JDK8/Java8源码在线阅读

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package java.awt.dnd;

import java.awt.event.InputEvent;

/**
 * The <code>DragSourceDragEvent</code> is
 * delivered from the <code>DragSourceContextPeer</code>,
 * via the <code>DragSourceContext</code>, to the <code>DragSourceListener</code>
 * registered with that <code>DragSourceContext</code> and with its associated
 * <code>DragSource</code>.
 * <p>
 * The <code>DragSourceDragEvent</code> reports the <i>target drop action</i>
 * and the <i>user drop action</i> that reflect the current state of
 * the drag operation.
 * <p>
 * <i>Target drop action</i> is one of <code>DnDConstants</code> that represents
 * the drop action selected by the current drop target if this drop action is
 * supported by the drag source or <code>DnDConstants.ACTION_NONE</code> if this
 * drop action is not supported by the drag source.
 * <p>
 * <i>User drop action</i> depends on the drop actions supported by the drag
 * source and the drop action selected by the user. The user can select a drop
 * action by pressing modifier keys during the drag operation:
 * <pre>
 *   Ctrl + Shift -&gt; ACTION_LINK
 *   Ctrl         -&gt; ACTION_COPY
 *   Shift        -&gt; ACTION_MOVE
 * </pre>
 * If the user selects a drop action, the <i>user drop action</i> is one of
 * <code>DnDConstants</code> that represents the selected drop action if this
 * drop action is supported by the drag source or
 * <code>DnDConstants.ACTION_NONE</code> if this drop action is not supported
 * by the drag source.
 * <p>
 * If the user doesn't select a drop action, the set of
 * <code>DnDConstants</code> that represents the set of drop actions supported
 * by the drag source is searched for <code>DnDConstants.ACTION_MOVE</code>,
 * then for <code>DnDConstants.ACTION_COPY</code>, then for
 * <code>DnDConstants.ACTION_LINK</code> and the <i>user drop action</i> is the
 * first constant found. If no constant is found the <i>user drop action</i>
 * is <code>DnDConstants.ACTION_NONE</code>.
 *
 * @since 1.2
 *
 */

public class DragSourceDragEvent extends DragSourceEvent {

    private static final long serialVersionUID = 481346297933902471L;

    /**
     * Constructs a <code>DragSourceDragEvent</code>.
     * This class is typically
     * instantiated by the <code>DragSourceContextPeer</code>
     * rather than directly
     * by client code.
     * The coordinates for this <code>DragSourceDragEvent</code>
     * are not specified, so <code>getLocation</code> will return
     * <code>null</code> for this event.
     * <p>
     * The arguments <code>dropAction</code> and <code>action</code> should
     * be one of <code>DnDConstants</code> that represents a single action.
     * The argument <code>modifiers</code> should be either a bitwise mask
     * of old <code>java.awt.event.InputEvent.*_MASK</code> constants or a
     * bitwise mask of extended <code>java.awt.event.InputEvent.*_DOWN_MASK</code>
     * constants.
     * This constructor does not throw any exception for invalid <code>dropAction</code>,
     * <code>action</code> and <code>modifiers</code>.
     *
     * @param dsc the <code>DragSourceContext</code> that is to manage
     *            notifications for this event.
     * @param dropAction the user drop action.
     * @param action the target drop action.
     * @param modifiers the modifier keys down during event (shift, ctrl,
     *        alt, meta)
     *        Either extended _DOWN_MASK or old _MASK modifiers
     *        should be used, but both models should not be mixed
     *        in one event. Use of the extended modifiers is
     *        preferred.
     *
     * @throws IllegalArgumentException if <code>dsc</code> is <code>null</code>.
     *
     * @see java.awt.event.InputEvent
     * @see DragSourceEvent#getLocation
     */

    public DragSourceDragEvent(DragSourceContext dsc, int dropAction,
                               int action, int modifiers) {
        super(dsc);

        targetActions    = action;
        gestureModifiers = modifiers;
        this.dropAction  = dropAction;
        if ((modifiers & ~(JDK_1_3_MODIFIERS | JDK_1_4_MODIFIERS)) != 0) {
            invalidModifiers = true;
        } else if ((getGestureModifiers() != 0) && (getGestureModifiersEx() == 0)) {
            setNewModifiers();
        } else if ((getGestureModifiers() == 0) && (getGestureModifiersEx() != 0)) {
            setOldModifiers();
        } else {
            invalidModifiers = true;
        }
    }

    /**
     * Constructs a <code>DragSourceDragEvent</code> given the specified
     * <code>DragSourceContext</code>, user drop action, target drop action,
     * modifiers and coordinates.
     * <p>
     * The arguments <code>dropAction</code> and <code>action</code> should
     * be one of <code>DnDConstants</code> that represents a single action.
     * The argument <code>modifiers</code> should be either a bitwise mask
     * of old <code>java.awt.event.InputEvent.*_MASK</code> constants or a
     * bitwise mask of extended <code>java.awt.event.InputEvent.*_DOWN_MASK</code>
     * constants.
     * This constructor does not throw any exception for invalid <code>dropAction</code>,
     * <code>action</code> and <code>modifiers</code>.
     *
     * @param dsc the <code>DragSourceContext</code> associated with this
     *        event.
     * @param dropAction the user drop action.
     * @param action the target drop action.
     * @param modifiers the modifier keys down during event (shift, ctrl,
     *        alt, meta)
     *        Either extended _DOWN_MASK or old _MASK modifiers
     *        should be used, but both models should not be mixed
     *        in one event. Use of the extended modifiers is
     *        preferred.
     * @param x   the horizontal coordinate for the cursor location
     * @param y   the vertical coordinate for the cursor location
     *
     * @throws IllegalArgumentException if <code>dsc</code> is <code>null</code>.
     *
     * @see java.awt.event.InputEvent
     * @since 1.4
     */
    public DragSourceDragEvent(DragSourceContext dsc, int dropAction,
                               int action, int modifiers, int x, int y) {
        super(dsc, x, y);

        targetActions    = action;
        gestureModifiers = modifiers;
        this.dropAction  = dropAction;
        if ((modifiers & ~(JDK_1_3_MODIFIERS | JDK_1_4_MODIFIERS)) != 0) {
            invalidModifiers = true;
        } else if ((getGestureModifiers() != 0) && (getGestureModifiersEx() == 0)) {
            setNewModifiers();
        } else if ((getGestureModifiers() == 0) && (getGestureModifiersEx() != 0)) {
            setOldModifiers();
        } else {
            invalidModifiers = true;
        }
    }

    /**
     * This method returns the target drop action.
     *
     * @return the target drop action.
     */
    public int getTargetActions() {
        return targetActions;
    }


    private static final int JDK_1_3_MODIFIERS = InputEvent.SHIFT_DOWN_MASK - 1;
    private static final int JDK_1_4_MODIFIERS =
            ((InputEvent.ALT_GRAPH_DOWN_MASK << 1) - 1) & ~JDK_1_3_MODIFIERS;

    /**
     * This method returns an <code>int</code> representing
     * the current state of the input device modifiers
     * associated with the user's gesture. Typically these
     * would be mouse buttons or keyboard modifiers.
     * <P>
     * If the <code>modifiers</code> passed to the constructor
     * are invalid, this method returns them unchanged.
     *
     * @return the current state of the input device modifiers
     */

    public int getGestureModifiers() {
        return invalidModifiers ? gestureModifiers : gestureModifiers & JDK_1_3_MODIFIERS;
    }

    /**
     * This method returns an <code>int</code> representing
     * the current state of the input device extended modifiers
     * associated with the user's gesture.
     * See {@link InputEvent#getModifiersEx}
     * <P>
     * If the <code>modifiers</code> passed to the constructor
     * are invalid, this method returns them unchanged.
     *
     * @return the current state of the input device extended modifiers
     * @since 1.4
     */

    public int getGestureModifiersEx() {
        return invalidModifiers ? gestureModifiers : gestureModifiers & JDK_1_4_MODIFIERS;
    }

    /**
     * This method returns the user drop action.
     *
     * @return the user drop action.
     */
    public int getUserAction() { return dropAction; }

    /**
     * This method returns the logical intersection of
     * the target drop action and the set of drop actions supported by
     * the drag source.
     *
     * @return the logical intersection of the target drop action and
     *         the set of drop actions supported by the drag source.
     */
    public int getDropAction() {
        return targetActions & getDragSourceContext().getSourceActions();
    }

    /*
     * fields
     */

    /**
     * The target drop action.
     *
     * @serial
     */
    private int     targetActions    = DnDConstants.ACTION_NONE;

    /**
     * The user drop action.
     *
     * @serial
     */
    private int     dropAction       = DnDConstants.ACTION_NONE;

    /**
     * The state of the input device modifiers associated with the user
     * gesture.
     *
     * @serial
     */
    private int     gestureModifiers = 0;

    /**
     * Indicates whether the <code>gestureModifiers</code> are invalid.
     *
     * @serial
     */
    private boolean invalidModifiers;

    /**
     * Sets new modifiers by the old ones.
     * The mouse modifiers have higher priority than overlaying key
     * modifiers.
     */
    private void setNewModifiers() {
        if ((gestureModifiers & InputEvent.BUTTON1_MASK) != 0) {
            gestureModifiers |= InputEvent.BUTTON1_DOWN_MASK;
        }
        if ((gestureModifiers & InputEvent.BUTTON2_MASK) != 0) {
            gestureModifiers |= InputEvent.BUTTON2_DOWN_MASK;
        }
        if ((gestureModifiers & InputEvent.BUTTON3_MASK) != 0) {
            gestureModifiers |= InputEvent.BUTTON3_DOWN_MASK;
        }
        if ((gestureModifiers & InputEvent.SHIFT_MASK) != 0) {

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