The transfer will not necessarily have been completed at the return of this call (i.e. the call does not block waiting for the drop). The transfer will take place through the Swing implementation of the java.awt.dnd mechanism, requiring no further effort from the developer. The exportDone method will be called when the transfer has completed.

The transfer will take place using the java.awt.datatransfer mechanism, requiring no further effort from the developer. Any data transfer will be complete and the exportDone method will be called with the action that occurred, before this method returns. Should the clipboard be unavailable when attempting to place data on it, the IllegalStateException thrown by Clipboard.setContents(Transferable, ClipboardOwner) will be propagated through this method. However, exportDone will first be called with an action of NONE for consistency.

While the drag and drop implementation calls canImport to determine the suitability of a transfer before calling this method, the implementation of paste does not. As such, it cannot be assumed that the transfer is acceptable upon a call to this method for paste. It is recommended that canImport be explicitly called to cover this case.

Note: The TransferSupport object passed to this method is only valid for the duration of the method call. It is undefined what values it may contain after this method returns.

Note: Swing now calls the newer version of importData that takes a TransferSupport, which in turn calls this method (if the component in the TransferSupport is a JComponent). Developers are encouraged to call and override the newer version as it provides more information (and is the only version that supports use with a TransferHandler set directly on a JFrame or other non-JComponent).

For those components that automatically display a drop location during drag and drop, accepting the transfer, by default, tells them to show the drop location. This can be changed by calling setShowDropLocation on the TransferSupport.

By default, when the transfer is accepted, the chosen drop action is that picked by the user via their drag gesture. The developer can override this and choose a different action, from the supported source actions, by calling setDropAction on the TransferSupport.

On every call to canImport, the TransferSupport contains fresh state. As such, any properties set on it must be set on every call. Upon a drop, canImport is called one final time before calling into importData. Any state set on the TransferSupport during that last call will be available in importData.

This method is not called internally in response to paste operations. As such, it is recommended that implementations of importData explicitly call this method for such cases and that this method be prepared to return the suitability of paste operations as well.

Note: The TransferSupport object passed to this method is only valid for the duration of the method call. It is undefined what values it may contain after this method returns.

Note: Swing now calls the newer version of canImport that takes a TransferSupport, which in turn calls this method (only if the component in the TransferSupport is a JComponent). Developers are encouraged to call and override the newer version as it provides more information (and is the only version that supports use with a TransferHandler set directly on a JFrame or other non-JComponent).

Some models are not mutable, so a transfer operation of MOVE should not be advertised in that case. Returning NONE disables transfers from the component.

The default Swing logic will not do an alpha blended drag animation if the return is null.