dragtracker.java

来自「开源（Open Source）项目JHotDraw的文档和源程序」· Java 代码 · 共 57 行

/*
 * @(#)DragTracker.java 5.2
 *
 */

package CH.ifa.draw.standard;

import java.awt.*;
import java.awt.event.MouseEvent;
import java.util.*;
import CH.ifa.draw.framework.*;

/**
 * DragTracker implements the dragging of the clicked
 * figure.
 *
 * @see SelectionTool
 */
public class DragTracker extends AbstractTool {

    private Figure  fAnchorFigure;
    private int     fLastX, fLastY;      // previous mouse position
    private boolean fMoved = false;

    public DragTracker(DrawingView view, Figure anchor) {
        super(view);
        fAnchorFigure = anchor;
    }

    public void mouseDown(MouseEvent e, int x, int y) {
        super.mouseDown(e, x, y);
        fLastX = x;
        fLastY = y;

        if (e.isShiftDown()) {
           view().toggleSelection(fAnchorFigure);
           fAnchorFigure = null;
        } else if (!view().selection().contains(fAnchorFigure)) {
            view().clearSelection();
            view().addToSelection(fAnchorFigure);
        }
    }

    public void mouseDrag(MouseEvent e, int x, int y) {
        super.mouseDrag(e, x, y);
        fMoved = (Math.abs(x - fAnchorX) > 4) || (Math.abs(y - fAnchorY) > 4);

        if (fMoved) {
            FigureEnumeration figures = view().selectionElements();
            while (figures.hasMoreElements())
                figures.nextFigure().moveBy(x - fLastX, y - fLastY);
        }
        fLastX = x;
        fLastY = y;
    }
}