创建一个可撤消的JTextField

Question

我实现了一个可撤消的JTextField，问题是当我创建多个JTextField时，它只是撤消创建的最后一个实例。代码如下-要复制，请在第三个字段中输入一些文本，然后在第一个文本字段中输入一些代码并键入ctrl-z以撤消-它只从第三个文本字段中删除文本。有人能看到我做错了什么吗？

import java.awt.BorderLayout;
import java.awt.Event;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import javax.swing.AbstractAction;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JTextField;
import javax.swing.KeyStroke;
import javax.swing.event.UndoableEditEvent;
import javax.swing.event.UndoableEditListener;
import javax.swing.undo.CannotRedoException;
import javax.swing.undo.CannotUndoException;
import javax.swing.undo.UndoManager;

public class UndoableTextFieldTest 
{
    public static void main(String... s)
    {
        new UndoableTextFieldTest();
    }

    public UndoableTextFieldTest() 
    {
        JFrame frame = new JFrame("UndoableTextFieldTest");

        UndoableTextField f1 = new UndoableTextField();
        UndoableTextField f2 = new UndoableTextField();
        UndoableTextField f3 = new UndoableTextField();

        frame.setLayout(new BorderLayout());
        frame.getContentPane().add(f1, BorderLayout.NORTH);
        frame.getContentPane().add(f2, BorderLayout.CENTER);
        frame.getContentPane().add(f3, BorderLayout.SOUTH);

        frame.setSize(360, 115);
        frame.setVisible(true);
    }


    public class UndoableTextField extends JTextField
    {    
        KeyStroke undoKeyStroke = KeyStroke.getKeyStroke(KeyEvent.VK_Z, Event.CTRL_MASK);
        KeyStroke redoKeyStroke = KeyStroke.getKeyStroke(KeyEvent.VK_Y, Event.CTRL_MASK);

        public UndoableTextField()
        {
            UndoManager undoManager = new UndoManager();

            getDocument().addUndoableEditListener(new UndoableEditListener() 
            {
                @Override
                public void undoableEditHappened(UndoableEditEvent e) 
                {
                    undoManager.addEdit(e.getEdit());
                }
            });

            getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(undoKeyStroke, "undoKeyStroke");

            getActionMap().put("undoKeyStroke", new AbstractAction() 
            {
                @Override
                public void actionPerformed(ActionEvent e) 
                {
                    try 
                    {
                        undoManager.undo();
                    } catch (CannotUndoException cue) {}
                }
            });

            getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(redoKeyStroke, "redoKeyStroke");
            getActionMap().put("redoKeyStroke", new AbstractAction() 
            {
                @Override
                public void actionPerformed(ActionEvent e) 
                {
                    try 
                    {
                        undoManager.redo();
                    } catch (CannotRedoException cre) {}
                }
            });
        }    
    }
}

Answer 1

我不是100%确定，但我的猜测是您使用的输入映射在窗口中的所有组件之间共享。前两个字段的放置被第三个字段的放置覆盖。

如果我使用getInputMap（），则撤消似乎对每个文本字段都有效。