qt 重写继承QGraphicsView类显示直方图

可以使用QGraphicsScene和QGraphicsRectItem来实现直方图的显示，具体实现可以参考以下代码：

class HistogramView : public QGraphicsView {
public:
    HistogramView(QWidget *parent = nullptr) : QGraphicsView(parent) {
        setScene(new QGraphicsScene(this));
    }

    void setHistogram(const QVector<int> &data) {
        scene()->clear();

        int maxValue = *std::max_element(data.constBegin(), data.constEnd());

        int barWidth = 20;
        int barSpacing = 5;
        int x = 0;

        for (int value : data) {
            int barHeight = (int)(height() * ((double)value / maxValue));
            QGraphicsRectItem *bar = new QGraphicsRectItem(x, height() - barHeight, barWidth, barHeight);
            bar->setBrush(QBrush(Qt::blue));
            scene()->addItem(bar);
            x += barWidth + barSpacing;
        }

        setSceneRect(0, 0, x - barSpacing, height());
    }
};

使用方法：

HistogramView *view = new HistogramView();
view->setHistogram({1, 2, 3, 4, 5});
view->show();

这样就可以在窗口中显示一个简单的直方图了。