在Qt自带例子中添加HideItem，并实现相应Undo和Redo功能

原工程：tools/undoframework.pro

//==========================mainwindow.h

//add the slot into mainwindow.h

private slots:
//Jingz添加
void hideItem();
//
    void deleteItem();

//add the action into mainwindow.h

private:
    void createActions();
    void createMenus();
    void createUndoView();


//Jingz添加
QAction *hideAction;
//

//==========================mainwindow.cpp

//! [2] initialize the action
void MainWindow::createActions()
{
    deleteAction = new QAction(tr("&Delete Item"), this);
    deleteAction->setShortcut(tr("Del"));
    connect(deleteAction, SIGNAL(triggered()), this, SLOT(deleteItem()));
//! [2] //! [3] -------------------------------------------------------------------------- Jingz 
hideAction = new QAction(tr("&Hide Item"),this);
hideAction->setShortcut(tr("Ctrl+H"));
connect(hideAction,SIGNAL(triggered()),this,SLOT(hideItem()));


//! [3] //! [4]

.............

undoAction = undoStack->createUndoAction(this, tr("&Undo"));
    undoAction->setShortcuts(QKeySequence::Undo);


    redoAction = undoStack->createRedoAction(this, tr("&Redo"));
    redoAction->setShortcuts(QKeySequence::Redo);
...............

void MainWindow::createMenus()
{
//! [6]
    fileMenu = menuBar()->addMenu(tr("&File"));
    fileMenu->addAction(exitAction);


//! [7]
    editMenu = menuBar()->addMenu(tr("&Edit"));
    editMenu->addAction(undoAction);
    editMenu->addAction(redoAction);
    editMenu->addSeparator();
    editMenu->addAction(deleteAction);
editMenu->addAction(hideAction);//---------------------------------Jingz add the action into menu

..............................

//! [16] ================Jingz realize hidItem 
void MainWindow::hideItem()
{
if (diagramScene->selectedItems().isEmpty())
return;


QUndoCommand *hideCommand = new HideCommand(diagramScene); 

//operation  to change the item status and keep previous diagramScene in the undoStack 

undoStack->push(hideCommand);//把压制的代码解决就行啦。


}
//! [16]

//! [3]   ================================================commands.h    Jingz
class HideCommand : public QUndoCommand
{
public:
HideCommand(QGraphicsScene *graphicsScene, QUndoCommand *parent = 0);
~HideCommand();
void undo();
void redo();


private:
DiagramItem *myDiagramItem;
QGraphicsScene *myGraphicsScene;
//QList <int> hideGraphics;
//int undoIndex;
};
//! [3]

//! [10]=================================================commands.cpp Jingz
HideCommand::HideCommand(QGraphicsScene *scene,QUndoCommand *parent)
: QUndoCommand(parent)
{


myGraphicsScene = scene;
QList<QGraphicsItem *> list = myGraphicsScene->selectedItems();
myGraphicsScene->selectedItems().first()->setVisible(false);
list.first()->setSelected(false);
myDiagramItem = static_cast<DiagramItem *>(list.first());
//QList<QGraphicsItem *> list = myGraphicsScene->selectedItems();
//list.first()->setSelected(false);
//myDiagramItem = static_cast<DiagramItem *>(list.first());
//setText(QObject::tr("Delete %1")
// .arg(createCommandString(myDiagramItem, myDiagramItem->pos())));


//if (hideGraphics.count()>undoIndex)//当出现undo后做新修改，覆盖后面的redo记录
//{
// hideGraphics.pop_back();
//}





//for (int i = 0;i < myGraphicsScene->items().count();i++ )
//{
// myDiagramItem = static_cast<DiagramItem *>(myGraphicsScene->items().value(i));
// if (!myGraphicsScene->items().value(i)->isVisible())
// {
// myGraphicsScene->items().value(i)->show();
// setText(QObject::tr("Show %1").arg(createCommandString(myDiagramItem, myDiagramItem->pos())));
// }
//
//}


// QList<QGraphicsItem *> list = myGraphicsScene->selectedItems();
/*for (int i = 0;i < myGraphicsScene->selectedItems().count();i++)
{
myGraphicsScene->selectedItems().value(i)->hide();
myDiagramItem = static_cast<DiagramItem *>(myGraphicsScene->selectedItems().value(i));
myGraphicsScene->selectedItems().value(i)->setSelected(false);
hideGraphics.append(i);
undoIndex = hideGraphics.count();
setText(QObject::tr("Hide %1").arg(createCommandString(myDiagramItem, myDiagramItem->pos())));
}*/
// myGraphicsScene->update();

//myGraphicsScene->selectedItems().first()->setSelected(false);
setText(QObject::tr("Hide %1").arg(createCommandString(myDiagramItem, myDiagramItem->pos())));
}
//! [10]


HideCommand::~HideCommand()
{
/*if (!myDiagramItem->scene())
delete myDiagramItem;*/
}


//! [11]
void HideCommand::undo()
{


/*int i = hideGraphics.at(--undoIndex);*///撤销本次操作
//if (myGraphicsScene->items().at(i)->isVisible())
//{
// myGraphicsScene->items().at(i)->hide();
//}
//else
//{
// myGraphicsScene->items().at(i)->show();


//}//


//i = hideGraphics.at(--undoIndex);//恢复现场
//if (myGraphicsScene->items().at(i)->isVisible())
//{
// myGraphicsScene->items().at(i)->hide();
//}
//else
//{
// myGraphicsScene->items().at(i)->show();


//}


// myGraphicsScene->items().at(i)->setVisible(false);
myDiagramItem->setVisible(true);
myGraphicsScene->update();
}
//! [11]


//! [12]
void HideCommand::redo()
{
/*int i = hideGraphics.at(++undoIndex);*/
/*if (myGraphicsScene->items().at(i)->isVisible())
{
myGraphicsScene->items().at(i)->hide();
}
else
{
myGraphicsScene->items().at(i)->show();


}


i = hideGraphics.at(++undoIndex);
if (myGraphicsScene->items().at(i)->isVisible())
{
myGraphicsScene->items().at(i)->hide();
}
else
{
myGraphicsScene->items().at(i)->show();


}*/
/*myGraphicsScene->items().at(i)->setVisible(true);*/
myDiagramItem->setVisible(false);
myGraphicsScene->update();
}
//! [12]








QString createCommandString(DiagramItem *item, const QPointF &pos)
{
    return QObject::tr("%1 at (%2, %3)")
        .arg(item->diagramType() == DiagramItem::Box ? "Box" : "Triangle")
        .arg(pos.x()).arg(pos.y());
}