Dragging and dropping images in java

Question

I want to drag an image from one JPanel to another. I was able to do this using the dnd libraries. But I am stuck with this because I cannot drag the image from the panel where I dropped it (from the target). this means that droptarget should also act as dragSource. How am i doing this?

Answer 1

Perhaps this helps:

http://www.java2s.com/Code/Java/Swing-JFC/DragPictureDemo2.htm

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IN NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE FOR ANY LOST * REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT, SPECIAL, CONSEQUENTIAL, * INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER CAUSED AND REGARDLESS OF THE THEORY * OF LIABILITY, ARISING OUT OF THE USE OF OR INABILITY TO USE THIS SOFTWARE, * EVEN IF SUN HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. * * You acknowledge that this software is not designed, licensed or intended * for use in the design, construction, operation or maintenance of any * nuclear facility. */ /* * DragPictureDemo2.java is a 1.4 example that requires the following files: * Picture.java DTPicture.java PictureTransferHandler.java * TransferActionListener.java images/Maya.jpg images/Anya.jpg images/Laine.jpg * images/Cosmo.jpg images/Adele.jpg images/Alexi.jpg */ import java.awt.BorderLayout; import java.awt.Color; import java.awt.Dimension; import java.awt.Graphics; import java.awt.GridLayout; import java.awt.Image; import java.awt.KeyboardFocusManager; import java.awt.datatransfer.DataFlavor; import java.awt.datatransfer.Transferable; import java.awt.datatransfer.UnsupportedFlavorException; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.awt.event.FocusEvent; import java.awt.event.FocusListener; import java.awt.event.InputEvent; import java.awt.event.KeyEvent; import java.awt.event.MouseEvent; import java.awt.event.MouseListener; import java.awt.event.MouseMotionListener; import java.beans.PropertyChangeEvent; import java.beans.PropertyChangeListener; import java.io.File; import java.io.IOException; import java.net.MalformedURLException; import javax.accessibility.Accessible; import javax.swing.Action; import javax.swing.ActionMap; import javax.swing.BorderFactory; import javax.swing.ImageIcon; import javax.swing.InputMap; import javax.swing.JComponent; import javax.swing.JFrame; import javax.swing.JMenu; import javax.swing.JMenuBar; import javax.swing.JMenuItem; import javax.swing.JPanel; import javax.swing.KeyStroke; import javax.swing.TransferHandler; //A version of DragPictureDemo that creates an //Edit menu with cut/copy/paste actions. //This demo adds a class called TransferActionDemo //that transfers the cut/copy/paste menu action //to the currently focused component. public class DragPictureDemo2 extends JPanel { DTPicture pic1, pic2, pic3, pic4, pic5, pic6, pic7, pic8, pic9, pic10, pic11, pic12; static String mayaString = "Maya"; static String anyaString = "Anya"; static String laineString = "Laine"; static String cosmoString = "Cosmo"; static String adeleString = "Adele"; static String alexiString = "Alexi"; PictureTransferHandler picHandler; public DragPictureDemo2() { super(new BorderLayout()); picHandler = new PictureTransferHandler(); //Since we are using keyboard accelerators, we don't //need the component to install its own input map //bindings. DTPicture.setInstallInputMapBindings(false); JPanel mugshots = new JPanel(new GridLayout(4, 3)); pic1 = new DTPicture(createImageIcon("images/" + mayaString + ".jpg", mayaString).getImage()); pic1.setTransferHandler(picHandler); mugshots.add(pic1); pic2 = new DTPicture(createImageIcon("images/" + anyaString + ".jpg", anyaString).getImage()); pic2.setTransferHandler(picHandler); mugshots.add(pic2); pic3 = new DTPicture(createImageIcon("images/" + laineString + ".jpg", laineString).getImage()); pic3.setTransferHandler(picHandler); mugshots.add(pic3); pic4 = new DTPicture(createImageIcon("images/" + cosmoString + ".jpg", cosmoString).getImage()); pic4.setTransferHandler(picHandler); mugshots.add(pic4); pic5 = new DTPicture(createImageIcon("images/" + adeleString + ".jpg", adeleString).getImage()); pic5.setTransferHandler(picHandler); mugshots.add(pic5); pic6 = new DTPicture(createImageIcon("images/" + alexiString + ".jpg", alexiString).getImage()); pic6.setTransferHandler(picHandler); mugshots.add(pic6); //These six components with no pictures provide handy //drop targets. pic7 = new DTPicture(null); pic7.setTransferHandler(picHandler); mugshots.add(pic7); pic8 = new DTPicture(null); pic8.setTransferHandler(picHandler); mugshots.add(pic8); pic9 = new DTPicture(null); pic9.setTransferHandler(picHandler); mugshots.add(pic9); pic10 = new DTPicture(null); pic10.setTransferHandler(picHandler); mugshots.add(pic10); pic11 = new DTPicture(null); pic11.setTransferHandler(picHandler); mugshots.add(pic11); pic12 = new DTPicture(null); pic12.setTransferHandler(picHandler); mugshots.add(pic12); setPreferredSize(new Dimension(450, 630)); add(mugshots, BorderLayout.CENTER); setBorder(BorderFactory.createEmptyBorder(20, 20, 20, 20)); } //Create an Edit menu to support cut/copy/paste. public JMenuBar createMenuBar() { JMenuItem menuItem = null; JMenuBar menuBar = new JMenuBar(); JMenu mainMenu = new JMenu("Edit"); mainMenu.setMnemonic(KeyEvent.VK_E); TransferActionListener actionListener = new TransferActionListener(); menuItem = new JMenuItem("Cut"); menuItem.setActionCommand((String) TransferHandler.getCutAction() .getValue(Action.NAME)); menuItem.addActionListener(actionListener); menuItem.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_X, ActionEvent.CTRL_MASK)); menuItem.setMnemonic(KeyEvent.VK_T); mainMenu.add(menuItem); menuItem = new JMenuItem("Copy"); menuItem.setActionCommand((String) TransferHandler.getCopyAction() .getValue(Action.NAME)); menuItem.addActionListener(actionListener); menuItem.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_C, ActionEvent.CTRL_MASK)); menuItem.setMnemonic(KeyEvent.VK_C); mainMenu.add(menuItem); menuItem = new JMenuItem("Paste"); menuItem.setActionCommand((String) TransferHandler.getPasteAction() .getValue(Action.NAME)); menuItem.addActionListener(actionListener); menuItem.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_V, ActionEvent.CTRL_MASK)); menuItem.setMnemonic(KeyEvent.VK_P); mainMenu.add(menuItem); menuBar.add(mainMenu); return menuBar; } /** Returns an ImageIcon, or null if the path was invalid. */ protected static ImageIcon createImageIcon(String path, String description) { try { File imageURL = new File(path); if (imageURL == null) { System.err.println("Resource not found: " + path); return null; } else { return new ImageIcon(imageURL.toURI().toURL(), description); } } catch( MalformedURLException e ) { e.printStackTrace(); } return null; } /** * Create the GUI and show it. For thread safety, this method should be * invoked from the event-dispatching thread. */ private static void createAndShowGUI() { //Make sure we have nice window decorations. JFrame.setDefaultLookAndFeelDecorated(true); //Create and set up the window. JFrame frame = new JFrame("DragPictureDemo2"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //Create and set up the menu bar and content pane. DragPictureDemo2 demo = new DragPictureDemo2(); frame.setJMenuBar(demo.createMenuBar()); demo.setOpaque(true); //content panes must be opaque frame.setContentPane(demo); //Display the window. frame.pack(); frame.setVisible(true); } public static void main(String[] args) { //Schedule a job for the event-dispatching thread: //creating and showing this application GUI. javax.swing.SwingUtilities.invokeLater(new Runnable() { public void run() { createAndShowGUI(); } }); } } /* * DTPicture.java is used by the 1.4 DragPictureDemo.java example. */ //A subclass of Picture that supports Data Transfer. class DTPicture extends Picture implements MouseMotionListener { private MouseEvent firstMouseEvent = null; private static boolean installInputMapBindings = true; public DTPicture(Image image) { super(image); addMouseMotionListener(this); //Add the cut/copy/paste key bindings to the input map. //Note that this step is redundant if you are installing //menu accelerators that cause these actions to be invoked. //DragPictureDemo does not use menu accelerators and, since //the default value of installInputMapBindings is true, //the bindings are installed. DragPictureDemo2 does use //menu accelerators and so calls setInstallInputMapBindings //with a value of false. Your program would do one or the //other, but not both. if (installInputMapBindings) { InputMap imap = this.getInputMap(); imap.put(KeyStroke.getKeyStroke("ctrl X"), TransferHandler .getCutAction().getValue(Action.NAME)); imap.put(KeyStroke.getKeyStroke("ctrl C"), TransferHandler .getCopyAction().getValue(Action.NAME)); imap.put(KeyStroke.getKeyStroke("ctrl V"), TransferHandler .getPasteAction().getValue(Action.NAME)); } //Add the cut/copy/paste actions to the action map. //This step is necessary because the menu action listener //looks for these actions to fire. ActionMap map = this.getActionMap(); map.put(TransferHandler.getCutAction().getValue(Action.NAME), TransferHandler.getCutAction()); map.put(TransferHandler.getCopyAction().getValue(Action.NAME), TransferHandler.getCopyAction()); map.put(TransferHandler.getPasteAction().getValue(Action.NAME), TransferHandler.getPasteAction()); } public void setImage(Image image) { this.image = image; this.repaint(); } public void mousePressed(MouseEvent e) { //Don't bother to drag if there is no image. if (image == null) return; firstMouseEvent = e; e.consume(); } public void mouseDragged(MouseEvent e) { //Don't bother to drag if the component displays no image. if (image == null) return; if (firstMouseEvent != null) { e.consume(); //If they are holding down the control key, COPY rather than MOVE int ctrlMask = InputEvent.CTRL_DOWN_MASK; int action = ((e.getModifiersEx() & ctrlMask) == ctrlMask) ? TransferHandler.COPY : TransferHandler.MOVE; int dx = Math.abs(e.getX() - firstMouseEvent.getX()); int dy = Math.abs(e.getY() - firstMouseEvent.getY()); //Arbitrarily define a 5-pixel shift as the //official beginning of a drag. if (dx > 5 || dy > 5) { //This is a drag, not a click. JComponent c = (JComponent) e.getSource(); TransferHandler handler = c.getTransferHandler(); //Tell the transfer handler to initiate the drag. handler.exportAsDrag(c, firstMouseEvent, action); firstMouseEvent = null; } } } public void mouseReleased(MouseEvent e) { firstMouseEvent = null; } public void mouseMoved(MouseEvent e) { } //This method is necessary because DragPictureDemo and //DragPictureDemo2 both use this class and DragPictureDemo //needs to have the input map bindings installed for //cut/copy/paste. DragPictureDemo2 uses menu accelerators //and does not need to have the input map bindings installed. //Your program would use one approach or the other, but not //both. The default for installInputMapBindings is true. public static void setInstallInputMapBindings(boolean flag) { installInputMapBindings = flag; } public static boolean getInstallInputMapBindingds() { //for completeness return installInputMapBindings; } } /* * Picture.java is used by the 1.4 TrackFocusDemo.java and DragPictureDemo.java * examples. */ class Picture extends JComponent implements MouseListener, FocusListener, Accessible { Image image; public Picture(Image image) { this.image = image; setFocusable(true); addMouseListener(this); addFocusListener(this); } public void mouseClicked(MouseEvent e) { //Since the user clicked on us, let get focus! requestFocusInWindow(); } public void mouseEntered(MouseEvent e) { } public void mouseExited(MouseEvent e) { } public void mousePressed(MouseEvent e) { } public void mouseReleased(MouseEvent e) { } public void focusGained(FocusEvent e) { //Draw the component with a red border //indicating that it has focus. this.repaint(); } public void focusLost(FocusEvent e) { //Draw the component with a black border //indicating that it doesn't have focus. this.repaint(); } protected void paintComponent(Graphics graphics) { Graphics g = graphics.create(); //Draw in our entire space, even if isOpaque is false. g.setColor(Color.WHITE); g.fillRect(0, 0, image == null ? 125 : image.getWidth(this), image == null ? 125 : image.getHeight(this)); if (image != null) { //Draw image at its natural size of 125x125. g.drawImage(image, 0, 0, this); } //Add a border, red if picture currently has focus if (isFocusOwner()) { g.setColor(Color.RED); } else { g.setColor(Color.BLACK); } g.drawRect(0, 0, image == null ? 125 : image.getWidth(this), image == null ? 125 : image.getHeight(this)); g.dispose(); } } /* * PictureTransferHandler.java is used by the 1.4 DragPictureDemo.java example. */ class PictureTransferHandler extends TransferHandler { DataFlavor pictureFlavor = DataFlavor.imageFlavor; DTPicture sourcePic; boolean shouldRemove; public boolean importData(JComponent c, Transferable t) { Image image; if (canImport(c, t.getTransferDataFlavors())) { DTPicture pic = (DTPicture) c; //Don't drop on myself. if (sourcePic == pic) { shouldRemove = false; return true; } try { image = (Image) t.getTransferData(pictureFlavor); //Set the component to the new picture. pic.setImage(image); return true; } catch (UnsupportedFlavorException ufe) { System.out.println("importData: unsupported data flavor"); } catch (IOException ioe) { System.out.println("importData: I/O exception"); } } return false; } protected Transferable createTransferable(JComponent c) { sourcePic = (DTPicture) c; shouldRemove = true; return new PictureTransferable(sourcePic); } public int getSourceActions(JComponent c) { return COPY_OR_MOVE; } protected void exportDone(JComponent c, Transferable data, int action) { if (shouldRemove && (action == MOVE)) { sourcePic.setImage(null); } sourcePic = null; } public boolean canImport(JComponent c, DataFlavor[] flavors) { for (int i = 0; i < flavors.length; i++) { if (pictureFlavor.equals(flavors[i])) { return true; } } return false; } class PictureTransferable implements Transferable { private Image image; PictureTransferable(DTPicture pic) { image = pic.image; } public Object getTransferData(DataFlavor flavor) throws UnsupportedFlavorException { if (!isDataFlavorSupported(flavor)) { throw new UnsupportedFlavorException(flavor); } return image; } public DataFlavor[] getTransferDataFlavors() { return new DataFlavor[] { pictureFlavor }; } public boolean isDataFlavorSupported(DataFlavor flavor) { return pictureFlavor.equals(flavor); } } } /* * TransferActionListener.java is used by the 1.4 DragPictureDemo.java example. */ /* * A class that tracks the focused component. This is necessary to delegate the * menu cut/copy/paste commands to the right component. An instance of this * class is listening and when the user fires one of these commands, it calls * the appropriate action on the currently focused component. */ class TransferActionListener implements ActionListener, PropertyChangeListener { private JComponent focusOwner = null; public TransferActionListener() { KeyboardFocusManager manager = KeyboardFocusManager .getCurrentKeyboardFocusManager(); manager.addPropertyChangeListener("permanentFocusOwner", this); } public void propertyChange(PropertyChangeEvent e) { Object o = e.getNewValue(); if (o instanceof JComponent) { focusOwner = (JComponent) o; } else { focusOwner = null; } } public void actionPerformed(ActionEvent e) { if (focusOwner == null) return; String action = (String) e.getActionCommand(); Action a = focusOwner.getActionMap().get(action); if (a != null) { a.actionPerformed(new ActionEvent(focusOwner, ActionEvent.ACTION_PERFORMED, null)); } } }