自学QT之键盘事件

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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：

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