Swing之拖动篇：将文本中的内容拖动到表中

拖动操作的很多地方都有用到，比如我们的用QQ的时候也可以拖动文本信息。下面这个例子是通过重写TransferHandler类来实现控件之间的数据拖动。

TransferHandler类用于处理往返于 Swing 组件的 Transferable 的传输。该 Transferable 用于表示通过往/返于剪贴板的剪切、复制或粘贴操作进行交换的数据。它还在拖放操作中使用，以表示对组件进行拖动和放置组件。Swing 提供自动支持剪切、复制和粘贴的键盘绑定的功能，该键盘绑定使用由此类的实现提供的功能。Swing 还提供自动支持拖放操作的功能，该拖放操作使用由此类的实现提供的功能。Swing 开发人员可以主要通过在 Swing 组件上设置 transferHandler 属性专门指定传输语义。

import java.awt.BorderLayout;   import java.awt.Dimension;   import java.awt.Rectangle;   import java.awt.datatransfer.DataFlavor;   import java.awt.datatransfer.UnsupportedFlavorException;   import java.awt.event.ActionEvent;   import java.awt.event.ActionListener;   import java.awt.event.MouseAdapter;   import java.awt.event.MouseEvent;   import java.io.IOException;     import javax.swing.BorderFactory;   import javax.swing.Box;   import javax.swing.BoxLayout;   import javax.swing.DefaultListModel;   import javax.swing.DropMode;   import javax.swing.JCheckBoxMenuItem;   import javax.swing.JFrame;   import javax.swing.JLabel;   import javax.swing.JList;   import javax.swing.JMenu;   import javax.swing.JMenuBar;   import javax.swing.JMenuItem;   import javax.swing.JPanel;   import javax.swing.JScrollPane;   import javax.swing.JTable;   import javax.swing.ListSelectionModel;   import javax.swing.SwingUtilities;   import javax.swing.TransferHandler;   import javax.swing.UIManager;   import javax.swing.table.DefaultTableModel;     public class FillViewportHeightDemo extends JFrame implements ActionListener {       private DefaultListModel model = new DefaultListModel();     private int count = 0;     private JTable table;     private JCheckBoxMenuItem fillBox;     private DefaultTableModel tableModel;       private static String getNextString(int count) {       StringBuffer buf = new StringBuffer();       for (int i = 0; i < 5; i++) {         buf.append(String.valueOf(count));         buf.append(",");       }         // remove last newline       buf.deleteCharAt(buf.length() - 1);       return buf.toString();     }       private static DefaultTableModel getDefaultTableModel() {       String[] cols = { "Foo", "Toto", "Kala", "Pippo", "Boing" };       return new DefaultTableModel(null, cols);     }       public FillViewportHeightDemo() {       super("Empty Table DnD Demo");         tableModel = getDefaultTableModel();       table = new JTable(tableModel);       table.setSelectionMode(ListSelectionModel.MULTIPLE_INTERVAL_SELECTION);       table.setDropMode(DropMode.INSERT_ROWS);         //增加表格拖动事件       table.setTransferHandler(new TransferHandler() {           //指示一个组件在实际尝试导入给定数据 flavor 的集合之前是否接受导入。         public boolean canImport(TransferSupport support) {           // for the demo, we'll only support drops (not clipboard paste)           if (!support.isDrop()) {             return false;           }             // we only import Strings           if (!support.isDataFlavorSupported(DataFlavor.stringFlavor)) {             return false;           }             return true;         }           //导致从剪贴板或 DND 放置操作向组件的传输。         public boolean importData(TransferSupport support) {           // if we can't handle the import, say so           if (!canImport(support)) {             return false;           }             // fetch the drop location           JTable.DropLocation dl = (JTable.DropLocation) support               .getDropLocation();             int row = dl.getRow();             // fetch the data and bail if this fails           String data;           try {             //获得拖动数据             data = (String) support.getTransferable().getTransferData(                 DataFlavor.stringFlavor);           } catch (UnsupportedFlavorException e) {             return false;           } catch (IOException e) {             return false;           }             String[] rowData = data.split(",");                      //将数据增加到表格中           tableModel.insertRow(row, rowData);             Rectangle rect = table.getCellRect(row, 0, false);           if (rect != null) {             table.scrollRectToVisible(rect);           }             // demo stuff - remove for blog           model.removeAllElements();           model.insertElementAt(getNextString(count++), 0);           // end demo stuff             return true;         }       });         JList dragFrom = new JList(model);       dragFrom.setFocusable(false);       dragFrom.setPrototypeCellValue(getNextString(100));       model.insertElementAt(getNextString(count++), 0);       dragFrom.setDragEnabled(true);       dragFrom.setBorder(BorderFactory.createLoweredBevelBorder());         dragFrom.addMouseListener(new MouseAdapter() {         public void mouseClicked(MouseEvent me) {           if (SwingUtilities.isLeftMouseButton(me) && me.getClickCount() % 2 == 0) {             String text = (String) model.getElementAt(0);             String[] rowData = text.split(",");             tableModel.insertRow(table.getRowCount(), rowData);             model.removeAllElements();             model.insertElementAt(getNextString(count++), 0);           }         }       });         JPanel p = new JPanel();       p.setLayout(new BoxLayout(p, BoxLayout.X_AXIS));       JPanel wrap = new JPanel();       wrap.add(new JLabel("Drag from here:"));       wrap.add(dragFrom);       p.add(Box.createHorizontalStrut(4));       p.add(Box.createGlue());       p.add(wrap);       p.add(Box.createGlue());       p.add(Box.createHorizontalStrut(4));       getContentPane().add(p, BorderLayout.NORTH);         JScrollPane sp = new JScrollPane(table);       getContentPane().add(sp, BorderLayout.CENTER);       fillBox = new JCheckBoxMenuItem("Fill Viewport Height");       fillBox.addActionListener(this);         JMenuBar mb = new JMenuBar();       JMenu options = new JMenu("Options");       mb.add(options);       setJMenuBar(mb);         JMenuItem clear = new JMenuItem("Reset");       clear.addActionListener(this);       options.add(clear);       options.add(fillBox);         getContentPane().setPreferredSize(new Dimension(260, 180));     }       public void actionPerformed(ActionEvent ae) {       if (ae.getSource() == fillBox) {         table.setFillsViewportHeight(fillBox.isSelected());       } else {         tableModel.setRowCount(0);         count = 0;         model.removeAllElements();         model.insertElementAt(getNextString(count++), 0);       }     }       private static void createAndShowGUI() {       // Create and set up the window.       FillViewportHeightDemo test = new FillViewportHeightDemo();       test.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);         // Display the window.       test.pack();       test.setVisible(true);     }       public static void main(String[] args) {       SwingUtilities.invokeLater(new Runnable() {         public void run() {           // Turn off metal's use of bold fonts           UIManager.put("swing.boldMetal", Boolean.FALSE);           createAndShowGUI();         }       });     }   }