A Clock with Drag and Copy Support

Another way to customize Swing drag-and-drop is to subclass a Swing component, define new property accessor methods for it, and then register a TransferHandler to transfer the value of the new property. This is what we do in Example 14-2: we define a custom Swing component that displays the current time and uses a TransferHandler to make the contents of its new time property available. Like Example 14-1, this program uses a MouseMotionListener to detect drags. It also defines a key binding so that Ctrl-C copies the time to the clipboard. This example defines a custom component, but not a main( ) method: use the ShowBean program of Chapter 11 to display the component. You may want to run ShowBean again to display a JTextField or similar component, so that you have somewhere to drop or paste the time values you’ve dragged or copied. Also try dropping or pasting the value into other non-Java applications (such as your text editor) that you have running on your desktop.

Example 14-2 also demonstrates the javax.swing.Timer and java.text.DateFormat classes, and shows how to use the (new in Java 1.4) InputMap and ActionMap Swing classes for associating key bindings with components.

Example 14-2. DigitalClock.java

package je3.datatransfer; import javax.swing.*; import javax.swing.border.*; import java.awt.*; import java.awt.event.*; import java.awt.datatransfer.*; import javax.swing.Timer; // disambiguate from java.util.Timer import java.text.DateFormat; ...

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