Class DragGestureRecognizer

java.lang.Object
- java.awt.dnd.DragGestureRecognizer

All Implemented Interfaces:: Serializable

Direct Known Subclasses:: MouseDragGestureRecognizer

public abstract class DragGestureRecognizer
extends Object
implements Serializable

The DragGestureRecognizer is an abstract base class for the specification of a platform-dependent listener that can be associated with a particular Component in order to identify platform-dependent drag initiating gestures.

The appropriate DragGestureRecognizer subclass instance is obtained from the DragSource associated with a particular Component, or from the Toolkit object via its createDragGestureRecognizer() method.

Once the DragGestureRecognizer is associated with a particular Component it will register the appropriate listener interfaces on that Component in order to track the input events delivered to the Component.

Once the DragGestureRecognizer identifies a sequence of events on the Component as a drag initiating gesture, it will notify its unicast DragGestureListener by invoking its gestureRecognized() method.

When a concrete DragGestureRecognizer instance detects a drag initiating gesture on the Component it is associated with, it fires a DragGestureEvent to the DragGestureListener registered on its unicast event source for DragGestureListener events. This DragGestureListener is responsible for causing the associated DragSource to start the Drag and Drop operation (if appropriate).

See Also:: DragGestureListener, DragGestureEvent, DragSource, Serialized Form

Field Summary

Fields
Modifier and Type	Field	Description
`protected Component`	`component`	The `Component` associated with this `DragGestureRecognizer`.
`protected DragGestureListener`	`dragGestureListener`	The `DragGestureListener` associated with this `DragGestureRecognizer`.
`protected DragSource`	`dragSource`	The `DragSource` associated with this `DragGestureRecognizer`.
`protected ArrayList<InputEvent>`	`events`	The list of events (in order) that the `DragGestureRecognizer` "recognized" as a "gesture" that triggers a drag.
`protected int`	`sourceActions`	An `int` representing the type(s) of action(s) used in this Drag and Drop operation.

Constructor Summary

Constructors
Modifier	Constructor	Description
`protected`	`DragGestureRecognizer(DragSource ds)`	Construct a new `DragGestureRecognizer` given the `DragSource` to be used in this Drag and Drop operation.
`protected`	`DragGestureRecognizer(DragSource ds, Component c)`	Construct a new `DragGestureRecognizer` given the `DragSource` to be used in this Drag and Drop operation, and the `Component` this `DragGestureRecognizer` should "observe" for drag initiating gestures.
`protected`	`DragGestureRecognizer(DragSource ds, Component c, int sa)`	Construct a new `DragGestureRecognizer` given the `DragSource` to be used in this Drag and Drop operation, the `Component` this `DragGestureRecognizer` should "observe" for drag initiating gestures, and the action(s) supported for this Drag and Drop operation.
`protected`	`DragGestureRecognizer(DragSource ds, Component c, int sa, DragGestureListener dgl)`	Construct a new `DragGestureRecognizer` given the `DragSource` to be used in this Drag and Drop operation, the `Component` this `DragGestureRecognizer` should "observe" for drag initiating gestures, the action(s) supported for this Drag and Drop operation, and the `DragGestureListener` to notify once a drag initiating gesture has been detected.

Method Summary

All Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method	Description
`void`	`addDragGestureListener(DragGestureListener dgl)`	Register a new `DragGestureListener`.
`protected void`	`appendEvent(InputEvent awtie)`	Listeners registered on the Component by this Recognizer shall record all Events that are recognized as part of the series of Events that go to comprise a Drag and Drop initiating gesture via this API.
`protected void`	`fireDragGestureRecognized(int dragAction, Point p)`	Notify the DragGestureListener that a Drag and Drop initiating gesture has occurred.
`Component`	`getComponent()`	This method returns the `Component` that is to be "observed" by the `DragGestureRecognizer` for drag initiating gestures.
`DragSource`	`getDragSource()`	This method returns the `DragSource` this `DragGestureRecognizer` will use in order to process the Drag and Drop operation.
`int`	`getSourceActions()`	This method returns an int representing the type of action(s) this Drag and Drop operation will support.
`InputEvent`	`getTriggerEvent()`	This method returns the first event in the series of events that initiated the Drag and Drop operation.
`protected abstract void`	`registerListeners()`	register this DragGestureRecognizer's Listeners with the Component subclasses must override this method
`void`	`removeDragGestureListener(DragGestureListener dgl)`	unregister the current DragGestureListener
`void`	`resetRecognizer()`	Reset the Recognizer, if its currently recognizing a gesture, ignore it.
`void`	`setComponent(Component c)`	set the Component that the DragGestureRecognizer is associated with registerListeners() and unregisterListeners() are called as a side effect as appropriate.
`void`	`setSourceActions(int actions)`	This method sets the permitted source drag action(s) for this Drag and Drop operation.
`protected abstract void`	`unregisterListeners()`	unregister this DragGestureRecognizer's Listeners with the Component subclasses must override this method

Methods declared in class java.lang.Object

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

Field Detail

dragSource

protected DragSource dragSource

The DragSource associated with this DragGestureRecognizer.

component

protected Component component

The Component associated with this DragGestureRecognizer.

dragGestureListener

protected transient DragGestureListener dragGestureListener

The DragGestureListener associated with this DragGestureRecognizer.

sourceActions

protected int sourceActions

An int representing the type(s) of action(s) used in this Drag and Drop operation.

events

protected ArrayList<InputEvent> events

The list of events (in order) that the DragGestureRecognizer "recognized" as a "gesture" that triggers a drag.

Constructor Detail

DragGestureRecognizer

protected DragGestureRecognizer(DragSource ds,
                                Component c,
                                int sa,
                                DragGestureListener dgl)

Construct a new DragGestureRecognizer given the DragSource to be used in this Drag and Drop operation, the Component this DragGestureRecognizer should "observe" for drag initiating gestures, the action(s) supported for this Drag and Drop operation, and the DragGestureListener to notify once a drag initiating gesture has been detected.

Parameters:: ds - the DragSource this DragGestureRecognizer will use to process the Drag and Drop operation; c - the Component this DragGestureRecognizer should "observe" the event stream to, in order to detect a drag initiating gesture. If this value is null, the DragGestureRecognizer is not associated with any Component.; sa - the set (logical OR) of the DnDConstants that this Drag and Drop operation will support; dgl - the DragGestureRecognizer to notify when a drag gesture is detected
Throws:: IllegalArgumentException - if ds is null.

DragGestureRecognizer

protected DragGestureRecognizer(DragSource ds,
                                Component c,
                                int sa)

Construct a new DragGestureRecognizer given the DragSource to be used in this Drag and Drop operation, the Component this DragGestureRecognizer should "observe" for drag initiating gestures, and the action(s) supported for this Drag and Drop operation.

Parameters:: ds - the DragSource this DragGestureRecognizer will use to process the Drag and Drop operation; c - the Component this DragGestureRecognizer should "observe" the event stream to, in order to detect a drag initiating gesture. If this value is null, the DragGestureRecognizer is not associated with any Component.; sa - the set (logical OR) of the DnDConstants that this Drag and Drop operation will support
Throws:: IllegalArgumentException - if ds is null.

DragGestureRecognizer

protected DragGestureRecognizer(DragSource ds,
                                Component c)

Construct a new DragGestureRecognizer given the DragSource to be used in this Drag and Drop operation, and the Component this DragGestureRecognizer should "observe" for drag initiating gestures.

Parameters:: ds - the DragSource this DragGestureRecognizer will use to process the Drag and Drop operation; c - the Component this DragGestureRecognizer should "observe" the event stream to, in order to detect a drag initiating gesture. If this value is null, the DragGestureRecognizer is not associated with any Component.
Throws:: IllegalArgumentException - if ds is null.

DragGestureRecognizer

protected DragGestureRecognizer(DragSource ds)

Construct a new DragGestureRecognizer given the DragSource to be used in this Drag and Drop operation.

Parameters:: ds - the DragSource this DragGestureRecognizer will use to process the Drag and Drop operation
Throws:: IllegalArgumentException - if ds is null.

Method Detail

registerListeners

protected abstract void registerListeners()

register this DragGestureRecognizer's Listeners with the Component subclasses must override this method

unregisterListeners

protected abstract void unregisterListeners()

unregister this DragGestureRecognizer's Listeners with the Component subclasses must override this method

getDragSource

public DragSource getDragSource()

This method returns the DragSource this DragGestureRecognizer will use in order to process the Drag and Drop operation.

Returns:: the DragSource

getComponent

public Component getComponent()

This method returns the Component that is to be "observed" by the DragGestureRecognizer for drag initiating gestures.

Returns:: The Component this DragGestureRecognizer is associated with

setComponent

public void setComponent(Component c)

set the Component that the DragGestureRecognizer is associated with registerListeners() and unregisterListeners() are called as a side effect as appropriate.

Parameters:: c - The Component or null

getSourceActions

public int getSourceActions()

This method returns an int representing the type of action(s) this Drag and Drop operation will support.

Returns:: the currently permitted source action(s)

setSourceActions

public void setSourceActions(int actions)

This method sets the permitted source drag action(s) for this Drag and Drop operation.

Parameters:: actions - the permitted source drag action(s)

getTriggerEvent

public InputEvent getTriggerEvent()

This method returns the first event in the series of events that initiated the Drag and Drop operation.

Returns:: the initial event that triggered the drag gesture

resetRecognizer

public void resetRecognizer()

Reset the Recognizer, if its currently recognizing a gesture, ignore it.

addDragGestureListener

public void addDragGestureListener(DragGestureListener dgl)
                            throws TooManyListenersException

Register a new DragGestureListener.

Parameters:: dgl - the DragGestureListener to register with this DragGestureRecognizer.
Throws:: TooManyListenersException - if a DragGestureListener has already been added.

removeDragGestureListener

public void removeDragGestureListener(DragGestureListener dgl)

unregister the current DragGestureListener

Parameters:: dgl - the DragGestureListener to unregister from this DragGestureRecognizer
Throws:: IllegalArgumentException - if dgl is not (equal to) the currently registered DragGestureListener.

fireDragGestureRecognized

protected void fireDragGestureRecognized(int dragAction,
                                         Point p)

Notify the DragGestureListener that a Drag and Drop initiating gesture has occurred. Then reset the state of the Recognizer.

Parameters:: dragAction - The action initially selected by the users gesture; p - The point (in Component coords) where the gesture originated

appendEvent

protected void appendEvent(InputEvent awtie)

Listeners registered on the Component by this Recognizer shall record all Events that are recognized as part of the series of Events that go to comprise a Drag and Drop initiating gesture via this API.

This method is used by a DragGestureRecognizer implementation to add an InputEvent subclass (that it believes is one in a series of events that comprise a Drag and Drop operation) to the array of events that this DragGestureRecognizer maintains internally.

Parameters:: awtie - the InputEvent to add to this DragGestureRecognizer's internal array of events. Note that null is not a valid value, and will be ignored.