問題描述

我創建了一個框架，然后在其中創建了面板.我已將圖像放在一個面板中，現在我需要將該圖像拖到另一個面板中.我怎么能那樣做.請作為初學者一步一步解釋.

I had created a frame and then panels in it. I had placed an image in one panel, now I need to drag that image to another panel. How could I do that. Please explain step by step as am a beginner.

推薦答案

使用純java、DragGestureListener、DropTargetAdapter和TransferHandler的快速示例一個面板上的圖像到另一個面板的 DnD 支持:

Quick example using pure java, DragGestureListener, DropTargetAdapter and TransferHandler for DnD support of images on one panel to another:

在單擊和拖動任何形狀之前:

Before any shape is clicked and dragged:

選擇綠色形狀并拖動到上面的空白面板后:

after green shape is selected and dragged onto empty panel above:

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);
    }
}

這篇關于如何將圖像從一個面板拖到另一個面板的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網！