JLabel Drag Source
/*
Core SWING Advanced Programming
By Kim Topley
ISBN: 0 13 083292 8
Publisher: Prentice Hall
*/
import java.awt.Font;
import java.awt.datatransfer.DataFlavor;
import java.awt.datatransfer.Transferable;
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.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.util.Iterator;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.UIManager;
public class JLabelDragSource implements DragGestureListener,
DragSourceListener {
public JLabelDragSource(JLabel label) {
this.label = label;
// Use the default DragSource
DragSource dragSource = DragSource.getDefaultDragSource();
// Create a DragGestureRecognizer and
// register as the listener
dragSource.createDefaultDragGestureRecognizer(label,
DnDConstants.ACTION_COPY_OR_MOVE, this);
}
// Implementation of DragGestureListener interface.
public void dragGestureRecognized(DragGestureEvent dge) {
if (DnDUtils.isDebugEnabled()) {
DnDUtils.debugPrintln("Initiating event is "
+ dge.getTriggerEvent());
DnDUtils.debugPrintln("Complete event set is:");
Iterator iter = dge.iterator();
while (iter.hasNext()) {
DnDUtils.debugPrintln("\t" + iter.next());
}
}
Transferable transferable = new JLabelTransferable(label);
dge.startDrag(null, transferable, this);
}
// Implementation of DragSourceListener interface
public void dragEnter(DragSourceDragEvent dsde) {
DnDUtils.debugPrintln("Drag Source: dragEnter, drop action = "
+ DnDUtils.showActions(dsde.getDropAction()));
}
public void dragOver(DragSourceDragEvent dsde) {
DnDUtils.debugPrintln("Drag Source: dragOver, drop action = "
+ DnDUtils.showActions(dsde.getDropAction()));
}
public void dragExit(DragSourceEvent dse) {
DnDUtils.debugPrintln("Drag Source: dragExit");
}
public void dropActionChanged(DragSourceDragEvent dsde) {
DnDUtils.debugPrintln("Drag Source: dropActionChanged, drop action = "
+ DnDUtils.showActions(dsde.getDropAction()));
}
public void dragDropEnd(DragSourceDropEvent dsde) {
DnDUtils.debugPrintln("Drag Source: drop completed, drop action = "
+ DnDUtils.showActions(dsde.getDropAction()) + ", success: "
+ dsde.getDropSuccess());
}
public static void main(String[] args) {
try {
UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
} catch (Exception evt) {}
JFrame f = new JFrame("Draggable JLabel");
JLabel label = new JLabel("Drag this text", JLabel.CENTER);
label.setFont(new Font("Serif", Font.BOLD, 32));
f.getContentPane().add(label);
f.pack();
f.setVisible(true);
// Attach the drag source
JLabelDragSource dragSource = new JLabelDragSource(label);
}
protected JLabel label; // The associated JLabel
}
class DnDUtils {
public static String showActions(int action) {
String actions = "";
if ((action & (DnDConstants.ACTION_LINK | DnDConstants.ACTION_COPY_OR_MOVE)) == 0) {
return "None";
}
if ((action & DnDConstants.ACTION_COPY) != 0) {
actions += "Copy ";
}
if ((action & DnDConstants.ACTION_MOVE) != 0) {
actions += "Move ";
}
if ((action & DnDConstants.ACTION_LINK) != 0) {
actions += "Link";
}
return actions;
}
public static boolean isDebugEnabled() {
return debugEnabled;
}
public static void debugPrintln(String s) {
if (debugEnabled) {
System.out.println(s);
}
}
private static boolean debugEnabled = (System
.getProperty("DnDExamples.debug") != null);
}
class JLabelTransferable implements Transferable {
public JLabelTransferable(JLabel label) {
this.label = label;
}
// Implementation of the Transferable interface
public DataFlavor[] getTransferDataFlavors() {
return flavors;
}
public boolean isDataFlavorSupported(DataFlavor fl) {
for (int i = 0; i < flavors.length; i++) {
if (fl.equals(flavors[i])) {
return true;
}
}
return false;
}
public Object getTransferData(DataFlavor fl) {
if (!isDataFlavorSupported(fl)) {
return null;
}
if (fl.equals(DataFlavor.stringFlavor)) {
// String - return the text as a String
return label.getText() + " (DataFlavor.stringFlavor)";
} else if (fl.equals(jLabelFlavor)) {
// The JLabel itself - just return the label.
return label;
} else {
// Plain text - return an InputStream
try {
String targetText = label.getText() + " (plain text flavor)";
int length = targetText.length();
ByteArrayOutputStream os = new ByteArrayOutputStream();
OutputStreamWriter w = new OutputStreamWriter(os);
w.write(targetText, 0, length);
w.flush();
byte[] bytes = os.toByteArray();
w.close();
return new ByteArrayInputStream(bytes);
} catch (IOException e) {
return null;
}
}
}
// A flavor that transfers a copy of the JLabel
public static final DataFlavor jLabelFlavor = new DataFlavor(JLabel.class,
"Swing JLabel");
private JLabel label; // The label being transferred
private static final DataFlavor[] flavors = new DataFlavor[] {
DataFlavor.stringFlavor,
new DataFlavor("text/plain; charset=ascii", "ASCII text"),
jLabelFlavor };
}
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