Question

我正在尝试通过单击并拖动它来制作滚动视图滚动。它确实滚动但不是很好，它看起来像是在正确的方向滚动和在相反的方向滚动之间快速交替。无论如何，这是我到目前为止所得到的（这是在自定义鼠标适配器中）：

point p;
JViewport viewport;
@Override
public void mousePressed(MouseEvent e) 
{
        p.setLocation(e.getX(),e.getY());
    }
@Override
public void mouseDragged(MouseEvent e)
{
        Point ep = new Point();
        ep.setLocation(e.getX(),e.getY());
        double changex =  e.getX() - p.getX();
        double changey = e.getY() - p.getY();
        Point q = viewport.getViewPosition();
        q.setLocation(q.getX()-changex, q.getY()-changey);
        p.setLocation(ep);
        viewport().setViewPosition(q);
    }

Answer 1

好的，所以我对这个想法有点玩耍。

基本上，当您单击时，我会计算您单击的位置和当前视口位置的偏移量。

当拖动鼠标时，我基本上用点击偏移来抵消拖动位置，在进行一些边界检查后，我只需设置视口位置......

import java.awt.Container;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JViewport;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class TestScrollPane101 {

    public static void main(String[] args) {
        new TestScrollPane101();
    }

    public TestScrollPane101() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new JScrollPane(new TestPane()));
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        private BufferedImage img;

        public TestPane() {
            try {
                img = ImageIO.read(new File("/Users/swhitehead/Dropbox/MegaTokyo/_cg_836___Tilting_Windmills___by_Serena_Clearwater.png"));
            } catch (IOException ex) {
                ex.printStackTrace();
            }

            MouseAdapter ma = new MouseAdapter() {

                private Point offset;

                @Override
                public void mouseDragged(MouseEvent e) {
                    Container parent = getParent();
                    if (parent instanceof JViewport) {
                        JViewport view = (JViewport) parent;
                        Dimension size = view.getViewRect().getSize();
                        Point mp = e.getPoint();
                        Point vp = new Point();
                        vp.x = mp.x - offset.x;
                        vp.y = mp.y - offset.y;

                        System.out.println("Guess = " + vp);

                        if (vp.x < 0) {
                            System.out.println("Under x");
                            vp.x = 0;
                        } else if (vp.x + size.width >= getWidth()) {
                            System.out.println("Over x - " + (vp.x + size.width) + " >= " + getWidth());
                            vp.x = getWidth() - size.width;
                        }

                        if (vp.y < 0) {
                            System.out.println("Under Y");
                            vp.y = 0;
                        } else if (vp.y + size.height >= getHeight()) {
                            System.out.println("Over Y");
                            vp.y = getHeight() - size.height;
                        }

                        System.out.println("Want = " + vp);

                        view.setViewPosition(vp);
                    }
                }

                @Override
                public void mouseReleased(MouseEvent e) {
                    offset = null;
                }

                @Override
                public void mousePressed(MouseEvent e) {
                    Container parent = getParent();
                    if (parent instanceof JViewport) {
                        JViewport view = (JViewport) parent;
                        Point vp = view.getViewPosition();
                        Point mp = e.getPoint();

                        offset = new Point();
                        offset.x = mp.x - vp.x;
                        offset.y = mp.y - vp.y;
                    }
                }

            };

            addMouseListener(ma);
            addMouseMotionListener(ma);
        }

        @Override
        public Dimension getPreferredSize() {
            return img == null ? new Dimension(200, 200) : new Dimension(img.getWidth(), img.getHeight());
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            if (img != null) {
                Graphics2D g2d = (Graphics2D) g.create();
                int x = (getWidth() - img.getWidth()) / 2;
                int y = (getHeight() - img.getHeight()) / 2;
                g2d.drawImage(img, x, y, this);
                g2d.dispose();
            }
        }

    }

}

在scrollview中抓取滚动不按预期工作

1 个答案: