Qt中多事件使用实例

/***************moveico.h************/
#ifndef MOVEICO_H
#define MOVEICO_H

#include <QWidget>
#include <QLabel>

namespace Ui {
    class MoveIco;
}

class MoveIco : public QWidget
{
    Q_OBJECT

public:
    explicit MoveIco(QWidget *parent = 0);
    ~MoveIco();

private:
    Ui::MoveIco *ui;
    QLabel *label;
    int x,y;
    int w,h;
protected:
    void mousePressEvent(QMouseEvent *);
    void paintEvent(QPaintEvent *);
    void keyPressEvent(QKeyEvent *);
    void wheelEvent(QWheelEvent *);
    void resizeEvent(QResizeEvent *);
};

#endif // MOVEICO_H

/************moveico.cpp*************/
#include "moveico.h"
#include "ui_moveico.h"
#include <QMouseEvent>
#include <QDebug>

MoveIco::MoveIco(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::MoveIco)
{
    x = y =0;
    w = h =50;
    label = new QLabel(this);
    label->setScaledContents(true);//设置图片自适应
    label->setPixmap(QPixmap("../image/qt2.png"));//插入图片
    ui->setupUi(this);
}

MoveIco::~MoveIco()
{
    delete ui;
}
void MoveIco::mousePressEvent(QMouseEvent *e)//鼠标点击事件
{
    switch(e->button())//判断键值
    {
        case Qt::LeftButton:
             if(this->label->pos().x() > 0)//左边界限定
             x -=10;
             break;
        case Qt::RightButton:
             if(this->label->pos().x() < this->rect().width() - this->label->width())//右边界限定
             x+=10;
             break;
    }
}

void MoveIco::paintEvent(QPaintEvent *e)//绘图事件
{
    this->label->move(0+x,0+y);
    this->label->resize(w,h);
    update();
}

void MoveIco::keyPressEvent(QKeyEvent *e)//键盘按键事件
{
    int flag = 1;
    switch(e->modifiers())//判断是否有辅助键按下
    {
    case Qt::AltModifier:
        flag=2;
        break;
    default:
        break;
    }
    switch(e->key())//判定按下键盘的什么键
    {
    case Qt::Key_Left:
        if(this->label->pos().x() > 0)//左边界限定
        x -= 10*flag;
        break;
    case Qt::Key_Right:
        if(this->label->pos().x() < this->rect().width() - this->label->width())//右边界限定
        x += 10*flag;
        break;
    case Qt::Key_Up:
        if(this->label->pos().y() > 0)
        y -= 10*flag;
        break;
    case Qt::Key_Down:
        if(this->label->pos().y() < this->rect().height() - this->label->height())
        y += 10*flag;
        break;
    }
}

void MoveIco::wheelEvent(QWheelEvent *e)//滚轮事件
{
    if(e->delta() > 0)//向上滚
    {
        w = this->label->width()+10;
        h = this->label->height()+10;
    }

    if(e->delta() < 0)//向下滚
    {
        w = this->label->width()-10;
        h = this->label->height()-10;
    }
}

void MoveIco::resizeEvent(QResizeEvent *e)//窗口大小变化事件
{
    if((this->label->pos().x() >= this->rect().width() - this->label->width()) || (this->label->pos().y() >= this->rect().height() - this->label->height()))
    {
        y = y*e->size().height()/e->oldSize().height();
        x = x*e->size().width()/e->oldSize().width();
        w = w*e->size().width()/e->oldSize().width();         h = h*e->size().height()/e->oldSize().height();
    }
}//先判断label的位置，然后在根据新旧窗口的大小比例计算新坐标。