swing实现拖拽效果（将本地文件拖拽到程序的文本框中显示内容）

import java.awt.BorderLayout;import java.awt.datatransfer.DataFlavor;import java.awt.datatransfer.Transferable;import java.awt.datatransfer.UnsupportedFlavorException;import java.awt.dnd.DnDConstants;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.awt.event.WindowAdapter;import java.awt.event.WindowEvent;import java.io.File;import java.io.IOException;import java.net.MalformedURLException;import java.net.URL;import java.util.List;import javax.swing.JEditorPane;import javax.swing.JFrame;import javax.swing.JScrollPane;import javax.swing.UIManager;public class EditorDropTarget implements DropTargetListener {  public EditorDropTarget(JEditorPane pane) {    this.pane = pane;    // Create the DropTarget and register    // it with the JEditorPane.    dropTarget = new DropTarget(pane, DnDConstants.ACTION_COPY_OR_MOVE,        this, true, null);  }  // Implementation of the DropTargetListener interface  public void dragEnter(DropTargetDragEvent dtde) {    DnDUtils.debugPrintln("dragEnter, drop action = "        + DnDUtils.showActions(dtde.getDropAction()));    // Get the type of object being transferred and determine    // whether it is appropriate.    checkTransferType(dtde);    // Accept or reject the drag.    acceptOrRejectDrag(dtde);  }  public void dragExit(DropTargetEvent dte) {    DnDUtils.debugPrintln("DropTarget dragExit");  }  public void dragOver(DropTargetDragEvent dtde) {    DnDUtils.debugPrintln("DropTarget dragOver, drop action = "        + DnDUtils.showActions(dtde.getDropAction()));    // Accept or reject the drag    acceptOrRejectDrag(dtde);  }  public void dropActionChanged(DropTargetDragEvent dtde) {    DnDUtils.debugPrintln("DropTarget dropActionChanged, drop action = "        + DnDUtils.showActions(dtde.getDropAction()));    // Accept or reject the drag    acceptOrRejectDrag(dtde);  }  public void drop(DropTargetDropEvent dtde) {    DnDUtils.debugPrintln("DropTarget drop, drop action = "        + DnDUtils.showActions(dtde.getDropAction()));    // Check the drop action    if ((dtde.getDropAction() & DnDConstants.ACTION_COPY_OR_MOVE) != 0) {      // Accept the drop and get the transfer data      dtde.acceptDrop(dtde.getDropAction());      Transferable transferable = dtde.getTransferable();      try {        boolean result = dropFile(transferable);        dtde.dropComplete(result);        DnDUtils.debugPrintln("Drop completed, success: " + result);      } catch (Exception e) {        DnDUtils.debugPrintln("Exception while handling drop " + e);        dtde.dropComplete(false);      }    } else {      DnDUtils.debugPrintln("Drop target rejected drop");      dtde.rejectDrop();    }  }  // Internal methods start here  protected boolean acceptOrRejectDrag(DropTargetDragEvent dtde) {    int dropAction = dtde.getDropAction();    int sourceActions = dtde.getSourceActions();    boolean acceptedDrag = false;    DnDUtils.debugPrintln("/tSource actions are "        + DnDUtils.showActions(sourceActions) + ", drop action is "        + DnDUtils.showActions(dropAction));    // Reject if the object being transferred    // or the operations available are not acceptable.    if (!acceptableType        || (sourceActions & DnDConstants.ACTION_COPY_OR_MOVE) == 0) {      DnDUtils.debugPrintln("Drop target rejecting drag");      dtde.rejectDrag();    } else if ((dropAction & DnDConstants.ACTION_COPY_OR_MOVE) == 0) {      // Not offering copy or move - suggest a copy      DnDUtils.debugPrintln("Drop target offering COPY");      dtde.acceptDrag(DnDConstants.ACTION_COPY);      acceptedDrag = true;    } else {      // Offering an acceptable operation: accept      DnDUtils.debugPrintln("Drop target accepting drag");      dtde.acceptDrag(dropAction);      acceptedDrag = true;    }    return acceptedDrag;  }  protected void checkTransferType(DropTargetDragEvent dtde) {    // Only accept a list of files    acceptableType = dtde        .isDataFlavorSupported(DataFlavor.javaFileListFlavor);    DnDUtils.debugPrintln("File type acceptable - " + acceptableType);  }  // This method handles a drop for a list of files  protected boolean dropFile(Transferable transferable) throws IOException,      UnsupportedFlavorException, MalformedURLException {    List fileList = (List) transferable        .getTransferData(DataFlavor.javaFileListFlavor);    File transferFile = (File) fileList.get(0);    final URL transferURL = transferFile.toURL();    DnDUtils.debugPrintln("File URL is " + transferURL);    pane.setPage(transferURL);    return true;  }  public static void main(String[] args) {    try {        UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");    } catch (Exception evt) {}      final JFrame f = new JFrame("JEditor Pane Drop Target Example 1");    JEditorPane pane = new JEditorPane();    // Add a drop target to the JEditorPane    EditorDropTarget target = new EditorDropTarget(pane);    f.addWindowListener(new WindowAdapter() {      public void windowClosing(WindowEvent evt) {        System.exit(0);      }    });    f.getContentPane().add(new JScrollPane(pane), BorderLayout.CENTER);    f.setSize(500, 400);    f.setVisible(true);  }  protected JEditorPane pane;  protected DropTarget dropTarget;  protected boolean acceptableType; // Indicates whether data is acceptable}class DnDUtils {  public static String showActions(int action) {    String actions = "";    if ((action & (DnDConstants.ACTION_LINK | DnDConstants.ACTION_COPY_OR_MOVE)) == 0) {      return "None";    }    if ((action & DnDConstants.ACTION_COPY) != 0) {      actions += "Copy ";    }    if ((action & DnDConstants.ACTION_MOVE) != 0) {      actions += "Move ";    }    if ((action & DnDConstants.ACTION_LINK) != 0) {      actions += "Link";    }    return actions;  }  public static boolean isDebugEnabled() {    return debugEnabled;  }  public static void debugPrintln(String s) {    if (debugEnabled) {      System.out.println(s);    }  }  private static boolean debugEnabled = (System      .getProperty("DnDExamples.debug") != null);}