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package java.awt.dnd;
import java.awt.event.InputEvent;
import java.awt.Component;
import java.awt.Point;
import java.util.TooManyListenersException;
import java.util.ArrayList;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
/**
* The <code>DragGestureRecognizer</code> is an
* abstract base class for the specification
* of a platform-dependent listener that can be associated with a particular
* <code>Component</code> in order to
* identify platform-dependent drag initiating gestures.
* <p>
* The appropriate <code>DragGestureRecognizer</code>
* subclass instance is obtained from the
* {@link DragSource} asssociated with
* a particular <code>Component</code>, or from the <code>Toolkit</code> object via its
* {@link java.awt.Toolkit#createDragGestureRecognizer createDragGestureRecognizer()}
* method.
* <p>
* Once the <code>DragGestureRecognizer</code>
* is associated with a particular <code>Component</code>
* it will register the appropriate listener interfaces on that
* <code>Component</code>
* in order to track the input events delivered to the <code>Component</code>.
* <p>
* Once the <code>DragGestureRecognizer</code> identifies a sequence of events
* on the <code>Component</code> as a drag initiating gesture, it will notify
* its unicast <code>DragGestureListener</code> by
* invoking its
* {@link java.awt.dnd.DragGestureListener#dragGestureRecognized gestureRecognized()}
* method.
* <P>
* When a concrete <code>DragGestureRecognizer</code>
* instance detects a drag initiating
* gesture on the <code>Component</code> it is associated with,
* it fires a {@link DragGestureEvent} to
* the <code>DragGestureListener</code> registered on
* its unicast event source for <code>DragGestureListener</code>
* events. This <code>DragGestureListener</code> is responsible
* for causing the associated
* <code>DragSource</code> to start the Drag and Drop operation (if
* appropriate).
* <P>
* @author Laurence P. G. Cable
* @see java.awt.dnd.DragGestureListener
* @see java.awt.dnd.DragGestureEvent
* @see java.awt.dnd.DragSource
*/
public abstract class DragGestureRecognizer implements Serializable {
private static final long serialVersionUID = 8996673345831063337L;
/**
* Construct a new <code>DragGestureRecognizer</code>
* given the <code>DragSource</code> to be used
* in this Drag and Drop operation, the <code>Component</code>
* this <code>DragGestureRecognizer</code> should "observe"
* for drag initiating gestures, the action(s) supported
* for this Drag and Drop operation, and the
* <code>DragGestureListener</code> to notify
* once a drag initiating gesture has been detected.
* <P>
* @param ds the <code>DragSource</code> this
* <code>DragGestureRecognizer</code>
* will use to process the Drag and Drop operation
*
* @param c the <code>Component</code>
* this <code>DragGestureRecognizer</code>
* should "observe" the event stream to,
* in order to detect a drag initiating gesture.
* If this value is <code>null</code>, the
* <code>DragGestureRecognizer</code>
* is not associated with any <code>Component</code>.
*
* @param sa the set (logical OR) of the
* <code>DnDConstants</code>
* that this Drag and Drop operation will support
*
* @param dgl the <code>DragGestureRecognizer</code>
* to notify when a drag gesture is detected
* <P>
* @throws <code>IllegalArgumentException</code>
* if ds is <code>null</code>.
*/
protected DragGestureRecognizer(DragSource ds, Component c, int sa, DragGestureListener dgl) {
super();
if (ds == null) throw new IllegalArgumentException("null DragSource");
dragSource = ds;
component = c;
sourceActions = sa & (DnDConstants.ACTION_COPY_OR_MOVE | DnDConstants.ACTION_LINK);
try {
if (dgl != null) addDragGestureListener(dgl);
} catch (TooManyListenersException tmle) {
// cant happen ...
}
}
/**
* Construct a new <code>DragGestureRecognizer</code>
* given the <code>DragSource</code> to be used in this
* Drag and Drop
* operation, the <code>Component</code> this
* <code>DragGestureRecognizer</code> should "observe"
* for drag initiating gestures, and the action(s)
* supported for this Drag and Drop operation.
* <P>
* @param ds the <code>DragSource</code> this
* <code>DragGestureRecognizer</code> will use to
* process the Drag and Drop operation
*
* @param c the <code>Component</code> this
* <code>DragGestureRecognizer</code> should "observe" the event
* stream to, in order to detect a drag initiating gesture.
* If this value is <code>null</code>, the
* <code>DragGestureRecognizer</code>
* is not associated with any <code>Component</code>.
*
* @param sa the set (logical OR) of the <code>DnDConstants</code>
* that this Drag and Drop operation will support
* <P>
* @throws <code>IllegalArgumentException</code>
* if ds is <code>null</code>.
*/
protected DragGestureRecognizer(DragSource ds, Component c, int sa) {
this(ds, c, sa, null);
}
/**
* Construct a new <code>DragGestureRecognizer</code>
* given the <code>DragSource</code> to be used
* in this Drag and Drop operation, and
* the <code>Component</code> this
* <code>DragGestureRecognizer</code>
* should "observe" for drag initiating gestures.
* <P>
* @param ds the <code>DragSource</code> this
* <code>DragGestureRecognizer</code>
* will use to process the Drag and Drop operation
*
* @param c the <code>Component</code>
* this <code>DragGestureRecognizer</code>
* should "observe" the event stream to,
* in order to detect a drag initiating gesture.
* If this value is <code>null</code>,
* the <code>DragGestureRecognizer</code>
* is not associated with any <code>Component</code>.
* <P>
* @throws <code>IllegalArgumentException</code>
* if ds is <code>null</code>.
*/
protected DragGestureRecognizer(DragSource ds, Component c) {
this(ds, c, DnDConstants.ACTION_NONE);
}
/**
* Construct a new <code>DragGestureRecognizer</code>
* given the <code>DragSource</code> to be used in this
* Drag and Drop operation.
* <P>
* @param ds the <code>DragSource</code> this
* <code>DragGestureRecognizer</code> will
* use to process the Drag and Drop operation
* <P>
* @throws <code>IllegalArgumentException</code>
* if ds is <code>null</code>.
*/
protected DragGestureRecognizer(DragSource ds) {
this(ds, null);
}
/**
* register this DragGestureRecognizer's Listeners with the Component
*
* subclasses must override this method
*/
protected abstract void registerListeners();
/**
* unregister this DragGestureRecognizer's Listeners with the Component
*
* subclasses must override this method
*/
protected abstract void unregisterListeners();
/**
* This method returns the <code>DragSource</code>
* this <code>DragGestureRecognizer</code>
* will use in order to process the Drag and Drop
* operation.
* <P>
* @return the DragSource
*/
public DragSource getDragSource() { return dragSource; }
/**
* This method returns the <code>Component</code>
* that is to be "observed" by the
* <code>DragGestureRecognizer</code>
* for drag initiating gestures.
* <P>
* @return The Component this DragGestureRecognizer
* is associated with
*/
public synchronized Component getComponent() { return component; }
/**
* set the Component that the DragGestureRecognizer is associated with
*
* registerListeners() and unregisterListeners() are called as a side
* effect as appropriate.
* <P>
* @param c The <code>Component</code> or <code>null</code>
*/
public synchronized void setComponent(Component c) {
if (component != null && dragGestureListener != null)
unregisterListeners();
component = c;
if (component != null && dragGestureListener != null)
registerListeners();
}
/**
* This method returns an int representing the
* type of action(s) this Drag and Drop
* operation will support.
* <P>
* @return the currently permitted source action(s)
*/
public synchronized int getSourceActions() { return sourceActions; }
/**
* This method sets the permitted source drag action(s)
* for this Drag and Drop operation.
* <P>
* @param actions the permitted source drag action(s)
*/
public synchronized void setSourceActions(int actions) {
sourceActions = actions & (DnDConstants.ACTION_COPY_OR_MOVE | DnDConstants.ACTION_LINK);
}
/**
* This method returns the first event in the
* series of events that initiated
* the Drag and Drop operation.
* <P>
* @return the initial event that triggered the drag gesture
*/
public InputEvent getTriggerEvent() { return events.isEmpty() ? null : events.get(0); }
/**
* Reset the Recognizer, if its currently recognizing a gesture, ignore
* it.
*/
public void resetRecognizer() { events.clear(); }
/**
* Register a new <code>DragGestureListener</code>.
* <P>
* @param dgl the <code>DragGestureListener</code> to register
* with this <code>DragGestureRecognizer</code>.
* <P>
* @throws java.util.TooManyListenersException if a
* <code>DragGestureListener</code> has already been added.
*/
public synchronized void addDragGestureListener(DragGestureListener dgl) throws TooManyListenersException {
if (dragGestureListener != null)
throw new TooManyListenersException();
else {
dragGestureListener = dgl;
if (component != null) registerListeners();
}
}
/**
* unregister the current DragGestureListener
* <P>
* @param dgl the <code>DragGestureListener</code> to unregister
* from this <code>DragGestureRecognizer</code>
* <P>
* @throws <code>IllegalArgumentException</code> if
* dgl is not (equal to) the currently registered <code>DragGestureListener</code>.
*/
public synchronized void removeDragGestureListener(DragGestureListener dgl) {
if (dragGestureListener == null || !dragGestureListener.equals(dgl))
throw new IllegalArgumentException();
else {
dragGestureListener = null;
if (component != null) unregisterListeners();
}
}
/**
* Notify the DragGestureListener that a Drag and Drop initiating
* gesture has occurred. Then reset the state of the Recognizer.
* <P>
* @param dragAction The action initially selected by the users gesture
* @param p The point (in Component coords) where the gesture originated
*/
protected synchronized void fireDragGestureRecognized(int dragAction, Point p) {
try {
if (dragGestureListener != null) {
dragGestureListener.dragGestureRecognized(new DragGestureEvent(this, dragAction, p, events));
}
} finally {
events.clear();
}
}
/**
* 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.
*<P>
* This method is used by a <code>DragGestureRecognizer</code>
* implementation to add an <code>InputEvent</code>
* 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
* <code>DragGestureRecognizer</code> maintains internally.
* <P>
* @param awtie the <code>InputEvent</code>
* to add to this <code>DragGestureRecognizer</code>'s
* internal array of events. Note that <code>null</code>
* is not a valid value, and will be ignored.
*/
protected synchronized void appendEvent(InputEvent awtie) {
events.add(awtie);
}
/**
* Serializes this <code>DragGestureRecognizer</code>. This method first
* performs default serialization. Then, this object's
* <code>DragGestureListener</code> is written out if and only if it can be
* serialized. If not, <code>null</code> is written instead.
*
* @serialData The default serializable fields, in alphabetical order,
* followed by either a <code>DragGestureListener</code>, or
* <code>null</code>.
* @since 1.4
*/
private void writeObject(ObjectOutputStream s) throws IOException {
s.defaultWriteObject();
s.writeObject(SerializationTester.test(dragGestureListener)
? dragGestureListener : null);
}
/**
* Deserializes this <code>DragGestureRecognizer</code>. This method first
* performs default deserialization for all non-<code>transient</code>
* fields. This object's <code>DragGestureListener</code> is then
* deserialized as well by using the next object in the stream.
*
* @since 1.4
*/
private void readObject(ObjectInputStream s)
throws ClassNotFoundException, IOException
{
s.defaultReadObject();
dragGestureListener = (DragGestureListener)s.readObject();
}
/*
* fields
*/
/**
* The <code>DragSource</code>
* associated with this
* <code>DragGestureRecognizer</code>.
*
* @serial
*/
protected DragSource dragSource;
/**
* The <code>Component</code>
* associated with this <code>DragGestureRecognizer</code>.
*
* @serial
*/
protected Component component;
/**
* The <code>DragGestureListener</code>
* associated with this <code>DragGestureRecognizer</code>.
*/
protected transient DragGestureListener dragGestureListener;
/**
* An <code>int</code> representing
* the type(s) of action(s) used
* in this Drag and Drop operation.
*
* @serial
*/
protected int sourceActions;
/**
* The list of events (in order) that
* the <code>DragGestureRecognizer</code>
* "recognized" as a "gesture" that triggers a drag.
*
* @serial
*/
protected ArrayList<InputEvent> events = new ArrayList<InputEvent>(1);
}