使用 TransferHandler 拖动 JLabel(拖放) [英] Dragging a JLabel with a TransferHandler (Drag and Drop)

问题描述

我正在使用 TransferHandler 将数据从 JPanel 传递到 JTextArea 作为 JLabel(单击左侧面板中的某处以创建要拖动的 JLabel)

I am using a TransferHandler to pass data from a JPanel to a JTextArea as a JLabel (Click somewhere in the left panel to create the JLabel to drag)

数据传输工作正常，但我还想显示"JLabel，因为它与鼠标指针一起被拖动.

The transfer of the data works fine, but I'd like to also "show" the JLabel as its being dragged along with the mouse pointer.

如果你注释掉

dropLabel.setTransferHandler(new TransferHandler("text"));

dropLabel.getTransferHandler().exportAsDrag(dropLabel, e,
            TransferHandler.COPY);

你会看到我想要的样子.(但当然数据不会被传输).

you will see how I want it to look. (but of course then the data won't be transferred).

如何让传输工作和 JLabel 跟随鼠标光标?

How can I get both the transfer to work and the JLabel to follow the mouse cursor?

代码如下:

import java.awt.*;
import java.awt.datatransfer.Transferable;
import java.awt.event.*;

import javax.swing.*;
import javax.swing.border.Border;

public class DragTest extends JFrame implements MouseMotionListener,
        MouseListener {

    private JPanel leftPanel = new JPanel(null);
    private JPanel rightPanel = new JPanel(null);
    private JLabel dragLabel = new JLabel("drop");
    private final JWindow window = new JWindow();
    JLabel dropLabel;

    public DragTest() {
        this.setLayout(new GridLayout(1, 2));

        leftPanel.setBorder(BorderFactory.createLineBorder(Color.black));
        rightPanel.setBorder(BorderFactory.createLineBorder(Color.black));
        this.add(leftPanel);
        this.add(rightPanel);
        leftPanel.addMouseListener(this);
        leftPanel.addMouseMotionListener(this);

        JTextArea area = new JTextArea();

        rightPanel.setLayout(new GridLayout(1, 1));
        rightPanel.add(area);

        dragLabel.setFont(new Font("Serif", Font.BOLD, 48));
    }

    @Override
    public void mousePressed(MouseEvent e) {

        dropLabel = new JLabel("drop");

        Dimension labelSize = dropLabel.getPreferredSize();
        dropLabel.setSize(labelSize);
        int x = e.getX() - labelSize.width / 2;
        int y = e.getY() - labelSize.height / 2;
        dropLabel.setLocation(x, y);
        leftPanel.add(dropLabel);

        dropLabel.setTransferHandler(new TransferHandler("text"));

        dropLabel.getTransferHandler().exportAsDrag(dropLabel, e,
                TransferHandler.COPY);

        repaint();

    }

    @Override
    public void mouseDragged(MouseEvent me) {
        dragLabel = new JLabel("drop");
        dragLabel.setFont(new Font("Serif", Font.BOLD, 48));
        int x = me.getPoint().x;
        int y = me.getPoint().y;
        window.add(dragLabel);
        window.pack();
        Point pt = new Point(x, y);
        Component c = (Component) me.getSource();
        SwingUtilities.convertPointToScreen(pt, c);
        window.setLocation(pt);
        window.setVisible(true);
        repaint();
    }

    @Override
    public void mouseMoved(MouseEvent e) {
    }

    @Override
    public void mouseClicked(MouseEvent e) {

    }

    @Override
    public void mouseReleased(MouseEvent e) {

//      leftPanel.remove(dropLabel);

        window.remove(dragLabel);
        window.setVisible(false);

        repaint();
    }

    @Override
    public void mouseEntered(MouseEvent e) {

    }

    @Override
    public void mouseExited(MouseEvent e) {

    }

    public static void main(String[] args) {

        DragTest frame = new DragTest();
        frame.setVisible(true);
        frame.setSize(600, 400);
        frame.setResizable(false);
        frame.setLocationRelativeTo(null);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
}

推荐答案

再举一个例子:

修复闪烁的光标

import java.awt.*;
import java.awt.datatransfer.*;
import java.awt.dnd.*;
import java.awt.event.*;
import java.io.*;
import java.util.*;
import javax.activation.*;
import javax.swing.*;
import javax.swing.text.*;

public class DragTest3 {
  public JComponent makeUI() {
    DragPanel p1 = new DragPanel();
    p1.setBorder(BorderFactory.createLineBorder(Color.BLACK));
    p1.add(new JLabel(UIManager.getIcon("OptionPane.warningIcon")));
    p1.add(new JLabel(UIManager.getIcon("OptionPane.errorIcon")));
    p1.add(new JLabel("Label1"));
    p1.add(new JLabel("Label2"));
    MouseListener handler = new Handler();
    p1.addMouseListener(handler);
    LabelTransferHandler th = new LabelTransferHandler();
    p1.setTransferHandler(th);
    JPanel p = new JPanel(new GridLayout(1,2));
    p.add(p1);

    DragPanel p2 = new DragPanel();
    p2.setBorder(BorderFactory.createLineBorder(Color.BLACK));
    p2.addMouseListener(handler);
    p2.setTransferHandler(th);
    p.add(p2);

    JPanel panel = new JPanel(new GridLayout(2,1));
    panel.add(p);
    panel.add(new JScrollPane(new JTextArea()));
    return panel;
  }
  public static void main(String[] args) {
    EventQueue.invokeLater(new Runnable() {
      @Override public void run() {
        createAndShowGUI();
      }
    });
  }
  public static void createAndShowGUI() {
    JFrame f = new JFrame();
    f.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
    f.getContentPane().add(new DragTest3().makeUI());
    f.setSize(320, 240);
    f.setLocationRelativeTo(null);
    f.setVisible(true);
  }
}
class DragPanel extends JPanel {
  public DragPanel() {
    super();
  }
  public JLabel draggingLabel;
}
class Handler extends MouseAdapter {
  @Override public void mousePressed(MouseEvent e) {
    DragPanel p = (DragPanel)e.getSource();
    Component c = SwingUtilities.getDeepestComponentAt(p, e.getX(), e.getY());
    if(c!=null && c instanceof JLabel) {
      p.draggingLabel = (JLabel)c;
      p.getTransferHandler().exportAsDrag(p, e, TransferHandler.MOVE);
    }
  }
}
class LabelTransferHandler extends TransferHandler {
  private final DataFlavor localObjectFlavor;
  private final JLabel label = new JLabel() {
    @Override public boolean contains(int x, int y) {
      return false;
    }
  };
  private final JWindow window = new JWindow();
  public LabelTransferHandler() {
    System.out.println("LabelTransferHandler");
    localObjectFlavor = new ActivationDataFlavor(
      DragPanel.class, DataFlavor.javaJVMLocalObjectMimeType, "JLabel");
    window.add(label);
    window.setAlwaysOnTop(true);
    window.setBackground(new Color(0,true));
    DragSource.getDefaultDragSource().addDragSourceMotionListener(
    new DragSourceMotionListener() {
      @Override public void dragMouseMoved(DragSourceDragEvent dsde) {
        Point pt = dsde.getLocation();
        pt.translate(5, 5); // offset
        window.setLocation(pt);
      }
    });
  }
  @Override protected Transferable createTransferable(JComponent c) {
    System.out.println("createTransferable");
    DragPanel p = (DragPanel)c;
    JLabel l = p.draggingLabel;
    String text = l.getText();
    //TEST
    //if(text==null) {
    //    text = l.getIcon().toString();
    //}
    //return new StringSelection(text+"
");
    final DataHandler dh = new DataHandler(c, localObjectFlavor.getMimeType());
    if(text==null) return dh;
    final StringSelection ss = new StringSelection(text+"
");
    return new Transferable() {
      @Override public DataFlavor[] getTransferDataFlavors() {
        ArrayList<DataFlavor> list = new ArrayList<>();
        for(DataFlavor f:ss.getTransferDataFlavors()) {
          list.add(f);
        }
        for(DataFlavor f:dh.getTransferDataFlavors()) {
          list.add(f);
        }
        return list.toArray(dh.getTransferDataFlavors());
      }
      public boolean isDataFlavorSupported(DataFlavor flavor) {
        for (DataFlavor f: getTransferDataFlavors()) {
          if (flavor.equals(f)) {
            return true;
          }
        }
        return false;
      }
      public Object getTransferData(DataFlavor flavor) throws UnsupportedFlavorException, IOException {
        if(flavor.equals(localObjectFlavor)) {
          return dh.getTransferData(flavor);
        } else {
          return ss.getTransferData(flavor);
        }
      }
    };
  }
  @Override public boolean canImport(TransferSupport support) {
    if(!support.isDrop()) {
      return false;
    }
    return true;
  }
  @Override public int getSourceActions(JComponent c) {
    System.out.println("getSourceActions");
    DragPanel p = (DragPanel)c;
    label.setIcon(p.draggingLabel.getIcon());
    label.setText(p.draggingLabel.getText());
    window.pack();
    Point pt = p.draggingLabel.getLocation();
    SwingUtilities.convertPointToScreen(pt, p);
    window.setLocation(pt);
    window.setVisible(true);
    return MOVE;
  }
  @Override public boolean importData(TransferSupport support) {
    System.out.println("importData");
    if(!canImport(support)) return false;
    DragPanel target = (DragPanel)support.getComponent();
    try {
      DragPanel src = (DragPanel)support.getTransferable().getTransferData(localObjectFlavor);
      JLabel l = new JLabel();
      l.setIcon(src.draggingLabel.getIcon());
      l.setText(src.draggingLabel.getText());
      target.add(l);
      target.revalidate();
      return true;
    } catch(UnsupportedFlavorException ufe) {
      ufe.printStackTrace();
    } catch(java.io.IOException ioe) {
      ioe.printStackTrace();
    }
    return false;
  }
  @Override protected void exportDone(JComponent c, Transferable data, int action) {
    System.out.println("exportDone");
    DragPanel src = (DragPanel)c;
    if(action == TransferHandler.MOVE) {
      src.remove(src.draggingLabel);
      src.revalidate();
      src.repaint();
    }
    src.draggingLabel = null;
    window.setVisible(false);
  }
}

这篇关于使用 TransferHandler 拖动 JLabel(拖放)的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！