src/java.desktop/share/classes/java/awt/dnd/DragSourceListener.java

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package java.awt.dnd;

import java.util.EventListener;

/**
 * The {@code DragSourceListener} defines the
 * event interface for originators of
 * Drag and Drop operations to track the state of the user's gesture, and to
 * provide appropriate "drag over"
 * feedback to the user throughout the
 * Drag and Drop operation.
 * <p>
 * The drop site is <i>associated with the previous {@code dragEnter()}
 * invocation</i> if the latest invocation of {@code dragEnter()} on this
 * listener:
 * <ul>
 * <li>corresponds to that drop site and
 * <li> is not followed by a {@code dragExit()} invocation on this listener.
 * </ul>
 *
 * @since 1.2
 */

public interface DragSourceListener extends EventListener {

    /**
     * Called as the cursor's hotspot enters a platform-dependent drop site.
     * This method is invoked when all the following conditions are true:
     * <UL>
     * <LI>The cursor's hotspot enters the operable part of a platform-
     * dependent drop site.
     * <LI>The drop site is active.
     * <LI>The drop site accepts the drag.
     * </UL>
     *
     * @param dsde the {@code DragSourceDragEvent}
     */
    void dragEnter(DragSourceDragEvent dsde);

    /**
     * Called as the cursor's hotspot moves over a platform-dependent drop site.
     * This method is invoked when all the following conditions are true:
     * <UL>
     * <LI>The cursor's hotspot has moved, but still intersects the
     * operable part of the drop site associated with the previous
     * dragEnter() invocation.
     * <LI>The drop site is still active.
     * <LI>The drop site accepts the drag.
     * </UL>
     *
     * @param dsde the {@code DragSourceDragEvent}
     */
    void dragOver(DragSourceDragEvent dsde);

    /**
     * Called when the user has modified the drop gesture.
     * This method is invoked when the state of the input
     * device(s) that the user is interacting with changes.
     * Such devices are typically the mouse buttons or keyboard
     * modifiers that the user is interacting with.
     *
     * @param dsde the {@code DragSourceDragEvent}
     */
    void dropActionChanged(DragSourceDragEvent dsde);

    /**
     * Called as the cursor's hotspot exits a platform-dependent drop site.
     * This method is invoked when any of the following conditions are true:
     * <UL>
     * <LI>The cursor's hotspot no longer intersects the operable part
     * of the drop site associated with the previous dragEnter() invocation.
     * </UL>
     * OR
     * <UL>
     * <LI>The drop site associated with the previous dragEnter() invocation
     * is no longer active.
     * </UL>
     * OR
     * <UL>
     * <LI> The drop site associated with the previous dragEnter() invocation
     * has rejected the drag.
     * </UL>
     *
     * @param dse the {@code DragSourceEvent}
     */
    void dragExit(DragSourceEvent dse);

    /**
     * This method is invoked to signify that the Drag and Drop
     * operation is complete. The getDropSuccess() method of
     * the {@code DragSourceDropEvent} can be used to
     * determine the termination state. The getDropAction() method
     * returns the operation that the drop site selected
     * to apply to the Drop operation. Once this method is complete, the
     * current {@code DragSourceContext} and
     * associated resources become invalid.
     *
     * @param dsde the {@code DragSourceDropEvent}
     */
    void dragDropEnd(DragSourceDropEvent dsde);
}