Qt 編程繼續為大家講解，還是接著文章 Qt 編程點滴 初學者必看 （6） ，繼續介紹，說編程那些細節。由于本話題是一節一節為大家介紹的，所以更多內容請看末尾編輯推薦。本文基本是用代碼實現的效果，所以并沒有太多的內容。

QPainterPath 畫出的圖形會閃爍的問題：

用下面的寫法畫出的圖形會閃爍

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);  
    //畫校正圖形  
    int insideR = 30;  
    int outsideR = 50;  
    QColor insideColor(237,29,12); //內圓線條顏色  
    QColor outSideColor(237,29,12); //外圓線條顏色  
    QColor lineColor(237,29,12); //直線顏色  
    QColor insideBrushColor(255,0,0,25);//內圓畫刷顏色,最后的參數代表透明度( 0(完全透明)-100(不透明) )  
    QColor outsideBrushColor(255,0,0,50);//外圓畫刷顏色,最后的參數代表透明度( 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;  
} 

如下用下面的寫法則不會閃爍:

void MyClass::paintEvent( QPaintEvent*e)  
{  
    QPainter *painter = new QPainter(this);  
    //畫校正圖形  
    int insideR = 30;  
    int outsideR = 50;  
    QColor insideColor(237,29,12); //內圓線條顏色  
    QColor outSideColor(237,29,12); //外圓線條顏色  
    QColor lineColor(237,29,12); //直線顏色  
    QColor insideBrushColor(255,0,0,25);//內圓畫刷顏色,最后的參數代表透明度( 0(完全透明)-100(不透明) )  
    QColor outsideBrushColor(255,0,0,50);//外圓畫刷顏色,最后的參數代表透明度( 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;  
} 

小結：本文主要介紹了在Qt 窗體的使用，通過Qt 編程點滴介紹，也給自己提高了編程過程中需要注意的細節問題，由于本話題是一節一節為大家展現的，所以更多內容，請看編輯推薦。