Mega Code Archive
Demonstrates how to add copy and drag support to a Swing component with TransferHandler
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/*
* Copyright (c) 2004 David Flanagan. All rights reserved.
* This code is from the book Java Examples in a Nutshell, 3nd Edition.
* It is provided AS-IS, WITHOUT ANY WARRANTY either expressed or implied.
* You may study, use, and modify it for any non-commercial purpose,
* including teaching and use in open-source projects.
* You may distribute it non-commercially as long as you retain this notice.
* For a commercial use license, or to purchase the book,
* please visit http://www.davidflanagan.com/javaexamples3.
*/
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.FocusEvent;
import java.awt.event.FocusListener;
import java.awt.event.InputEvent;
import java.awt.event.KeyEvent;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionAdapter;
import java.text.DateFormat;
import java.util.Date;
import javax.swing.ActionMap;
import javax.swing.InputMap;
import javax.swing.JLabel;
import javax.swing.KeyStroke;
import javax.swing.Timer;
import javax.swing.TransferHandler;
import javax.swing.border.LineBorder;
/**
* A custom Swing component that displays a simple digital clock. Demonstrates
* how to add copy and drag support to a Swing component with TransferHandler.
*/
public class DigitalClock extends JLabel {
DateFormat format; // How to display the time in string form
int updateFrequency; // How often to update the time (in milliseconds)
Timer timer; // Triggers repeated updates to the clock
public DigitalClock() {
// Set default values for our properties
setFormat(DateFormat.getTimeInstance(DateFormat.MEDIUM, getLocale()));
setUpdateFrequency(1000); // Update once a second
// Specify a Swing TransferHandler object to do the dirty work of
// copy-and-paste and drag-and-drop for us. This one will transfer
// the value of the "time" property. Since this property is read-only
// it will allow drags but not drops.
setTransferHandler(new TransferHandler("time"));
// Since JLabel does not normally support drag-and-drop, we need an
// event handler to detect a drag and start the transfer.
addMouseMotionListener(new MouseMotionAdapter() {
public void mouseDragged(MouseEvent e) {
getTransferHandler().exportAsDrag(DigitalClock.this, e, TransferHandler.COPY);
}
});
// Before we can have a keyboard binding for a Copy command,
// the component needs to be able to accept keyboard focus.
setFocusable(true);
// Request focus when we're clicked on
addMouseListener(new MouseAdapter() {
public void mouseClicked(MouseEvent e) {
requestFocus();
}
});
// Use a LineBorder to indicate when we've got the keyboard focus
addFocusListener(new FocusListener() {
public void focusGained(FocusEvent e) {
setBorder(LineBorder.createBlackLineBorder());
}
public void focusLost(FocusEvent e) {
setBorder(null);
}
});
// Now bind the Ctrl-C keystroke to a "Copy" command.
InputMap im = new InputMap();
im.setParent(getInputMap(WHEN_FOCUSED));
im.put(KeyStroke.getKeyStroke(KeyEvent.VK_C, InputEvent.CTRL_MASK), "Copy");
setInputMap(WHEN_FOCUSED, im);
// And bind the "Copy" command to a pre-defined Action that performs
// a copy using the TransferHandler we've installed.
ActionMap am = new ActionMap();
am.setParent(getActionMap());
am.put("Copy", TransferHandler.getCopyAction());
setActionMap(am);
// Create a javax.swing.Timer object that will generate ActionEvents
// to tell us when to update the displayed time. Every updateFrequency
// milliseconds, this timer will cause the actionPerformed() method
// to be invoked. (For non-GUI applications, see java.util.Timer.)
timer = new Timer(updateFrequency, new ActionListener() {
public void actionPerformed(ActionEvent e) {
setText(getTime()); // set label to current time string
}
});
timer.setInitialDelay(0); // Do the first update immediately
timer.start(); // Start timing now!
}
// Return the current time as a String.
// This is the property accessor method used by the TransferHandler.
// Since there is a getter, but no setter, the TransferHandler will
// reject any attempts to drop data on us.
public String getTime() {
// Use the DateFormat object to convert current time to a string
return format.format(new Date());
}
// Here are two related property setter methods
public void setFormat(DateFormat format) {
this.format = format;
}
public void setUpdateFrequency(int ms) {
this.updateFrequency = ms;
}
}
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