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。

例子：

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();      }    });  }}