一步不三步撤消JEditorPane的setText()方法的效果

Question

我正在尝试撤消 JEditorPane 中的 setText() 方法效果。这是我的代码：

public final class UndoManagerTestForJEditorPane {

private final JEditorPane editor = new JEditorPane();
private final UndoManager undoManager = new UndoManager();

public JComponent makeUI() {
    editor.setContentType("text/html");
    HTMLDocument document = (HTMLDocument) editor.getDocument();
    document.addUndoableEditListener(undoManager);
    editor.setText("Hello");

    JPanel p = new JPanel();
    p.add(new JButton(new AbstractAction("undo") {
        @Override
        public void actionPerformed(ActionEvent e) {
            if (undoManager.canUndo()) {
                undoManager.undo();
            }
        }
    }));
    p.add(new JButton(new AbstractAction("redo") {
        @Override
        public void actionPerformed(ActionEvent e) {
            if (undoManager.canRedo()) {
                undoManager.redo();
            }
        }
    }));
    p.add(new JButton(new AbstractAction("setText(new Date())") {
        @Override
        public void actionPerformed(ActionEvent e) {
            String str = new Date().toString();
            editor.setText(str);
        }
    }));

    Box box = Box.createVerticalBox();
    box.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
    box.add(makePanel("Default", editor));

    JPanel pp = new JPanel(new BorderLayout());
    pp.add(box, BorderLayout.NORTH);
    pp.add(p, BorderLayout.SOUTH);
    return pp;
}

private static JPanel makePanel(String title, JComponent c) {
    JPanel p = new JPanel(new BorderLayout());
    p.setBorder(BorderFactory.createTitledBorder(title));
    p.add(c);
    return p;
}

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

public static void createAndShowGUI() {
    JFrame f = new JFrame();
    f.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
    f.getContentPane().add(new UndoManagerTestForJEditorPane().makeUI());
    f.setSize(320, 240);
    f.setLocationRelativeTo(null);
    f.setVisible(true);
}
}

默认行为通过四个步骤完成：

1) 什么都没做，光标甚至没有移动..

2) 光标下降到插入的单词下将近 10 行..

3) 文字消失了..

4) 旧文本终于出现了..

那么，除了这些步骤，我们是否可以只使用一个撤消步骤（如 JTextField JTextArea setText() & UndoManager 的此链接中的一个撤消步骤，但使用 JEditorPane 呢？

在JEditorPane上调用setText()时，JEditorPane的replace方法没有被执行的问题...

请帮忙？

谢谢

Answer 1

您可以使用扩展AbstractUndoableEdit 的单独类来完成此操作（如果您只需要使用来自一个类的信息进行编辑，则可以嵌套以直接访问必要的 GUI 元素）。您可以保存在一次 undo 操作后要加载的确切旧状态，以及在 redo 操作后要重新加载的确切新状态。然后，您可以在redo 和undo 方法中直接设置正确的值，方法是在State 类中覆盖它们。这可能如下所示：

public final class UndoManagerTestForJEditorPane {

private final JEditorPane editor = new JEditorPane();
private final UndoManager undoManager = new UndoManager();

public JComponent makeUI() {
    editor.setContentType("text/html");
    HTMLDocument document = (HTMLDocument) editor.getDocument();
    //document.addUndoableEditListener(undoManager);  -> Not used anymore
    editor.setText("Hello");

    JPanel p = new JPanel();
    p.add(new JButton(new AbstractAction("undo") {
        @Override
        public void actionPerformed(ActionEvent e) {
            if (undoManager.canUndo()) {
                undoManager.undo();
            }
        }
    }));

    // New class to hold the state and load the correct string
    class State extends AbstractUndoableEdit
    {
        String oldText;
        String newText;

        State(String oldText, String newText)
        {
            this.oldText = oldText;
            this.newText = newText;
        }

        @Override
        public void undo() throws CannotUndoException {
            editor.setText(oldText);
        }

        @Override
        public boolean canUndo() {
            return true;
        }

        @Override
        public void redo() throws CannotRedoException {
            editor.setText(newText);
        }

        @Override
        public boolean canRedo() {
            return true;
        }


    }
    p.add(new JButton(new AbstractAction("redo") {
        @Override
        public void actionPerformed(ActionEvent e) {
            if (undoManager.canRedo()) {
                undoManager.redo();
            }
        }
    }));
    p.add(new JButton(new AbstractAction("setText(new Date())") {
        @Override
        public void actionPerformed(ActionEvent e) {
            String str = new Date().toString();
            // Add a new edit by saving the old string (by calling getText) and the new string 'str'
            undoManager.addEdit(new State(editor.getText(), str));
            editor.setText(str);
        }
    }));



    Box box = Box.createVerticalBox();
    box.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
    box.add(makePanel("Default", editor));

    JPanel pp = new JPanel(new BorderLayout());
    pp.add(box, BorderLayout.NORTH);
    pp.add(p, BorderLayout.SOUTH);
    return pp;
}

private static JPanel makePanel(String title, JComponent c) {
    JPanel p = new JPanel(new BorderLayout());
    p.setBorder(BorderFactory.createTitledBorder(title));
    p.add(c);
    return p;
}

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

public static void createAndShowGUI() {
    JFrame f = new JFrame();
    f.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
    f.getContentPane().add(new UndoManagerTestForJEditorPane().makeUI());
    f.setSize(320, 240);
    f.setLocationRelativeTo(null);
    f.setVisible(true);
}
}