c++ - Qt橡皮筋未绘制

我正在尝试建立橡皮筋。这是我的代码。

void TOTMain::mousePressEvent(QMouseEvent * event)
{
    QPoint origin = event->pos();
    _selectionSquare = new QRubberBand(QRubberBand::Rectangle, this);
    _selectionSquare->setGeometry(QRect(origin, QSize()));
    _selectionSquare->raise();
    _selectionSquare->show();
}

void TOTMain::mouseMoveEvent(QMouseEvent *event)
{
    QPoint origin = event->pos();
    _selectionSquare->setGeometry(QRect(origin, event->pos()).normalized());
}

void TOTMain::mouseReleaseEvent(QMouseEvent *event)
{
    _selectionSquare->hide();
    // determine selection, for example using QRect::intersects()
    // and QRect::contains().
}

问题是没有绘制乐队。我确认它正在构建并且在拖动过程中仍然存在，但是没有渲染。

任何想法表示赞赏。

最佳答案

看看您的mouseMoveEvent实现...

void TOTMain::mouseMoveEvent(QMouseEvent *event)
{
    QPoint origin = event->pos();
    _selectionSquare->setGeometry(QRect(origin, event->pos()).normalized());
}

您将橡皮筋的几何形状设置为QRect(origin, event->pos())，但是之前已将origin = event->pos()设置为矩形的左上角和右下角相同。

使origin成为您类的成员变量变量（未经测试）...

class TOTMain: public QWidget {
public:
protected:
    virtual void mousePressEvent (QMouseEvent *event) override
    {
        _origin = event->pos();
        _selectionSquare = new QRubberBand(QRubberBand::Rectangle, this);
        _selectionSquare->setGeometry(QRect(_origin, QSize()));
        _selectionSquare->raise();
        _selectionSquare->setStyleSheet("{ background-color : red; }");
        _selectionSquare->show();
    }
    virtual void mouseMoveEvent (QMouseEvent *event) override
    {
        _selectionSquare->setGeometry(QRect(_origin, event->pos()).normalized());
    }
    virtual void mouseReleaseEvent (QMouseEvent *event) override
    {
        _selectionSquare->hide();
        // determine selection, for example using QRect::intersects()
        // and QRect::contains().
    }
private:
    QPoint       _origin;
    QRubberBand *_selectionSquare = nullptr;
};

关于c++ - Qt橡皮筋未绘制，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/58523864/