对于MVC模型，在Swing中使用undo/redo？

Question

我有一个MVC模型，我试图在其中添加一个撤销/重做功能。用户可以在JTextField中放置一个数字，当他们单击UNDO按钮时，它应该被擦除。我已经为实现此功能的类提供了代码。我所犯的错误在最下面。

控制包：

ButtonnGUIControl.java

包装控制；

/** *这个类将控制GUI.It实现actionListener()方法*的按钮动作，并根据单击的按钮初始化模型类中的*对应组件。* */

public class ButtonGUIControl implements ActionListener{
private SudokuModel model;
private ButtonGUI bgui;
final UndoManager manager = new UndoManager();



public ButtonGUIControl(SudokuModel model) {
    this.model = model;
}

/*This method will listen for user events, and act accordingly
 * */

public void actionPerformed(ActionEvent e) {
    try {   
         if(e.getActionCommand().equals("Check My Answer!")){

            model.checkGame();
        }


         else if (e.getActionCommand().equals("Undo")){

             try {

                    manager.undo();
                } catch (CannotUndoException ex) { ex.printStackTrace(); }
                finally {
                    //updateButtons();
                }                   
         }
         else if (e.getActionCommand().equals("Redo")){

             manager.redo();
             System.out.println("e.getActionCommand().equals redo");
         }

        //otherwise, it simply places the selected number in the grid
        else{

            model.setNumber(Integer.parseInt(e.getActionCommand()));
        }

    } catch (NumberFormatException e1) {}

    catch (IOException e1) {}
    catch (CannotUndoException ex) {
        System.out.println("Unable to undo: " + ex);
        ex.printStackTrace();
        }
    catch (CannotRedoException ex) {
        System.out.println("Unable to redo: " + ex);
        ex.printStackTrace();
    }    

}

public void undoableEditHappened(UndoableEditEvent evt) {

    manager.addEdit(evt.getEdit());

    //bgui.updateButtons();

}

}

在视图包中: ButtonGUI.java

我在按钮中添加了一个actionListner：

RedoBttn.addActionListener(buttonController)；

UndoBttn.addActionListener(buttonController)；

在Grid.java中，它扩展了JTextField：

public class Grid extends JTextField {
private int x;       
private int y; 

final UndoManager manager = new UndoManager();


public Grid(int x, int y) {
    super("");
    this.x = x;
    this.y = y;
    getDocument().addUndoableEditListener(manager);



    setPreferredSize(new Dimension(40, 40));
    setBorder(BorderFactory.createLineBorder(Color.GREEN));
    setOpaque(true);
}


public void setNumber(int number, boolean userInput)  {


    if(number > 0 & !userInput){
        setText(""+number);
        setEditable(false);


    }

    //These set of numbers are the only ones that the user can undo/redo
    else if (number > 0 & userInput){
        setText(""+number);
        setEditable(true);
}
    else
    setText("");

我还在视图包中的另一个类中的每个JTextFields中添加了一个鼠标listenr。所以我想我的撤销/重做结构是正确的。当我运行该程序时，我可以选择一个数字并将其放在JTextField(网格)中，但一旦我单击“撤销”，就会得到以下异常：

    javax.swing.undo.CannotUndoException
at javax.swing.undo.UndoManager.undo(UndoManager.java:411)
at control.ButtonGUIControl.actionPerformed(ButtonGUIControl.java:76)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
at java.awt.Component.processMouseEvent(Component.java:6505)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
at java.awt.Component.processEvent(Component.java:6270)
at java.awt.Container.processEvent(Container.java:2229)
at java.awt.Component.dispatchEventImpl(Component.java:4861)
at java.awt.Container.dispatchEventImpl(Container.java:2287)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
at java.awt.Container.dispatchEventImpl(Container.java:2273)
at java.awt.Window.dispatchEventImpl(Window.java:2713)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:707)
at java.awt.EventQueue.access$000(EventQueue.java:101)
at java.awt.EventQueue$3.run(EventQueue.java:666)
at java.awt.EventQueue$3.run(EventQueue.java:664)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
at java.awt.EventQueue$4.run(EventQueue.java:680)
at java.awt.EventQueue$4.run(EventQueue.java:678)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:677)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:211)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:128)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:117)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:113)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:90)

第76行是我所称的：

    manager.undo() 

在一个尝试/捕捉块中。

你知道怎么回事吗？是我的撤销/重做实现还是别的什么？

谢谢！

Answer 1

尝试像这样包装manager.undo();：

if(manager.canUndo())
    manager.undo();

我怀疑默认的UndoListener实现JTextField不会添加系统更新(即。将setText(""+number);调用到撤消队列)--仅从UI进行更新。

编辑

在进行了一些测试之后，setText("")函数似乎确实向UndoManager添加了undos，所以这不是您遇到的问题。因此，您可以通过确保有任何可撤消的操作来防止错误；但是，如果您在UndoManager中没有得到任何可撤消的操作，那么这个问题可能发生在代码的其他地方。