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); }