如何将图像从一个面板拖动到另一个面板 [英] How to drag an image from one panel to other

问题描述

我已经创建了一个框架，然后在其中显示面板。我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上。我该怎么做请稍等一下解释一下。

解决方案

使用纯java的简单示例 DragGestureListener ， DropTargetAdapter 和 TransferHandler 用于DnD支持一个面板上的图像到另一个面板：

在任何形状被点击并拖动之前：

选择绿色形状并拖动到上面的空白面板上：

  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）; //这必须完成，否则我们无法将任何图像放到空面板上
 
 frame.add（panel，BorderLayout.CENTER）; 
 
 try {
 frame.add（createJLabelPanel（），BorderLayout.SOUTH）; 
} catch（Exception ex）{
 ex.printStackTrace（）; 
} 
 
 frame.pack（）; 
 
返回框架; 
} 
 
 private static JPanel createEmptyJPanel（）{
 final JPanel p = new JPanel（）{
 @Override 
 public Dimension getPreferredSize（）{
返回新维度（300,300）; 
} 
}; 
 p.setBorder（new TitledBorder（Drag Image to this panel））; 
 
 TransferHandler dnd = new TransferHandler（）{
 @Override 
 public boolean canImport（TransferSupport support）{
 if（！support.isDrop（））{
返回false; 
} 
 //只有Strings 
 if（！support.isDataFlavorSupported（DataFlavor.imageFlavor））{
 return false; 
} 
返回true; 
} 
 
 @Override 
 public boolean importData（TransferSupport support）{
 if（！canImport（support））{
 return false; 
} 
 
可转让tansferable = support.getTransferable（）; 
图标ico; 
 try {
 ico =（Icon）tansferable.getTransferData（DataFlavor.imageFlavor）; 
} catch（Exception e）{
 e.printStackTrace（）; 
返回false; 
} 
 p.add（new JLabel（ico））; 
返回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）; 
返回面板; 
} 
} 
 
 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 （）; 
组件ca =（Component）test.getComponent（）; 
点dropPoint = ca.getMousePosition（）; 
可转移tr = event.getTransferable（）; 
 
 if（event.isDataFlavorSupported（DataFlavor.imageFlavor））{
图标ico =（图标）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实现DragGestureListener {
 
 @Override 
 public void dragGestureRecognized（DragGestureEvent event）{ 
 JLabel label =（JLabel）event.getComponent（）; 
 final Icon ico = label.getIcon（）; 
 
 
可转移转移= new可转移（）{
 @Override 
 public DataFlavor [] getTransferDataFlavors（）{
返回新的DataFlavor [] {DataFlavor。 imageFlavor}; 
} 
 
 @Override 
 public boolean isDataFlavorSupported（DataFlavor flavor）{
 if（！isDataFlavorSupported（flavor））{
 return false; 
} 
返回true; 
} 
 
 @Override 
 public Object getTransferData（DataFlavor flavor）throws UnsupportedFlavorException，IOException {
 return ico; 
} 
}; 
 event.startDrag（null，transferable）; 
} 
} 
  

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.

解决方案

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

Before any shape is clicked and dragged:

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);
    }
}

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