DragGestureRecognizer (Java Platform SE 8 )

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 and 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 and 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 and 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 inherited from 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.

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Class DragGestureRecognizer

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

dragSource

component

dragGestureListener

sourceActions

events

Constructor Detail

DragGestureRecognizer

DragGestureRecognizer

DragGestureRecognizer

DragGestureRecognizer

Method Detail

registerListeners

unregisterListeners

getDragSource

getComponent

setComponent

getSourceActions

setSourceActions

getTriggerEvent

resetRecognizer

addDragGestureListener

removeDragGestureListener

fireDragGestureRecognized

appendEvent