首先新建一个项目：为了方便，直接拷贝的书上源码，书为《QT5开发及实例（第二版）》
头文件：
#ifndef KEYEVENT_H #define KEYEVENT_H #include <QWidget> #include <QKeyEvent> #include <QPaintEvent> class KeyEvent : public QWidget { Q_OBJECT public: KeyEvent(QWidget *parent = 0); ~KeyEvent(); void drawPix(); void keyPressEvent(QKeyEvent *); void paintEvent(QPaintEvent *); private: QPixmap *pix; QImage image; int startX; int startY; int width; int height; int step; }; #endif // KEYEVENT_H源代码：
#include "keyevent.h"
#include <QPainter>KeyEvent::KeyEvent(QWidget *parent) : QWidget(parent){ setWindowTitle(tr("键盘事件")); setAutoFillBackground(true); QPalette palette = this->palette(); palette.setColor(QPalette::Window,Qt::white); setPalette(palette); setMinimumSize(512,256); setMaximumSize(512,256); width=size().width(); height=size().height(); pix = new QPixmap(width,height); pix->fill(Qt::white); image.load("../image/image.png"); startX=100; startY=100; step=20; drawPix(); resize(512,256);}KeyEvent::~KeyEvent(){ }void KeyEvent::drawPix(){ pix->fill(Qt::white); QPainter *painter = new QPainter; QPen pen(Qt::DotLine); for(int i=step;i<width;i=i+step) { painter->begin(pix); painter->setPen(pen); painter->drawLine(QPoint(i,0),QPoint(i,height)); painter->end(); } for(int j=step;j<height;j=j+step) { painter->begin(pix); painter->setPen(pen); painter->drawLine(QPoint(0,j),QPoint(width,j)); painter->end(); } painter->begin(pix); painter->drawImage(QPoint(startX,startY),image); painter->end();}void KeyEvent::keyPressEvent(QKeyEvent *event){ if(event->modifiers()==Qt::ControlModifier) { if(event->key()==Qt::Key_Left) { startX=(startX-1<0)?startX:startX-1; } if(event->key()==Qt::Key_Right) { startX=(startX+1+image.width()>width)?startX:startX+1; } if(event->key()==Qt::Key_Up) { startY=(startY-1<0)?startY:startY-1; } if(event->key()==Qt::Key_Down) { startY=(startY+1+image.height()>height)?startY:startY+1; } } else { startX=startX-startX%step; startY=startY-startY%step; if(event->key()==Qt::Key_Left) { startX=(startX-step<0)?startX:startX-step; } if(event->key()==Qt::Key_Right) { startX=(startX+step+image.width()>width)?startX:startX+step; } if(event->key()==Qt::Key_Up) { startY=(startY-step<0)?startY:startY-step; } if(event->key()==Qt::Key_Down) { startY=(startY+step+image.height()>height)?startY:startY+step; } if(event->key()==Qt::Key_Home) { startX=0; startY=0; } if(event->key()==Qt::Key_End) { startX=width-image.width(); startY=height-image.height(); } } drawPix(); update();}void KeyEvent::paintEvent(QPaintEvent *){ QPainter painter; painter.begin(this); painter.drawPixmap(QPoint(0,0),*pix); painter.end();}运行图：
