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Message:

drag and drop of images in an applet

Posted by Vidya Setlur on June 14, 2001 at 7:11 PM

Hi,
I have been trying to implement drag and drop of images in an applet. I basically am trying to drag images from a JList and put them on a JPanel.
The problem with it is that, the drop methods never get invoked. Only the startDrag event is invoked when an image is dragged but I can't drop it in the panel.

Here is the code:

import javax.swing.event.*;
import java.awt.event.*;
import javax.swing.*;
import java.awt.*;
import java.io.*;
import java.applet.*;
import java.awt.datatransfer.*;
import java.awt.dnd.*;

public class dndApplet extends JApplet implements Runnable {
private DragContainer dragcontainer;
private DropContainer dropcontainer;
private DefaultListModel listModel;
public void start() {
Thread kicker = new Thread(this);
kicker.start(); }
public void run() {
dndApplet dndapplet = new dndApplet();
dndapplet.init();
}
public void init() {
try {
getContentPane().setLayout(new BorderLayout());
listModel = new DefaultListModel();
dragcontainer = new DragContainer(listModel);
getContentPane().add(BorderLayout.EAST, new JScrollPane(dragcontainer));
dropcontainer = new DropContainer();
getContentPane().add(BorderLayout.CENTER,dropcontainer);
}
catch (Exception e) {
System.out.println("error");
}
fillUpList("c:\\dnd\\images");
setSize(700,300);
}
public static void main(String[] args) {
Frame f = new Frame("dndframe");
dndApplet dndapplet = new dndApplet();
dndapplet.init();
dndapplet.start();
f.show();
}

private void fillUpList(String directory) {
File dir = new File(directory);
File[] files = dir.listFiles();
for (int i= 0; i listModel.addElement(new ImageIcon(directory + "\\" + files[i].getName()));
}
}
}

class ImageSelection implements Transferable, Serializable {

public DataFlavor[] getTransferDataFlavors() {
DataFlavor[] supported = new DataFlavor[1];
supported[0] = new DataFlavor(getClass(),"SelectedImage");
System.out.println(supported);
return supported;
}

public Object getTransferData(DataFlavor f)
throws UnsupportedFlavorException {
return this;
}

public boolean isDataFlavorSupported(DataFlavor aFlavor)
{
return aFlavor.equals(new DataFlavor(getClass(),"SelectedImage"));
}

}

class DragContainer extends JList implements DragGestureListener, DragSourceListener {
private DragSource iDragSource = null;
DataFlavor DATA_FLAVOR;
public DragContainer(ListModel lm) {
super(lm);

try {
DATA_FLAVOR = new DataFlavor(ImageIcon.class,"SelectedImage");
}
catch (Exception e) {
System.out.println("Error in dataflavor for dragcontainer");
}
iDragSource = new DragSource();
iDragSource.createDefaultDragGestureRecognizer(this,DnDConstants.ACTION_MOVE, this);
}
public void dragGestureRecognized(DragGestureEvent aEvt) {
ImageIcon imageSelected = (ImageIcon) getSelectedValue();
ImageSelection imsel = new ImageSelection();
if (imageSelected != null) {
System.out.println("startdrag...");
iDragSource.startDrag(aEvt,DragSource.DefaultCopyNoDrop,imsel,this);
}
else
System.out.println("Nothing Selected");
}

public void dropActionChanged(DropTargetDragEvent event) {
}

public void dropActionChanged(DragSourceDragEvent event) {
}

public void dragDropEnd(DragSourceDropEvent event) {
}

public void dragEnter(DragSourceDragEvent event) {
}

public void dragExit (DragSourceEvent event) {
}

public void dragOver(DragSourceDragEvent event) {
DragSourceContext context = event.getDragSourceContext();
context.setCursor(null);
context.setCursor(DragSource.DefaultCopyDrop);
}
}

class DropContainer extends JPanel implements DropTargetListener {
private DropTarget iDropTarget = null;
public DropContainer() {
iDropTarget = new DropTarget(this,this);
setBackground(Color.red);
}

public void dragEnter (DropTargetDragEvent event) {
System.out.println("dragenter");
event.acceptDrag(DnDConstants.ACTION_MOVE);
}

public void dragExit(DropTargetEvent event) {
System.out.println("dragexit");
}

public void dragOver (DropTargetDragEvent event) {
System.out.println("dragover");
event.acceptDrag(DnDConstants.ACTION_COPY);
}

public void dropActionChanged (DropTargetDragEvent event) {
System.out.println("dropactionchanged");
event.acceptDrag(DnDConstants.ACTION_COPY);
}

public void drop(DropTargetDropEvent aEvt) {
System.out.println("drop");
try {
Transferable transferable = aEvt.getTransferable();
DataFlavor aliFlavor = new DataFlavor(getClass(),"Selected Image");
System.out.println(aliFlavor);
if (transferable.isDataFlavorSupported(aliFlavor)) {
aEvt.acceptDrop(DnDConstants.ACTION_MOVE);
ImageIcon icon = (ImageIcon)transferable.getTransferData(aliFlavor);
aEvt.getDropTargetContext().dropComplete(true);
}
else {
System.out.println("rejecting drop");
aEvt.rejectDrop();
aEvt.getDropTargetContext().dropComplete(false);
}
}
catch (Exception exc) {
exc.printStackTrace();
aEvt.rejectDrop();
aEvt.getDropTargetContext().dropComplete(false);
}
}

}//class DropContainer

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