一、简介

本文基于QGroupBox扩展了一种可以伸缩的组合框，正常状态下，组合框处于收缩状态，内部的控件是隐藏的；需要的时候，可以将组合框进行伸展，并将内部控件显示出来。

二、主要思路

实现的代码比较简单，主要有以下几点：
1、该组合框继承于QGroupBox;

2、将QGroupBox的可选择属性setCheckable设置为true

3、通过QGroupBox的setFlat函数显示隐藏垂直边框

4、根据QGroupBox的点击事件判断其展开还是收缩

5、右侧的展开或缩放的样式是一个Label，通过设置相对布局实现，“+”“-”均为字符串；边框是使用QSS样式

三、显示效果

四、代码

extendedgroupbox.h

#ifndef EXTENDEDGROUPBOX_H
#define EXTENDEDGROUPBOX_H
#include <QGroupBox>
#include <QLabel>
#include <QMouseEvent>
#include <QWidget>
class QClickableLabel;
class ExtendedGroupBox : public QGroupBox {
    Q_OBJECT
public:
    enum State {
        STATE_NORMAL,
        STATE_EXPAND
    };
    ExtendedGroupBox(QWidget* parent = nullptr, State state = STATE_EXPAND);
    ExtendedGroupBox(const QString& title, QWidget* parent = nullptr, 
                     State state = STATE_EXPAND);
private:
    void init(State state);
    void setLabelInfo();
    void slotOnChecked();
    void hidenWidget(bool isVisible);
    void setLabelGeometry(QSize size);
protected:
    void resizeEvent(QResizeEvent* event) override;
public:
    State getState() const;
private:
    QClickableLabel* clickedLabel;
    // 存放要隐藏的控件的名称（通过 QWidget->metaObject()->className()）
    QList<QString> hideWidgets_;
    // 点击状态
    State state_;
};
// QLabel增加点击事件
class QClickableLabel : public QLabel {
    Q_OBJECT
public:
    using QLabel::QLabel;
    ~QClickableLabel() { }
signals:
    void clicked();
protected:
    void mousePressEvent(QMouseEvent* ev) override
    {
        if (ev->button() == Qt::LeftButton) {
            emit clicked();
        }
    }
};
#endif // EXTENDEDGROUPBOX_H

extendedgroupbox.cpp

#include "extendedgroupbox.h"
#include <QDebug>
#include <QLabel>
#include <QLayout>
ExtendedGroupBox::ExtendedGroupBox(QWidget* parent, State state)
    : QGroupBox(parent)
{
    init(state);
}
ExtendedGroupBox::ExtendedGroupBox(const QString& title, QWidget* parent, State state)
    : QGroupBox(title, parent)
{
    init(state);
}
// 初始化
void ExtendedGroupBox::init(State state)
{
    state_ = state;
    hideWidgets_ = { "QLabel", "QLineEdit", "QComboBox", "QGroupBox", "ExtendedGroupBox" };
    // 添加label
    setLabelInfo();
    // 设置选中状态
    this->setCheckable(true);
    if (state_ == STATE_NORMAL) {
        this->setFlat(true);
        this->setChecked(false);
        clickedLabel->setText("-");
    } else {
        this->setFlat(false);
        this->setChecked(true);
        clickedLabel->setText("+");
    }
    connect(clickedLabel, &QClickableLabel::clicked, this, &ExtendedGroupBox::slotOnChecked);
    connect(this, &ExtendedGroupBox::clicked, this, &ExtendedGroupBox::slotOnChecked);
}
// 设置label的信息
void ExtendedGroupBox::setLabelInfo()
{
    clickedLabel = new QClickableLabel(this);
    clickedLabel->setFixedSize(13, 13);
    clickedLabel->setStyleSheet("border:1px solid black");
    clickedLabel->setAlignment(Qt::AlignHCenter);
    setLabelGeometry(this->size());
    QFont font;
    font.setWeight(13);
    clickedLabel->setFont(font);
}
// 根据点击状态显示隐藏QGroupBox的控件
void ExtendedGroupBox::slotOnChecked()
{
    bool checked = state_ == STATE_NORMAL;
    if (checked) {
        //显示垂直边框
        this->setFlat(false);
        clickedLabel->setText("+");
        hidenWidget(true);
        state_ = STATE_EXPAND;
    } else {
        //隐藏垂直边框
        this->setFlat(true);
        clickedLabel->setText("-");
        hidenWidget(false);
        state_ = STATE_NORMAL;
    }
}
// 显示或隐藏QGroupBox里的控件
void ExtendedGroupBox::hidenWidget(bool isVisible)
{
    for (QObject* child : this->children()) {
        QWidget* widget = static_cast<QWidget*>(child);
        QString className = widget->metaObject()->className();
        if (widget != nullptr && hideWidgets_.contains(className)) {
            widget->setVisible(isVisible);
        }
    }
}
// 设置label的位置
void ExtendedGroupBox::setLabelGeometry(QSize size)
{
    int width = size.width() - 30;
    clickedLabel->setGeometry(width, 0, 13, 13);
}
//  窗口大小改变时更新label的位置
void ExtendedGroupBox::resizeEvent(QResizeEvent*)
{
    setLabelGeometry(this->size());
}
// 返回展开状态
ExtendedGroupBox::State ExtendedGroupBox::getState() const
{
    return state_;
}

widget.h

#ifndef WIDGET_H
#define WIDGET_H
#include <QWidget>
class ExtendedGroupBox;
class Widget : public QWidget {
    Q_OBJECT
public:
    Widget(QWidget* parent = nullptr);
    ~Widget();
private:
    ExtendedGroupBox* groupBox;
};
#endif // WIDGET_H

widget.cpp

#include "widget.h"
#include "extendedgroupbox.h"
#include <QFormLayout>
#include <QGroupBox>
#include <QLayout>
#include <QLineEdit>
Widget::Widget(QWidget* parent)
    : QWidget(parent)
{
    this->resize(350, 200);
    this->setWindowTitle("A collapsible GroupBox");
    QVBoxLayout* mainLayout = new QVBoxLayout(this);
    this->setLayout(mainLayout);
    groupBox = new ExtendedGroupBox("title", parent);
    mainLayout->addWidget(groupBox);
    QFormLayout* groupLayout = new QFormLayout(groupBox);
    groupBox->setLayout(groupLayout);
    QLabel* label1 = new QLabel("group1", groupBox);
    QLineEdit* lineEdit1 = new QLineEdit(groupBox);
    QLabel* label2 = new QLabel("group2", groupBox);
    QLineEdit* lineEdit2 = new QLineEdit(groupBox);
    groupLayout->addRow(label1, lineEdit1);
    groupLayout->addRow(label2, lineEdit2);
}
Widget::~Widget()
{
}

五、项目代码

ExtendedGroupBox.zip

六、参考链接

https://www.cnblogs.com/jiangbin/p/6752957.html