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"));
}