Java Foundation Classes in a Nutshell

•Atsome point, the user moves his attention to some other application and

issues a paste command in that application. This receiving first application

calls

Toolkit.getSystemClipboard() to obtain a Clipboard object. Then it

calls

getContents() to obtain a Transferable object that repr esents the data

available on the clipboard. The application uses

getTransferDataFlavors()

or isDataFlavorSupported() to see if the clipboard data is available in a for-

mat it is willing to accept. If there is such a format, the application calls

get-

TransferData() to transfer the data.

•Atsome point after this cut-and-paste operation, the user cuts or copies a new

piece of data in an application. At this point, the original application ceases to

be the clipboard owner and no longer has to make its data available for past-

ing. The

lostOwnership() method of the originating application’s Clipboard-

Owner object is called to notify the application of this occurrence.

Drag-and-Drop

Java 1.2 adds drag-and-drop support to Java. Drag-and-drop requir es quite a bit

mor e infrastructur e than cut-and-paste, and this infrastructure is added in a pack-

age of its own,

java.awt.dnd. Despite the complexity of the infrastructure, drag-

and-dr op is built upon the same data transfer architectur e as cut-and-paste. The

key classes are still

DataFlavor and Transferable.

Her e’s the general outline of a drag-and-drop transaction from the ...