import java.awt.*;
import java.awt.datatransfer.*;
import java.awt.dnd.*;
import javax.swing.*;
import java.io.IOException;
import java.util.*;
import java.awt.image.*;
public class ReorderableJList extends JList
implements DragSourceListener, DropTargetListener, DragGestureListener {
static DataFlavor localObjectFlavor;
static {
try {
localObjectFlavor =
new DataFlavor (DataFlavor.javaJVMLocalObjectMimeType);
} catch (ClassNotFoundException cnfe) { cnfe.printStackTrace(); }
}
static DataFlavor[] supportedFlavors = { localObjectFlavor };
DragSource dragSource;
DropTarget dropTarget;
Object dropTargetCell;
int draggedIndex = -1;
public ReorderableJList () {
super();
setCellRenderer (new ReorderableListCellRenderer());
setModel (new DefaultListModel());
dragSource = new DragSource();
DragGestureRecognizer dgr =
dragSource.createDefaultDragGestureRecognizer (this,
DnDConstants.ACTION_MOVE,
this);
dropTarget = new DropTarget (this, this);
}
// DragGestureListener
public void dragGestureRecognized (DragGestureEvent dge) {
System.out.println ("dragGestureRecognized");
// find object at this x,y
Point clickPoint = dge.getDragOrigin();
int index = locationToIndex(clickPoint);
if (index == -1)
return;
Object target = getModel().getElementAt(index);
Transferable trans = new RJLTransferable (target);
draggedIndex = index;
dragSource.startDrag (dge,Cursor.getDefaultCursor(),
trans, this);
}
// DragSourceListener events
public void dragDropEnd (DragSourceDropEvent dsde) {
System.out.println ("dragDropEnd()");
dropTargetCell = null;
draggedIndex = -1;
repaint();
}
public void dragEnter (DragSourceDragEvent dsde) {}
public void dragExit (DragSourceEvent dse) {}
public void dragOver (DragSourceDragEvent dsde) {}
public void dropActionChanged (DragSourceDragEvent dsde) {}
// DropTargetListener events
public void dragEnter (DropTargetDragEvent dtde) {
System.out.println ("dragEnter");
if (dtde.getSource() != dropTarget)
dtde.rejectDrag();
else {
dtde.acceptDrag(DnDConstants.ACTION_COPY_OR_MOVE);
System.out.println ("accepted dragEnter");
}
}
public void dragExit (DropTargetEvent dte) {}
public void dragOver (DropTargetDragEvent dtde) {
// figure out which cell it's over, no drag to self
if (dtde.getSource() != dropTarget)
dtde.rejectDrag();
Point dragPoint = dtde.getLocation();
int index = locationToIndex (dragPoint);
if (index == -1)
dropTargetCell = null;
else
dropTargetCell = getModel().getElementAt(index);
repaint();
}
public void drop (DropTargetDropEvent dtde) {
System.out.println ("drop()!");
if (dtde.getSource() != dropTarget) {
System.out.println ("rejecting for bad source (" +
dtde.getSource().getClass().getName() + ")");
dtde.rejectDrop();
return;
}
Point dropPoint = dtde.getLocation();
int index = locationToIndex (dropPoint);
System.out.println ("drop index is " + index);
boolean dropped = false;
try {
if ((index == -1) || (index == draggedIndex)) {
System.out.println ("dropped onto self");
dtde.rejectDrop();
return;
}
dtde.acceptDrop (DnDConstants.ACTION_MOVE);
System.out.println ("accepted");
Object dragged =
dtde.getTransferable().getTransferData(localObjectFlavor);
// move items - note that indicies for insert will
// change if [removed] source was before target
System.out.println ("drop " + draggedIndex + " to " + index);
boolean sourceBeforeTarget = (draggedIndex < index);
System.out.println ("source is" +
(sourceBeforeTarget ? "" : " not") +
" before target");
System.out.println ("insert at " +
(sourceBeforeTarget ? index-1 : index));
DefaultListModel mod = (DefaultListModel) getModel();
mod.remove (draggedIndex);
mod.add ((sourceBeforeTarget ? index-1 : index), dragged);
dropped = true;
} catch (Exception e) {
e.printStackTrace();
}
dtde.dropComplete (dropped);
}
public void dropActionChanged (DropTargetDragEvent dtde) {}
// test
public static void main (String[] args) {
JList list = new ReorderableJList ();
DefaultListModel defModel = new DefaultListModel();
list.setModel (defModel);
String[] listItems = {
"Chris", "Joshua", "Daniel", "Michael",
"Don", "Kimi", "Kelly", "Keagan"
};
Iterator it = Arrays.asList(listItems).iterator();
while (it.hasNext())
defModel.addElement (it.next());
// show list
JScrollPane scroller =
new JScrollPane (list,
ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS,
ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);
JFrame frame = new JFrame ("Checkbox JList");
frame.getContentPane().add (scroller);
frame.pack();
frame.setVisible(true);
}
class RJLTransferable implements Transferable {
Object object;
public RJLTransferable (Object o) {
object = o;
}
public Object getTransferData(DataFlavor df)
throws UnsupportedFlavorException, IOException {
if (isDataFlavorSupported (df))
return object;
else
throw new UnsupportedFlavorException(df);
}
public boolean isDataFlavorSupported (DataFlavor df) {
return (df.equals (localObjectFlavor));
}
public DataFlavor[] getTransferDataFlavors () {
return supportedFlavors;
}
}
// custom renderer
class ReorderableListCellRenderer
extends DefaultListCellRenderer {
boolean isTargetCell;
boolean isLastItem;
Insets normalInsets, lastItemInsets;
int BOTTOM_PAD = 30;
public ReorderableListCellRenderer() {
super();
normalInsets = super.getInsets();
lastItemInsets =
new Insets (normalInsets.top,
normalInsets.left,
normalInsets.bottom + BOTTOM_PAD,
normalInsets.right);
}
public Component getListCellRendererComponent (JList list,
Object value,
int index,
boolean isSelected,
boolean hasFocus) {
isTargetCell = (value == dropTargetCell);
isLastItem = (index == list.getModel().getSize()-1);
boolean showSelected = isSelected &
(dropTargetCell == null);
return super.getListCellRendererComponent (list, value,
index, showSelected,
hasFocus);
}
/*
// this isn't helping, neither does overriding getSize()
public Insets getInsets(Insets in) {
Insets useInsets = (isLastItem ? lastItemInsets : normalInsets);
in.top = useInsets.top;
in.bottom = useInsets.bottom;
in.left = useInsets.left;
in.right = useInsets.right;
return in;
}
*/
public void paintComponent (Graphics g) {
super.paintComponent(g);
if (isTargetCell) {
g.setColor(Color.black);
g.drawLine (0, 0, getSize().width, 0);
}
}
}
}
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