用Qt的GraphicsItem 自绘一个QLinedit

以下是一个使用Qt的GraphicsItem自绘QLinedit的示例代码：

#include <QGraphicsItem>
#include <QPainter>
#include <QLineEdit>

class CustomLineEdit : public QGraphicsItem
{
public:
    CustomLineEdit(QGraphicsItem *parent = nullptr)
        : QGraphicsItem(parent)
    {
        m_lineEdit.setParent(nullptr);
        m_lineEdit.installEventFilter(this);
    }

    QRectF boundingRect() const override
    {
        return QRectF(0, 0, 100, 20);
    }

    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget) override
    {
        Q_UNUSED(option)
        Q_UNUSED(widget)
        painter->setPen(Qt::black);
        painter->drawRect(boundingRect());

        QRectF textRect = boundingRect().adjusted(2, 2, -2, -2);
        painter->setFont(m_lineEdit.font());
        painter->drawText(textRect, m_lineEdit.text());
    }

    bool eventFilter(QObject *obj, QEvent *event) override
    {
        if (obj == &m_lineEdit && event->type() == QEvent::TextEdited)
        {
            update();
            return true;
        }
        return false;
    }

private:
    QLineEdit m_lineEdit;
};

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);

    QGraphicsScene scene;
    CustomLineEdit *customLineEdit = new CustomLineEdit();
    scene.addItem(customLineEdit);
    customLineEdit->setPos(20, 20);

    QGraphicsView view(&scene);
    view.show();

    return app.exec();
}

在这个示例中，我们创建了一个名为CustomLineEdit的自定义GraphicsItem，它继承自QGraphicsItem。在CustomLineEdit的构造函数中，我们创建了一个QLineEdit，并使用eventFilter来捕获TextEdit的文本编辑事件，并在其上绘制文本。在paint函数中，我们使用QPainter来绘制一个矩形和文本。CustomLineEdit的boundingRect函数返回矩形的大小。最后，我们将CustomLineEdit添加到QGraphicsScene中并在QGraphicsView中显示它。