Qt学习（一）——– 定时器、绘图

1.定时器 QTimer

⭐创建定时器对象QTimer *timer = new QTimer(this);

⭐ 启动定时器timer->start(毫秒);

⭐ 监听信号 connect(timer,&QTimer::timeout,[=](){ });

———————————————————–例子———————————————————–

    QTimer *timer = new QTimer(this);    timer->start(500);    connect(timer,&QTimer::timeout,[=](){        static int num = 1;        ui->label->setText(QString::number(num++));    });

⭐ 点击暂停，实现停止，点击开始，继续计时

    connect(ui->pushButton_stop,&QPushButton::clicked,[=](){        timer->stop();    });    connect(ui->pushButton_start,&QPushButton::clicked,[=](){        timer->start();    });

2.绘图 QPainter

⭐创建绘图事件 void paintEvent(QPaintEvent *);

⭐ 实例化画家对象QPainter painter(this);

⭐ 画线—drawLine，画圆—drawEllipse，画矩形—drawRect，画文字—drawText

⭐ 设置画笔—QPen pen， 设置画刷—QBrush brush，让画家使用画笔、画刷

———————————————————–例子———————————————————–

void MainWindow::paintEvent(QPaintEvent *){    QPainter painter(this);    // 设置画笔    QPen pen(QColor(255,0,0));    pen.setWidth(3);    pen.setStyle(Qt::DotLine);    painter.setPen(pen);    // 设置画刷    QBrush brush(Qt::cyan);    brush.setStyle(Qt::Dense7Pattern);    painter.setBrush(brush);    // 画线    painter.drawLine(QPoint(0,0), QPoint(100,100));    // 画圆    painter.drawEllipse(QPoint(100,100), 50 ,50);    // 画矩形    painter.drawRect(QRect(20,20,50,50));    // 画文字    painter.drawText(QRect(20,200,120,50),"好好学习，天天向上");
}

⭐ 抗锯齿，效率低 painter.setRenderHint(QPainter::Antialiasing);

⭐ 对画家进行移动 painter.translate(100,0);

⭐ 保存状态—save，还原状态—restore

———————————————————–例子———————————————————–

    painter.drawRect(QRect(20,300,50,50));    painter.translate(100,0);    painter.save(); // 保存画家状态    painter.drawRect(QRect(20,300,50,50));    painter.restore(); // 还原画家保存状态    painter.drawRect(QRect(20,300,50,50));

⭐ 手动调用绘图事件，点击按钮，进行图片移动

———————————————————–例子———————————————————–

connect(ui->pushButton_move,&QPushButton::clicked,[=](){        posX+=20;        update(); // 手动调用，用update更新    });void MainWindow::paintEvent(QPaintEvent *){    QPainter painter(this);    // 如果超出屏幕，从0开始    if(posX > this->width())    {        posX = 0;    }    painter.drawPixmap(posX,200,QPixmap(":/img/lufei.jpg"));}