jtreedroptarget.java

JRemoteControl is a simple Java&#8482 driven bluetooth remote control.It allows you to initiate virt

/*
 * JRemCntl - Copyright (C) 2007 Filippo Di Vattimo <[e-mail]>
 * See COPYING
 */

package fildiv.jremcntl.server.gui.util.swing;

import java.awt.Insets;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.dnd.DnDConstants;
import java.awt.dnd.DropTarget;
import java.awt.dnd.DropTargetDragEvent;
import java.awt.dnd.DropTargetDropEvent;
import java.awt.dnd.DropTargetEvent;

import javax.swing.JTree;
import javax.swing.tree.TreeCellRenderer;
import javax.swing.tree.TreePath;

public class JTreeDropTarget extends DropTarget {

	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;
	
	private Insets autoscrollInsets = new Insets(20, 20, 20, 20);
	private TreeCellRenderer prevCellRender;
	
	public synchronized void dragEnter(DropTargetDragEvent dtde) {
		JTree tree = (JTree) dtde.getDropTargetContext().getComponent();
		
		prevCellRender = tree.getCellRenderer();
		tree.setCellRenderer(new JTreeDropCellRender());
		super.dragEnter(dtde);
	}
	
	public void dragOver(DropTargetDragEvent dtde) {

		JTree tree = (JTree) dtde.getDropTargetContext().getComponent();
		Point loc = dtde.getLocation();

		manageDragOver(tree, loc, dtde);
		autoscroll(tree, loc);
				
		super.dragOver(dtde);
	}
		
	public synchronized void drop(DropTargetDropEvent dtde) {
		
		JTree tree = (JTree) dtde.getDropTargetContext().getComponent();
		onDragFinish(tree);

		super.drop(dtde);
	}
	
	public synchronized void dragExit(DropTargetEvent dtde) {
		
		JTree tree = (JTree) dtde.getDropTargetContext().getComponent();
		onDragFinish(tree);
		
		super.dragExit(dtde);
}
	
	private void onDragFinish(JTree tree) {
		
		tree.setCellRenderer(prevCellRender);
	}

	private void autoscroll(JTree tree, Point cursorLocation) {
		
		Insets insets = autoscrollInsets;
		Rectangle outer = tree.getVisibleRect();
		Rectangle inner = new Rectangle(outer.x + insets.left, outer.y
				+ insets.top, outer.width - (insets.left + insets.right),
				outer.height - (insets.top + insets.bottom));
		if (!inner.contains(cursorLocation)) {
			Rectangle scrollRect = new Rectangle(
					cursorLocation.x - insets.left, cursorLocation.y
							- insets.top, insets.left + insets.right,
					insets.top + insets.bottom);
			tree.scrollRectToVisible(scrollRect);
		}
	}

	public void manageDragOver(JTree tree, Point location, DropTargetDragEvent dtde) {

		int row = tree.getRowForPath(tree.getClosestPathForLocation(location.x,
				location.y));
		TreePath path = tree.getPathForRow(row);
		if (path != null) {
			Object nodeOver = markNode(tree, location);
			
			if (nodeOver != null) {
				boolean acceptDrop = acceptDrop(tree, nodeOver);
				
				if (!acceptDrop)
					dtde.rejectDrag();
				else 
					dtde.acceptDrag(DnDConstants.ACTION_COPY_OR_MOVE);
			}
		}
	}

	private Object markNode(JTree tree, Point location) {
		
		Object nodeOver = null;
		
		TreePath path = tree.getClosestPathForLocation(location.x, location.y);
		if (path != null) {
			tree.setSelectionPath(path);
			
			if (canExpandPath(tree, nodeOver))
				tree.expandPath(path);
			
			nodeOver = path.getLastPathComponent();
		}
		
		return nodeOver;
	}
	
	protected boolean acceptDrop(JTree tree, Object nodeOver) {
		return true;
	}
	
	protected boolean canExpandPath(JTree tree, Object nodeOver) {
		return true;
	}	

}