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")); }