QChart 画饼图

Qt QChartView 实现如图

Answer

To achieve the desired pie chart display in Qt with percentages shown on each slice, you need to create a QPieSeries, add slices to it, calculate and display the percentage for each slice, and add the series to a QChart. Then, display the chart using a QChartView.

Here’s a detailed example to implement this:

Step-by-Step Implementation

1. Create QPieSeries: Add slices to the QPieSeries.
2. Calculate Percentages: Calculate the percentage of each slice and set the label accordingly.
3. Customize Chart Appearance: Set up the chart title, legend, and other properties.
4. Display the Chart: Use QChartView to display the chart.

Example Code

CustomChartView.h

Define the class to manage the chart and the pie series.

#ifndef CUSTOMCHARTVIEW_H
#define CUSTOMCHARTVIEW_H

#include 
#include 
#include 

QT_CHARTS_USE_NAMESPACE

class CustomChartView : public QChartView {
    Q_OBJECT

public:
    explicit CustomChartView(QWidget* parent = nullptr);
    void updatePieSeriesWithPercentages();

private:
    QChart* chart;
    QPieSeries* pieSeries;
};

#endif // CUSTOMCHARTVIEW_H

CustomChartView.cpp

Implement the logic for creating the pie chart and updating the slice labels with percentages.

#include "CustomChartView.h"
#include 
#include 

CustomChartView::CustomChartView(QWidget* parent)
    : QChartView(new QChart(), parent), chart(chart()) {
    setRenderHint(QPainter::Antialiasing);

    // Set up the pie series
    pieSeries = new QPieSeries();
    pieSeries->append("Advanced Digital Camera", 13);
    pieSeries->append("Full Frame Digital Camera", 12);
    pieSeries->append("Independent Filmmaker Camcorder", 22);
    pieSeries->append("Lens Adapter", 2);
    pieSeries->append("Macro Zoom Lens", 2);
    pieSeries->append("Slim Digital Camera", 8);
    pieSeries->append("SLR Digital Camera", 39);
    pieSeries->append("USB Cable", 3);

    // Add the series to the chart
    chart->addSeries(pieSeries);
    chart->setTitle("Chart Title");

    // Customize the legend
    chart->legend()->setVisible(true);
    chart->legend()->setAlignment(Qt::AlignRight);

    // Update the pie series to show percentages
    updatePieSeriesWithPercentages();
}

void CustomChartView::updatePieSeriesWithPercentages() {
    // Calculate the total value of all slices
    qreal totalValue = 0;
    for (const QPieSlice* slice : pieSeries->slices()) {
        totalValue += slice->value();
    }

    // Update each slice's label to show the percentage
    for (QPieSlice* slice : pieSeries->slices()) {
        qreal percentage = (slice->value() / totalValue) * 100;
        slice->setLabel(QString("%1 %2%").arg(slice->label()).arg(percentage, 0, 'f', 0));
    }
}

main.cpp

Set up the main application to display the chart.

#include 
#include 
#include "CustomChartView.h"

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

    QMainWindow window;
    CustomChartView* chartView = new CustomChartView(&window);

    window.setCentralWidget(chartView);
    window.resize(800, 600);
    window.show();

    return a.exec();
}

Explanation

1. CustomChartView Class:

   • The CustomChartView class inherits from QChartView and manages the pie chart and pie series.
   • The constructor sets up the pie series with example data and updates the labels to show percentages.

2. updatePieSeriesWithPercentages Method:

   • This method calculates the total value of all slices.
   • It then iterates over each slice, calculates its percentage, and updates the label to include the percentage.
   • slice->setLabel is used to update the label, formatted with the original label and the calculated percentage.

3. Main Application:

   • The main application creates an instance of CustomChartView and sets it as the central widget of the main window.

This setup will create a pie chart with each slice labeled with both its name and its percentage of the total. The labels will be formatted to show no decimal places for the percentage. You can adjust the formatting as needed for your specific requirements.

Additional Customizations

You can further customize the appearance and behavior of the chart and slices, such as:

• Exploding Slices: Highlight a particular slice.
• Changing Colors: Customize slice colors.
• Interactivity: Add hover and click events for slices.

Example of Additional Customizations

void CustomChartView::updatePieSeriesWithPercentages() {
    // Calculate the total value of all slices
    qreal totalValue = 0;
    for (const QPieSlice* slice : pieSeries->slices()) {
        totalValue += slice->value();
    }

    // Update each slice's label to show the percentage
    for (QPieSlice* slice : pieSeries->slices()) {
        qreal percentage = (slice->value() / totalValue) * 100;
        slice->setLabel(QString("%1 %2%").arg(slice->label()).arg(percentage, 0, 'f', 0));

        // Customize each slice
        slice->setLabelVisible(true);
        slice->setPen(QPen(Qt::black, 1));
        slice->setBrush(QBrush(Qt::lightGray));

        // Example of exploding a particular slice
        if (slice->label().contains("SLR Digital Camera")) {
            slice->setExploded(true);
            slice->setBrush(QBrush(Qt::red));
        }
    }
}

This example adds further customization to each slice, making the chart more interactive and visually appealing.

want t ---> slice->setLabel only show percentage

If you want each slice's label to only show the percentage without the category name, you can update the updatePieSeriesWithPercentages method to set the label accordingly. Here's how you can modify the existing implementation to achieve this:

Updated Example Code

CustomChartView.h

No changes needed here.

CustomChartView.cpp

Update the updatePieSeriesWithPercentages method to set the label to only display the percentage.

cpp

#include "CustomChartView.h"
#include 
#include 

CustomChartView::CustomChartView(QWidget* parent)
    : QChartView(new QChart(), parent), chart(chart()) {
    setRenderHint(QPainter::Antialiasing);

    // Set up the pie series
    pieSeries = new QPieSeries();
    pieSeries->append("Advanced Digital Camera", 13);
    pieSeries->append("Full Frame Digital Camera", 12);
    pieSeries->append("Independent Filmmaker Camcorder", 22);
    pieSeries->append("Lens Adapter", 2);
    pieSeries->append("Macro Zoom Lens", 2);
    pieSeries->append("Slim Digital Camera", 8);
    pieSeries->append("SLR Digital Camera", 39);
    pieSeries->append("USB Cable", 3);

    // Add the series to the chart
    chart->addSeries(pieSeries);
    chart->setTitle("Chart Title");

    // Customize the legend
    chart->legend()->setVisible(true);
    chart->legend()->setAlignment(Qt::AlignRight);

    // Update the pie series to show percentages
    updatePieSeriesWithPercentages();
}

void CustomChartView::updatePieSeriesWithPercentages() {
    // Calculate the total value of all slices
    qreal totalValue = 0;
    for (const QPieSlice* slice : pieSeries->slices()) {
        totalValue += slice->value();
    }

    // Update each slice's label to show only the percentage
    for (QPieSlice* slice : pieSeries->slices()) {
        qreal percentage = (slice->value() / totalValue) * 100;
        slice->setLabel(QString("%1%").arg(percentage, 0, 'f', 0));

        // Optional: Customize each slice
        slice->setLabelVisible(true);
        slice->setPen(QPen(Qt::black, 1));
        slice->setBrush(slice->color());  // Keep the default color
    }
}

cpp

main.cpp

No changes needed here.

Explanation

1. CustomChartView Class:

   • The CustomChartView class inherits from QChartView and manages the pie chart and pie series.
   • The constructor sets up the pie series with example data and updates the labels to show percentages.

2. updatePieSeriesWithPercentages Method:

   • This method calculates the total value of all slices.
   • It then iterates over each slice, calculates its percentage, and updates the label to include only the percentage.
   • slice->setLabel is used to update the label, formatted to show the percentage with no decimal places.
   • The label is made visible, and the slice's pen and brush are optionally customized.

3. Main Application:

   • The main application creates an instance of CustomChartView and sets it as the central widget of the main window.

This setup will create a pie chart with each slice labeled only with its percentage of the total. The labels will be formatted to show no decimal places for the percentage. You can adjust the formatting as needed for your specific requirements.

Want to -->1, only show the percentage on the pie slice. And 2, on AlignRight, only show the whole name

I apologize for the mistake. Let's correct it properly. The issue arises because we overwrite the slice's label with the percentage, and we need to preserve the original label (the name) for the legend.

Here's a revised approach:

1. Set the slice's label to the percentage.
2. Set the legend label manually to the original name.

Corrected Example Code

CustomChartView.h

No changes needed here.

CustomChartView.cpp

Update the updatePieSeriesWithPercentages method and ensure the legend labels are set correctly.

#include "CustomChartView.h"
#include 
#include 

CustomChartView::CustomChartView(QWidget* parent)
    : QChartView(new QChart(), parent), chart(chart()) {
    setRenderHint(QPainter::Antialiasing);

    // Set up the pie series
    pieSeries = new QPieSeries();
    pieSeries->append("Advanced Digital Camera", 13);
    pieSeries->append("Full Frame Digital Camera", 12);
    pieSeries->append("Independent Filmmaker Camcorder", 22);
    pieSeries->append("Lens Adapter", 2);
    pieSeries->append("Macro Zoom Lens", 2);
    pieSeries->append("Slim Digital Camera", 8);
    pieSeries->append("SLR Digital Camera", 39);
    pieSeries->append("USB Cable", 3);

    // Add the series to the chart
    chart->addSeries(pieSeries);
    chart->setTitle("Chart Title");

    // Customize the legend
    chart->legend()->setVisible(true);
    chart->legend()->setAlignment(Qt::AlignRight);

    // Update the pie series to show percentages
    updatePieSeriesWithPercentages();
}

void CustomChartView::updatePieSeriesWithPercentages() {
    // Calculate the total value of all slices
    qreal totalValue = 0;
    for (const QPieSlice* slice : pieSeries->slices()) {
        totalValue += slice->value();
    }

    // Update each slice's label to show only the percentage
    int index = 0;
    for (QPieSlice* slice : pieSeries->slices()) {
        qreal percentage = (slice->value() / totalValue) * 100;
        QString originalLabel = slice->label();
        slice->setLabel(QString("%1%").arg(percentage, 0, 'f', 0));
        chart->legend()->markers(pieSeries).at(index++)->setLabel(originalLabel);
        
        // Optional: Customize each slice
        slice->setLabelVisible(true);
        slice->setPen(QPen(Qt::black, 1));
        slice->setBrush(slice->color());  // Keep the default color
    }
}

Explanation

1. CustomChartView Class:

   • The CustomChartView class inherits from QChartView and manages the pie chart and pie series.
   • The constructor sets up the pie series with example data and updates the labels to show percentages.

2. updatePieSeriesWithPercentages Method:

   • This method calculates the total value of all slices.
   • It then iterates over each slice, calculates its percentage, and updates the label to include only the percentage.
   • While updating the slice label, it preserves the original label (the name) and sets it to the legend marker.
   • The slice label is updated to show only the percentage.
   • The label is made visible, and the slice's pen and brush are optionally customized.

3. Main Application:

   • The main application creates an instance of CustomChartView and sets it as the central widget of the main window.

This corrected setup ensures that each pie slice is labeled with its percentage of the total, and the legend on the right displays the full names of the slices. This approach keeps the chart clear and informative.

Reference:

c++ - 在 Qt 饼图中显示百分比？ - IT工具网 (coder.work)