1.themewidget.h

#ifndef THEMEWIDGET_H
#define THEMEWIDGET_H

#include <QtWidgets/QWidget>
#include <QtCharts/QChartGlobal>

QT_BEGIN_NAMESPACE
class QComboBox;
class QCheckBox;
class Ui_ThemeWidgetForm;
QT_END_NAMESPACE

QT_CHARTS_BEGIN_NAMESPACE
class QChartView;
class QChart;
QT_CHARTS_END_NAMESPACE

typedef QPair<QPointF, QString> Data;
typedef QList<Data> DataList;
typedef QList<DataList> DataTable;

QT_CHARTS_USE_NAMESPACE

class ThemeWidget: public QWidget
{
    Q_OBJECT
public:
    explicit ThemeWidget(QWidget *parent = 0);
    ~ThemeWidget();

private Q_SLOTS:
    void updateUI();

private:
    DataTable generateRandomData(int listCount, int valueMax, int valueCount) const;
    void populateThemeBox();
    void populateAnimationBox();
    void populateLegendBox();
    void connectSignals();
    QChart *createAreaChart() const;
    QChart *createBarChart(int valueCount) const;
    QChart *createPieChart() const;
    QChart *createLineChart() const;
    QChart *createSplineChart() const;
    QChart *createScatterChart() const;

private:
    int m_listCount;
    int m_valueMax;
    int m_valueCount;
    QList<QChartView *> m_charts;
    DataTable m_dataTable;

    Ui_ThemeWidgetForm *m_ui;
};

#endif /* THEMEWIDGET_H */

1）关于QT_CHARTS_USE_NAMESPACE

相当于using namespace QtCharts

2）关于Q_OBJECT

信号和槽是Qt应用开发的基础，它可是将两个毫无关系的对象连接在一起，槽和普通的C++函数是一样的，只是当它和信号连接在一起后，当发送信号的时候，槽会自动被调用。只有加入了Q_OBJECT，你才能使用QT中的signal和slot机制。

3）关于关键字explicit

首先, C++中的explicit关键字只能用于修饰只有一个参数的类构造函数, 它的作用是表明该构造函数是显示的, 而非隐式的, 跟它相对应的另一个关键字是implicit, 意思是隐藏的,类构造函数默认情况下即声明为implicit(隐式)。

显式是强制转换，而隐式是编译器自动转换的，一般同一数据类型（如byte,int,float,double），由低级转为高级为隐式（如int转为float或double），而高级转为低级为强制类型转换，即显式转换，须用户在代码中写的（如float转为int）。

2.ui_Themewidget.h

#ifndef UI_THEMEWIDGET_H
#define UI_THEMEWIDGET_H

#include <QtCore/QVariant>
#include <QtWidgets/QApplication>
#include <QtWidgets/QCheckBox>
#include <QtWidgets/QComboBox>
#include <QtWidgets/QGridLayout>
#include <QtWidgets/QHBoxLayout>
#include <QtWidgets/QLabel>
#include <QtWidgets/QSpacerItem>
#include <QtWidgets/QWidget>

QT_BEGIN_NAMESPACE

class Ui_ThemeWidgetForm
{
public:
　　 //布局管理器
    QGridLayout *gridLayout;
　　 //水平布局
    QHBoxLayout *horizontalLayout;
　　 //标签
    QLabel *themeLabel;
　　 //下拉框
    QComboBox *themeComboBox;
    QLabel *animatedLabel;
    QComboBox *animatedComboBox;
    QLabel *legendLabel;
    QComboBox *legendComboBox;
　　 //复选钮
    QCheckBox *antialiasCheckBox;
　　 //空白区
    QSpacerItem *horizontalSpacer;

    void setupUi(QWidget *ThemeWidgetForm)
    {
        if (ThemeWidgetForm->objectName().isEmpty())
            ThemeWidgetForm->setObjectName(QString::fromUtf8("ThemeWidgetForm"));
        ThemeWidgetForm->resize(900, 600);
        gridLayout = new QGridLayout(ThemeWidgetForm);
        gridLayout->setObjectName(QString::fromUtf8("gridLayout"));
        horizontalLayout = new QHBoxLayout();
        horizontalLayout->setObjectName(QString::fromUtf8("horizontalLayout"));
        themeLabel = new QLabel(ThemeWidgetForm);
        themeLabel->setObjectName(QString::fromUtf8("themeLabel"));

        horizontalLayout->addWidget(themeLabel);

        themeComboBox = new QComboBox(ThemeWidgetForm);
        themeComboBox->setObjectName(QString::fromUtf8("themeComboBox"));

        horizontalLayout->addWidget(themeComboBox);

        animatedLabel = new QLabel(ThemeWidgetForm);
        animatedLabel->setObjectName(QString::fromUtf8("animatedLabel"));

        horizontalLayout->addWidget(animatedLabel);

        animatedComboBox = new QComboBox(ThemeWidgetForm);
        animatedComboBox->setObjectName(QString::fromUtf8("animatedComboBox"));

        horizontalLayout->addWidget(animatedComboBox);

        legendLabel = new QLabel(ThemeWidgetForm);
        legendLabel->setObjectName(QString::fromUtf8("legendLabel"));

        horizontalLayout->addWidget(legendLabel);

        legendComboBox = new QComboBox(ThemeWidgetForm);
        legendComboBox->setObjectName(QString::fromUtf8("legendComboBox"));

        horizontalLayout->addWidget(legendComboBox);

        antialiasCheckBox = new QCheckBox(ThemeWidgetForm);
        antialiasCheckBox->setObjectName(QString::fromUtf8("antialiasCheckBox"));
        antialiasCheckBox->setChecked(false);

        horizontalLayout->addWidget(antialiasCheckBox);

        horizontalSpacer = new QSpacerItem(40, 20, QSizePolicy::Expanding, QSizePolicy::Minimum);

        horizontalLayout->addItem(horizontalSpacer);


        gridLayout->addLayout(horizontalLayout, 0, 0, 1, 3);


        retranslateUi(ThemeWidgetForm);
        QObject::connect(themeComboBox, SIGNAL(currentIndexChanged(int)), ThemeWidgetForm, SLOT(updateUI()));
        QObject::connect(antialiasCheckBox, SIGNAL(toggled(bool)), ThemeWidgetForm, SLOT(updateUI()));
        QObject::connect(legendComboBox, SIGNAL(currentIndexChanged(int)), ThemeWidgetForm, SLOT(updateUI()));
        QObject::connect(animatedComboBox, SIGNAL(currentIndexChanged(int)), ThemeWidgetForm, SLOT(updateUI()));

        QMetaObject::connectSlotsByName(ThemeWidgetForm);
    } // setupUi

    void retranslateUi(QWidget *ThemeWidgetForm)
    {
        themeLabel->setText(QCoreApplication::translate("ThemeWidgetForm", "Theme:", nullptr));
        animatedLabel->setText(QCoreApplication::translate("ThemeWidgetForm", "Animation:", nullptr));
        legendLabel->setText(QCoreApplication::translate("ThemeWidgetForm", "Legend:", nullptr));
        antialiasCheckBox->setText(QCoreApplication::translate("ThemeWidgetForm", "Anti-aliasing", nullptr));
        (void)ThemeWidgetForm;
    } // retranslateUi

};

namespace Ui {
    class ThemeWidgetForm: public Ui_ThemeWidgetForm {};
} // namespace Ui

QT_END_NAMESPACE

#endif // UI_THEMEWIDGET_H