Java 使用单个JTextArea和多个管理器

我有一个

JTextArea

和一个

JComboBox

来允许我循环浏览各种打开的文件-当我选择不同的文件时，

JTextArea

的内容会发生变化。我试图为每个文件维护一个不同的撤消缓冲区，并为每个文件定义了一个单独的

UndoManager

我创建了一个更简单的SSCCE来演示我的问题，它使用了两个缓冲区，我称之为“一”和“二”——通过一个简单的按钮在它们之间切换。一旦发生

undoabledit

，它将检查活动缓冲区并在相应的

undoabledit管理器上执行
addEdit（）
。按下“撤消”按钮后，它将检查
canUndo（）
，并在相应的
UndoManager
上执行
Undo（）
。我有一个名为
ignoreEdit
的标志，在缓冲区之间切换时使用该标志来忽略记录的编辑

如果我从不在缓冲区之间切换，那么我就不会有问题，撤消会按预期工作。只有当我在缓冲区之间切换并似乎“破坏”文档时，它才会失败。可以使用以下步骤重新创建问题：

在缓冲区“一”中，键入：

切换到缓冲区“2”，类型：

切换到缓冲区“一”并多次按下“撤消”按钮。经过几次撤消操作后，缓冲区看起来是这样的（光标无法选择前两行）。但是，根据
System.out.println（）
，text.getText（）的内容是正确的-那么，它看起来像是一个渲染问题

THIS

THISIS ONE

这不可能是第一次有人尝试为每个文件实现独立的撤消缓冲区吗？很明显，我在文档模型上做了一些错误的事情，并且固有地破坏了它，但是我正在寻找一些关于如何最好地解决这个问题的建议

SSCCE的代码如下所示：

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.text.*;
import javax.swing.undo.*;

public class SSCCE extends JFrame implements ActionListener, UndoableEditListener {
  private final JLabel labTextArea;
  private final JTextArea textArea;
  private final JScrollPane scrollTextArea;
  private final Document docTextArea;
  private final JButton bOne, bTwo, bUndo;
  private final UndoManager uOne, uTwo;
  private String sOne, sTwo;
  private boolean ignoreEdit = false;

  public SSCCE(String[] args) {
    setTitle("SSCCE - Short, Self Contained, Correct Example");
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    setSize(300, 200);
    setLocationRelativeTo(null);

    labTextArea = new JLabel("One");
    getContentPane().add(labTextArea, BorderLayout.PAGE_START);

    uOne = new UndoManager();
    uTwo = new UndoManager();
    sOne = new String();
    sTwo = new String();

    textArea = new JTextArea();
    docTextArea = textArea.getDocument();
    docTextArea.addUndoableEditListener(this);
    scrollTextArea = new JScrollPane(textArea);
    getContentPane().add(scrollTextArea, BorderLayout.CENTER);

    JPanel pButtons = new JPanel();
    bOne = new JButton("One");
    bOne.addActionListener(this);
    bOne.setFocusable(false);
    pButtons.add(bOne, BorderLayout.LINE_START);
    bTwo = new JButton("Two");
    bTwo.addActionListener(this);
    bTwo.setFocusable(false);
    pButtons.add(bTwo, BorderLayout.LINE_END);
    bUndo = new JButton("Undo");
    bUndo.addActionListener(this);
    bUndo.setFocusable(false);
    pButtons.add(bUndo, BorderLayout.LINE_END);
    getContentPane().add(pButtons, BorderLayout.PAGE_END);

    setVisible(true);
  }

  @Override
  public void actionPerformed(ActionEvent e) {
    if (e.getSource().equals(bOne)) {
      if (!labTextArea.getText().equals("One")) {
        sTwo = textArea.getText();
        ignoreEdit = true;
        textArea.setText(sOne);
        ignoreEdit = false;
        labTextArea.setText("One");
      }
    }
    else if (e.getSource().equals(bTwo)) {
      if (!labTextArea.getText().equals("Two")) {
        sOne = textArea.getText();
        ignoreEdit = true;
        textArea.setText(sTwo);
        ignoreEdit = false;
        labTextArea.setText("Two");
      }
    }
    else if (e.getSource().equals(bUndo)) {
      if (labTextArea.getText().equals("One")) {
        try {
          if (uOne.canUndo()) {
            System.out.println("Performing Undo for One");
            uOne.undo();
            System.out.println("Buffer One is now:\n" + textArea.getText() + "\n");
          }
          else {
            System.out.println("Nothing to Undo for One");
          }
        }
        catch (CannotUndoException ex) {
          ex.printStackTrace();
        }
      }
      else if (labTextArea.getText().equals("Two")) {
        try {
          if (uTwo.canUndo()) {
            System.out.println("Performing Undo for Two");
            uTwo.undo();
            System.out.println("Buffer Two is now:\n" + textArea.getText() + "\n");
          }
          else {
            System.out.println("Nothing to Undo for Two");
          }
        }
        catch (CannotUndoException ex) {
          ex.printStackTrace();
        }
      }
    }
  }

  @Override
  public void undoableEditHappened(UndoableEditEvent e) {
    if (!ignoreEdit) {
      if (labTextArea.getText().equals("One")) {
        System.out.println("Adding Edit for One");
        uOne.addEdit(e.getEdit());
      }
      else if (labTextArea.getText().equals("Two")) {
        System.out.println("Adding Edit for Two");
        uTwo.addEdit(e.getEdit());
      }
    }
  }

  public static void main(final String[] args) {
    SwingUtilities.invokeLater(new Runnable() {
      @Override
      public void run() {
        new SSCCE(args);
      }
    });
  }
}

之前，我曾尝试创建
Document
类的一个新实例（每个实例引用相同的撤消侦听器），并打算使用
JTextArea.setDocument（）
而不是
JTextArea.setText（）
。然而，
Document
是一个接口，无法实例化，但是在阅读了mKorbel发布的参考资料后，我尝试使用
PlainDocument
类来实现这一点，但效果很好

我决定维护一个
HashMap
来包含我的
文档
类，并在它们之间切换。当我切换
文档
时，我看不到撤消/重做问题-我想是因为我不再破坏
文档

更新了下面的SSCCE，它现在使用
JTextArea.setDocument（）
而不是
JTextArea.setText（）
。这还具有不需要
ignoreEdit
布尔值的优点，因为
setDocument（）
不会触发
UndoableEditEvent
，而
setText（）
会触发。每个
文档
然后引用本地类
UndoableEditListener

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.text.*;
import javax.swing.undo.*;

public class SSCCE extends JFrame implements ActionListener, UndoableEditListener {
  private final JLabel labTextArea;
  private final JTextArea textArea;
  private final JScrollPane scrollTextArea;
  private final Document docTextArea;
  private final JButton bOne, bTwo, bUndo;
  private final UndoManager uOne, uTwo;
  private Document dOne, dTwo;

  public SSCCE(String[] args) {
    setTitle("SSCCE - Short, Self Contained, Correct Example");
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    setSize(300, 200);
    setLocationRelativeTo(null);

    labTextArea = new JLabel("One");
    getContentPane().add(labTextArea, BorderLayout.PAGE_START);

    uOne = new UndoManager();
    uTwo = new UndoManager();
    dOne = new PlainDocument();
    dTwo = new PlainDocument();
    dOne.addUndoableEditListener(this);
    dTwo.addUndoableEditListener(this);

    textArea = new JTextArea();
    docTextArea = textArea.getDocument();
    docTextArea.addUndoableEditListener(this);
    textArea.setDocument(dOne);
    scrollTextArea = new JScrollPane(textArea);
    getContentPane().add(scrollTextArea, BorderLayout.CENTER);

    JPanel pButtons = new JPanel();
    bOne = new JButton("One");
    bOne.addActionListener(this);
    bOne.setFocusable(false);
    pButtons.add(bOne, BorderLayout.LINE_START);
    bTwo = new JButton("Two");
    bTwo.addActionListener(this);
    bTwo.setFocusable(false);
    pButtons.add(bTwo, BorderLayout.LINE_END);
    bUndo = new JButton("Undo");
    bUndo.addActionListener(this);
    bUndo.setFocusable(false);
    pButtons.add(bUndo, BorderLayout.LINE_END);
    getContentPane().add(pButtons, BorderLayout.PAGE_END);

    setVisible(true);
  }

  @Override
  public void actionPerformed(ActionEvent e) {
    if (e.getSource().equals(bOne)) {
      if (!labTextArea.getText().equals("One")) {
        textArea.setDocument(dOne);
        labTextArea.setText("One");
      }
    }
    else if (e.getSource().equals(bTwo)) {
      if (!labTextArea.getText().equals("Two")) {
        textArea.setDocument(dTwo);
        labTextArea.setText("Two");
      }
    }
    else if (e.getSource().equals(bUndo)) {
      if (labTextArea.getText().equals("One")) {
        try {
          if (uOne.canUndo()) {
            System.out.println("Performing Undo for One");
            uOne.undo();
            System.out.println("Buffer One is now:\n" + textArea.getText() + "\n");
          }
          else {
            System.out.println("Nothing to Undo for One");
          }
        }
        catch (CannotUndoException ex) {
          ex.printStackTrace();
        }
      }
      else if (labTextArea.getText().equals("Two")) {
        try {
          if (uTwo.canUndo()) {
            System.out.println("Performing Undo for Two");
            uTwo.undo();
            System.out.println("Buffer Two is now:\n" + textArea.getText() + "\n");
          }
          else {
            System.out.println("Nothing to Undo for Two");
          }
        }
        catch (CannotUndoException ex) {
          ex.printStackTrace();
        }
      }
    }
  }

  @Override
  public void undoableEditHappened(UndoableEditEvent e) {
    if (labTextArea.getText().equals("One")) {
      System.out.println("Adding Edit for One");
      uOne.addEdit(e.getEdit());
    }
    else if (labTextArea.getText().equals("Two")) {
      System.out.println("Adding Edit for Two");
      uTwo.addEdit(e.getEdit());
    }
  }

  public static void main(final String[] args) {
    SwingUtilities.invokeLater(new Runnable() {
      @Override
      public void run() {
        new SSCCE(args);
      }
    });
  }
}

这本身并不是一个答案，而是一个解决同一问题的不同方式的证明

这样做的目的是将
UndoableEditListener
包装在一个自我管理的代理中，该代理具有自己的
UndoManager
和
文档

使用Java 7和Java 8对此进行了测试：

import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.HashMap;
import java.util.Map;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.event.UndoableEditEvent;
import javax.swing.event.UndoableEditListener;
import javax.swing.text.Document;
import javax.swing.text.JTextComponent;
import javax.swing.text.PlainDocument;
import javax.swing.undo.UndoManager;

public class UndoExample {

    public static void main(String[] args) {
        new UndoExample();
    }

    private int index = 0;
    private Map<String, Undoer> mapUndoers;
    private JTextArea ta;
    private Undoer current;

    public UndoExample() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }

                mapUndoers = new HashMap<>(2);
                mapUndoers.put("One", new Undoer());
                mapUndoers.put("Two", new Undoer());

                ta = new JTextArea(4, 20);
                ta.setWrapStyleWord(true);
                ta.setLineWrap(true);

                JButton btnOne = new JButton("One");
                JButton btnTwo = new JButton("Two");
                ActionListener al = new ActionListener() {
                    @Override
                    public void actionPerformed(ActionEvent e) {
                        install(e.getActionCommand());
                    }
                };
                btnOne.addActionListener(al);
                btnTwo.addActionListener(al);

                JButton undo = new JButton("Undo");
                undo.addActionListener(new ActionListener() {
                    @Override
                    public void actionPerformed(ActionEvent e) {
                        if (current != null) {
                            current.undo();
                        }
                    }
                });

                JPanel panel = new JPanel(new GridBagLayout());
                panel.add(btnOne);
                panel.add(btnTwo);
                panel.add(undo);

                install("One");

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(new JScrollPane(ta));
                frame.add(panel, BorderLayout.SOUTH);
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    protected void install(String name) {
        Undoer undoer = mapUndoers.get(name);
        if (undoer != null) {
            current = undoer;
            undoer.install(ta);
        }
    }

    public class Undoer implements UndoableEditListener {

        private UndoManager undoManager;
        private Document doc;

        public Undoer() {
            undoManager = new UndoManager();
            doc = createDocument();
            doc.addUndoableEditListener(this);
        }

        public void undo() {
            undoManager.undo();
        }

        public void undoOrRedo() {
            undoManager.undoOrRedo();
        }

        protected Document createDocument() {
            return new PlainDocument();
        }

        public void install(JTextComponent comp) {
            comp.setDocument(doc);
        }

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

    }

}

导入java.awt.BorderLayout；
导入java.awt.EventQueue；
导入java.awt.GridBagConstraints；
导入java.awt.GridBagLayout；
导入java.awt.event.ActionEvent；
导入java.awt.event.ActionListener；
导入java.util.HashMap；
导入java.util.Map；
导入javax.swing.JButton；
导入javax.swing.JFrame；
导入javax.swing.JPanel；
导入javax.swing.JScrollPane；
导入javax.swing.JTextArea；
导入javax.swing.UIManager；
导入javax.swing.UnsupportedLookAndFeelException；
导入javax.swing.event.UndoableEditEvent；
导入javax.swing.event.UndoableEditListener；
导入javax.swing.text.Document；
导入javax.swing.text.JTextComponent；
导入javax.swing.text.PlainDocument；
导入javax.swing.undo.UndoManager；
公共类示例{
公共静态void main（字符串[]args）{
新示例（）；
}
私有整数指数=0；
私人地图绘制者；
私人住宅区；
私有撤消电流；
公共示例（）{
invokeLater（新的Runnable（）{
@凌驾
公开募捐{
试一试{
UIManager.setLookAndFeel（UIManager.getSystemLookAndFeelClassName（））；
}catch（ClassNotFoundException |实例化Exception | IllegalacessException |不支持ookandfeelException ex）{
}
mapendoers=新HashMap（2）；
放置（“一个”，新的撤消器（））；
放置（“两个”，新的撤消器（））；
ta=新的JTextArea（4,20）；
ta.setWrapStyleWord（真）；
ta.setLineWrap（真）；
JButton btnOne=新JButton（“一”）；
JButton btnTwo=新JButton（“两个”）；
ActionListener al=新的ActionListener（）{
@凌驾
已执行的公共无效操作（操作事件e）{
安装（如getActionCommand（））；
}
};
btnOne.addActionListener（al）；
btnTwo.addActionListener（al）；
JButton undo=新JButton（“undo”）；
undo.addActionListener（新建ActionListener（））{
@凌驾
已执行的公共无效操作（操作事件e）{
如果（当前！=null）{
current.undo（）；
}
}
});
JPanel panel=newjpanel（newgridbagloayout（））；
面板。添加（btnOne）；
面板。添加（btnTwo）；
面板。添加（撤消）；
安装（“一个”）；
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.text.*;
import javax.swing.undo.*;

public class SSCCE extends JFrame implements ActionListener, UndoableEditListener {
  private final JLabel labTextArea;
  private final JTextArea textArea;
  private final JScrollPane scrollTextArea;
  private final Document docTextArea;
  private final JButton bOne, bTwo, bUndo;
  private final UndoManager uOne, uTwo;
  private Document dOne, dTwo;

  public SSCCE(String[] args) {
    setTitle("SSCCE - Short, Self Contained, Correct Example");
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    setSize(300, 200);
    setLocationRelativeTo(null);

    labTextArea = new JLabel("One");
    getContentPane().add(labTextArea, BorderLayout.PAGE_START);

    uOne = new UndoManager();
    uTwo = new UndoManager();
    dOne = new PlainDocument();
    dTwo = new PlainDocument();
    dOne.addUndoableEditListener(this);
    dTwo.addUndoableEditListener(this);

    textArea = new JTextArea();
    docTextArea = textArea.getDocument();
    docTextArea.addUndoableEditListener(this);
    textArea.setDocument(dOne);
    scrollTextArea = new JScrollPane(textArea);
    getContentPane().add(scrollTextArea, BorderLayout.CENTER);

    JPanel pButtons = new JPanel();
    bOne = new JButton("One");
    bOne.addActionListener(this);
    bOne.setFocusable(false);
    pButtons.add(bOne, BorderLayout.LINE_START);
    bTwo = new JButton("Two");
    bTwo.addActionListener(this);
    bTwo.setFocusable(false);
    pButtons.add(bTwo, BorderLayout.LINE_END);
    bUndo = new JButton("Undo");
    bUndo.addActionListener(this);
    bUndo.setFocusable(false);
    pButtons.add(bUndo, BorderLayout.LINE_END);
    getContentPane().add(pButtons, BorderLayout.PAGE_END);

    setVisible(true);
  }

  @Override
  public void actionPerformed(ActionEvent e) {
    if (e.getSource().equals(bOne)) {
      if (!labTextArea.getText().equals("One")) {
        textArea.setDocument(dOne);
        labTextArea.setText("One");
      }
    }
    else if (e.getSource().equals(bTwo)) {
      if (!labTextArea.getText().equals("Two")) {
        textArea.setDocument(dTwo);
        labTextArea.setText("Two");
      }
    }
    else if (e.getSource().equals(bUndo)) {
      if (labTextArea.getText().equals("One")) {
        try {
          if (uOne.canUndo()) {
            System.out.println("Performing Undo for One");
            uOne.undo();
            System.out.println("Buffer One is now:\n" + textArea.getText() + "\n");
          }
          else {
            System.out.println("Nothing to Undo for One");
          }
        }
        catch (CannotUndoException ex) {
          ex.printStackTrace();
        }
      }
      else if (labTextArea.getText().equals("Two")) {
        try {
          if (uTwo.canUndo()) {
            System.out.println("Performing Undo for Two");
            uTwo.undo();
            System.out.println("Buffer Two is now:\n" + textArea.getText() + "\n");
          }
          else {
            System.out.println("Nothing to Undo for Two");
          }
        }
        catch (CannotUndoException ex) {
          ex.printStackTrace();
        }
      }
    }
  }

  @Override
  public void undoableEditHappened(UndoableEditEvent e) {
    if (labTextArea.getText().equals("One")) {
      System.out.println("Adding Edit for One");
      uOne.addEdit(e.getEdit());
    }
    else if (labTextArea.getText().equals("Two")) {
      System.out.println("Adding Edit for Two");
      uTwo.addEdit(e.getEdit());
    }
  }

  public static void main(final String[] args) {
    SwingUtilities.invokeLater(new Runnable() {
      @Override
      public void run() {
        new SSCCE(args);
      }
    });
  }
}

import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.HashMap;
import java.util.Map;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.event.UndoableEditEvent;
import javax.swing.event.UndoableEditListener;
import javax.swing.text.Document;
import javax.swing.text.JTextComponent;
import javax.swing.text.PlainDocument;
import javax.swing.undo.UndoManager;

public class UndoExample {

    public static void main(String[] args) {
        new UndoExample();
    }

    private int index = 0;
    private Map<String, Undoer> mapUndoers;
    private JTextArea ta;
    private Undoer current;

    public UndoExample() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }

                mapUndoers = new HashMap<>(2);
                mapUndoers.put("One", new Undoer());
                mapUndoers.put("Two", new Undoer());

                ta = new JTextArea(4, 20);
                ta.setWrapStyleWord(true);
                ta.setLineWrap(true);

                JButton btnOne = new JButton("One");
                JButton btnTwo = new JButton("Two");
                ActionListener al = new ActionListener() {
                    @Override
                    public void actionPerformed(ActionEvent e) {
                        install(e.getActionCommand());
                    }
                };
                btnOne.addActionListener(al);
                btnTwo.addActionListener(al);

                JButton undo = new JButton("Undo");
                undo.addActionListener(new ActionListener() {
                    @Override
                    public void actionPerformed(ActionEvent e) {
                        if (current != null) {
                            current.undo();
                        }
                    }
                });

                JPanel panel = new JPanel(new GridBagLayout());
                panel.add(btnOne);
                panel.add(btnTwo);
                panel.add(undo);

                install("One");

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(new JScrollPane(ta));
                frame.add(panel, BorderLayout.SOUTH);
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    protected void install(String name) {
        Undoer undoer = mapUndoers.get(name);
        if (undoer != null) {
            current = undoer;
            undoer.install(ta);
        }
    }

    public class Undoer implements UndoableEditListener {

        private UndoManager undoManager;
        private Document doc;

        public Undoer() {
            undoManager = new UndoManager();
            doc = createDocument();
            doc.addUndoableEditListener(this);
        }

        public void undo() {
            undoManager.undo();
        }

        public void undoOrRedo() {
            undoManager.undoOrRedo();
        }

        protected Document createDocument() {
            return new PlainDocument();
        }

        public void install(JTextComponent comp) {
            comp.setDocument(doc);
        }

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

    }

}