1.实现绘图的时候，颜色的随时调整
void Widget::paintEvent(QPaintEvent *event)
{painter.begin(this);for(int i = 0; i < lines.size();i++){pen.setColor(colors[i]);pen.setWidth(widths[i]);painter.setPen(pen);painter.drawLine(lines[i]);}painter.end();
}void Widget::mouseMoveEvent(QMouseEvent *event)
{end = event->pos();QLine line(start,end);lines << line;if (!eraser){colors << color;widths << width;}else{colors << backgroundColor;widths << width;}start = end;update();
}运行结果：
2.追加橡皮擦功能
void Widget::mouseMoveEvent(QMouseEvent *event)
{end = event->pos();QLine line(start,end);lines << line;if (!eraser){colors << color;widths << width;}else{colors << backgroundColor;widths << width;}start = end;update();
}void Widget::on_pushButton_5_clicked()
{eraser=!eraser;
}运行效果：
