（十二）绘图，不规则窗口，蝴蝶飞舞

#include "mywidget.h"
#include "ui_mywidget.h"
#include <QPainter>
#include <QMouseEvent>
#include <QTimer>
MyWidget::MyWidget(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::MyWidget),
    flag(true),
    x(0),
    y(0)
{
    ui->setupUi(this);
    pix.load(":/Image/Sunny.jpg");
    up.load(":/Image/up.png");
    down.load(":/Image/down.png");
    this->setWindowFlags(Qt::FramelessWindowHint);// 去掉边框
    this->setAttribute(Qt::WA_TranslucentBackground);// 设置背景透明

    QTimer *timer = new QTimer(this);
    timer->start(200);
    connect(timer,&QTimer::timeout,this,[=](){
        // 切换图片
        flag = !flag;
        // 设置时间种子
        qsrand(time(NULL));
        // 计算飞行路径
        x = qrand()%20 + x;
        y = qrand()%20 + y;
        if (x > width()){
            x = 0;
        }
        if (x < 0) {
            x = width();
        }
        if (y < 0) {
            y = height();
        }
        if (y > height()) {
            y = 0;
        }
        update();
    });
    this->showMaximized();//窗口最大化
//    x = qrand() % width();
//    y = qrand() %height();
}

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

void MyWidget::paintEvent(QPaintEvent *)
{
    QPainter p(this);
    if (flag){
        p.drawPixmap(0,0,up);// 在窗口中将图片画出来

    }
    else{
        p.drawPixmap(0,0,down);
    }
    this->move(x,y);
}

void MyWidget::mousePressEvent(QMouseEvent *e)
{
    if(e->button() == Qt::LeftButton) {
        dt_point = e->globalPos() - this->frameGeometry().topLeft();// 求差值 左键按下的点 - 窗口坐上角的点坐标
    }
    else if (e->button() == Qt::RightButton) {
        this->close();
    }
}

void MyWidget::mouseMoveEvent(QMouseEvent *e)
{
    this->move(e->globalPos() - dt_point);// mvoe x , y 使用的屏幕坐标系，// e->x() , e->y() 窗口的坐标系 Widget
}

#ifndef MYWIDGET_H
#define MYWIDGET_H

#include <QWidget>

namespace Ui {
class MyWidget;
}

class MyWidget : public QWidget
{
    Q_OBJECT

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

private:
    Ui::MyWidget *ui;
    QPixmap pix;
    QPixmap up;
    QPixmap down;
    QPoint dt_point;
    bool flag;
    int x;
    int y;
protected:
    void paintEvent(QPaintEvent *);
    void mouseMoveEvent(QMouseEvent *);
    void mousePressEvent(QMouseEvent *);

};

#endif // MYWIDGET_H