import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

/**
 * A Component that supports drag-and-drop for Image objects.
 * 
 * @author  Prof. David Bernstein
 * @version DnD (Move or Copy); Custom TransferHandler
 */
public class ImagePanel extends JPanel implements ImageTransferer
{
  private static final long serialVersionUID = 1L;

  private boolean      dragEnabled;
  private Image        image;
  
  /**
   * Default Constructor.
   */
  public ImagePanel()
  {
    super();
    image = null;
    
    setTransferHandler(new ImageTransferHandler());

    // Add a MouseListener that will forward mousePressed messages
    // to a TransferHandler as drags
    addMouseListener(
        new MouseAdapter()
        // An anonymous inner class that overrides mousePressed() in MouseAdapter
        {
          public void mousePressed(MouseEvent e) 
          {
            JComponent c = (JComponent)e.getSource();
            TransferHandler handler = c.getTransferHandler();
            handler.exportAsDrag(c, e, TransferHandler.MOVE);
          }
        }
    );
  }

  // Methods required by ImageTransferer

  /**
   * Get the Image associated with this ImagePanel.
   * 
   * @return  The Image
   */
  public Image getImage()
  {
    return image;
  }
  
  /**
   * Get the source actions supported by this ImageTransferer.
   * 
   * @return TransferHandler.MOVE
   */
  public int getSourceActions()
  {
    return TransferHandler.MOVE;
  }
  
  /**
   * Set the Image on this Component.
   * 
   * @param image  The Image to use.
   */
  public void setImage(Image image)
  {
    this.image = image;
    repaint();
  }
  
  // Methods that provide the desired GUI functionality

  /**
   * Is drag enabled for this Component?
   * 
   * @return true if enabled; false otherwise
   */
  public boolean getDragEnabled()
  {
    return dragEnabled;
  }

  /**
   * Render this Component.
   * 
   * @param g  The rendering engine to use
   */
  public void paint(Graphics g)
  {
    super.paint(g);
    
    if (image != null)
    {
      int width  = getWidth();
      int height = getHeight();
      int iw = image.getWidth(null);
      int ih = image.getHeight(null);
      
      g.drawImage(image, width/2 - iw/2, height/2 - ih/2, null);
    }
  }
  
  /**
   * Determine whether drag is enabled on this Component.
   * 
   * @param enabled  true to enable; false to disable
   */
  public void setDragEnabled(boolean enabled)
  {
    dragEnabled = enabled;
  }
}