一个SWING拖拽的例子及简单分析
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 {
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() {
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 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();
}
}
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 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) {
}
}
从上面可以看出第一个类实现了DragGestureListener，DragSourceListener，DropTargetListener三个接口。
第二个类实现了DropTargetListener接口。
DragGestureListener是用于监听拖拽时间的发生的，发生时触发dragGestureRecognized方法，该方法讲解如下
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 = getRowForLocation(ptDragOrigin.x, ptDragOrigin.y);
//lbl是用来获得当前选中目录的cellRenderer
JLabel lbl = (JLabel) getCellRenderer().getTreeCellRendererComponent(
this, // tree
path.getLastPathComponent(), // value
true, // 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
//把lbl画到BufferedImage中去
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拖拽时的鼠标样式？
ghostImage, new Point(5, 5),
new StringSelection(getFilename()), // transferable
this); // drag source listener 被拖拽组件在源组件中的事件
}
DropTargetListener接口用于描述被拖拽到某个组件（如ComponentEaxmple）上时触发的事件。添加该事件的操作例子如下：
new DropTarget(ComponentEaxmple, DnDConstants.ACTION_COPY_OR_MOVE, DropTargetListener);