Eclipse Plug-in Developer Guide (Galileo) - ViewerDropAdapter (Eclipse Platform API Specification)

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Eclipse Platform
Release 3.5

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org.eclipse.jface.viewers
Class ViewerDropAdapter


java.lang.Object
  

org.eclipse.swt.dnd.DropTargetAdapter
      
org.eclipse.jface.viewers.ViewerDropAdapter

All Implemented Interfaces:: EventListener, DropTargetListener, org.eclipse.swt.internal.SWTEventListener

Direct Known Subclasses:: PluginDropAdapter

public abstract class ViewerDropAdapter
extends DropTargetAdapter
extends DropTargetAdapter

This adapter class provides generic drag-and-drop support for a viewer.

Subclasses must implement the following methods:

validateDrop - identifies valid drop targets in viewer
performDrop - carries out a drop into a viewer

The setFeedbackEnabled method can be called to turn on and off visual insertion feedback (on by default).

Field Summary

static int LOCATION_AFTER
          Constant describing the position of the cursor relative to the target object.

static int LOCATION_BEFORE
          Constant describing the position of the cursor relative to the target object.

static int LOCATION_NONE
          Constant describing the position of the cursor relative to the target object.

static int LOCATION_ON
          Constant describing the position of the cursor relative to the target object.

Constructor Summary

protected ViewerDropAdapter ( Viewer viewer)
          Creates a new drop adapter for the given viewer.

Method Summary

protected void clearState ()
          Clears internal state of this drop adapter.

protected int determineLocation ( DropTargetEvent event)
          Returns the position of the given event's coordinates relative to its target.

protected Object determineTarget ( DropTargetEvent event)
          Returns the target item of the given drop event.

void dragEnter ( DropTargetEvent event)
          This implementation of dragEnter permits the default operation defined in event.detailto be performed on the current data type defined in event.currentDataType.

void dragOperationChanged ( DropTargetEvent event)
          This implementation of dragOperationChanged permits the default operation defined in event.detailto be performed on the current data type defined in event.currentDataType.

void dragOver ( DropTargetEvent event)
          This implementation of dragOver permits the default operation defined in event.detailto be performed on the current data type defined in event.currentDataType.

void drop ( DropTargetEvent event)
          This implementation of drop does nothing.

void dropAccept ( DropTargetEvent event)
          This implementation of dropAccept permits the default operation defined in event.detailto be performed on the current data type defined in event.currentDataType.

protected Rectangle getBounds ( Item item)
          Returns the bounds of the given SWT tree or table item.

protected DropTargetEvent getCurrentEvent ()
          Returns the current DropTargetEvent.

protected int getCurrentLocation ()
          Returns a constant describing the position of the mouse relative to the target (before, on, or after the target.

protected int getCurrentOperation ()
          Returns the current operation.

protected Object getCurrentTarget ()
          Returns the target object currently under the mouse.

boolean getFeedbackEnabled ()
          Returns whether visible insertion feedback should be presented to the user.

protected Object getSelectedObject ()
          Returns the object currently selected by the viewer.

protected Viewer getViewer ()


protected void handleException ( Throwable exception, DropTargetEvent event)
          Deprecated. this method should not be used. Exception handling has been removed from DropTargetAdapter methods overridden by this class. Handles any exception that occurs during callback, including rethrowing behavior.
[Issue: Implementation prints stack trace and eats exception to avoid crashing VA/J. Consider conditionalizing the implementation to do one thing in VAJ and something more reasonable in other operating environments. ]

protected void overrideOperation (int operation)
          Overrides the current operation for a drop that happens immediately after the current validateDrop.

abstract boolean performDrop ( Object data)
          Performs any work associated with the drop.

void setExpandEnabled (boolean value)
          Sets whether auto expanding should be provided during dragging.

void setFeedbackEnabled (boolean value)
          Sets whether visible insertion feedback should be presented to the user.

void setScrollEnabled (boolean value)
          Sets whether auto scrolling should be provided during dragging.

void setScrollExpandEnabled (boolean value)
          Sets whether auto scrolling and expanding should be provided during dragging.

void setSelectionFeedbackEnabled (boolean value)
          Sets whether selection feedback should be provided during dragging.

abstract boolean validateDrop ( Object target, int operation, TransferData transferType)
          Validates dropping on the given object.

Methods inherited from class org.eclipse.swt.dnd. DropTargetAdapter

dragLeave

Methods inherited from class java.lang. Object

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

Field Detail

LOCATION_BEFORE

public static final int LOCATION_BEFORE

Constant describing the position of the cursor relative to the target object. This means the mouse is positioned slightly before the target.

See Also:: getCurrentLocation(), Constant Field Values

LOCATION_AFTER

public static final int LOCATION_AFTER

Constant describing the position of the cursor relative to the target object. This means the mouse is positioned slightly after the target.

See Also:: getCurrentLocation(), Constant Field Values

LOCATION_ON

public static final int LOCATION_ON

Constant describing the position of the cursor relative to the target object. This means the mouse is positioned directly on the target.

See Also:: getCurrentLocation(), Constant Field Values

LOCATION_NONE

public static final int LOCATION_NONE

Constant describing the position of the cursor relative to the target object. This means the mouse is not positioned over or near any valid target.

See Also:: getCurrentLocation(), Constant Field Values

Constructor Detail

ViewerDropAdapter

protected ViewerDropAdapter(
Viewer viewer)

Creates a new drop adapter for the given viewer.

Parameters:: viewer - the viewer

Method Detail

clearState

protected void clearState()

Clears internal state of this drop adapter. This method can be called when no DnD operation is underway, to clear internal state from previous drop operations.

Since:: 3.5

determineLocation

protected int determineLocation(
DropTargetEvent event)

Returns the position of the given event's coordinates relative to its target. The position is determined to be before, after, or on the item, based on some threshold value.

Parameters:: event - the event
Returns:: one of the LOCATION_* constants defined in this class

determineTarget

protected 
Object determineTarget(
DropTargetEvent event)

Returns the target item of the given drop event.

Parameters:: event - the event
Returns:: The target of the drop, may be null.