Qt 编程点滴 初学者必看 （7）

Qt 编程继续为大家讲解，还是接着文章 Qt 编程点滴 初学者必看 （6） ，继续介绍，说编程那些细节。由于本话题是一节一节为大家介绍的，所以更多内容请看末尾编辑推荐。本文基本是用代码实现的效果，所以并没有太多的内容。

QPainterPath 画出的图形会闪烁的问题：

用下面的写法画出的图形会闪烁

class MyClass: public QWidget  
{  
public:  
  MyClass(QWidget*);  
private:  
    QPainterPath* route;  
    void paintEvent(QPaintEvent*e);  
};  
MyClass::MyClass()  
{  
  route = new QPainterPath();  
}  
void MyClass::paintEvent( QPaintEvent*e)  
{  
    QPainter *painter = new QPainter(this);  
    //画校正图形  
    int insideR = 30;  
    int outsideR = 50;  
    QColor insideColor(237,29,12); //内圆线条颜色  
    QColor outSideColor(237,29,12); //外圆线条颜色  
    QColor lineColor(237,29,12); //直线颜色  
    QColor insideBrushColor(255,0,0,25);//内圆画刷颜色,最后的参数代表透明度( 0(完全透明)-100(不透明) )  
    QColor outsideBrushColor(255,0,0,50);//外圆画刷颜色,最后的参数代表透明度( 0(完全透明)-100(不透明) )  
 
    //QPainterPath path;  
    route->moveTo(insideR,0);  
    route->lineTo(outsideR,0);  
    route->arcTo(0-outsideR,0-outsideR,outsideR*2,outsideR*2,0,180);  
    route->lineTo(0-insideR,0);  
    route->arcTo(0-insideR,0-insideR,insideR*2,insideR*2,0,180);  
    route->moveTo(0-insideR,0);  
    route->lineTo(0-outsideR,0);  
    route->arcTo(0-outsideR,0-outsideR,outsideR*2,outsideR*2,180,180);  
    route->lineTo(insideR,0);  
    route->arcTo(0-insideR,0-insideR,insideR*2,insideR*2,180,180);  
    painter->setPen(Qt::NoPen);  
    painter->setBrush(outsideBrushColor);  
    painter->drawPath(*route);  
 
    painter->setBrush(Qt::NoBrush);  
    painter->setPen(outSideColor);  
    painter->drawEllipse( QPointF(0,0),outsideR,outsideR );  
    painter->setBrush(insideBrushColor);  
    painter->setPen(insideColor);  
    painter->drawEllipse( QPointF(0,0),insideR,insideR );  
    painter->setPen(lineColor);  
    QPoint p1(0,  0- outsideR - 10  );  
    QPoint p2(0,  outsideR + 10  );  
    painter->drawLine(p1,p2);  
    painter->rotate(90);  
    painter->drawLine(p1,p2);  
    painter->rotate(-90);  
    delete painter;  
} 

如下用下面的写法则不会闪烁:

void MyClass::paintEvent( QPaintEvent*e)  
{  
    QPainter *painter = new QPainter(this);  
    //画校正图形  
    int insideR = 30;  
    int outsideR = 50;  
    QColor insideColor(237,29,12); //内圆线条颜色  
    QColor outSideColor(237,29,12); //外圆线条颜色  
    QColor lineColor(237,29,12); //直线颜色  
    QColor insideBrushColor(255,0,0,25);//内圆画刷颜色,最后的参数代表透明度( 0(完全透明)-100(不透明) )  
    QColor outsideBrushColor(255,0,0,50);//外圆画刷颜色,最后的参数代表透明度( 0(完全透明)-100(不透明) )  
    QPainterPath path;  
    path.moveTo(insideR,0);  
    path.lineTo(outsideR,0);  
    path.arcTo(0-outsideR,0-outsideR,outsideR*2,outsideR*2,0,180);  
    path.lineTo(0-insideR,0);  
    path.arcTo(0-insideR,0-insideR,insideR*2,insideR*2,0,180);  
    path.moveTo(0-insideR,0);  
    path.lineTo(0-outsideR,0);  
    path.arcTo(0-outsideR,0-outsideR,outsideR*2,outsideR*2,180,180);  
    path.lineTo(insideR,0);  
    path.arcTo(0-insideR,0-insideR,insideR*2,insideR*2,180,180);  
    painter->setPen(Qt::NoPen);  
    painter->setBrush(outsideBrushColor);  
    painter->drawPath(path);  
    painter->setBrush(Qt::NoBrush);  
    painter->setPen(outSideColor);  
    painter->drawEllipse( QPointF(0,0),outsideR,outsideR );  
    painter->setBrush(insideBrushColor);  
    painter->setPen(insideColor);  
    painter->drawEllipse( QPointF(0,0),insideR,insideR );  
    painter->setPen(lineColor);  
    QPoint p1(0,  0- outsideR - 10  );  
    QPoint p2(0,  outsideR + 10  );  
    painter->drawLine(p1,p2);  
    painter->rotate(90);  
    painter->drawLine(p1,p2);  
    painter->rotate(-90);  
    delete painter;  
} 

小结：本文主要介绍了在Qt 窗体的使用，通过Qt 编程点滴介绍，也给自己提高了编程过程中需要注意的细节问题，由于本话题是一节一节为大家展现的，所以更多内容，请看编辑推荐。