Use BufferedImage during Drag and Drop in Swing

[Chaz Branham]

Everyone I am having some problems starting the Drag operation showing an image of the object I want to drag around. I can't seem to get the StartDrag function to work with the parameters I am giving it. If anyone can offer some help I would truly appreciate it.

package manning;

import java.awt.Color;
import java.awt.Cursor;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.GradientPaint;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.RenderingHints;
import java.awt.Toolkit;
import java.awt.datatransfer.DataFlavor;
import java.awt.datatransfer.Transferable;
import java.awt.datatransfer.UnsupportedFlavorException;
import java.awt.dnd.DnDConstants;
import java.awt.dnd.DragGestureEvent;
import java.awt.dnd.DragGestureListener;
import java.awt.dnd.DragSource;
import java.awt.dnd.DragSourceDragEvent;
import java.awt.dnd.DragSourceDropEvent;
import java.awt.dnd.DragSourceEvent;
import java.awt.dnd.DragSourceListener;
import java.awt.dnd.DragSourceMotionListener;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import java.awt.image.BufferedImage;
import java.io.IOException;

import javax.swing.BorderFactory;
import javax.swing.JComponent;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.TransferHandler;

public class GangsPanel extends JPanel implements DragSourceListener, DragSourceMotionListener, MouseListener,
		MouseMotionListener, Transferable, DragGestureListener {

	private static final long serialVersionUID = 1491876616276982469L;
	
	Dimension prefSize = new Dimension(400, 300);
	int I;
	int LastX;
	int LastY;
	MainGangsPanel m;
	
	private DragSource source; private TransferHandler t;
	 

	public GangsPanel(final int I) {
		this.setDoubleBuffered(true);
		
		 t = new TransferHandler(){ 
			 public Transferable createTransferable(JComponent c){ 
				 return new GangsPanel(I); 
				 } 
			 };
		 setTransferHandler(t);
		 
		 source = new DragSource();
		 source.createDefaultDragGestureRecognizer(this,
		 DnDConstants.ACTION_MOVE, this);
		 

		setI(I);

		this.setVisible(true);
		this.addMouseListener(this);
		this.addMouseMotionListener(this);
		this.setLayout(new FlowLayout());
		System.out.println("Gangs Panel: " + Thread.currentThread());
		this.setBorder(BorderFactory.createTitledBorder("Gang: " + I));
		
		
		for (int i=1; i<2; i++){
			this.add(new person(i));
		}

	}

	public Dimension getPreferredSize() {
		return prefSize;
	}

	protected void paintComponent(Graphics g) {
		//super.paintComponent(g);
		Graphics2D g2d = (Graphics2D) g;
		g2d.setRenderingHint(RenderingHints.KEY_RENDERING,
				RenderingHints.VALUE_RENDER_QUALITY);
		g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
				RenderingHints.VALUE_ANTIALIAS_ON);
		int w = getWidth();
		int h = getHeight();
		Color color1 = Color.WHITE;
		Color color2 = Color.CYAN;
		GradientPaint gp = new GradientPaint(0, 0, color1, 0, h, color2);
		g2d.setPaint(gp);
		g2d.fillRect(0, 0, w, h);
		// System.out.println(this.getX() + " - " + this.getY());
	}

	public void setI(int i) {
		I = i;
	}
	
	public void disableControls(Boolean disable){
		
		person p;
		if (disable == true){
			for(int i = 0; i< this.getComponentCount(); i++){
				p = (person)this.getComponent(i);
				p.setEnabled(false);
				p.removeMouseListener(p);
				p.removeMouseMotionListener(p);
			}
		}else{
			for(int i = 0; i< this.getComponentCount(); i++){
				p = (person)this.getComponent(i);
				p.setEnabled(true);
				p.addMouseListener(p);
				p.addMouseMotionListener(p);
			}
		}
		
	}

	public void mouseClicked(MouseEvent e) {
		if ((e.getButton()) == 1 && this.contains(e.getX(), e.getY())) { // Left
																			// Click
			JOptionPane.showMessageDialog(null, "Just a test! Item:" + I);
			e.consume();
		} else if ((e.getButton()) == 3 && this.contains(e.getX(), e.getY())) { // Right
																				// Click
			JOptionPane.showMessageDialog(null, "Right Click! YES! Item:" + I);
			e.consume();
		}

	}

	@Override
	public void mouseEntered(MouseEvent e) {
		// TODO Auto-generated method stub

	}

	@Override
	public void mouseExited(MouseEvent e) {
		// TODO Auto-generated method stub

	}

	@Override
	public void mousePressed(MouseEvent e) {
		// TODO Auto-generated method stub
		/*if (this.contains(e.getPoint()) && !e.isConsumed()) {
			Point point = new Point();
			point.setLocation(getParent().getMousePosition());
			disableControls(true);
			LastX = this.getX() - point.x;
			LastY = this.getY() - point.y;
			m = (MainGangsPanel) getParent();
			m.draggingZ(this, true);
			m.disableControls(true, this);
			
		};*/
		BufferedImage img = new BufferedImage(this.getWidth(), this.getHeight(), BufferedImage.TYPE_INT_ARGB_PRE);
		Graphics g = img.getGraphics();
		g.setColor(this.getForeground());
	    g.setFont(this.getFont());
	    //this.paintAll(g);
	    //Rectangle region = new Rectangle(0, 0, img.getWidth(), img.getHeight());
	    


	}

	@Override
	public void mouseReleased(MouseEvent e) {
		
		if (!e.isConsumed()){
			m = (MainGangsPanel) getParent();
			m.draggingZ(this, false);
			m.disableControls(false, this);
			disableControls(false);
		}
	}

	@Override
	public void mouseDragged(MouseEvent e) {
		
		/*Point point = new Point();
		point.setLocation(getParent().getMousePosition());
		this.setLocation(LastX + point.x, LastY + point.y);*/
		
	}

	@Override
	public void mouseMoved(MouseEvent e) {
		// TODO Auto-generated method stub

	}

	@Override
	public void dragDropEnd(DragSourceDropEvent arg0) {
		// TODO Auto-generated method stub
		
	}

	@Override
	public void dragEnter(DragSourceDragEvent arg0) {
		// TODO Auto-generated method stub
		
	}

	@Override
	public void dragExit(DragSourceEvent arg0) {
		// TODO Auto-generated method stub
		
	}

	@Override
	public void dragOver(DragSourceDragEvent arg0) {
		// TODO Auto-generated method stub
		
	}

	@Override
	public void dropActionChanged(DragSourceDragEvent arg0) {
		// TODO Auto-generated method stub
		
	}

	@Override
	public void dragMouseMoved(DragSourceDragEvent arg0) {
		// TODO Auto-generated method stub
		
	}

	@Override
	public void dragGestureRecognized(DragGestureEvent e) {
		System.out.println("Drag Started! " + e.getDragAction());
		BufferedImage img = new BufferedImage(this.getWidth(), this.getHeight(), BufferedImage.TYPE_INT_ARGB_PRE);
		
		e.startDrag(null, img, 0, this, this);
	}

	@Override
	public Object getTransferData(DataFlavor arg0)
			throws UnsupportedFlavorException, IOException {
		// TODO Auto-generated method stub
		return null;
	}

	@Override
	public DataFlavor[] getTransferDataFlavors() {
		// TODO Auto-generated method stub
		return null;
	}

	@Override
	public boolean isDataFlavorSupported(DataFlavor arg0) {
		// TODO Auto-generated method stub
		return false;
	}  
	 
}

public void dragGestureRecognized(DragGestureEvent e) {
		System.out.println("Drag Started! " + e.getDragAction());
		BufferedImage img = new BufferedImage(this.getWidth(), this.getHeight(), BufferedImage.TYPE_INT_ARGB_PRE);
		
		e.startDrag(null, img, 0, this, this);
	}

The function above is where my hard spot is as I can't seem to get it to accept the last two parameters for the Transferable and the DragSourceListener.

Thank you for your help and time,

TheChazm

[Chaz Branham]

I still have not made any headway with this problem. I have looked around the internet and other forums and still can't seem to nail down what am I missing? Any guidance on this would be greatly appreciated and will let me continue to move forward on my project.

Thank you so very much,

Chaz

[Paul Clapham]

Perhaps you could provide a little bit more detail than just

I can't seem to get it to accept the last two parameters

?

[Chaz Branham]

I apologies if I was not clear enough and I'll try to straighten that up.

I am trying to use the StartDrag method to start the drag process. The user would see a semi-transparent image of what they are dragging around is the entire goal.

When I try to use:

startDrag(Cursor dragCursor, Image dragImage, Point imageOffset, Transferable transferable, DragSourceListener dsl)

When I hover over what I have provided it in code the Transferable and the DragSourceListener do not have the proper types even though they are implemented in the class. It says it has a type of GangsPanel which is the name of the class that implements both of those methods.

So it has a red X next to that line of code and no matter what I try I can't seem to get it to take the class for those requirements and is where I am stuck. Does that make more sense? I cannot think of any other way of explaining it.

Thanks,

Chaz

[Maxim Karvonen]

Hi, Chaz.

It's better to provide compiler message as exactly as they are. Problem is in the third method argument. Look at it. This method requires a point but you are passing an integer.

[Chaz Branham]

Maxim,

Thank you so much for pointing that out for me! It was just the point that was erroring out and I am surprised I didn't catch that.

It does start the StartDrag method now but does not show the image during the drag. Is there something else I am missing?

Thank you so very much!

[Maxim Karvonen]

Probably, it shows an image during the drag. You create a fresh new image with alpha support and then use it for the drag "icon". I didn't check, but that image may be transparent from the start. So it is displayed but you can't see any change on the screen. For tests you should take something more-appropriate than a possible-completely-transparent image. Maybe some external image. Or an image filled with some colour (pure red or green, for example). And try to uses a non-transparent image for some time. It much harder to miss a non-transparent image then a transparent one.

[Paul Clapham]

Maxim has the right idea there: when you're testing a new feature which you aren't certain about, start with a simple test and then once you have that working, add the complexities one at a time. Starting out with a complex test provides the opportunity for too many things to go wrong all at once.

[Chaz Branham]

Thanks again for the recommendation and your right I should have kept it simple and have been jumping the gun a little bit. I'll give it a go with a non transparent image and see what I get. Thanks