Editor Drop Target 3
/*
Core SWING Advanced Programming
By Kim Topley
ISBN: 0 13 083292 8
Publisher: Prentice Hall
*/
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Point;
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.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.UnsupportedEncodingException;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.List;
import javax.swing.JCheckBox;
import javax.swing.JEditorPane;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.UIManager;
public class EditorDropTarget3 implements DropTargetListener,
PropertyChangeListener {
public EditorDropTarget3(JEditorPane pane) {
this.pane = pane;
// Listen for changes in the enabled property
pane.addPropertyChangeListener(this);
// Save the JEditorPane's background color
backgroundColor = pane.getBackground();
// Create the DropTarget and register
// it with the JEditorPane.
dropTarget = new DropTarget(pane, DnDConstants.ACTION_COPY_OR_MOVE,
this, pane.isEnabled(), null);
}
// Implementation of the DropTargetListener interface
public void dragEnter(DropTargetDragEvent dtde) {
DnDUtils.debugPrintln("dragEnter, drop action = "
+ DnDUtils.showActions(dtde.getDropAction()));
// Get the type of object being transferred and determine
// whether it is appropriate.
checkTransferType(dtde);
// Accept or reject the drag.
boolean acceptedDrag = acceptOrRejectDrag(dtde);
// Do drag-under feedback
dragUnderFeedback(dtde, acceptedDrag);
}
public void dragExit(DropTargetEvent dte) {
DnDUtils.debugPrintln("DropTarget dragExit");
// Do drag-under feedback
dragUnderFeedback(null, false);
}
public void dragOver(DropTargetDragEvent dtde) {
DnDUtils.debugPrintln("DropTarget dragOver, drop action = "
+ DnDUtils.showActions(dtde.getDropAction()));
// Accept or reject the drag
boolean acceptedDrag = acceptOrRejectDrag(dtde);
// Do drag-under feedback
dragUnderFeedback(dtde, acceptedDrag);
}
public void dropActionChanged(DropTargetDragEvent dtde) {
DnDUtils.debugPrintln("DropTarget dropActionChanged, drop action = "
+ DnDUtils.showActions(dtde.getDropAction()));
// Accept or reject the drag
boolean acceptedDrag = acceptOrRejectDrag(dtde);
// Do drag-under feedback
dragUnderFeedback(dtde, acceptedDrag);
}
public void drop(DropTargetDropEvent dtde) {
DnDUtils.debugPrintln("DropTarget drop, drop action = "
+ DnDUtils.showActions(dtde.getDropAction()));
// Check the drop action
if ((dtde.getDropAction() & DnDConstants.ACTION_COPY_OR_MOVE) != 0) {
// Accept the drop and get the transfer data
dtde.acceptDrop(dtde.getDropAction());
Transferable transferable = dtde.getTransferable();
try {
boolean result = false;
if (draggingFile) {
result = dropFile(transferable);
} else {
result = dropContent(transferable, dtde);
}
dtde.dropComplete(result);
DnDUtils.debugPrintln("Drop completed, success: " + result);
} catch (Exception e) {
DnDUtils.debugPrintln("Exception while handling drop " + e);
dtde.dropComplete(false);
}
} else {
DnDUtils.debugPrintln("Drop target rejected drop");
dtde.rejectDrop();
}
}
// PropertyChangeListener interface
public void propertyChange(PropertyChangeEvent evt) {
String propertyName = evt.getPropertyName();
if (propertyName.equals("enabled")) {
// Enable the drop target if the JEditorPane is enabled
// and vice versa.
dropTarget.setActive(pane.isEnabled());
} else if (!changingBackground && propertyName.equals("background")) {
backgroundColor = pane.getBackground();
}
}
// Internal methods start here
protected boolean acceptOrRejectDrag(DropTargetDragEvent dtde) {
int dropAction = dtde.getDropAction();
int sourceActions = dtde.getSourceActions();
boolean acceptedDrag = false;
DnDUtils.debugPrintln("\tSource actions are "
+ DnDUtils.showActions(sourceActions) + ", drop action is "
+ DnDUtils.showActions(dropAction));
// Reject if the object being transferred
// or the operations available are not acceptable.
if (!acceptableType
|| (sourceActions & DnDConstants.ACTION_COPY_OR_MOVE) == 0) {
DnDUtils.debugPrintln("Drop target rejecting drag");
dtde.rejectDrag();
} else if (!draggingFile && !pane.isEditable()) {
// Can't drag text to a read-only JEditorPane
DnDUtils.debugPrintln("Drop target rejecting drag");
dtde.rejectDrag();
} else if ((dropAction & DnDConstants.ACTION_COPY_OR_MOVE) == 0) {
// Not offering copy or move - suggest a copy
DnDUtils.debugPrintln("Drop target offering COPY");
dtde.acceptDrag(DnDConstants.ACTION_COPY);
acceptedDrag = true;
} else {
// Offering an acceptable operation: accept
DnDUtils.debugPrintln("Drop target accepting drag");
dtde.acceptDrag(dropAction);
acceptedDrag = true;
}
return acceptedDrag;
}
protected void dragUnderFeedback(DropTargetDragEvent dtde,
boolean acceptedDrag) {
if (draggingFile) {
// When dragging a file, change the background color
Color newColor = (dtde != null && acceptedDrag ? feedbackColor
: backgroundColor);
if (newColor.equals(pane.getBackground()) == false) {
changingBackground = true;
pane.setBackground(newColor);
changingBackground = false;
pane.repaint();
}
} else {
if (dtde != null && acceptedDrag) {
// Dragging text - move the insertion cursor
Point location = dtde.getLocation();
pane.getCaret().setVisible(true);
pane.setCaretPosition(pane.viewToModel(location));
} else {
pane.getCaret().setVisible(false);
}
}
}
protected void checkTransferType(DropTargetDragEvent dtde) {
// Accept a list of files, or data content that
// amounts to plain text or a Unicode text string
acceptableType = false;
draggingFile = false;
if (dtde.isDataFlavorSupported(DataFlavor.javaFileListFlavor)) {
acceptableType = true;
draggingFile = true;
} else if (dtde.isDataFlavorSupported(DataFlavor.plainTextFlavor)
|| dtde.isDataFlavorSupported(DataFlavor.stringFlavor)) {
acceptableType = true;
}
DnDUtils.debugPrintln("File type acceptable - " + acceptableType);
DnDUtils.debugPrintln("Dragging a file - " + draggingFile);
}
// This method handles a drop for a list of files
protected boolean dropFile(Transferable transferable) throws IOException,
UnsupportedFlavorException, MalformedURLException {
List fileList = (List) transferable
.getTransferData(DataFlavor.javaFileListFlavor);
File transferFile = (File) fileList.get(0);
final URL transferURL = transferFile.toURL();
DnDUtils.debugPrintln("File URL is " + transferURL);
pane.setPage(transferURL);
return true;
}
// This method handles a drop with data content
protected boolean dropContent(Transferable transferable,
DropTargetDropEvent dtde) {
if (!pane.isEditable()) {
// Can't drop content on a read-only text control
return false;
}
try {
// Check for a match with the current content type
DataFlavor[] flavors = dtde.getCurrentDataFlavors();
DataFlavor selectedFlavor = null;
// Look for either plain text or a String.
for (int i = 0; i < flavors.length; i++) {
DataFlavor flavor = flavors[i];
DnDUtils.debugPrintln("Drop MIME type " + flavor.getMimeType()
+ " is available");
if (flavor.equals(DataFlavor.plainTextFlavor)
|| flavor.equals(DataFlavor.stringFlavor)) {
selectedFlavor = flavor;
break;
}
}
if (selectedFlavor == null) {
// No compatible flavor - should never happen
return false;
}
DnDUtils.debugPrintln("Selected flavor is "
+ selectedFlavor.getHumanPresentableName());
// Get the transferable and then obtain the data
Object data = transferable.getTransferData(selectedFlavor);
DnDUtils.debugPrintln("Transfer data type is "
+ data.getClass().getName());
String insertData = null;
if (data instanceof InputStream) {
// Plain text flavor
String charSet = selectedFlavor.getParameter("charset");
InputStream is = (InputStream) data;
byte[] bytes = new byte[is.available()];
is.read(bytes);
try {
insertData = new String(bytes, charSet);
} catch (UnsupportedEncodingException e) {
// Use the platform default encoding
insertData = new String(bytes);
}
} else if (data instanceof String) {
// String flavor
insertData = (String) data;
}
if (insertData != null) {
int selectionStart = pane.getCaretPosition();
pane.replaceSelection(insertData);
pane.select(selectionStart, selectionStart
+ insertData.length());
return true;
}
return false;
} catch (Exception e) {
return false;
}
}
public static void main(String[] args) {
try {
UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
} catch (Exception evt) {}
final JFrame f = new JFrame("JEditor Pane Drop Target Example 3");
final JEditorPane pane = new JEditorPane();
// Add a drop target to the JEditorPane
EditorDropTarget3 target = new EditorDropTarget3(pane);
f.addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent evt) {
System.exit(0);
}
});
JPanel panel = new JPanel();
final JCheckBox editable = new JCheckBox("Editable");
editable.setSelected(true);
panel.add(editable);
editable.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent evt) {
pane.setEditable(editable.isSelected());
}
});
final JCheckBox enabled = new JCheckBox("Enabled");
enabled.setSelected(true);
panel.add(enabled);
enabled.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent evt) {
pane.setEnabled(enabled.isSelected());
}
});
f.getContentPane().add(new JScrollPane(pane), BorderLayout.CENTER);
f.getContentPane().add(panel, BorderLayout.SOUTH);
f.setSize(500, 400);
f.setVisible(true);
}
protected JEditorPane pane;
protected DropTarget dropTarget;
protected boolean acceptableType; // Indicates whether data is acceptable
protected boolean draggingFile; // True if dragging an entire file
protected Color backgroundColor; // Original background color of JEditorPane
protected boolean changingBackground;
protected static final Color feedbackColor = Color.gray;
}
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);
}
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