qt学习之事件

事件经过：事件派发（QApplication调用notify()）->事件过滤（eventFilter()）->事件分发（窗口事件分发器event()）->事件处理（事件处理器函数,鼠标事件，键盘事件，绘图事件）
以上函数由qt控件维护，会在合适的时机执行，是虚函数可以重写。
两张蝴蝶图片实现飞舞效果

//.h文件
#ifndef BUTTERFLY_H
#define BUTTERFLY_H

#include <QPaintEvent>
#include <QWidget>

class Butterfly : public QWidget
{
    Q_OBJECT
public:
    explicit Butterfly(QWidget *parent = nullptr);
    void fly(int min, int max);
private:
    QPixmap m_pixmap;
    int m_index = 1;
    QPoint m_pt;
protected:
    void paintEvent(QPaintEvent *ev);
    void timerEvent(QTimerEvent *ev);
    void mousePressEvent(QMouseEvent *ev);
    void mouseMoveEvent(QMouseEvent *ev);
    void enterEvent(QEvent *ev);
signals:
};

#endif // BUTTERFLY_H

//cpp文件
#include "butterfly.h"

#include <QApplication>
#include <QDesktopWidget>
#include <QPainter>
#include <QRandomGenerator>
Butterfly::Butterfly(QWidget *parent)
    : QWidget{parent}
{
    m_pixmap.load(":/1");
    setFixedSize(m_pixmap.size());
    startTimer(100);
}
void Butterfly::fly(int min,int max)
{
    m_index++;
    if(m_index>2)
    {
        m_index = 1;
    }
    QString name = QString(":/%1").arg(m_index);
    m_pixmap.load(name);
    update();

    int stepX = QRandomGenerator::global()->bounded(min,max);
    int stepY = QRandomGenerator::global()->bounded(min,max);
    int curX = this->geometry().topLeft().x() - stepX;
    int curY = this->geometry().topLeft().y() + stepY;

    QDesktopWidget *desk = QApplication::desktop();
    if(curX <= desk->screenGeometry().left())
    {
        curX = desk->screenGeometry().right();
    }
    if(curY >= desk->screenGeometry().bottom())
    {
        curY = desk->screenGeometry().top();
    }
    move(curX,curY);
}

void Butterfly::paintEvent(QPaintEvent *ev)
{
    QPainter p(this);
    p.drawPixmap(rect(),m_pixmap);
}

void Butterfly::timerEvent(QTimerEvent *ev)
{
    fly(100,300);
}

void Butterfly::mousePressEvent(QMouseEvent *ev)
{
    if(ev->button() == Qt::LeftButton)
    {
        m_pt = ev->globalPos()-this->geometry().topLeft();
    }
}

void Butterfly::mouseMoveEvent(QMouseEvent *ev)
{
    if(ev->buttons()&Qt::LeftButton)
    {
        this->move(ev->globalPos()-m_pt);
    }
}

void Butterfly::enterEvent(QEvent *ev)
{
    fly(-600,600);
}

//主窗口
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "butterfly.h"

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


    //去边框
    setWindowFlags(windowFlags()|Qt::FramelessWindowHint);

    //设置窗口透明
    setAttribute(Qt::WA_TintedBackground);

    //最大化
    showMaximized();
    for (int var = 0; var < 100; ++var) {
        Butterfly *win = new Butterfly(this);
        win->move(QRandomGenerator::global()->bounded(this->width()),
                  QRandomGenerator::global()->bounded(this->height()));
        win->show();
    }
}

MainWindow::~MainWindow()
{
    delete ui;
}