Swing, JTree拖拽的例子

一个Java(JTree)拖拽的例子，其核心思想还是去实现Java拖拽的三个接口：DragGestureListener,
  DragSourceListener, DropTargetListener。实现后的效果如下图：从左侧树上拖拽一个文件到右侧打开。代码已经编译通过，不需要第三方Java包。

package com.zakisoft.drug;

import java.awt.AlphaComposite;
import java.awt.Component;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.Toolkit;
import java.awt.datatransfer.DataFlavor;
import java.awt.datatransfer.StringSelection;
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.DropTarget;
import java.awt.dnd.DropTargetDragEvent;
import java.awt.dnd.DropTargetDropEvent;
import java.awt.dnd.DropTargetEvent;
import java.awt.dnd.DropTargetListener;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.awt.geom.AffineTransform;
import java.awt.geom.Rectangle2D;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Iterator;
import java.util.List;

import javax.swing.Icon;
import javax.swing.JLabel;
import javax.swing.JTree;
import javax.swing.Timer;
import javax.swing.event.TreeExpansionEvent;
import javax.swing.event.TreeExpansionListener;
import javax.swing.filechooser.FileSystemView;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeCellRenderer;
import javax.swing.tree.DefaultTreeModel;
import javax.swing.tree.TreePath;

class DragTree extends JTree implements DragGestureListener,
		DragSourceListener, DropTargetListener {

	private static final long serialVersionUID = -7123350256666099899L;

	BufferedImage ghostImage;

	private Rectangle2D ghostRect = new Rectangle2D.Float();

	private Point ptOffset = new Point();

	private Point lastPoint = new Point();

	private TreePath lastPath;

	private Timer hoverTimer;

	FileNode sourceNode;

	public DragTree() {
		DragSource dragSource = DragSource.getDefaultDragSource();

		dragSource.createDefaultDragGestureRecognizer(this, // component where
				// drag originates
				DnDConstants.ACTION_COPY_OR_MOVE, // actions
				this); // drag gesture recognizer
		setModel(createTreeModel());

		addTreeExpansionListener(new TreeExpansionListener() {
			public void treeCollapsed(TreeExpansionEvent e) {
			}

			public void treeExpanded(TreeExpansionEvent e) {
				TreePath path = e.getPath();

				if (path != null) {
					FileNode node = (FileNode) path.getLastPathComponent();

					if (!node.isExplored()) {
						DefaultTreeModel model = (DefaultTreeModel) getModel();
						node.explore();
						model.nodeStructureChanged(node);
					}
				}
			}
		});
		this.setCellRenderer(new DefaultTreeCellRenderer() {

			private static final long serialVersionUID = 7616415055309322562L;

			public Component getTreeCellRendererComponent(JTree tree,
					Object value, boolean selected, boolean expanded,
					boolean leaf, int row, boolean hasFocus) {
				TreePath tp = tree.getPathForRow(row);
				if (tp != null) {
					FileNode node = (FileNode) tp.getLastPathComponent();
					File f = node.getFile();
					try {
						Icon icon = FileSystemView.getFileSystemView()
								.getSystemIcon(f);
						this.setIcon(icon);
						this.setLeafIcon(icon);
						this.setOpenIcon(icon);
						this.setClosedIcon(icon);
						this.setDisabledIcon(icon);
					} catch (Exception e) {
						e.printStackTrace();
					}
				}
				return super.getTreeCellRendererComponent(tree, value,
						selected, expanded, leaf, row, hasFocus);
			}

		});

		super.setScrollsOnExpand(true);
		new DropTarget(this, DnDConstants.ACTION_COPY_OR_MOVE, this);

		// Set up a hover timer, so that a node will be automatically expanded
		// or collapsed
		// if the user lingers on it for more than a short time
		hoverTimer = new Timer(1000, new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				if (lastPath == null) {
					return;
				}
				if (getRowForPath(lastPath) == 0)
					return; // Do nothing if we are hovering over the root node
				if (isExpanded(lastPath))
					collapsePath(lastPath);
				else
					expandPath(lastPath);
			}
		});
		hoverTimer.setRepeats(false); // Set timer to one-shot mode

		this.addKeyListener(new KeyAdapter() {

			public void keyPressed(KeyEvent e) {
				int code = e.getKeyCode();
				int modifiers = e.getModifiers();
				if (code == 'v' || code == 'V') {
					System.out.println("find v");
					System.out.println("modifiers:" + modifiers + "\t"
							+ ((modifiers & KeyEvent.CTRL_MASK) != 0));
				}

				if ((modifiers & KeyEvent.CTRL_MASK) != 0
						&& (code == 'v' || code == 'V')) {
					Transferable tr = Toolkit.getDefaultToolkit()
							.getSystemClipboard().getContents(null);

					TreePath path = getSelectionPath();
					if (path == null) {
						return;
					}
					FileNode node = (FileNode) path.getLastPathComponent();
					if (node.isDirectory()) {
						System.out.println("file cp");
						try {
							List<?> list = (List<?>) (tr
									.getTransferData(DataFlavor.javaFileListFlavor));
							Iterator<?> iterator = list.iterator();
							File parent = node.getFile();
							while (iterator.hasNext()) {
								File f = (File) iterator.next();
								cp(f, new File(parent, f.getName()));
							}
							node.reexplore();
						} catch (Exception ioe) {
							ioe.printStackTrace();
						}
						updateUI();
					}
				}
			}

		});
	}

	public void dragGestureRecognized(DragGestureEvent e) {
		// drag anything …

		TreePath path = getLeadSelectionPath();
		if (path == null)
			return;
		FileNode node = (FileNode) path.getLastPathComponent();
		sourceNode = node;
		// Work out the offset of the drag point from the TreePath bounding
		// rectangle origin
		Rectangle raPath = getPathBounds(path);
		Point ptDragOrigin = e.getDragOrigin();
		ptOffset.setLocation(ptDragOrigin.x - raPath.x, ptDragOrigin.y
				- raPath.y);
		// Get the cell renderer (which is a JLabel) for the path being dragged
		int row = this.getRowForLocation(ptDragOrigin.x, ptDragOrigin.y);
		JLabel lbl = (JLabel) getCellRenderer().getTreeCellRendererComponent(
				this, // tree
				path.getLastPathComponent(), // value
				false, // isSelected (dont want a colored background)
				isExpanded(path), // isExpanded
				getModel().isLeaf(path.getLastPathComponent()), // isLeaf
				row, // row (not important for rendering)
				false // hasFocus (dont want a focus rectangle)
				);
		lbl.setSize((int) raPath.getWidth(), (int) raPath.getHeight()); // <-
		// The
		// layout
		// manager
		// would
		// normally
		// do
		// this

		// Get a buffered image of the selection for dragging a ghost image
		this.ghostImage = new BufferedImage((int) raPath.getWidth(),
				(int) raPath.getHeight(), BufferedImage.TYPE_INT_ARGB_PRE);
		Graphics2D g2 = ghostImage.createGraphics();

		// Ask the cell renderer to paint itself into the BufferedImage
		g2.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC, 0.5f));
		// Make the image ghostlike
		lbl.paint(g2);

		g2.dispose();
		// this.getGraphics().drawImage(ghostImage, e.getDragOrigin().x,
		// e.getDragOrigin().y, this);

		e.startDrag(
				null, // cursor
				ghostImage, new Point(5, 5),
				new StringSelection(getFilename()), // transferable
				this); // drag source listener
	}

	public void dragDropEnd(DragSourceDropEvent e) {
		ghostImage = null;
		sourceNode = null;
	}

	public void dragEnter(DragSourceDragEvent e) {
	}

	public void dragExit(DragSourceEvent e) {
		if (!DragSource.isDragImageSupported()) {
			repaint(ghostRect.getBounds());
		}
	}

	public void dragOver(DragSourceDragEvent e) {

	}

	public void dropActionChanged(DragSourceDragEvent e) {
	}

	public String getFilename() {
		TreePath path = getLeadSelectionPath();
		FileNode node = (FileNode) path.getLastPathComponent();
		return ((File) node.getUserObject()).getAbsolutePath();
	}

	private DefaultTreeModel createTreeModel() {
		File root = FileSystemView.getFileSystemView().getRoots()[0];
		FileNode rootNode = new FileNode(root);

		rootNode.explore();
		return new DefaultTreeModel(rootNode);
	}

	public void dragEnter(DropTargetDragEvent dtde) {

	}

	public void dragOver(DropTargetDragEvent dtde) {

		Point pt = dtde.getLocation();
		if (pt.equals(lastPoint)) {
			return;
		}
		if (ghostImage != null) {
			Graphics2D g2 = (Graphics2D) getGraphics();
			// If a drag image is not supported by the platform, then draw my
			// own drag image
			if (!DragSource.isDragImageSupported()) {
				paintImmediately(ghostRect.getBounds()); // Rub out the last
				// ghost image and cue
				// line
				// And remember where we are about to draw the new ghost image
				ghostRect.setRect(pt.x - ptOffset.x, pt.y - ptOffset.y,
						ghostImage.getWidth(), ghostImage.getHeight());
				g2.drawImage((ghostImage), AffineTransform
						.getTranslateInstance(ghostRect.getX(), ghostRect
								.getY()), null);
			}
		}
		TreePath path = getClosestPathForLocation(pt.x, pt.y);
		if (!(path == lastPath)) {
			lastPath = path;
			hoverTimer.restart();
		}
	}

	public void dropActionChanged(DropTargetDragEvent dtde) {

	}

	public void drop(DropTargetDropEvent e) {
		try {
			DataFlavor stringFlavor = DataFlavor.stringFlavor;
			Transferable tr = e.getTransferable();

			TreePath path = this.getPathForLocation(e.getLocation().x, e
					.getLocation().y);
			if (path == null) {
				e.rejectDrop();
				return;
			}
			FileNode node = (FileNode) path.getLastPathComponent();
			if (e.isDataFlavorSupported(DataFlavor.javaFileListFlavor)
					&& node.isDirectory()) {
				e.acceptDrop(DnDConstants.ACTION_COPY_OR_MOVE);
				System.out.println("file cp");
				List<?> list = (List<?>) (e.getTransferable()
						.getTransferData(DataFlavor.javaFileListFlavor));
				Iterator<?> iterator = list.iterator();
				File parent = node.getFile();
				while (iterator.hasNext()) {
					File f = (File) iterator.next();
					cp(f, new File(parent, f.getName()));
				}
				node.reexplore();
				e.dropComplete(true);
				this.updateUI();
			} else if (e.isDataFlavorSupported(stringFlavor)
					&& node.isDirectory()) {
				String filename = (String) tr.getTransferData(stringFlavor);
				if (filename.endsWith(".txt") || filename.endsWith(".java")
						|| filename.endsWith(".jsp")
						|| filename.endsWith(".html")
						|| filename.endsWith(".htm")) {
					e.acceptDrop(DnDConstants.ACTION_COPY_OR_MOVE);
					File f = new File(filename);
					if (f.exists()) {
						f.renameTo(new File(node.getFile(), f.getName()));
						node.reexplore();
						((FileNode) sourceNode.getParent()).remove(sourceNode);
						e.dropComplete(true);
						this.updateUI();
					} else {
						e.rejectDrop();
					}
				} else {
					e.rejectDrop();
				}
			} else {
				e.rejectDrop();
			}
		} catch (IOException ioe) {
			ioe.printStackTrace();
		} catch (UnsupportedFlavorException ufe) {
			ufe.printStackTrace();
		} finally {
			ghostImage = null;
			this.repaint();
		}
	}

	private void cp(File src, File dest) throws IOException {
		if (src.isDirectory()) {
			if (!dest.exists()) {
				boolean ret = dest.mkdir();
				if (ret == false)
					return;
			}
			File[] fs = src.listFiles();
			for (int i = 0; i < fs.length; i++) {
				cp(fs[i], new File(dest, fs[i].getName()));
			}
			return;
		}
		byte[] buf = new byte[1024];
		FileInputStream in = new FileInputStream(src);
		FileOutputStream out = new FileOutputStream(dest);
		int len;
		try {
			while ((len = in.read(buf)) > 0) {
				out.write(buf, 0, len);
			}
		} finally {
			in.close();
			out.close();
		}
	}

	public void dragExit(DropTargetEvent dte) {

	}
}

class FileNode extends DefaultMutableTreeNode {
	private static final long serialVersionUID = -6713369593920467035L;
	private boolean explored = false;

	public FileNode(File file) {
		setUserObject(file);
	}

	public boolean getAllowsChildren() {
		return isDirectory();
	}

	public boolean isLeaf() {
		return !isDirectory();
	}

	public File getFile() {
		return (File) getUserObject();
	}

	public boolean isExplored() {
		return explored;
	}

	public boolean isDirectory() {
		File file = getFile();
		return file.isDirectory();
	}

	public String toString() {
		File file = (File) getUserObject();
		String filename = file.toString();
		int index = filename.lastIndexOf(File.separator);

		return (index != -1 && index != filename.length() - 1) ? filename
				.substring(index + 1) : filename;
	}

	public void explore() {
		if (!isDirectory())
			return;

		if (!isExplored()) {
			File file = getFile();
			File[] children = file.listFiles();

			for (int i = 0; i < children.length; ++i) {
				if (children[i].isDirectory())
					add(new FileNode(children[i]));
			}
			for (int i = 0; i < children.length; ++i) {
				if (!children[i].isDirectory())
					add(new FileNode(children[i]));
			}
			explored = true;
		}
	}

	public void reexplore() {
		this.removeAllChildren();
		explored = false;
		explore();
	}
}

package com.zakisoft.drug;

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.datatransfer.DataFlavor;
import java.awt.datatransfer.Transferable;
import java.awt.datatransfer.UnsupportedFlavorException;
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 java.awt.dnd.DropTargetListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;

import javax.swing.BorderFactory;
import javax.swing.JEditorPane;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JSplitPane;
import javax.swing.UIManager;
import javax.swing.WindowConstants;
import javax.swing.text.Document;
import javax.swing.text.EditorKit;

public class Test extends JFrame implements DropTargetListener {

	private static final long serialVersionUID = -5037743965292608371L;
	private JEditorPane textPane = new JEditorPane();

	public Test() {
		super("Drag and Drop With Swing");

		new DropTarget(textPane, DnDConstants.ACTION_COPY_OR_MOVE, this);

		JSplitPane splitPane = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT,
				createTreePanel(), createTextPanel());

		splitPane.setDividerLocation(250);
		splitPane.setOneTouchExpandable(true);

		getContentPane().add(splitPane, BorderLayout.CENTER);
	}

	public static void main(String args[]) {

		try {
			UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
		} catch (Exception e1) {
			e1.printStackTrace();
		}
		Test test = new Test();

		test.setBounds(300, 300, 850, 350);
		test.setVisible(true);
		test.setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
		test.addWindowListener(new WindowAdapter() {
			public void windowClosed(WindowEvent e) {
				System.exit(0);
			}
		});
	}

	private JPanel createTreePanel() {
		JPanel treePanel = new JPanel();
		DragTree tree = new DragTree();

		treePanel.setLayout(new BorderLayout());
		treePanel.add(new JScrollPane(tree), BorderLayout.CENTER);
		treePanel.setBorder(BorderFactory
				.createTitledBorder("Drag source for filenames"));

		return treePanel;
	}

	private JPanel createTextPanel() {
		JPanel textPanel = new JPanel();

		textPanel.setLayout(new BorderLayout());
		textPanel.add(new JScrollPane(textPane), BorderLayout.CENTER);
		textPanel.setMinimumSize(new Dimension(375, 0));
		textPanel.setBorder(BorderFactory
				.createTitledBorder("Drop target for filenames"));

		return textPanel;
	}

	private void readFile(final String filename) {
		try {
			textPane.setPage(new File(filename).toURL());
		} catch (IOException e) {
			EditorKit kit = textPane.getEditorKit();
			Document document = textPane.getDocument();

			try {
				document.remove(0, document.getLength());
				kit.read(new FileReader(filename), document, 0);
			} catch (Exception ex) {
				ex.printStackTrace();
			}
		}
	}

	public void drop(DropTargetDropEvent e) {
		try {
			DataFlavor stringFlavor = DataFlavor.stringFlavor;
			Transferable tr = e.getTransferable();

			if (e.isDataFlavorSupported(stringFlavor)) {
				String filename = (String) tr.getTransferData(stringFlavor);
				if (filename.endsWith(".txt") || filename.endsWith(".java")
						|| filename.endsWith(".jsp")
						|| filename.endsWith(".html")
						|| filename.endsWith(".htm")) {
					e.acceptDrop(DnDConstants.ACTION_COPY_OR_MOVE);
					readFile(filename);
					textPane.setCaretPosition(0);
					e.dropComplete(true);
				} else {
					e.rejectDrop();
				}
			} else {
				e.rejectDrop();
			}
		} catch (IOException ioe) {
			ioe.printStackTrace();
		} catch (UnsupportedFlavorException ufe) {
			ufe.printStackTrace();
		}
	}

	public void dragEnter(DropTargetDragEvent e) {
	}

	public void dragExit(DropTargetEvent e) {
	}

	public void dragOver(DropTargetDragEvent e) {
	}

	public void dropActionChanged(DropTargetDragEvent e) {
	}
}