QTChart沒有填滿整個ChartView導致鏡像效果

我基本上是在嘗試在 Qt 中制作甘特圖。我打算在影像上繪制條形圖。我可以在圖表的開頭繪制一個條形（綠色），但我也可以在靠近圖表末尾的地方繪制第二個條形（綠色）。我認為 Chart 的可繪制區域沒有填滿整個 ChartView，因此它正在對缺失的資料進行某種重復填充（可能？）。希望有人能告訴我我做錯了什么。QT 版本 5.15.0。

    ui.setupUi(parent);
    QGridLayout *gridLayout = new QGridLayout(ui.widget);

    //Build a series to add to the chart
    QtCharts::QLineSeries *series = new QtCharts::QLineSeries();
    *series << QPointF(11, 1) << QPointF(13, 3) << QPointF(17, 6) << QPointF(18, 3) << QPointF(20, 2);

    //Create a chart object and format
    QtCharts::QChart *chart = new QtCharts::QChart();
    chart->legend()->hide();
    chart->addSeries(series);
    chart->createDefaultAxes();

    chart->axes(Qt::Vertical).first()->setGridLineVisible(false);
    chart->axes(Qt::Horizontal).first()->setGridLineVisible(false);

    // ===== CHART VIEWER ===== //
    // Create a Chart Viewer:
    QtCharts::QChartView* chartView = new QtCharts::QChartView();
    // Add widget to GUI:
    gridLayout->addWidget(chartView);
    //Add the chart to the view widget
    chartView->setChart(chart);
    chartView->setRenderHint(QPainter::Antialiasing, true);

    //Note: Since we added the chart to the view we can now
    //scale and translate the image appropriately. The chart
    //has an appropriate size.

    //Grab the size of the plot and view areas
    chart->setPlotArea(QRectF());

    int width = static_cast<int>(chart->plotArea().width());
    int height = static_cast<int>(chart->plotArea().height());
    int ViewW = static_cast<int>(chartView->width());
    int ViewH = static_cast<int>(chartView->height());

    //We have to translate the image because setPlotAreaBackGround
    //starts the image in the top left corner of the view not the
    //plot area. So, to offset we will make a new image the size of
    //view and offset our image within that image with white
    QImage translated(ViewW, ViewH, QImage::Format_ARGB32);
    translated.fill(Qt::gray);
    QPainter painter(&translated);
    QPointF TopLeft = chart->plotArea().topLeft();
    QPointF BotRight = chart->plotArea().bottomRight();
    painter.fillRect(TopLeft.x(), TopLeft.y(), 10, BotRight.y() - TopLeft.y(), Qt::green);

    //Display image in background
    chart->setPlotAreaBackgroundBrush(translated);
    chart->setPlotAreaBackgroundVisible(true);

uj5u.com熱心網友回復：

我做了兩個改變：

1. 在槽函式中繪制背景。
2. 發出 slotAreaChanged 信號。

這是代碼

#include<QGridLayout>
#include<QLineSeries>
#include<QChartView>
#include<QChart>
#include<QApplication>

int main()
{
    int a = 0;
    QApplication b(a, nullptr);
    QWidget w;
    QGridLayout* gridLayout = new QGridLayout();

    //Build a series to add to the chart
    QtCharts::QLineSeries* series = new QtCharts::QLineSeries();
    *series << QPointF(11, 1) << QPointF(13, 3) << QPointF(17, 6) << QPointF(18, 3) << QPointF(20, 2);

    //Create a chart object and format
    QtCharts::QChart* chart = new QtCharts::QChart();
    chart->legend()->hide();
    chart->addSeries(series);
    chart->createDefaultAxes();

    chart->axes(Qt::Vertical).first()->setGridLineVisible(false);
    chart->axes(Qt::Horizontal).first()->setGridLineVisible(false);

    // ===== CHART VIEWER ===== //
    // Create a Chart Viewer:
    QtCharts::QChartView* chartView = new QtCharts::QChartView();
    // Add widget to GUI:
    gridLayout->addWidget(chartView);
    //Add the chart to the view widget
    chartView->setChart(chart);
    chartView->setRenderHint(QPainter::Antialiasing, true);

    //Note: Since we added the chart to the view we can now
    //scale and translate the image appropriately. The chart
    //has an appropriate size.

    //Grab the size of the plot and view areas
    chart->setPlotArea(QRectF());

    QObject::connect(chart, &QtCharts::QChart::plotAreaChanged, [&](const QRectF& plotArea) {

    int width = static_cast<int>(chart->plotArea().width());
    int height = static_cast<int>(chart->plotArea().height());
    int ViewW = static_cast<int>(chartView->width());
    int ViewH = static_cast<int>(chartView->height());

    //We have to translate the image because setPlotAreaBackGround
    //starts the image in the top left corner of the view not the
    //plot area. So, to offset we will make a new image the size of
    //view and offset our image within that image with white
    QImage translated(ViewW, ViewH, QImage::Format_ARGB32);
    translated.fill(Qt::gray);
    QPainter painter(&translated);
    QPointF TopLeft = chart->plotArea().topLeft();
    QPointF BotRight = chart->plotArea().bottomRight();
    painter.fillRect(TopLeft.x(), TopLeft.y(), 10, BotRight.y() - TopLeft.y(), Qt::green);

    //Display image in background
    chart->setPlotAreaBackgroundBrush(translated);
    chart->setPlotAreaBackgroundVisible(true);
});
    w.setLayout(gridLayout);
    chart->plotAreaChanged(QRectF());
    w.show();
    return b.exec();
}

標籤：C qt 甘特图 qtcharts

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