Clipboard and Drop-and-Drop

• Enables "user-interface level data transfer" within and in between applicatins

Clipboard - copy, cut, paste

Drag-and-Drop - drag data from one view/application to another

Clipboard Transfer

• Uses a system-level generic data buffer

  • Copy/Cut data from document to clipboard
  • Paste data from clipboard to document

• When a data is placed on a clipboard, application indicates formats

  • e.g. vector image, bitmap image, text etc.

• Also need to deal with

  • Formatted text (HTML, RTF, MS Office)
  • Vector-based rawing
  • Different format images
  • PostScript/PDF drawing?
• MacOS Human Interface Guidelines specify all application must
  • At least support plaintext or image on clipboard
  • At least accept plaintext or image from clipboard

Java Clipboard API

• Key classes Clipboard, DataFlavor, Transferable, ClipboardOwner

• Supports local and system clipboards

  • Local clipboards are named clipboards holding data only accessible by the application
  • System clipboard is operating-system-wide clipboard

• See slide for sample code

Transferable Object

• Encapsulates all data to copy

• Data formats are called "flavours"

• See slide for sample code

Drag-and-Drop

• Also uses Transferable, DataFlavor objects
• Attach a TransferHandler to each widget to manage data transfer
• Need to detect the start-of-drag gesture

Supporting Drop

• Pasting data into your widget at end of drag

• Create a TransferHandler

• Override TransferHandler.importData method

• Set the TransferHandler on the widget

• See the slides for sample code

Supporting Drag

• Copying data out of your widget at start of drag

• Create a TransferHandler

• Override createTransferable with data Transferable

• Set the TransferHandler on the widget
• Define a mouse listener that knows when drag starts

• On drag, get widget's transfer handler and call exportAsDrag

• See slides for sample code