前言：本次設計很粗糙的實現的魚的自由遊動，大體思路是設定定時器，每隔一段時間呼叫一次repaint()函式，達到呼叫paintEvent（）函式的目的，在paintEvent（）函式中實現一次顯示魚兒遊動的圖片達到動態效果，並不斷改變圖片的位置，實現魚兒的遊動。

1、新建工程如下圖所示

2、修改widget.h

#ifndef WIDGET_H
#define WIDGET_H

#include <QWidget>
#include <QPainter>
#include <QPixmap>
namespace Ui {
class Widget;
}

class Widget : public QWidget
{
    Q_OBJECT
    
public:
    explicit Widget(QWidget *parent = 0);
    ~Widget();
    QTimer *time;
    int i;
    int f_x,f_y;
public:
     void paintEvent(QPaintEvent *);
     void move();
private:
    Ui::Widget *ui;
};

#endif // WIDGET_H

3、修改widget.cpp

#include "widget.h"
#include "ui_widget.h"
#include <QTimer>
#include <QDebug>
#include <QString>
#include <QPixmap>
#include<qstring.h>

Widget::Widget(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::Widget)
{
    ui->setupUi(this);
    time = new QTimer;
    time->setInterval(50);
    time->start();
    i = 0;
    this->setFixedSize(800,480);
    f_y= 480;
    f_x = 800;
    connect(time,SIGNAL(timeout()),this,SLOT(repaint()));
}

Widget::~Widget()
{
    delete ui;
}

void Widget::paintEvent(QPaintEvent *)
{
    //QString *str;
    QPainter painter(this);
    QPixmap fash;
    //i=rand()%10;

    i++;
    if (i > 9 )
    {
        i = 0;
    }
    //fash.load("fish01_00.png");
    //QPixmap pixmap;
    //str = "fish01_00.png";
    //pixmap.load(str);
    //pixmap("fish01_00.png");
    //str=tr(":images/")+tr("fish01")+tr("_0")+tr(QString::number(i))+tr(".png");
    //QPixmap pixmap;
    switch (i)
    {
        case 0:
         {
            fash.load("fish01_00.png");
            qDebug() << "fish01_00.png"<< endl;

            break;
        }
        case 1:
        {
            fash.load("fish01_01.png");
            qDebug() << "fish01_01.png"<< endl;

            break;
        }
        case 2:
        {
            fash.load("fish01_02.png");
            qDebug() << "fish01_02.png"<< endl;

            break;
        }
        case 3:
        {
            fash.load("fish01_03.png");
            qDebug() << "fish01_03.png"<< endl;

            break;
        }
            case 4:
        {
            fash.load("fish01_04.png");
            qDebug() << "fish01_04.png"<< endl;

            break;
        }
            case 5:
        {
            fash.load("fish01_05.png");
            qDebug() << "fish01_05.png"<< endl;

            break;
        }
            case 6:
        {
            fash.load("fish01_06.png");
            qDebug() << "fish01_06.png"<< endl;

            break;
        }
            case 7:
        {
            fash.load("fish01_07.png");
            qDebug() << "fish01_07.png"<< endl;

            break;
        }
            case 8:
        {
            fash.load("fish01_08.png");
            qDebug() << "fish01_08.png"<< endl;

            break;
        }
            default:
                qDebug() << "default!!!!"<< endl;
            break;
    }
    //QPixmap pixmap(str);
    f_y=f_y-0.5;
    if (f_y < 50)
    {
        f_y=480;
    }

    f_x=f_x-0.5;
    if (f_x < 50)
    {
        f_x=800;
    }
    //qDebug() << "void Widget::paintEvent(QPaintEvent *)" << endl;
    painter.save();
    //painter.translate(100,100);
    //painter.rotate(90);
    //str=":images/fish01_00.png";
    //fash.load("fish01_00.png");
    painter.drawPixmap(f_x,f_y,fash.width(),fash.height(),fash);

    //painter.drawPixmap(-fash.width()/2,-fash.height()/2,fash.width(),fash.height(),fash);
    painter.restore();

}

3、執行結果