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1、pos机刷卡怎么撤回
1 QUndoStack： 一个存放 QUndoCommand 命令的栈.2 QUndoCommand：The QUndoCommand class is the base class of all commands stored on a QUndoStack.3 QUndoView：The QUndoView class displays the contents of a QUndoStack.（显示QUndoStack的内容）
下面的例子是根据 Qt 自带的例子(undoframework)写的:
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myitem.h
#ifndef MYITEM_H#define MYITEM_H#include <QGraphicsItem>class myItem :public QGraphicsPolygonItem{public: enum {Type = UserType +1}; explicit myItem(QGraphicsItem *parent = 0); int type() const override{return Type;}private: QPolygonF m_boxItem;};#endif // MYITEM_H
myitem.cpp
#include "myitem.h"#include <QBrush>myItem::myItem(QGraphicsItem *parent){ m_boxItem << QPointF(0,0) << QPointF(30,0) << QPointF(30,30) << QPointF(0,30) << QPointF(0,0); setPolygon(m_boxItem); //颜色随机 QColor color( (qrand() % 256),(qrand() % 256),(qrand() % 256) ); QBrush brush(color); setBrush(brush); //可移动 setFlag(QGraphicsItem::ItemIsMovable); //可选中 setFlag(QGraphicsItem::ItemIsSelectable);}重写 QGraphicsScene(场景)
myscene.h
#ifndef MYSCENE_H#define MYSCENE_H#include <QGraphicsScene>#include <QObject>#include "myitem.h"class myScene : public QGraphicsScene{ Q_OBJECTpublic: myScene(QObject *parent = 0);signals: void itemMoveSignal(myItem* item,const QPointF position);protected: void mousePressEvent(QGraphicsSceneMouseEvent *event); void mouseReleaseEvent(QGraphicsSceneMouseEvent *event);private: QGraphicsItem * m_Item; QPointF m_oldPos;};#endif // MYSCENE_H
myscene.cpp
#include "myscene.h"#include <QGraphicsSceneMouseEvent>#include <QDebug>myScene::myScene(QObject *parent){ m_Item = 0;}void myScene::mousePressEvent(QGraphicsSceneMouseEvent *event){ QPointF mousePos (event->buttonDownScenePos(Qt::LeftButton).x(), event->buttonDownScenePos(Qt::LeftButton).y()); const QList<QGraphicsItem* >itemList = items(mousePos); m_Item = itemList.isEmpty() ? 0 :itemList.first(); if(m_Item != 0 && event->button() == Qt::LeftButton) m_oldPos = m_Item->pos(); QGraphicsScene::mousePressEvent(event);}void myScene::mouseReleaseEvent(QGraphicsSceneMouseEvent *event){ if(m_Item != 0 && event->button() == Qt::LeftButton) { if(m_oldPos != m_Item->pos()) //发送位置移动的信号 emit itemMoveSignal(qgraphicsitem_cast<myItem*>(m_Item),m_oldPos); m_Item = 0; } QGraphicsScene::mouseReleaseEvent(event);}下面重写的 QUndoCommand 才是实现撤回和回撤的模块
重写 QUndoCommand 就是重写父类的 undo() 和 redo() 方法
mycommand.h
1 #ifndef MYCOMMAND_H 2 #define MYCOMMAND_H 3 4 #include <QUndoCommand> 5 #include "myitem.h" 6 #include "myscene.h" 7 //添加item 8 class addCommand :public QUndoCommand 9 {10 public :11 addCommand(QGraphicsScene* graphicsScene,QUndoCommand* parent = 0);12 13 void redo() override;//重写这两个函数14 void undo() override;15 private:16 17 myItem* m_item;18 19 QGraphicsScene* m_scene;20 21 QPointF m_initPos;22};23 //移动item24 class moveCommand:public QUndoCommand25 {26 public:27 moveCommand(myItem* item,const QPointF oldPos,QUndoCommand* parent = 0);28 29 void redo() override;//重写这两个函数30 void undo() override;31 private:32 myItem* m_item;33 QPointF m_oldPos;34 QPointF m_newPos;35 36};37 38 #endif // MYCOMMAND_H
mycommand.cpp
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1 #include "mycommand.h" 2 3 4 addCommand::addCommand(QGraphicsScene *graphicsScene, QUndoCommand *parent) 5 { 6 m_scene = graphicsScene; 7 8 m_item = new myItem(); 9 10 m_initPos = QPointF(10,10); //初始化item 生成的位置11 12 setText("add item");//undoView 中就会显示（父类的方法）13 }14 15 void addCommand::redo()//stack push 时 会自动调用16 {17 m_scene->addItem(m_item);18 m_item->setPos(m_initPos);19 m_scene->clearSelection();20 m_scene->update();21}22 23 void addCommand::undo()24 {25 m_scene->removeItem(m_item);26 m_scene->update();27}28 29 moveCommand::moveCommand(myItem *item, const QPointF oldPos, QUndoCommand *parent)30 {31 m_item = item;32 33 m_newPos = m_item->pos();34 35 m_oldPos = oldPos;36}37 38 void moveCommand::redo()39 {40 m_item->setPos(m_newPos);41 setText(QString("Move Item:(%1,%2)").arg(m_item->pos().rx()).arg(m_item->pos().ry()));42}43 44 void moveCommand::undo()45 {46 m_item->setPos(m_oldPos);47 m_item->scene()->update();48 setText(QString("Move Item:(%1,%2)").arg(m_item->pos().rx()).arg(m_item->pos().ry()));49}主界面
widget.h
1 #ifndef WIDGET_H 2 #define WIDGET_H 3 4 #include <QWidget> 5 #include <QPushButton> 6 #include <QGraphicsView> 7 #include <QUndoStack> 8 #include <QUndoView> 9 10 #include "myscene.h"11 #include "myitem.h"12 #include "mycommand.h"13 namespace Ui {14 class Widget;15}16 17 class Widget : public QWidget18 {19 Q_OBJECT20 21 public:22 explicit Widget(QWidget *parent = 0);23 ~Widget();24 25 void initUi();26 27 void initAction();28 29 void addItem();30 31 void itemMoved(myItem* item,QPointF pos);32 33 private:34 Ui::Widget *ui;35 QPushButton* m_addItemBtn;36 QAction* m_undoAction;37 QAction* m_redoAction;38 myScene *m_scene;39 40 QUndoStack* m_undoStack;41 QUndoView* m_undoView;42};43 44 #endif // WIDGET_H
widget.cpp
1 #include "widget.h" 2 #include "ui_widget.h" 3 #include <QLayout> 4 5 Widget::Widget(QWidget *parent) : 6 QWidget(parent), 7 ui(new Ui::Widget) 8 { 9 ui->setupUi(this);10 11 12 initAction();13 14 initUi();15 }16 17 Widget::~Widget()18 {19 delete ui;20}21 22 void Widget::initUi()23 {24 this->setWindowTitle("码农小明--撤销回撤");25 26 m_addItemBtn = new QPushButton();27 m_addItemBtn->setText("add Item");28 29 connect(m_addItemBtn,&QPushButton::clicked,this,&Widget::addItem);30 31 m_scene = new myScene();32 QBrush brush(Qt::gray);33 m_scene->setSceneRect(QRect(0,0,200,300));34 m_scene->setBackgroundBrush(brush);35 36 connect(m_scene,&myScene::itemMoveSignal,this,&Widget::itemMoved);37 38 39 QGraphicsView *view = new QGraphicsView(m_scene);40 41 QVBoxLayout *pLayout = new QVBoxLayout();42 pLayout->addWidget(m_addItemBtn);43 pLayout->addWidget(view);44 45 46 m_undoView = new QUndoView(m_undoStack);//右面显示栈内容的view(不setText就是空的)47 QHBoxLayout *pHLayout = new QHBoxLayout();48 pHLayout->addLayout(pLayout);49 pHLayout->addWidget(m_undoView);50 51 52 this->setLayout(pHLayout);53 54 this->resize(500,400);55 56}57 58 void Widget::initAction()59 {60 m_undoStack = new QUndoStack(this);//存放操作的栈61 62 m_undoAction = m_undoStack->createUndoAction(this,"Undo");63 m_undoAction->setShortcut(QKeySequence::Undo);64 65 m_redoAction = m_undoStack->createRedoAction(this,"Redo");66 m_redoAction->setShortcut(QKeySequence::Redo);67 68 this->addAction(m_undoAction);69 this->addAction(m_redoAction);70}71 72 void Widget::addItem()73 {74 QUndoCommand* add = new addCommand(m_scene);75 m_undoStack->push(add);//入栈操作 会自动调用 addCommand 的 redo76 77}78 79 void Widget::itemMoved(myItem *item, QPointF pos)80 {81 m_undoStack->push(new moveCommand(item,pos));//入栈操作
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