使用moveBy移动QGraphicsItem

Question

我尝试通过moveBy()来移动QGraphicsItem "box“。如果我将keyPressEvent放在item类中-这是工作，但如果我把这个函数放在mainwindow类中并尝试通过指针调用moveBy()函数-它不能工作。我做错了什么？

item.h：

#ifndef ITEM_H
#define ITEM_H


#include <QGraphicsItem>
#include <QGraphicsView>
#include <QKeyEvent>
class item: public QGraphicsItem
{
public:
  //virtual void keyPressEvent(QKeyEvent *event);

  item(QGraphicsItem *parent =NULL);
  QRectF boundingRect() const;


  protected:
void paint(QPainter *painter, const QStyleOptionGraphicsItem *option,QWidget *widget);
};

#endif // ITEM_H

mainwindow.h：

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include "item.h"

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    item *box;
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();
    virtual void keyPressEvent(QKeyEvent *event);
private:
    Ui::MainWindow *ui;
};

#endif // MAINWINDOW_H

item.cpp：

#include "item.h"

item::item(QGraphicsItem *parent): QGraphicsItem(parent)
{
    setFlag(QGraphicsItem::ItemIsFocusable);
}

QRectF item::boundingRect() const
{
    return QRectF(0,0,200,200);

}

void item::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{

    painter->drawPixmap(1,1, QPixmap(":/Graphics/Untitled.png"));
}

/*
void item::keyPressEvent(QKeyEvent *event)
{
    switch(event->key())
    {
    case Qt::Key_Right:
         moveBy(3,0);
         break;


    case Qt::Key_Left:
         moveBy(-3,0);
         break;


    case Qt::Key_Up:
         moveBy(0,-3);
         break;


     case Qt::Key_Down:
          moveBy(0,3);

      break;

  }


}
*/

mainwindow.cpp：

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "QGraphicsScene"
#include "QGraphicsView"

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    QGraphicsScene *scene = new QGraphicsScene;
    box = new item;
    scene->addItem(box);
    QGraphicsView *view = new QGraphicsView;
    view->setScene(scene);
    view->show();
}
MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::keyPressEvent(QKeyEvent *event)
{
    switch(event->key())
    {
    case Qt::Key_Right:
         box->moveBy(3,3);
         break;


    case Qt::Key_Left:

         break;


    case Qt::Key_Up:

         break;


     case Qt::Key_Down:


      break;

  }


}

Answer 1

当您按下键时，您确定您的程序甚至可以访问MainWindow::keyPressEvent(QKeyEvent *event)吗？尝试调试或将smth放入MainWindow::keyPressEvent(QKeyEvent *event)方法中，就像这样的qDebug() << "mouse key press in mainwindow";。

您的小部件需要获取鼠标事件来处理此事件。我很确定这不是在挖老鼠。换句话说，它需要聚焦。