java - 鼠标拖动滚动JScrollPane(Java swing)

Question

我正在为我正在开发的游戏制作 map 编辑器。 JScrollPane中有一个JPanel，显示要编辑的 map 。我想要做的是当用户按住空格键并在 JPanel 中拖动鼠标时，JScrollPanel 将随着拖动一起滚动。这是我目前所拥有的:

panelMapPanel.addMouseMotionListener(new MouseMotionListener(){

        @Override
        public void mouseDragged(MouseEvent e) {
            //Gets difference in distance x and y from last time this listener was called
            int deltaX = mouseX - e.getX();
            int deltaY = mouseY - e.getY();
            mouseX = e.getX();
            mouseY = e.getY();
            if(spacePressed){
                //Scroll the scrollpane according to the distance travelled
                scrollPane.getVerticalScrollBar().setValue(scrollPane.getVerticalScrollBar().getValue() + deltaY);
                scrollPane.getHorizontalScrollBar().setValue(scrollPane.getHorizontalScrollBar().getValue() + deltaX);
            }
        }

});

目前它可以工作，但滚动一点也不流畅。一次移动鼠标很多是可以的，但小的拖动会使滚动 Pane 变得疯狂。

有什么改进方法吗？

对于那些喜欢视觉的人有帮助，这里是编辑:

补充说明(编辑):

• 我已经尝试过 scrollPane.getViewport().setViewPosition(new Point(scrollPane.getViewport().getViewPosition().x + deltaX, scrollPane.getViewport().getViewPosition().y + deltaY));
• 慢速移动鼠标时拖动比较烦躁，大移动时比较流畅
• 我试过使用 scrollRectToVisible 但运气不好

Answer 1

好吧，这最终比我想的要简单得多......

首先，不要乱用 JViewport ，而是使用 JComponent#scrollRectToVisible直接在充当 JScrollPane 内容的组件上, 在其上 MouseListener应附上。

下面的例子简单地计算了用户点击的点和他们拖动的量之间的差异。然后它将此增量应用于 JViewport的 viewRect并使用 JComponent#scrollRectToVisible更新可视区域，简单:)

public class Test {

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

    public Test() {
        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 TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        private JLabel map;

        public TestPane() {
            setLayout(new BorderLayout());
            try {
                map = new JLabel(new ImageIcon(ImageIO.read(new File("c:/treasuremap.jpg"))));
                map.setAutoscrolls(true);
                add(new JScrollPane(map));

                MouseAdapter ma = new MouseAdapter() {

                    private Point origin;

                    @Override
                    public void mousePressed(MouseEvent e) {
                        origin = new Point(e.getPoint());
                    }

                    @Override
                    public void mouseReleased(MouseEvent e) {
                    }

                    @Override
                    public void mouseDragged(MouseEvent e) {
                        if (origin != null) {
                            JViewport viewPort = (JViewport) SwingUtilities.getAncestorOfClass(JViewport.class, map);
                            if (viewPort != null) {
                                int deltaX = origin.x - e.getX();
                                int deltaY = origin.y - e.getY();

                                Rectangle view = viewPort.getViewRect();
                                view.x += deltaX;
                                view.y += deltaY;

                                map.scrollRectToVisible(view);
                            }
                        }
                    }

                };

                map.addMouseListener(ma);
                map.addMouseMotionListener(ma);
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(200, 200);
        }

    }

}