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:

Field Summary

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

DragGestureRecognizer(DragSource ds)
DragGestureRecognizer(DragSource ds, Component c)
DragGestureRecognizer(DragSource ds, Component c, int sa)
DragGestureRecognizer(DragSource ds, Component c, int sa, DragGestureListener dgl)
Modifier Constructor Description
protected
Construct a new DragGestureRecognizer given the DragSource to be used in this Drag and Drop operation.
protected
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
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
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

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 Details

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 Details

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 Details

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.

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https://docs.oracle.com/en/java/javase/17/docs/api/java.desktop/java/awt/dnd/DragGestureRecognizer.html