java - 如何将图像从一个面板拖到另一个面板

Question

我创建了一个框架，然后在其中创建了面板。我已将图像放在一个面板中，现在我需要将该图像拖到另一个面板中。我怎么能那样做。请作为初学者一步一步解释。

Answer 1

使用纯 java 的快速示例DragGestureListener，DropTargetAdapter 以及TransferHandler一个面板上的图像到另一个面板的 DnD 支持：

在单击并拖动任何形状之前：

选择绿色形状并拖动到上面的空面板后：

import java.awt.BorderLayout;
import java.awt.Component;
import java.awt.Dimension;
import java.awt.Point;
import java.awt.datatransfer.DataFlavor;
import java.awt.datatransfer.Transferable;
import java.awt.datatransfer.UnsupportedFlavorException;
import java.awt.dnd.DnDConstants;
import java.awt.dnd.DragGestureEvent;
import java.awt.dnd.DragGestureListener;
import java.awt.dnd.DragSource;
import java.awt.dnd.DropTarget;
import java.awt.dnd.DropTargetAdapter;
import java.awt.dnd.DropTargetDropEvent;
import java.io.IOException;
import java.net.URL;
import javax.swing.Icon;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.TransferHandler;
import javax.swing.TransferHandler.TransferSupport;
import javax.swing.border.TitledBorder;

public class Test {

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

    public static void createAndShowJFrame() {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {

                JFrame frame = createJFrame();
                frame.setVisible(true);

            }
        });
    }

    private static JFrame createJFrame() {
        JFrame frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);

        frame.setTitle("Test");

        JPanel panel = createEmptyJPanel();
        new MyDropTargetListener(panel);//this must be done or we wont be able to drop any image onto the empty panel

        frame.add(panel, BorderLayout.CENTER);

        try {
            frame.add(createJLabelPanel(), BorderLayout.SOUTH);
        } catch (Exception ex) {
            ex.printStackTrace();
        }

        frame.pack();

        return frame;
    }

    private static JPanel createEmptyJPanel() {
        final JPanel p = new JPanel() {
            @Override
            public Dimension getPreferredSize() {
                return new Dimension(300, 300);
            }
        };
        p.setBorder(new TitledBorder("Drag Image onto this panel"));

        TransferHandler dnd = new TransferHandler() {
            @Override
            public boolean canImport(TransferSupport support) {
                if (!support.isDrop()) {
                    return false;
                }
                //only Strings
                if (!support.isDataFlavorSupported(DataFlavor.imageFlavor)) {
                    return false;
                }
                return true;
            }

            @Override
            public boolean importData(TransferSupport support) {
                if (!canImport(support)) {
                    return false;
                }

                Transferable tansferable = support.getTransferable();
                Icon ico;
                try {
                    ico = (Icon) tansferable.getTransferData(DataFlavor.imageFlavor);
                } catch (Exception e) {
                    e.printStackTrace();
                    return false;
                }
                p.add(new JLabel(ico));
                return true;
            }
        };

        p.setTransferHandler(dnd);

        return p;
    }

    private static JPanel createJLabelPanel() throws Exception {
        JPanel panel = new JPanel();
        panel.setBorder(new TitledBorder("Drag Image from here to Panel above"));

        JLabel label1 = new JLabel(new ImageIcon(new URL("http://i.stack.imgur.com/gJmeJ.png")));
        JLabel label2 = new JLabel(new ImageIcon(new URL("http://i.stack.imgur.com/8BGfi.png")));
        JLabel label3 = new JLabel(new ImageIcon(new URL("http://i.stack.imgur.com/1lgtq.png")));

        MyDragGestureListener dlistener = new MyDragGestureListener();
        DragSource ds1 = new DragSource();
        ds1.createDefaultDragGestureRecognizer(label1, DnDConstants.ACTION_COPY, dlistener);

        DragSource ds2 = new DragSource();
        ds2.createDefaultDragGestureRecognizer(label2, DnDConstants.ACTION_COPY, dlistener);

        DragSource ds3 = new DragSource();
        ds3.createDefaultDragGestureRecognizer(label3, DnDConstants.ACTION_COPY, dlistener);

        panel.add(label1);
        panel.add(label2);
        panel.add(label3);
        return panel;
    }
}

class MyDropTargetListener extends DropTargetAdapter {

    private DropTarget dropTarget;
    private JPanel p;

    public MyDropTargetListener(JPanel panel) {
        p = panel;
        dropTarget = new DropTarget(panel, DnDConstants.ACTION_COPY, this, true, null);

    }

    @Override
    public void drop(DropTargetDropEvent event) {
        try {
            DropTarget test = (DropTarget) event.getSource();
            Component ca = (Component) test.getComponent();
            Point dropPoint = ca.getMousePosition();
            Transferable tr = event.getTransferable();

            if (event.isDataFlavorSupported(DataFlavor.imageFlavor)) {
                Icon ico = (Icon) tr.getTransferData(DataFlavor.imageFlavor);

                if (ico != null) {

                    p.add(new JLabel(ico));
                    p.revalidate();
                    p.repaint();
                    event.dropComplete(true);
                }
            } else {
                event.rejectDrop();
            }
        } catch (Exception e) {
            e.printStackTrace();
            event.rejectDrop();
        }
    }
}

class MyDragGestureListener implements DragGestureListener {

    @Override
    public void dragGestureRecognized(DragGestureEvent event) {
        JLabel label = (JLabel) event.getComponent();
        final Icon ico = label.getIcon();


        Transferable transferable = new Transferable() {
            @Override
            public DataFlavor[] getTransferDataFlavors() {
                return new DataFlavor[]{DataFlavor.imageFlavor};
            }

            @Override
            public boolean isDataFlavorSupported(DataFlavor flavor) {
                if (!isDataFlavorSupported(flavor)) {
                    return false;
                }
                return true;
            }

            @Override
            public Object getTransferData(DataFlavor flavor) throws UnsupportedFlavorException, IOException {
                return ico;
            }
        };
        event.startDrag(null, transferable);
    }
}

Answer 2

1. 可能有多种方法可以实现您想要的。您可以使用玻璃窗格或 JXLayer，或者您可以
2. 停止将两个面板视为单独的元素，而更像是它们只是进入大型虚拟空间的窗口。
3. 此示例基本上将父组件视为两个图像窗格作为窗口的“虚拟空间”。
4. 它们都共享相同的图像和图像位置详细信息。他们，个人，将图像位置（在虚拟坐标中）转换为局部坐标，并绘制尽可能多的图像......
5. 鼠标控制由父级维护。这大大简化了流程，因为它可以同时通知两个面板

代码是...

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.GridLayout;
import java.awt.Image;
import java.awt.Point;
import java.awt.Rectangle;
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.SwingUtilities;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.border.EmptyBorder;
import javax.swing.border.LineBorder;

public class CrossImage {

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

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

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

    public class TestPane extends JPanel {

        private BufferedImage img;
        private ImagePane left;
        private ImagePane right;
        private Point imagePoint;

        public TestPane() {
            setBorder(new EmptyBorder(10, 10, 10, 10));
            setLayout(new GridLayout(0, 2, 10, 10));
            left = new ImagePane();
            right = new ImagePane();
            imagePoint = new Point(10, 10);
            left.setImageLocation(imagePoint);
            right.setImageLocation(imagePoint);
            try {
                img = ImageIO.read(new File("Background.jpg"));
                left.setImage(img);
                right.setImage(img);
            } catch (IOException ex) {
                ex.printStackTrace();
            }
            add(left);
            add(right);

            MouseAdapter mouseHandler = new MouseAdapter() {
                private Point delta;

                @Override
                public void mousePressed(MouseEvent e) {
                    Point origin = e.getPoint();
                    Rectangle bounds = new Rectangle(imagePoint, new Dimension(img.getWidth(), img.getHeight()));
                    if (bounds.contains(origin)) {
                        delta = new Point(origin.x - imagePoint.x, origin.y - imagePoint.y);
                    }
                }

                @Override
                public void mouseDragged(MouseEvent e) {
                    if (delta != null) {
                        imagePoint = e.getPoint();
                        imagePoint.translate(-delta.x, -delta.y);
                        left.setImageLocation(imagePoint);
                        right.setImageLocation(imagePoint);
                    }
                }

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

            addMouseListener(mouseHandler);
            addMouseMotionListener(mouseHandler);
        }
    }

    public class ImagePane extends JPanel {

        private Image image;
        private Point imageLocation;

        public ImagePane() {
            setBorder(new LineBorder(Color.DARK_GRAY));
        }

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

        public void setImage(Image image) {
            this.image = image;
            repaint();
        }

        public void setImageLocation(Point imageLocation) {
            this.imageLocation = imageLocation;
            repaint();
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            if (image != null && imageLocation != null) {
                Point p = SwingUtilities.convertPoint(getParent(), imageLocation, this);
                g.drawImage(image, p.x, p.y, this);
            }
        }
    }
}