c++ - 当窗口大小改变时，如何在 Qt 中自动缩放图表？

Question

我使用 QChart & QGraphicsScene & QGraphicsView 创建了一个图表，但是图表不会在窗口更改时自动放大或缩小。我怎么能那样做？我在 QChart、QGraphicsScene 或 QGraphicsView 类中没有任何信号或插​​槽。我知道我可以使用 QChart & QChartView，但出于某种目的我想要 QChart & QGraphicsScene & QGraphicsView。这是我绘制图表的代码:

void MainWindow::on_actionDraw_Sine_Chart_triggered()
{
    QSplineSeries *spline = new QSplineSeries;

    for (double x = -M_PI; x < M_PI; x += 0.01) {
        spline->append(x, sin(x));
    }

    spline->setName(tr("Sine Curve"));    
    QChart *chart = new QChart;
    chart->addSeries(spline);
    chart->createDefaultAxes();
    chart->axisX()->setRange(-4, 4);
    chart->axisY()->setRange(-1.2, 1.2);
    chart->setGeometry(ui->graphicsView->rect());

    QGraphicsScene *scene = new QGraphicsScene;
    scene->addItem(chart);
    ui->graphicsView->setScene(scene);
}

完整代码可用here .

Answer 1

您必须跟踪 viewport 的大小变化并更改 QChart 的大小，为此我们使用 eventFilter，但是由于这是您需要的另一种方法，图表是该类的属性。

除此之外不建议在one slot中创建场景，而是在constructor中，和QChart一样，然后只添加series。

*.h

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();
    ...
    bool eventFilter(QObject *watched, QEvent *event); // +++
private:
    Ui::MainWindow *ui;
    QChart *chart; // +++
    QGraphicsScene *scene; // +++
};

*.cpp

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    scene = new QGraphicsScene;
    chart = new QChart;
    scene->addItem(chart);
    ui->graphicsView->setScene(scene);
    ui->graphicsView->viewport()->installEventFilter(this);

}

void MainWindow::on_actionDraw_Sine_Chart_triggered(){
    QSplineSeries *spline = new QSplineSeries;

    for (double x = -M_PI; x < M_PI; x += 0.01) {
        spline->append(x, sin(x));
    }
    spline->setName(tr("Sine Curve"));
    chart->addSeries(spline);
}


bool MainWindow::eventFilter(QObject *watched, QEvent *event)
{
    if(watched == ui->graphicsView->viewport() && event->type() == QEvent::Resize){
        if(chart)
            chart->resize(ui->graphicsView->viewport()->size());
    }
    return QMainWindow::eventFilter(watched, event);
}