使用QPainter绘制饼状图，并显示所占百分比

2024-02-13 03:03| 来源: 网络整理| 查看: 265

绘制饼状图qt就有现成的函数来用，要在相应部分的弧形里显示百分比就需要做一点处理。

做法就是在获取扇形二等分线的中点坐标，以这个中点坐标为中心的一个区域再绘制文字。

获取中点坐标使用三角函数即可，半径懂，角度也有，很容易就算出距离，再根据所在的象限添加符号就是坐标了

效果图：

下面上代码

头文件

#include #include #include class ArcWidget : public QWidget { Q_OBJECT public: explicit ArcWidget(QWidget *parent = 0); ~ArcWidget(); protected: void paintEvent(QPaintEvent *e); private: QString getPercentInt(const QString &percentStr); private: QMap m_answerMap; QList m_numList; QList m_answerStrList; int m_nPeopleCount; qreal m_pi = 3.1415; };

cpp文件

#include "arcwidget.h" ArcWidget::ArcWidget(QWidget *parent) : QWidget(parent), m_nPeopleCount(0) { this->resize(600, 600); m_answerMap.insert("A", 3); m_answerMap.insert("B", 5); m_answerMap.insert("C", 8); m_answerMap.insert("D", 2); m_answerStrList = m_answerMap.keys(); m_numList = m_answerMap.values(); foreach (int num, m_numList) { m_nPeopleCount += num; } } ArcWidget::~ArcWidget() { } void ArcWidget::paintEvent(QPaintEvent *e) { QPainter painter(this); painter.setRenderHint(QPainter::Antialiasing, true); painter.setPen(Qt::NoPen); painter.setBrush(Qt::NoBrush); // painter.drawImage(this->rect(),m_bg); QRectF rect(-120, -120, (120 = 90 && middleAngle < 180) { radianNum = (180 - middleAngle)*m_pi/180; } else if(middleAngle >= 180 && middleAngle < 270) { radianNum = (middleAngle - 180)*m_pi/180; } else if(middleAngle >= 270 && middleAngle < 360) { radianNum = (360 - middleAngle)*m_pi/180; } //二等分线的中点距原点的距离 qreal textPosY = 60*sin(radianNum); qreal textPosX = 60*cos(radianNum); //根据二等分线所在的象限确定二等分线的中点坐标 if(middleAngle >= 0 && middleAngle < 90) { textPosY = -textPosY; } else if(middleAngle >= 90 && middleAngle < 180) { textPosX = -textPosX; textPosY = -textPosY; } else if(middleAngle >= 180 && middleAngle < 270) { textPosX = -textPosX; } startAngle += arcLength; QString percentStr = QString::number(percentNum*100 + 0.5); percentStr = getPercentInt(percentStr) + "%"; painter.drawPath(path); painter.setPen(QColor(Qt::white)); painter.drawText(textPosX - 25, textPosY -10, 50, 20, Qt::AlignCenter, percentStr); } painter.setBrush(Qt::NoBrush); painter.setPen(QColor(0, 0, 0)); painter.translate(-220, -255); //绘制右侧的标注栏 QFont ft; ft.setPixelSize(15); painter.setFont(ft); int textStart = 140; foreach (QString answerStr, m_answerStrList) { painter.drawText(350, textStart, 40, 16, Qt::AlignRight, answerStr); textStart += 30; } textStart = 143; painter.setPen(Qt::NoPen); foreach (QColor color, colorList) { painter.setBrush(QBrush(color)); painter.drawRect(402, textStart, 15, 15); textStart += 30; } QWidget::paintEvent(e); } QString ArcWidget::getPercentInt(const QString &percentStr) { QString percentIntStr; for(int i = 0;i < percentStr.size();++i) { if(percentStr.at(i) == '.') { break; } percentIntStr += percentStr.at(i); } return percentIntStr; }

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