java拖放

我试着熟悉java中的拖放，但我找到的所有教程都是……（让我生气）

我想要的是从JList（包含在名为“UserPanel”的自制JPanel中）拖动“PublicUserLabel”并将其放入从JTabbedPanel无效的自制类中。 拖动对象本身而不是它的字符串表示非常重要！

这就是我到目前为止：PublicUserLabel

public class PublicUserLabel extends JLabel implements DragSourceListener, DragGestureListener, Transferable { private DragSource ds; private PublicUser user; public PublicUserLabel(PublicUser user) { super(user.getName()); this.user = user; ds = new DragSource(); ds.createDefaultDragGestureRecognizer(this, DnDConstants.ACTION_COPY_OR_MOVE, this); } @Override public void dragGestureRecognized(DragGestureEvent e) { ds.startDrag(e, DragSource.DefaultCopyDrop, this, this); } @Override public Object getTransferData(DataFlavor flavor) throws UnsupportedFlavorException, IOException { if (flavor.equals(PublicUserFlavor.publicUserFlavor)) { return this;//TODO ? } throw new UnsupportedFlavorException(flavor); } @Override public DataFlavor[] getTransferDataFlavors() { DataFlavor[] df = new DataFlavor[2]; df[0] = DataFlavor.stringFlavor; df[1] = PublicUserFlavor.publicUserFlavor; return df; } @Override public boolean isDataFlavorSupported(DataFlavor flavor) { return flavor.equals(PublicUserFlavor.publicUserFlavor); } //some more methods } 

UserPanel：

 public class UserPanel extends JPanel { private JTextField search; private List allUser; private JList list; private JScrollPane scrollPane; private DefaultListModel listModel; public UserPanel() { allUser = new LinkedList(); listModel = new DefaultListModel(); list = new JList(listModel); list.setDragEnabled(true); 

PublicUserFlavor：

 public class PublicUserFlavor extends DataFlavor { public static DataFlavor publicUserFlavor; static { publicUserFlavor = new DataFlavor(PublicUser.class, "PublicUser"); } } 

的TabPanel：

 public class TabPanel extends JTabbedPane implements DropTargetListener { public TabPanel() { setTabPlacement(JTabbedPane.BOTTOM); addNewTabComponent("bla"); addNewTabComponent("blub"); setDropTarget(new DropTarget(this, this)); } @Override public void drop(DropTargetDropEvent e) { Transferable transferable = e.getTransferable(); if (transferable.isDataFlavorSupported(PublicUserFlavor.publicUserFlavor)) { e.acceptDrop(DnDConstants.ACTION_COPY_OR_MOVE); try { Object o = transferable.getTransferData(PublicUserFlavor.publicUserFlavor); System.out.println(o); if (o instanceof PublicUserLabel) { PublicUserLabel l = (PublicUserLabel)o; PublicUser u = l.getUser(); System.out.println(u); } } catch (UnsupportedFlavorException e1) { // TODO Auto-generated catch block e1.printStackTrace(); } catch (IOException e1) { // TODO Auto-generated catch block e1.printStackTrace(); } e.getDropTargetContext().dropComplete(true); } } 

在drop方法中，如果用户在面板中被droped，则应执行一些syso。 但事实并非如此。 我做了一些完全错误的事吗？ 感谢您的帮助！

Answer 1

我能看到的主要问题是你混合了两种不同的API。 您正在使用低级D’n’D API和较新的“组件D’n’D”API。

就个人而言，较新的API会让我烦恼，所以我倾向于避免它。

我不明白为什么你需要传输标签，当传输底层的PublicUser对象会更好，但那只是我。

 import java.awt.BorderLayout; import java.awt.EventQueue; import java.awt.GridBagLayout; 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.DragGestureRecognizer; import java.awt.dnd.DragSource; import java.awt.dnd.DragSourceDragEvent; import java.awt.dnd.DragSourceDropEvent; import java.awt.dnd.DragSourceEvent; import java.awt.dnd.DragSourceListener; import java.awt.dnd.DropTarget; import java.awt.dnd.DropTargetDragEvent; import java.awt.dnd.DropTargetDropEvent; import java.awt.dnd.DropTargetEvent; import java.awt.dnd.DropTargetListener; import java.io.IOException; import javax.swing.DefaultListModel; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JList; import javax.swing.JPanel; import javax.swing.JScrollPane; import javax.swing.UIManager; import javax.swing.UnsupportedLookAndFeelException; public class TestDnD { public static void main(String[] args) { new TestDnD(); } public TestDnD() { EventQueue.invokeLater(new Runnable() { @Override public void run() { try { UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName()); } catch (ClassNotFoundException ex) { } catch (InstantiationException ex) { } catch (IllegalAccessException ex) { } catch (UnsupportedLookAndFeelException ex) { } JFrame frame = new JFrame("Test"); 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 JList list; public TestPane() { setLayout(new BorderLayout()); list = new JList(); DefaultListModel model = new DefaultListModel(); model.addElement(new User("Shaun")); model.addElement(new User("Andy")); model.addElement(new User("Luke")); model.addElement(new User("Han")); model.addElement(new User("Liea")); model.addElement(new User("Yoda")); list.setModel(model); add(new JScrollPane(list), BorderLayout.WEST); DragGestureRecognizer dgr = DragSource.getDefaultDragSource().createDefaultDragGestureRecognizer( list, DnDConstants.ACTION_COPY_OR_MOVE, new DragGestureHandler(list)); JPanel panel = new JPanel(new GridBagLayout()); add(panel); DropTarget dt = new DropTarget( panel, DnDConstants.ACTION_COPY_OR_MOVE, new DropTargetHandler(panel), true); } } public static class User { private String name; public User(String name) { this.name = name; } public String getName() { return name; } @Override public String toString() { return name; } } public static class UserTransferable implements Transferable { public static final DataFlavor USER_DATA_FLAVOR = new DataFlavor(User.class, "User"); private User user; public UserTransferable(User user) { this.user = user; } @Override public DataFlavor[] getTransferDataFlavors() { return new DataFlavor[]{USER_DATA_FLAVOR}; } @Override public boolean isDataFlavorSupported(DataFlavor flavor) { return USER_DATA_FLAVOR.equals(flavor); } @Override public Object getTransferData(DataFlavor flavor) throws UnsupportedFlavorException, IOException { Object value = null; if (USER_DATA_FLAVOR.equals(flavor)) { value = user; } else { throw new UnsupportedFlavorException(flavor); } return value; } } protected class DragGestureHandler implements DragGestureListener { private JList list; public DragGestureHandler(JList list) { this.list = list; } @Override public void dragGestureRecognized(DragGestureEvent dge) { Object selectedValue = list.getSelectedValue(); if (selectedValue instanceof User) { User user = (User) selectedValue; Transferable t = new UserTransferable(user); DragSource ds = dge.getDragSource(); ds.startDrag( dge, null, t, new DragSourceHandler()); } } } protected class DragSourceHandler implements DragSourceListener { public void dragEnter(DragSourceDragEvent dsde) { } public void dragOver(DragSourceDragEvent dsde) { } public void dropActionChanged(DragSourceDragEvent dsde) { } public void dragExit(DragSourceEvent dse) { } public void dragDropEnd(DragSourceDropEvent dsde) { System.out.println("Drag ended..."); } } protected class DropTargetHandler implements DropTargetListener { private JPanel panel; public DropTargetHandler(JPanel panel) { this.panel = panel; } public void dragEnter(DropTargetDragEvent dtde) { if (dtde.getTransferable().isDataFlavorSupported(UserTransferable.USER_DATA_FLAVOR)) { System.out.println("Accept..."); dtde.acceptDrag(DnDConstants.ACTION_COPY_OR_MOVE); } else { System.out.println("Drag..."); dtde.rejectDrag(); } } public void dragOver(DropTargetDragEvent dtde) { } public void dropActionChanged(DropTargetDragEvent dtde) { } public void dragExit(DropTargetEvent dte) { } public void drop(DropTargetDropEvent dtde) { System.out.println("Dropped..."); if (dtde.getTransferable().isDataFlavorSupported(UserTransferable.USER_DATA_FLAVOR)) { Transferable t = dtde.getTransferable(); if (t.isDataFlavorSupported(UserTransferable.USER_DATA_FLAVOR)) { try { Object transferData = t.getTransferData(UserTransferable.USER_DATA_FLAVOR); if (transferData instanceof User) { User user = (User) transferData; dtde.acceptDrop(DnDConstants.ACTION_COPY_OR_MOVE); panel.add(new JLabel(user.getName())); panel.revalidate(); panel.repaint(); } else { dtde.rejectDrop(); } } catch (UnsupportedFlavorException ex) { ex.printStackTrace(); dtde.rejectDrop(); } catch (IOException ex) { ex.printStackTrace(); dtde.rejectDrop(); } } else { dtde.rejectDrop(); } } } } }