Question

我遇到了一个使用Drag and Drop重新排序JList中的元素的问题。以下代码是对代码的修改，您可以将元素从一个JList拖动到另一个JList（仅以一种方式工作）。我试图让它只用于一个JList，但是元素甚至不能被拖出列表。所以我想这不可能这样做。我有什么不对的想法？

我的想法是让它为带有缩略图的Jlist工作，但是因为我甚至无法让它只用于字符串......我一直在研究几个D'n'D教程，但我仍然无法让它发挥作用。任何帮助表示赞赏。

import javax.swing.*;
import javax.swing.border.*;
import java.awt.*;
import java.awt.datatransfer.*;
import java.io.IOException;

public class DragAndDrop extends JFrame {


DefaultListModel<String> transport = new DefaultListModel<String>();
JList<String> transportList = new JList<String>(transport);

public DragAndDrop() {
    setLayout(new FlowLayout());

    transport.addElement("Bike");
    transport.addElement("Car");
    transport.addElement("Truck");
    transport.addElement("Boat");

    JScrollPane transportScroll = new JScrollPane(transportList);
    transportScroll.setBorder(new TitledBorder("Transportation"));

    add(transportScroll);

    transportList.setDragEnabled(true);

    transportList.setTransferHandler(new TransferHandler() {
        int index;  

        @Override
        public int getSourceActions(JComponent comp) {
            return COPY_OR_MOVE;
        }

        @Override
        public Transferable createTransferable(JComponent comp) {
            index = transportList.getSelectedIndex(); 
            return new StringSelection(transportList.getSelectedValue());
        }


        @Override
        public void exportDone( JComponent comp, Transferable trans, int action ) {
            if (action==MOVE) {
                transport.remove(index);
            }
        }
    });

    transportList.setDropMode(DropMode.ON);

    transportList.setTransferHandler(new TransferHandler() {
        @Override
        public boolean canImport(TransferHandler.TransferSupport support) {
            // data of type string?
            return support.isDataFlavorSupported(DataFlavor.stringFlavor);
        }

        @Override
        public boolean importData(TransferHandler.TransferSupport support) {
            try {
                // convert data to string
                String s = (String)support.getTransferable().getTransferData(DataFlavor.stringFlavor);
                JList.DropLocation dl = (JList.DropLocation)support.getDropLocation();
                transport.add(dl.getIndex(),s);
                return true;
            } 
            catch (UnsupportedFlavorException e) {} 
            catch (IOException e) {}

            return false;
        }
    });

    pack();

    setDefaultCloseOperation(EXIT_ON_CLOSE);
    setVisible(true);
}

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

}

PS。很抱歉，如果这是一个重新发布。

修改我想我已经解决了这个问题：不得不使用不同的transferHandlers - 只应该使用第二个方法中的所有方法。

Answer 1

enter image description here

import java.awt.BorderLayout;
import java.awt.Component;
import java.awt.EventQueue;
import java.awt.datatransfer.DataFlavor;
import java.awt.datatransfer.Transferable;
import java.awt.datatransfer.UnsupportedFlavorException;
import java.awt.dnd.DragSource;
import java.io.IOException;
import java.io.Serializable;
import java.util.Arrays;
import java.util.Objects;
// import javax.activation.ActivationDataFlavor;
// import javax.activation.DataHandler;
import javax.swing.BorderFactory;
import javax.swing.DefaultListModel;
import javax.swing.DropMode;
import javax.swing.Icon;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.ListCellRenderer;
import javax.swing.ListSelectionModel;
import javax.swing.TransferHandler;
import javax.swing.UIManager;
import javax.swing.WindowConstants;

public class DragAndDropTest {
  public JComponent makeUI() {
    DefaultListModel<Thumbnail> m = new DefaultListModel<>();
    for (String s : Arrays.asList("error", "information", "question", "warning")) {
      m.addElement(new Thumbnail(s));
    }

    JList<Thumbnail> list = new JList<>(m);
    list.getSelectionModel().setSelectionMode(
      ListSelectionModel.MULTIPLE_INTERVAL_SELECTION);
    list.setTransferHandler(new ListItemTransferHandler());
    list.setDropMode(DropMode.INSERT);
    list.setDragEnabled(true);
    // https://java-swing-tips.blogspot.com/2008/10/rubber-band-selection-drag-and-drop.html
    list.setLayoutOrientation(JList.HORIZONTAL_WRAP);
    list.setVisibleRowCount(0);
    list.setFixedCellWidth(80);
    list.setFixedCellHeight(80);
    list.setBorder(BorderFactory.createEmptyBorder(10, 10, 10, 10));

    list.setCellRenderer(new ListCellRenderer<Thumbnail>() {
      private final JPanel p = new JPanel(new BorderLayout());
      private final JLabel icon = new JLabel((Icon)null, JLabel.CENTER);
      private final JLabel label = new JLabel("", JLabel.CENTER);

      @Override
      public Component getListCellRendererComponent(
        JList<? extends Thumbnail> list, Thumbnail value, int index,
        boolean isSelected, boolean cellHasFocus) {
        icon.setIcon(value.icon);
        label.setText(value.name);
        label.setForeground(isSelected ? list.getSelectionForeground()
                            : list.getForeground());
        p.add(icon);
        p.add(label, BorderLayout.SOUTH);
        p.setBackground(isSelected ? list.getSelectionBackground()
                        : list.getBackground());
        return p;
      }
    });
    return new JScrollPane(list);
  }

  public static void main(String[] args) {
    EventQueue.invokeLater(() -> createAndShowGUI());
  }

  public static void createAndShowGUI() {
    JFrame f = new JFrame();
    f.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
    f.getContentPane().add(new DragAndDropTest().makeUI());
    f.setSize(320, 240);
    f.setLocationRelativeTo(null);
    f.setVisible(true);
  }
}

class Thumbnail implements Serializable {
  public final String name;
  public final Icon icon;
  public Thumbnail(String name) {
    this.name = name;
    this.icon = UIManager.getIcon("OptionPane." + name + "Icon");
  }
}

// @camickr already suggested above.
// https://docs.oracle.com/javase/tutorial/uiswing/dnd/dropmodedemo.html
@SuppressWarnings("serial")
class ListItemTransferHandler extends TransferHandler {
  protected final DataFlavor localObjectFlavor;
  protected int[] indices;
  protected int addIndex = -1; // Location where items were added
  protected int addCount; // Number of items added.

  public ListItemTransferHandler() {
    super();
    // localObjectFlavor = new ActivationDataFlavor(
    //   Object[].class, DataFlavor.javaJVMLocalObjectMimeType, "Array of items");
    localObjectFlavor = new DataFlavor(Object[].class, "Array of items");
  }

  @Override
  protected Transferable createTransferable(JComponent c) {
    JList<?> source = (JList<?>) c;
    c.getRootPane().getGlassPane().setVisible(true);

    indices = source.getSelectedIndices();
    Object[] transferedObjects = source.getSelectedValuesList().toArray(new Object[0]);
    // return new DataHandler(transferedObjects, localObjectFlavor.getMimeType());
    return new Transferable() {
      @Override public DataFlavor[] getTransferDataFlavors() {
        return new DataFlavor[] {localObjectFlavor};
      }
      @Override public boolean isDataFlavorSupported(DataFlavor flavor) {
        return Objects.equals(localObjectFlavor, flavor);
      }
      @Override public Object getTransferData(DataFlavor flavor)
            throws UnsupportedFlavorException, IOException {
        if (isDataFlavorSupported(flavor)) {
          return transferedObjects;
        } else {
          throw new UnsupportedFlavorException(flavor);
        }
      }
    };
  }

  @Override
  public boolean canImport(TransferSupport info) {
    return info.isDrop() && info.isDataFlavorSupported(localObjectFlavor);
  }

  @Override
  public int getSourceActions(JComponent c) {
    Component glassPane = c.getRootPane().getGlassPane();
    glassPane.setCursor(DragSource.DefaultMoveDrop);
    return MOVE; // COPY_OR_MOVE;
  }

  @SuppressWarnings("unchecked")
  @Override
  public boolean importData(TransferSupport info) {
    TransferHandler.DropLocation tdl = info.getDropLocation();
    if (!canImport(info) || !(tdl instanceof JList.DropLocation)) {
      return false;
    }

    JList.DropLocation dl = (JList.DropLocation) tdl;
    JList target = (JList) info.getComponent();
    DefaultListModel listModel = (DefaultListModel) target.getModel();
    int max = listModel.getSize();
    int index = dl.getIndex();
    index = index < 0 ? max : index; // If it is out of range, it is appended to the end
    index = Math.min(index, max);

    addIndex = index;

    try {
      Object[] values = (Object[]) info.getTransferable().getTransferData(localObjectFlavor);
      for (int i = 0; i < values.length; i++) {
        int idx = index++;
        listModel.add(idx, values[i]);
        target.addSelectionInterval(idx, idx);
      }
      addCount = values.length;
      return true;
    } catch (UnsupportedFlavorException | IOException ex) {
      ex.printStackTrace();
    }

    return false;
  }

  @Override
  protected void exportDone(JComponent c, Transferable data, int action) {
    c.getRootPane().getGlassPane().setVisible(false);
    cleanup(c, action == MOVE);
  }

  private void cleanup(JComponent c, boolean remove) {
    if (remove && Objects.nonNull(indices)) {
      if (addCount > 0) {
        // https://github.com/aterai/java-swing-tips/blob/master/DragSelectDropReordering/src/java/example/MainPanel.java
        for (int i = 0; i < indices.length; i++) {
          if (indices[i] >= addIndex) {
            indices[i] += addCount;
          }
        }
      }
      JList source = (JList) c;
      DefaultListModel model = (DefaultListModel) source.getModel();
      for (int i = indices.length - 1; i >= 0; i--) {
        model.remove(indices[i]);
      }
    }

    indices = null;
    addCount = 0;
    addIndex = -1;
  }
}

Answer 2

请参阅DnD上Swing教程中的Drop Demo，了解将放在同一个JList或另一个JList上的示例。

Answer 3

正如OP在对原始问题的编辑中所指出的那样，给出的示例中的问题是有两个传输处理程序，并且在他们的答案中正确地指出了camickr，Java教程中有一个示例这将有效。

Java教程中示例的问题在于，当使用DropMode.INSERT并将当前JList中的项目移动到所选索引之前时，该项目是重复的。这将删除JList中的项目，将项目的副本放在您想要的位置，并保留原始所选项目。

因此，对于那些感兴趣的人，这里有一个例子可以根据OP问题中提供的JList<String>示例修复该问题。

import java.awt.EventQueue;
import java.awt.datatransfer.DataFlavor;
import java.awt.datatransfer.StringSelection;
import java.awt.datatransfer.Transferable;
import java.awt.datatransfer.UnsupportedFlavorException;
import java.io.IOException;

import javax.swing.DefaultListModel;
import javax.swing.DropMode;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JList;
import javax.swing.JScrollPane;
import javax.swing.ListSelectionModel;
import javax.swing.TransferHandler;

@SuppressWarnings("serial")
public class GUI extends JFrame {
    protected GUI() {
        super("Simple Rearrangeable List");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        createPanel();
        setBounds(10, 10, 350, 500);
        setVisible(true);
    }

    private void createPanel() {
        DefaultListModel<String> strings = new DefaultListModel<String>();

        for(int i = 1; i <= 100; i++) {
            strings.addElement("Item " + i);
        }

        JList<String> dndList = new JList<String>(strings);
        dndList.setDragEnabled(true);
        dndList.setDropMode(DropMode.INSERT);
        dndList.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
        dndList.setTransferHandler(new TransferHandler() {
            private int index;
            private boolean beforeIndex = false; //Start with `false` therefore if it is removed from or added to the list it still works

            @Override
            public int getSourceActions(JComponent comp) {
                return MOVE;
            }

            @Override
            public Transferable createTransferable(JComponent comp) {
                index = dndList.getSelectedIndex(); 
                return new StringSelection(dndList.getSelectedValue());
            }

            @Override
            public void exportDone(JComponent comp, Transferable trans, int action) {
                if (action == MOVE) {
                    if(beforeIndex)
                        strings.remove(index + 1);
                    else
                        strings.remove(index);
                }
            }

            @Override
            public boolean canImport(TransferHandler.TransferSupport support) {
                return support.isDataFlavorSupported(DataFlavor.stringFlavor);
            }

            @Override
            public boolean importData(TransferHandler.TransferSupport support) {
                try {
                    String s = (String) support.getTransferable().getTransferData(DataFlavor.stringFlavor);
                    JList.DropLocation dl = (JList.DropLocation) support.getDropLocation();
                    strings.add(dl.getIndex(), s);
                    beforeIndex = dl.getIndex() < index ? true : false;
                    return true;
                } catch (UnsupportedFlavorException | IOException e) {
                    e.printStackTrace();
                }

                return false;
            }
        });

        JScrollPane scrollPane = new JScrollPane(dndList);
        getContentPane().add(scrollPane);
    }

    public static void main(String[] args) {
        EventQueue.invokeLater(() -> new GUI());
    }
}

Answer 4

import json
import tkinter as tk
from tkinter import messagebox

class Application(tk.Frame):
    def __init__(self, master=None):
        super().__init__(master)
        self.read_state()
        self.master = master
        self.hi_there = tk.Button(self, text="Cliquer ici!", command=self.say_hi)
        self.hi_there.pack(side="top")
        self.moneybtn = tk.Button(self, text=f"Revenus : {self.earnings}€.", command=self.money, state='disabled')
        self.moneybtn.pack(side="top")
        self.upgrade = tk.Button(self, text=f"Ammeliorer les revenus ({self.upgradePrice}€.).", command=self.upgradefunc)
        self.upgrade.pack(side ="left")
        self.showMoney = tk.Button(self, text=f'Argent : {self.playerMoney}€.', state="disabled")
        self.showMoney.pack(side = "right")
        self.autofarmbtn = tk.Button(self, text="Debloquer l'autofarm. (1000€)", command=self.autofarmfunc)
        self.autofarmbtn.pack(side = 'left')
        self.quit = tk.Button(self, text="Sauvegarder et quitter.", command=self.save_and_quit)
        self.quit.pack(side="bottom")

    def say_hi(self):
        print(f"Vous avez gagné {self.earnings} euros.")
        self.playerMoney += self.earnings
        self.showMoney['text'] = f'Argent : {self.playerMoney}€.'
    
    def money(self):
        print(self.playerMoney)
    
    def upgradefunc(self):
        if self.playerMoney >= self.upgradePrice:
            print(f'Vous avez ammélioré vos revenus pour {self.upgradePrice} €.')
            self.earnings += 10
            self.upgradePrice += 20
            self.playerMoney -= self.upgradePrice
            self.upgrade["text"] = f"Ammeliorer les revenus ({self.upgradePrice}€.)."
            self.showMoney['text'] = f'Argent : {self.playerMoney}€.'
            self.moneybtn["text"] = f"Revenus : {self.earnings}€."
        else:
            print("Vous n'avez pas assez d'argent pour acheter cette ammélioration!")

    def autofarm(self):
        self.playerMoney += self.autoFarmEarnings
        self.after(1000, self.autofarm)
    
    def autofarmfunc(self):
        print(f"Vous avez ammelioré l'autofarm pour {self.priceAutoFarm}€.")
        self.priceAutoFarm += 1000 * self.counter
        self.counter += 1
        self.autofarmbtn['text'] = f"Ammeliorer l'autofarm. ({self.priceAutoFarm}€.)"
        self.autoFarmEarnings += 2
        self.autofarm()
    
    def save_and_quit(self):
        if messagebox.askokcancel("Sauvegarder et quitter.", "Voulez vous sauvegarder et quitter?"):
            self.write_state()
            self.master.destroy()
            
        def write_state(self):
            with open('game.json', 'w') as file:
                json.dump({
                    "playerMoney": self.playerMoney,
                    "autoFarmEarnings": self.autoFarmEarnings,
                    "priceAutoFarm": self.priceAutoFarm,
                    "earnings": self.earnings,
                    "upgradePrice": self.upgradePrice,
                }, file)

        def read_state(self):
            with open('game.json') as file:
                state = json.load(file)
            self.playerMoney = state["playerMoney"]
            self.autoFarmEarnings = state["autoFarmEarnings"]
            self.priceAutoFarm = state["priceAutoFarm"]
            self.earnings = state["earnings"]
            self.upgradePrice = state["upgradePrice"]


def main():    
    root = tk.Tk()
    root.title('Clicker')
    app = Application(master=root)
    app.pack()
    root.mainloop()

if __name__ == "__main__":
    main()

试试这个

使用拖放重新排序JList

4 个答案: