Class VDragAndDropManager

java.lang.Object
  com.vaadin.terminal.gwt.client.ui.dd.VDragAndDropManager

public class VDragAndDropManager
extends Object

Helper class to manage the state of drag and drop event on Vaadin client side. Can be used to implement most of the drag and drop operation automatically via cross-browser event preview method or just as a helper when implementing own low level drag and drop operation (like with HTML5 api).

Singleton. Only one drag and drop operation can be active anyways. Use get() to get instance. TODO cancel drag and drop if more than one touches !?

Nested Class Summary
static class	VDragAndDropManager.DragEventType

 

Field Summary
static String	ACTIVE_DRAG_SOURCE_STYLENAME

 

Constructor Summary
protected	VDragAndDropManager()

 

Method Summary
void	endDrag()           Drag is ended (drop happened) on current drop handler.
void	executeWhenReady(com.google.gwt.user.client.Command command)           Method to execute commands when all existing dd related tasks are completed (some may require server visit).
static VDragAndDropManager	get()
VDropHandler	getCurrentDropHandler()
void	handleServerResponse(ValueMap valueMap)
void	interruptDrag()           The drag and drop operation is ended, but drop did not happen.
void	setCurrentDropHandler(VDropHandler currentDropHandler)           If drag and drop operation is not handled by VDragAndDropManagers internal handler, this can be used to update current VDropHandler .
VDragEvent	startDrag(VTransferable transferable, com.google.gwt.dom.client.NativeEvent startEvent, boolean handleDragEvents)           This method is used to start Vaadin client side drag and drop operation.
void	visitServer(VDragEventServerCallback acceptCallback)           Visits server during drag and drop procedure.

 

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

 

Field Detail

ACTIVE_DRAG_SOURCE_STYLENAME

public static final String ACTIVE_DRAG_SOURCE_STYLENAME

See Also:

Constant Field Values

Constructor Detail

VDragAndDropManager

protected VDragAndDropManager()

Method Detail

getCurrentDropHandler

public VDropHandler getCurrentDropHandler()

setCurrentDropHandler

public void setCurrentDropHandler(VDropHandler currentDropHandler)

If drag and drop operation is not handled by VDragAndDropManagers internal handler, this can be used to update current VDropHandler .

Parameters:

currentDropHandler -

get

public static VDragAndDropManager get()

startDrag

public VDragEvent startDrag(VTransferable transferable,
                            com.google.gwt.dom.client.NativeEvent startEvent,
                            boolean handleDragEvents)

This method is used to start Vaadin client side drag and drop operation. Operation may be started by virtually any Widget.

Cancels possible existing drag. TODO figure out if this is always a bug if one is active. Maybe a good and cheap lifesaver thought.

If possible, method automatically detects current VDropHandler and fires VDropHandler.dragEnter(VDragEvent) event on it.

May also be used to control the drag and drop operation. If this option is used, VDropHandler is searched on mouse events and appropriate methods on it called automatically.

Parameters:

transferable -

nativeEvent -

handleDragEvents - if true, VDragAndDropManager handles the drag and drop operation GWT event preview.

Returns:

endDrag

public void endDrag()

Drag is ended (drop happened) on current drop handler. Calls drop method on current drop handler and does appropriate cleanup.

interruptDrag

public void interruptDrag()

The drag and drop operation is ended, but drop did not happen. If operation is currently on a drop handler, its dragLeave method is called and appropriate cleanup happens.

visitServer

public void visitServer(VDragEventServerCallback acceptCallback)

Visits server during drag and drop procedure. Transferable and event type is given to server side counterpart of DropHandler. If another server visit is started before the current is received, the current is just dropped. TODO consider if callback should have interrupted() method for cleanup.

Parameters:

acceptCallback -

handleServerResponse

public void handleServerResponse(ValueMap valueMap)

executeWhenReady

public void executeWhenReady(com.google.gwt.user.client.Command command)

Method to execute commands when all existing dd related tasks are completed (some may require server visit).

Using this method may be handy if criterion that uses lazy initialization are used. Check

TODO Optimization: consider if we actually only need to keep the last command in queue here.

Parameters:

command -