Package org.eclipse.ui.navigator

Class CommonDropAdapterAssistant

java.lang.Object

org.eclipse.ui.navigator.CommonDropAdapterAssistant

Direct Known Subclasses:

ResourceDropAdapterAssistant

public abstract class CommonDropAdapterAssistant
extends Object

Used by the org.eclipse.ui.navigator.navigatorContent/navigatorContent/commonDropAdapter extension point to carry out pluggable drop operations.

Each CommonDropAdapterAssistant is contained by single content extension. The opportunity for each assistant to handle the drop operation is determined by the possibleChildren expression of the org.eclipse.ui.navigator.navigatorContent/navigatorContent extension; whenever every element in the drag set matches the possibleChildren expression of an extension, it is eligible to handle the drop operation. This initial set is further culled using the possibleDropTargets expression of the commonDropAdapter using the current drop target.

If drag operations originate outside of Eclipse, then the set of eligible drop adapters is determined based on the drop target (using the possibleDropTargets expression). Each assistant can then indicate whether the incoming type is supported.

Whenever a match is found, the assistant will be given an opportunity to first validateDrop(Object, int, TransferData), and then if the assistant returns true, the assist must handleDrop(CommonDropAdapter, DropTargetEvent, Object). If multiple assistants match the drop target, then the potential assistants are ordered based on priority and their override relationships and given an opportunity to validate the drop operation in turn. The first one to validate will have the opportunty to carry out the drop.

Clients may handle DND operations that begin and end in the current viewer by overriding the following methods:

• validateDrop(Object, int, TransferData): Indicate whether this assistant can handle a drop onto the current viewer.
• handleDrop(CommonDropAdapter, DropTargetEvent, Object): Handle the drop operation onto the current viewer.

If a user originates a drag operation to another viewer that cannot handle one of the available drag transfer types, drop assistants may handle the drop operation for the target viewer. Clients must override :

• validatePluginTransferDrop(IStructuredSelection, Object): Indicate whether this assistant can handle the drop onto another viewer.
• handlePluginTransferDrop(IStructuredSelection, Object): Handle the drop operation onto the other viewer.

Clients may subclass this.

Since:

3.2

See Also:

INavigatorDnDService, INavigatorDnDService.findCommonDropAdapterAssistants(Object, TransferData)

Constructor Summary

Constructors

Constructor	Description
CommonDropAdapterAssistant()

Method Summary

Modifier and Type	Method	Description
protected void	doInit()	Override to perform any one-time initialization.
protected CommonDropAdapter	getCommonDropAdapter()	Returns the CommonDropAdapter.
protected INavigatorContentService	getContentService()
DropTargetEvent	getCurrentEvent()	Returns the current DropTargetEvent.
protected Shell	getShell()
abstract IStatus	handleDrop(CommonDropAdapter aDropAdapter, DropTargetEvent aDropTargetEvent, Object aTarget)	Carry out the DND operation.
IStatus	handlePluginTransferDrop(IStructuredSelection aDragSelection, Object aDropTarget)	Handle the drop operation for the target viewer.
void	init(INavigatorContentService aContentService)	Perform any necessary initialization using the INavigatorContentService.
boolean	isSupportedType(TransferData aTransferType)	Clients may extend the supported transfer types beyond the default LocalSelectionTransfer.getTransfer() and PluginTransfer.getInstance() transfer types.
void	setCommonDropAdapter(CommonDropAdapter dropAdapter)	Sets the CommonDropAdapter.
abstract IStatus	validateDrop(Object target, int operation, TransferData transferType)	Validates dropping on the given object.
IStatus	validatePluginTransferDrop(IStructuredSelection aDragSelection, Object aDropTarget)	Return true if the client can handle the drop onto the target viewer of the drop operation.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

CommonDropAdapterAssistant

public CommonDropAdapterAssistant()

Method Detail

init

public final void init(INavigatorContentService aContentService)

Perform any necessary initialization using the INavigatorContentService.

Parameters:

aContentService - The instance of INavigatorContentService that the current CommonDropAdapterAssistant will be associated with

doInit

protected void doInit()

Override to perform any one-time initialization.

validateDrop

public abstract IStatus validateDrop(Object target,
                                     int operation,
                                     TransferData transferType)

Validates dropping on the given object. This method is called whenever some aspect of the drop operation changes.

Subclasses must implement this method to define which drops make sense. If clients return true, then they will be allowed to handle the drop in handleDrop(CommonDropAdapter, DropTargetEvent, Object).

Parameters:

target - the object that the mouse is currently hovering over, or null if the mouse is hovering over empty space

operation - the current drag operation (copy, move, etc.)

transferType - the current transfer type

Returns:

A status indicating whether the drop is valid.

handleDrop

public abstract IStatus handleDrop(CommonDropAdapter aDropAdapter,
                                   DropTargetEvent aDropTargetEvent,
                                   Object aTarget)

Carry out the DND operation.

Note: Contrary to the SWT DropTargetListener specification, you must make sure that the aDropTargetEvent.detail is not set to DND.DROP_MOVE unless actual work is required in the DragSourceListener.dragFinished(org.eclipse.swt.dnd.DragSourceEvent) to complete the operation (for example removing the moved file). In particular for the LocalSelectionTransfer case, DND.DROP_MOVE cannot be used as it will cause incorrect behavior in some existing drag handlers. In case of move operations where no action is required on the source side (e.g. LocalSelectionTransfer) you must set aDropTargetEvent.detail to DND.DROP_NONE to signal this to the drag source. Even though the SWT specification says this is canceling the drop, it is not really doing so, it is only preventing the DND.DROP_MOVE from being passed through to the dragFinished() method.

Parameters:

aDropAdapter - The Drop Adapter contains information that has already been parsed from the drop event.

aDropTargetEvent - The drop target event.

aTarget - The object being dragged onto

Returns:

A status indicating whether the drop completed OK.

isSupportedType

public boolean isSupportedType(TransferData aTransferType)

Clients may extend the supported transfer types beyond the default LocalSelectionTransfer.getTransfer() and PluginTransfer.getInstance() transfer types. When a transfer type other than one of these is encountered, the DND Service will query the visible and active descriptors that are enabled for the drop target of the current operation.

Parameters:

aTransferType - The transfer data from the drop operation

Returns:

True if the given TransferData can be understood by this assistant.

validatePluginTransferDrop

public IStatus validatePluginTransferDrop(IStructuredSelection aDragSelection,
                                          Object aDropTarget)

Return true if the client can handle the drop onto the target viewer of the drop operation.

The default behavior of this method is to return Status.CANCEL_STATUS.

Parameters:

aDragSelection - The selection dragged from the viewer.

aDropTarget - The target of the drop operation.

Returns:

OK if the plugin transfer can be handled by this assistant.

handlePluginTransferDrop

public IStatus handlePluginTransferDrop(IStructuredSelection aDragSelection,
                                        Object aDropTarget)

Handle the drop operation for the target viewer.

The default behavior of this method is to return Status.CANCEL_STATUS.

Parameters:

aDragSelection - The selection dragged from the viewer.

aDropTarget - The target of the drop operation.

Returns:

OK if the drop operation succeeded.

getContentService

protected INavigatorContentService getContentService()

Returns:

The associated content service.

getShell

protected final Shell getShell()

Returns:

A shell for the viewer currently used by the INavigatorContentService.

getCurrentEvent

public DropTargetEvent getCurrentEvent()

Returns the current DropTargetEvent.

Returns:

event the current DropTargetEvent.

Since:

3.4

setCommonDropAdapter

public void setCommonDropAdapter(CommonDropAdapter dropAdapter)

Sets the CommonDropAdapter.

Parameters:

dropAdapter - the drop adapter

Restriction:

This method is not intended to be referenced by clients.

Restriction:

This method is not intended to be re-implemented or extended by clients.

getCommonDropAdapter

protected CommonDropAdapter getCommonDropAdapter()

Returns the CommonDropAdapter.

Returns:

the CommonDropAdapter.

Since:

3.4