Question

请考虑以下代码：

import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.datatransfer.DataFlavor;
import java.awt.datatransfer.Transferable;
import java.awt.datatransfer.UnsupportedFlavorException;
import java.io.IOException;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTree;
import javax.swing.TransferHandler;
import javax.swing.TransferHandler.TransferSupport;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeModel;
import javax.swing.tree.TreeModel;

class Element {
  String s;
  public Element(String s) {
    this.s = s;
  }
}

public class DnDTest {
  public static void main(String args[]) {
    JFrame f = new JFrame("Test");
    f.setSize(640, 400);
    Container c = f.getContentPane();
    c.setLayout(new BorderLayout());
    JTree t = new JTree();
    t.setDragEnabled(true);
    DefaultMutableTreeNode root = new DefaultMutableTreeNode(new Element("root"));
    root.add(new DefaultMutableTreeNode(new Element("child")));
    t.setModel(new DefaultTreeModel(root));
    c.add(t, BorderLayout.WEST);
    JPanel p = new JPanel();
    c.add(p, BorderLayout.CENTER);
    p.setTransferHandler(new TransferHandler("entity") {
      @Override
      public boolean canImport(TransferSupport support) {
        return true;
      }
      @Override
      public boolean importData(TransferHandler.TransferSupport support) {
        Transferable t = support.getTransferable();
        DataFlavor[] fv = t.getTransferDataFlavors();
        Object o;
        try {
          for (DataFlavor f: fv) {
            o = t.getTransferData(f);
            System.out.println(f + " => " + o.getClass().getName()+", " + o);
          }
        } catch (UnsupportedFlavorException | IOException e) {
          // TODO Auto-generated catch block
          e.printStackTrace();
        }
        return false;
      }
    });
    f.setVisible(true);
  }
}

当我将节点从树中拖动到右侧面板时，会打印以下输出：

java.awt.datatransfer.DataFlavor[mimetype=text/html;representationclass=java.lang.String] => java.lang.String, <html>
<body>
<ul>
  <li>Element@4d405ef7
</ul>
</body>
</html>
java.awt.datatransfer.DataFlavor[mimetype=text/html;representationclass=java.io.Reader] => java.io.StringReader, java.io.StringReader@217d12b3
java.awt.datatransfer.DataFlavor[mimetype=text/html;representationclass=java.io.InputStream;charset=unicode] => java.io.ByteArrayInputStream, java.io.ByteArrayInputStream@5c9992b3
java.awt.datatransfer.DataFlavor[mimetype=text/plain;representationclass=java.lang.String] => java.lang.String, Element@4d405ef7
java.awt.datatransfer.DataFlavor[mimetype=text/plain;representationclass=java.io.Reader] => java.io.StringReader, java.io.StringReader@34715be
java.awt.datatransfer.DataFlavor[mimetype=text/plain;representationclass=java.io.InputStream;charset=unicode] => java.io.ByteArrayInputStream, java.io.ByteArrayInputStream@325e55cd
java.awt.datatransfer.DataFlavor[mimetype=application/x-java-jvm-local-objectref;representationclass=java.lang.String] => java.lang.String, Element@4d405ef7
java.awt.datatransfer.DataFlavor[mimetype=application/x-java-serialized-object;representationclass=java.lang.String] => java.lang.String, Element@4d405ef7

因此，无论我使用哪个DataFlavor，结果始终为String。我需要更改以实际获取对作为树节点的用户对象关联的Element实例的引用？

Answer 1

我做了一些挖掘，并找到了解决方案。发布供参考：

flatMap

jtree拖放到面板作为对象

1 个答案: