Java 如何修改JTextArea中tab键的行为？

我正在JavaSwing中创建一个表单，其中一个字段是

JTextArea

。当我在所有其他字段上使用Tab键时，它将焦点提供给下一个小部件，但在

JTextArea

中，它在文本中插入一个制表符（水平空格）

如何修改此行为？

按下“tab”键时，可以在JTextArea的keylistener中使用“NextWidget.grabFocus（）”方法

使用后一种方法，在焦点移开之前，制表符仍将被插入JTextArea。如果不希望出现这种行为，可以创建JTextArea的子类，其isManagingFocus（）方法总是返回false，而不是true。例如：

import javax.swing.*;

public class NoTabTextArea extends JTextArea {
    public boolean isManagingFocus() {
        return false;
    }
}

---

NoTabTextArea的实例可以像JTextArea一样使用，只是tab键会导致焦点从它移开，而不会插入制表符

您可以在主

JFrame

或

JPanel

构造函数中调用以下方法。

/*
    This is my understanding of how tabbing works. The focus manager
    recognizes the following default KeyStrokes for tabbing:

    forwards:  TAB or Ctrl-TAB
    backwards: Shift-TAB or Ctrl-Shift-TAB

    In the case of JTextArea, TAB and Shift-TAB have been removed from
    the defaults which means the KeyStroke is passed to the text area.
    The TAB KeyStroke inserts a tab into the Document. Shift-TAB seems
    to be ignored.

    This example shows different approaches for tabbing out of a JTextArea

    Also, a text area is typically added to a scroll pane. So when
    tabbing forward the vertical scroll bar would get focus by default.
    Each approach shows how to prevent the scrollbar from getting focus.
*/
import java.awt.*;
import java.util.*;
import java.awt.event.*;
import javax.swing.*;

public class TextAreaTab extends JFrame
{
    public TextAreaTab()
    {
        Container contentPane = getContentPane();
        contentPane.setLayout(new BoxLayout(contentPane, BoxLayout.Y_AXIS));

        contentPane.add( nullTraversalKeys() );
        contentPane.add( writeYourOwnAction() );
        contentPane.add( useKeyListener() );
        contentPane.add( addTraversalKeys() );
    }

    //  Reset the text area to use the default tab keys.
    //  This is probably the best solution.

    private JComponent nullTraversalKeys()
    {
        JTextArea textArea = new JTextArea(3, 30);

        textArea.setText("Null Traversal Keys\n2\n3\n4\n5\n6\n7\n8\n9");
        JScrollPane scrollPane = new JScrollPane( textArea );
//        scrollPane.getVerticalScrollBar().setFocusable(false);

        textArea.setFocusTraversalKeys(KeyboardFocusManager.FORWARD_TRAVERSAL_KEYS, null);
        textArea.setFocusTraversalKeys(KeyboardFocusManager.BACKWARD_TRAVERSAL_KEYS, null);

        return scrollPane;
    }

    //  Replace the Tab Actions. A little more complicated but this is the
    //  only solution that will place focus on the component, not the
    //  vertical scroll bar, when tabbing backwards (unless of course you
    //  have manually prevented the scroll bar from getting focus).

    private JComponent writeYourOwnAction()
    {
        JTextArea textArea = new JTextArea(3, 30);
        textArea.setText("Write Your Own Tab Actions\n2\n3\n4\n5\n6\n7\n8\n9");
        JScrollPane scrollPane = new JScrollPane( textArea );

        InputMap im = textArea.getInputMap();
        KeyStroke tab = KeyStroke.getKeyStroke("TAB");
        textArea.getActionMap().put(im.get(tab), new TabAction(true));
        KeyStroke shiftTab = KeyStroke.getKeyStroke("shift TAB");
        im.put(shiftTab, shiftTab);
        textArea.getActionMap().put(im.get(shiftTab), new TabAction(false));

        return scrollPane;
    }

    //  Use a KeyListener

    private JComponent useKeyListener()
    {
        JTextArea textArea = new JTextArea(3, 30);
        textArea.setText("Use Key Listener\n2\n3\n4\n5\n6\n7\n8\n9");
        JScrollPane scrollPane = new JScrollPane( textArea );
        scrollPane.getVerticalScrollBar().setFocusable(false);

        textArea.addKeyListener(new KeyAdapter()
        {
            public void keyPressed(KeyEvent e)
            {
                if (e.getKeyCode() == KeyEvent.VK_TAB)
                {
                    e.consume();
                    KeyboardFocusManager.
                        getCurrentKeyboardFocusManager().focusNextComponent();
                }

                if (e.getKeyCode() == KeyEvent.VK_TAB
                &&  e.isShiftDown())
                {
                    e.consume();
                    KeyboardFocusManager.
                        getCurrentKeyboardFocusManager().focusPreviousComponent();
                }
            }
        });

        return scrollPane;
    }

    //  Add Tab and Shift-Tab KeyStrokes back as focus traversal keys.
    //  Seems more complicated then just using null, but at least
    //  it shows how to add a KeyStroke as a focus traversal key.

    private JComponent addTraversalKeys()
    {
        JTextArea textArea = new JTextArea(3, 30);
        textArea.setText("Add Traversal Keys\n2\n3\n4\n5\n6\n7\n8\n9");
        JScrollPane scrollPane = new JScrollPane( textArea );
        scrollPane.getVerticalScrollBar().setFocusable(false);

        Set set = new HashSet( textArea.getFocusTraversalKeys(
            KeyboardFocusManager.FORWARD_TRAVERSAL_KEYS ) );
        set.add( KeyStroke.getKeyStroke( "TAB" ) );
        textArea.setFocusTraversalKeys(
            KeyboardFocusManager.FORWARD_TRAVERSAL_KEYS, set );

        set = new HashSet( textArea.getFocusTraversalKeys(
            KeyboardFocusManager.BACKWARD_TRAVERSAL_KEYS ) );
        set.add( KeyStroke.getKeyStroke( "shift TAB" ) );
        textArea.setFocusTraversalKeys(
            KeyboardFocusManager.BACKWARD_TRAVERSAL_KEYS, set );

        return scrollPane;
    }

    class TabAction extends AbstractAction
    {
        private boolean forward;

        public TabAction(boolean forward)
        {
            this.forward = forward;
        }

        public void actionPerformed(ActionEvent e)
        {
            if (forward)
                tabForward();
            else
                tabBackward();
        }

        private void tabForward()
        {
            final KeyboardFocusManager manager =
                KeyboardFocusManager.getCurrentKeyboardFocusManager();
            manager.focusNextComponent();

            SwingUtilities.invokeLater(new Runnable()
            {
                public void run()
                {
                    if (manager.getFocusOwner() instanceof JScrollBar)
                        manager.focusNextComponent();
                }
            });
        }

        private void tabBackward()
        {
            final KeyboardFocusManager manager =
                KeyboardFocusManager.getCurrentKeyboardFocusManager();
            manager.focusPreviousComponent();

            SwingUtilities.invokeLater(new Runnable()
            {
                public void run()
                {
                    if (manager.getFocusOwner() instanceof JScrollBar)
                        manager.focusPreviousComponent();
                }
            });
        }
    }

    public static void main(String[] args)
    {
        TextAreaTab frame = new TextAreaTab();
        frame.setDefaultCloseOperation( EXIT_ON_CLOSE );
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }
}

按如下方式调用使用：

disableTabbingInTextAreas（this）

---

谢谢你的完整回答！要添加null工作的原因，“setFocusTraversalKeys:…如果为集合指定了null值，则此组件从其父级继承集合。如果此组件的所有祖先都为集合指定了null，则使用当前KeyboardFocusManager的默认集合。”非常类似于isManagingFocus，从1.4开始就不推荐使用，请参阅

import javax.swing.* ;
import java.awt.event.* ;
/**
 * This simple subclass of JTextArea does not allow the 'Tab'  
 * to be pressed. Instead of putting in 3 blank spaces, the tab
 * will transfer focus
 */



/*-----------------------------------------------------------*/
/*                                                           */
/*   NoTabJTextArea                                          */
/*                                                           */
/*-----------------------------------------------------------*/
public class NoTabJTextArea extends JTextArea implements KeyListener {

   public NoTabJTextArea ( String text ) {
      super ( text ) ;
      initialize () ;
   }

   public NoTabJTextArea ( ) {
      super() ;
      initialize() ;
   }

   public NoTabJTextArea ( MaskDocument document ) {
      super ( document ) ;
      initialize() ;
   }

   private void initialize () {
      addKeyListener ( this ) ;
   }

   public void keyPressed ( KeyEvent e ) {

      switch ( e.getKeyCode() ) {
         case KeyEvent.VK_TAB :
            e.consume() ;
            transferFocus() ;
            break ;
      }
   }

   public void keyReleased ( KeyEvent e ) {
      switch ( e.getKeyCode() ) {
         case KeyEvent.VK_TAB :
            System.out.println ( "KEY RELEASED TAB" ) ;
            break ;
      }
   }

   public void keyTyped ( KeyEvent e ) {
      switch ( e.getKeyCode() ) {
         case KeyEvent.VK_TAB :
            System.out.println ( "KEY TYPED TAB" ) ;
            break ;
      }

   }
} /* NoTabJTextArea */

public static void disableTabbingInTextAreas(Component component){
    if(component instanceof Container && !(component instanceof JTextArea)){
        for(final Component c : ((Container) component).getComponents() ){
            disableTabbingInTextAreas(c);
        }
    }else if(component instanceof JTextArea){
        final Component c = component;
        c.addKeyListener(new KeyListener() {
            @Override
            public void keyTyped(KeyEvent e) {}

            @Override
            public void keyPressed(KeyEvent e) {
                if(e.getKeyChar() == '\t'){
                    c.transferFocus();
                    e.consume();
                }
            }

            @Override
            public void keyReleased(KeyEvent e) {}
        });
    }
}