我试图熟悉 Java 中的拖放操作，但我找到的所有教程都是......(让我生气)
我想要的只是从 JList(包含在名为“UserPanel”的自制 JPanel 中)中拖出一个“PublicUserLabel”，并将其放入从 JTabbedPanel 继承的自制类中。 拖动对象本身而不是它的字符串表示非常重要!!!
这就是我目前所拥有的: 公共(public)用户标签
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
}
用户面板:
public class UserPanel extends JPanel
{
private JTextField search;
private List<PublicUser> allUser;
private JList<PublicUserLabel> list;
private JScrollPane scrollPane;
private DefaultListModel<PublicUserLabel> listModel;
public UserPanel()
{
allUser = new LinkedList<PublicUser>();
listModel = new DefaultListModel<PublicUserLabel>();
list = new JList<PublicUserLabel>(listModel);
list.setDragEnabled(true);
公共(public)用户风格:
public class PublicUserFlavor extends DataFlavor
{
public static DataFlavor publicUserFlavor;
static
{
publicUserFlavor = new DataFlavor(PublicUser.class, "PublicUser");
}
}
选项卡面板:
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 方法中有一些 syso，如果用户被拖放到面板中，这些系统将被执行。但事实并非如此。我做错了什么吗？ 感谢您的帮助!
最佳答案
我看到的主要问题是您混合了两个不同的 API。您正在使用低级 D'n'D API 和较新的“组件 D'n'D”API。
就我个人而言，较新的 API 让我很烦，所以我倾向于避免使用它。
我不明白为什么你需要转移标签，什么时候转移底层的 PublicUser 对象会更好，但我就是这样。
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();
}
}
}
}
}
关于java 拖放，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/15520610/