I am using drag and drop in swing to place a button on one of four components. To make it more appealing instead of just the mouse indicating something being dragged (which is working fine) I wanted to show it in real time. This works except if the mouse goes back over the component being dragged the drag listener registers a dragExit event which removes the button which causes the listener to focus back on the parent component and fire a dragEnter causing a flicker. I need to make the button not affect the drag listener somehow. Any ideas?
this is the jlabel I'm adding it too (I know jlabel is not a good choice but it is working well and easily can display an image which I need)
import java.awt.Point;
import java.awt.datatransfer.DataFlavor;
import java.awt.datatransfer.Transferable;
import java.awt.datatransfer.UnsupportedFlavorException;
import java.awt.dnd.*;
import java.io.IOException;
import javax.swing.*;
//and here is the button to drag
public class DndLabel extends JLabel implements DropTargetListener {
private DropTarget target;
private DndButton button;
public DndLabel last;
//initialize the JTable with the data
public DndLabel() {
super();
//mark this a DropTarget
target = new DropTarget(this, this);
//have it utilize a custom transfer handler
setTransferHandler(new MyTransferHandler());
}
public void dragEnter(DropTargetDragEvent dtde) {
System.out.println("enter");
try {
//get the Point where the drop occurred
Point loc = dtde.getLocation();
//get Transfer data
Transferable t = dtde.getTransferable();
//get the Data flavors transferred with the Transferable
DataFlavor[] d = t.getTransferDataFlavors();
button = (DndButton) t.getTransferData(d[0]);
button.setBounds(loc.x, 0, 100, 50);
add(button);
//and if the DataFlavors match for the DnDTable
//(ie., we don't want an ImageFlavor marking an image transfer)
if (getTransferHandler().canImport(this, d)) {
//then import the Draggable JComponent and repaint() the JTable
((MyTransferHandler) getTransferHandler()).importData(this, (DndButton) t.getTransferData(d[0]), loc);
repaint();
} else {
return;
}
} catch (UnsupportedFlavorException ex) {
ex.printStackTrace();
} catch(IOException ex){
ex.printStackTrace();
}
}
@Override
public void dragOver(DropTargetDragEvent dtde) {
button.setLocation(dtde.getLocation().x, 0);
}
public void dragExit(DropTargetEvent dte) {
System.out.println("remove");
last = null;
remove(button);
repaint();
}
//This is what happens when a Drop occurs
public void drop(DropTargetDropEvent dtde) {
System.out.println("drop!");
try {
//get the Point where the drop occurred
Point loc = dtde.getLocation();
//get Transfer data
Transferable t = dtde.getTransferable();
//get the Data flavors transferred with the Transferable
DataFlavor[] d = t.getTransferDataFlavors();
DndButton tempButton = (DndButton) t.getTransferData(d[0]);
tempButton.setBounds(loc.x, 0, 100, 50);
add(tempButton);
//and if the DataFlavors match for the DnDTable
//(ie., we don't want an ImageFlavor marking an image transfer)
if (getTransferHandler().canImport(this, d)) {
//then import the Draggable JComponent and repaint() the JTable
((MyTransferHandler) getTransferHandler()).importData(this, (DndButton) t.getTransferData(d[0]), loc);
repaint();
} else {
return;
}
} catch (UnsupportedFlavorException ex) {
ex.printStackTrace();
}catch(IOException ex){
}finally {
dtde.dropComplete(true);
}
}
@Override
public void dropActionChanged(DropTargetDragEvent dtde) {
}
class MyTransferHandler extends TransferHandler {
//tests for a valid JButton DataFlavor
public boolean canImport(JComponent c, DataFlavor[] f) {
DataFlavor temp = new DataFlavor(DndButton.class, "JButton");
for (DataFlavor d : f) {
if (d.equals(temp)) {
return true;
}
}
return false;
}
//add the data into the JTable
public boolean importData(JComponent comp, Transferable t, Point p) {
try {
DndButton tempButton = (DndButton) t.getTransferData(new DataFlavor(DndButton.class, "JButton"));
} catch (UnsupportedFlavorException | IOException ex) {
System.err.println(ex);
}
return true;
}
}
}
class DndButton extends JButton implements Transferable, DragSourceListener, DragGestureListener {
//marks this JButton as the source of the Drag
private DragSource source;
private TransferHandler t;
public DndButton() {
this("");
}
public DndButton(String message) {
super(message);
//The TransferHandler returns a new DnDButton
//to be transferred in the Drag
t = new TransferHandler() {
public Transferable createTransferable(JComponent c) {
return new DndButton(getText());
}
};
setTransferHandler(t);
//The Drag will copy the DnDButton rather than moving it
source = new DragSource();
source.createDefaultDragGestureRecognizer(this, DnDConstants.ACTION_MOVE, this);
}
//The DataFlavor is a marker to let the DropTarget know how to
//handle the Transferable
public DataFlavor[] getTransferDataFlavors() {
return new DataFlavor[]{new DataFlavor(DndButton.class, "JButton")};
}
public boolean isDataFlavorSupported(DataFlavor flavor) {
return true;
}
public Object getTransferData(DataFlavor flavor) {
return this;
}
public void dragEnter(DragSourceDragEvent dsde) {
}
public void dragOver(DragSourceDragEvent dsde) {
//this.setLocation(dsde.getX()-150,0);
}
public void dropActionchanged(DragSourceDragEvent dsde) {
}
public void dragExit(DragSourceEvent dse) {
}
//when the drag finishes, then repaint the DnDButton
//so it doesn't look like it has still been pressed down
public void dragDropEnd(DragSourceDropEvent dsde) {
// JComponent c = (JComponent) this.getParent();
//c.remove(this);
//c.repaint();
}
//when a DragGesture is recognized, initiate the Drag
public void dragGestureRecognized(DragGestureEvent dge) {
source.startDrag(dge, DragSource.DefaultMoveDrop, DndButton.this, this);
}
@Override
public void dropActionChanged(DragSourceDragEvent dsde) {
}
}
class Main {
public static void main(String[] args) {
JFrame f = new JFrame("sscce");
f.setBounds(0, 0, 500, 80);
f.setVisible(true);
DndLabel trackOne = new DndLabel();
trackOne.setBounds(0, 0, 500, 50);
f.add(trackOne);
DndButton b = new DndButton("hello");
b.setBounds(0, 0, 100, trackOne.getHeight());
trackOne.add(b);
trackOne.revalidate();
trackOne.repaint();
}
}
