
          }
        }

        dragging = false;
        tabImage = null;
      }
    });
  }

  protected void paintComponent(Graphics g) {
    super.paintComponent(g);

    // Are we dragging?
    if(dragging && currentMouseLocation != null && tabImage != null) {
      // Draw the dragged tab
      g.drawImage(tabImage, currentMouseLocation.x, currentMouseLocation.y, this);
    }
  }

  public static void main(String[] args) {
    JFrame test = new JFrame("Tab test");
    test.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    test.setSize(400, 400);

    DraggableTabbedPane tabs = new DraggableTabbedPane();
    tabs.addTab("One", new JButton("One"));
    tabs.addTab("Two", new JButton("Two"));
    tabs.addTab("Three", new JButton("Three"));
    tabs.addTab("Four", new JButton("Four"));

    test.add(tabs);
    test.setVisible(true);
  }
}

Answer 3

Encontré este código en el tubos:

class DnDTabbedPane extends JTabbedPane {
  private static final int LINEWIDTH = 3;
  private static final String NAME = "test";
  private final GhostGlassPane glassPane = new GhostGlassPane();
  private final Rectangle2D lineRect   = new Rectangle2D.Double();
  private final Color     lineColor  = new Color(0, 100, 255);
  //private final DragSource dragSource  = new DragSource();
  //private final DropTarget dropTarget;
  private int dragTabIndex = -1;

  public DnDTabbedPane() {
    super();
    final DragSourceListener dsl = new DragSourceListener() {
      public void dragEnter(DragSourceDragEvent e) {
        e.getDragSourceContext().setCursor(DragSource.DefaultMoveDrop);
      }
      public void dragExit(DragSourceEvent e) {
        e.getDragSourceContext().setCursor(DragSource.DefaultMoveNoDrop);
        lineRect.setRect(0,0,0,0);
        glassPane.setPoint(new Point(-1000,-1000));
        glassPane.repaint();
      }
      public void dragOver(DragSourceDragEvent e) {
        //e.getLocation()
        //This method returns a Point indicating the cursor location in screen coordinates at the moment
        Point tabPt = e.getLocation();
        SwingUtilities.convertPointFromScreen(tabPt, DnDTabbedPane.this);
        Point glassPt = e.getLocation();
        SwingUtilities.convertPointFromScreen(glassPt, glassPane);
        int targetIdx = getTargetTabIndex(glassPt);
        if(getTabAreaBound().contains(tabPt) && targetIdx>=0 &&
           targetIdx!=dragTabIndex && targetIdx!=dragTabIndex+1) {
          e.getDragSourceContext().setCursor(DragSource.DefaultMoveDrop);
        }else{
          e.getDragSourceContext().setCursor(DragSource.DefaultMoveNoDrop);
        }
      }
      public void dragDropEnd(DragSourceDropEvent e) {
        lineRect.setRect(0,0,0,0);
        dragTabIndex = -1;
        if(hasGhost()) {
          glassPane.setVisible(false);
          glassPane.setImage(null);
        }
      }
      public void dropActionChanged(DragSourceDragEvent e) {}
    };
    final Transferable t = new Transferable() {
      private final DataFlavor FLAVOR = new DataFlavor(DataFlavor.javaJVMLocalObjectMimeType, NAME);
      public Object getTransferData(DataFlavor flavor) {
        return DnDTabbedPane.this;
      }
      public DataFlavor[] getTransferDataFlavors() {
        DataFlavor[] f = new DataFlavor[1];
        f[0] = this.FLAVOR;
        return f;
      }
      public boolean isDataFlavorSupported(DataFlavor flavor) {
        return flavor.getHumanPresentableName().equals(NAME);
      }
    };
    final DragGestureListener dgl = new DragGestureListener() {
      public void dragGestureRecognized(DragGestureEvent e) {
        Point tabPt = e.getDragOrigin();
        dragTabIndex = indexAtLocation(tabPt.x, tabPt.y);
        if(dragTabIndex<0) return;
        initGlassPane(e.getComponent(), e.getDragOrigin());
        try{
          e.startDrag(DragSource.DefaultMoveDrop, t, dsl);
        }catch(InvalidDnDOperationException idoe) {
          idoe.printStackTrace();
        }
      }
    };
    //dropTarget =
    new DropTarget(glassPane, DnDConstants.ACTION_COPY_OR_MOVE, new CDropTargetListener(), true);
    new DragSource().createDefaultDragGestureRecognizer(this, DnDConstants.ACTION_COPY_OR_MOVE, dgl);
  }

  class CDropTargetListener implements DropTargetListener{
    public void dragEnter(DropTargetDragEvent e) {
      if(isDragAcceptable(e)) e.acceptDrag(e.getDropAction());
      else e.rejectDrag();
    }
    public void dragExit(DropTargetEvent e) {}
    public void dropActionChanged(DropTargetDragEvent e) {}
    public void dragOver(final DropTargetDragEvent e) {
      if(getTabPlacement()==JTabbedPane.TOP || getTabPlacement()==JTabbedPane.BOTTOM) {
        initTargetLeftRightLine(getTargetTabIndex(e.getLocation()));
      }else{
        initTargetTopBottomLine(getTargetTabIndex(e.getLocation()));
      }
      repaint();
      if(hasGhost()) {
        glassPane.setPoint(e.getLocation());
        glassPane.repaint();
      }
    }

    public void drop(DropTargetDropEvent e) {
      if(isDropAcceptable(e)) {
        convertTab(dragTabIndex, getTargetTabIndex(e.getLocation()));
        e.dropComplete(true);
      }else{
        e.dropComplete(false);
      }
      repaint();
    }
    public boolean isDragAcceptable(DropTargetDragEvent e) {
      Transferable t = e.getTransferable();
      if(t==null) return false;
      DataFlavor[] f = e.getCurrentDataFlavors();
      if(t.isDataFlavorSupported(f[0]) && dragTabIndex>=0) {
        return true;
      }
      return false;
    }
    public boolean isDropAcceptable(DropTargetDropEvent e) {
      Transferable t = e.getTransferable();
      if(t==null) return false;
      DataFlavor[] f = t.getTransferDataFlavors();
      if(t.isDataFlavorSupported(f[0]) && dragTabIndex>=0) {
        return true;
      }
      return false;
    }
  }

  private boolean hasGhost = true;
  public void setPaintGhost(boolean flag) {
    hasGhost = flag;
  }
  public boolean hasGhost() {
    return hasGhost;
  }
  private int getTargetTabIndex(Point glassPt) {
    Point tabPt = SwingUtilities.convertPoint(glassPane, glassPt, DnDTabbedPane.this);
    boolean isTB = getTabPlacement()==JTabbedPane.TOP || getTabPlacement()==JTabbedPane.BOTTOM;
    for(int i=0;i<getTabCount();i++) {
      Rectangle r = getBoundsAt(i);
      if(isTB) r.setRect(r.x-r.width/2, r.y,  r.width, r.height);
      else   r.setRect(r.x, r.y-r.height/2, r.width, r.height);
      if(r.contains(tabPt)) return i;
    }
    Rectangle r = getBoundsAt(getTabCount()-1);
    if(isTB) r.setRect(r.x+r.width/2, r.y,  r.width, r.height);
    else   r.setRect(r.x, r.y+r.height/2, r.width, r.height);
    return   r.contains(tabPt)?getTabCount():-1;
  }
  private void convertTab(int prev, int next) {
    if(next<0 || prev==next) {
      //System.out.println("press="+prev+" next="+next);
      return;
    }
    Component cmp = getComponentAt(prev);
    String str = getTitleAt(prev);
    if(next==getTabCount()) {
      //System.out.println("last: press="+prev+" next="+next);
      remove(prev);
      addTab(str, cmp);
      setSelectedIndex(getTabCount()-1);
    }else if(prev>next) {
      //System.out.println("   >: press="+prev+" next="+next);
      remove(prev);
      insertTab(str, null, cmp, null, next);
      setSelectedIndex(next);
    }else{
      //System.out.println("   <: press="+prev+" next="+next);
      remove(prev);
      insertTab(str, null, cmp, null, next-1);
      setSelectedIndex(next-1);
    }
  }

  private void initTargetLeftRightLine(int next) {
    if(next<0 || dragTabIndex==next || next-dragTabIndex==1) {
      lineRect.setRect(0,0,0,0);
    }else if(next==getTabCount()) {
      Rectangle rect = getBoundsAt(getTabCount()-1);
      lineRect.setRect(rect.x+rect.width-LINEWIDTH/2,rect.y,LINEWIDTH,rect.height);
    }else if(next==0) {
      Rectangle rect = getBoundsAt(0);
      lineRect.setRect(-LINEWIDTH/2,rect.y,LINEWIDTH,rect.height);
    }else{
      Rectangle rect = getBoundsAt(next-1);
      lineRect.setRect(rect.x+rect.width-LINEWIDTH/2,rect.y,LINEWIDTH,rect.height);
    }
  }
  private void initTargetTopBottomLine(int next) {
    if(next<0 || dragTabIndex==next || next-dragTabIndex==1) {
      lineRect.setRect(0,0,0,0);
    }else if(next==getTabCount()) {
      Rectangle rect = getBoundsAt(getTabCount()-1);
      lineRect.setRect(rect.x,rect.y+rect.height-LINEWIDTH/2,rect.width,LINEWIDTH);
    }else if(next==0) {
      Rectangle rect = getBoundsAt(0);
      lineRect.setRect(rect.x,-LINEWIDTH/2,rect.width,LINEWIDTH);
    }else{
      Rectangle rect = getBoundsAt(next-1);
      lineRect.setRect(rect.x,rect.y+rect.height-LINEWIDTH/2,rect.width,LINEWIDTH);
    }
  }

  private void initGlassPane(Component c, Point tabPt) {
    //Point p = (Point) pt.clone();
    getRootPane().setGlassPane(glassPane);
    if(hasGhost()) {
      Rectangle rect = getBoundsAt(dragTabIndex);
      BufferedImage image = new BufferedImage(c.getWidth(), c.getHeight(), BufferedImage.TYPE_INT_ARGB);
      Graphics g = image.getGraphics();
      c.paint(g);
      image = image.getSubimage(rect.x,rect.y,rect.width,rect.height);
      glassPane.setImage(image);
    }
    Point glassPt = SwingUtilities.convertPoint(c, tabPt, glassPane);
    glassPane.setPoint(glassPt);
    glassPane.setVisible(true);
  }

  private Rectangle getTabAreaBound() {
    Rectangle lastTab  = getUI().getTabBounds(this, getTabCount()-1);
    return new Rectangle(0,0,getWidth(),lastTab.y+lastTab.height);
  }

  public void paintComponent(Graphics g) {
    super.paintComponent(g);
    if(dragTabIndex>=0) {
      Graphics2D g2 = (Graphics2D)g;
      g2.setPaint(lineColor);
      g2.fill(lineRect);
    }
  }
}

class GhostGlassPane extends JPanel {
  private final AlphaComposite composite;
  private Point location = new Point(0, 0);
  private BufferedImage draggingGhost = null;
  public GhostGlassPane() {
    setOpaque(false);
    composite = AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 0.5f);
  }
  public void setImage(BufferedImage draggingGhost) {
    this.draggingGhost = draggingGhost;
  }
  public void setPoint(Point location) {
    this.location = location;
  }
  public void paintComponent(Graphics g) {
    if(draggingGhost == null) return;
    Graphics2D g2 = (Graphics2D) g;
    g2.setComposite(composite);
    double xx = location.getX() - (draggingGhost.getWidth(this) /2d);
    double yy = location.getY() - (draggingGhost.getHeight(this)/2d);
    g2.drawImage(draggingGhost, (int)xx, (int)yy , null);
  }
}

Answer 4

@Tony:Parece que solución de euguenes simplemente pasa por alto la preservación de TabComponents durante un intercambio.

El método convertTab solo necesita recordar el TabComponent y configurarlo en las nuevas pestañas que crea.

Intenta usar esto:

    private void convertTab(TabTransferData a_data, int a_targetIndex) {

            DnDTabbedPane source = a_data.getTabbedPane();
            System.out.println("this=source? " + (this == source));
            int sourceIndex = a_data.getTabIndex();
            if (sourceIndex < 0) {
                    return;
            } // if
            //Save the tab's component, title, and TabComponent.
            Component cmp = source.getComponentAt(sourceIndex);
            String str = source.getTitleAt(sourceIndex);
            Component tcmp = source.getTabComponentAt(sourceIndex);

            if (this != source) {
                    source.remove(sourceIndex);

                    if (a_targetIndex == getTabCount()) {
                            addTab(str, cmp);
                            setTabComponentAt(getTabCount()-1, tcmp);
                    } else {
                            if (a_targetIndex < 0) {
                                    a_targetIndex = 0;
                            } // if

                            insertTab(str, null, cmp, null, a_targetIndex);
                            setTabComponentAt(a_targetIndex, tcmp);
                    } // if

                    setSelectedComponent(cmp);
                    return;
            } // if
            if (a_targetIndex < 0 || sourceIndex == a_targetIndex) {
                    return;
            } // if
            if (a_targetIndex == getTabCount()) {    
                    source.remove(sourceIndex);
                    addTab(str, cmp);
                    setTabComponentAt(getTabCount() - 1, tcmp);
                    setSelectedIndex(getTabCount() - 1);
            } else if (sourceIndex > a_targetIndex) {
                    source.remove(sourceIndex);
                    insertTab(str, null, cmp, null, a_targetIndex);
                    setTabComponentAt(a_targetIndex, tcmp);
                    setSelectedIndex(a_targetIndex);
            } else {
                    source.remove(sourceIndex);
                    insertTab(str, null, cmp, null, a_targetIndex - 1);
                    setTabComponentAt(a_targetIndex - 1, tcmp);
                    setSelectedIndex(a_targetIndex - 1);
            }

    }

Answer 5

Agregue esto a isDragAcceptable para evitar excepciones:

boolean transferDataFlavorFound = false;
for (DataFlavor transferDataFlavor : t.getTransferDataFlavors()) {
    if (FLAVOR.equals(transferDataFlavor)) {
        transferDataFlavorFound = true;
        break;
    }
}
if (transferDataFlavorFound == false) {
    return false;
}