QPainter的一些实例测试

话不多说，直接上码！

void Widget::paintEvent(QPaintEvent *e)
{
    QBrush brush(QColor(0,0,255));
    QFont font;
    font.setFamily("Microsoft YaHei");
    font.setPointSize(20);

    QPainter painter(this);
    painter.setRenderHints(QPainter::Antialiasing, true);
    painter.setRenderHint(QPainter::Antialiasing, true);

    painter.setPen(QColor(0, 0, 0));//black
    //写文字
    //painter.drawText(rect, Qt::AlignCenter, QString("Qt by\nThe Qt Company"));
    painter.drawText(QPoint(10,30), QString("The Text"));
    //画线
    painter.drawLine(QPointF(10,35),QPointF(100,35));
    //画矩形
    painter.save();
    painter.setPen(QColor(255, 0, 0));//red
    painter.drawRect(QRect(10,40,100,25));
    //画圆角矩形
    painter.restore();

    painter.save();
    painter.setBrush(brush);
    painter.drawRoundedRect(10,70,100,25,5,5);
    painter.restore();
    //画弧线
    painter.drawArc(15,100,80,80,0,16*90);//90度
    //画整圆
    painter.drawArc(15,120,80,80,0,5760);
    //画扇形
    painter.drawPie ( 15, 200, 80, 80, 0, 16*180 );//180度
    //画椭圆
    painter.drawEllipse(15,250,100,40);
    //画多边形
    static const QPointF points[4] = {QPointF(20, 290), QPointF(50, 400), QPointF(140, 410), QPointF(200, 350)};
    painter.drawPolygon(points, 4);
    //---渐变线段
    QLinearGradient linearGradient(60, 50,200, 200);
    linearGradient.setColorAt(0.2,Qt::red);
    linearGradient.setColorAt(0.6,Qt::green);
    linearGradient.setColorAt(1.0,Qt::black);
    painter.setPen(QPen(QBrush(linearGradient),5));
    painter.drawLine(150, 20, 350, 20);

    //---渐变文字
    QLinearGradient linear;
    linear.setStart(150,50);
    linear.setFinalStop(150,130);
    linear.setColorAt(0,Qt::red);
    linear.setColorAt(0.5,Qt::green);
    linear.setColorAt(0.8,Qt::black);
    linear.setColorAt(1.0,Qt::yellow);
    painter.setFont(font);
    painter.setPen(QPen(QBrush(linear),5));
    painter.drawText(150,50,200,80,Qt::AlignLeft, QString("ABCDEFGHIJK") );

    //---渐变矩形
    QLinearGradient linear2(QPointF(150, 100), QPointF(210, 180));//设置渐变的起始和结束点，也可做设置渐变方向
    linear2.setColorAt(0, Qt::black);
    linear2.setColorAt(1, Qt::white);
    linear2.setSpread(QGradient::PadSpread);
    painter.setPen(QPen(QColor(0, 160, 230), 2));
    painter.setBrush(linear2);
    painter.drawRect(QRect(150, 100, 60, 60));

    //卡拉OK歌词效果
    if(paintWith>0){
        painter.setPen(QColor(0, 0, 0));//black
        painter.drawText(150,50,paintWith,80,Qt::AlignLeft, QString("ABCDEFGHIJK") );
    }
    this->update();
}