Qt实现手动切换多种布局的完美方案

#include "manullayoutdialog.h"
#include <QApplication>
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    ManulLayoutDialog w;
    w.show();
    ObjectPooling*m_pool = ObjectPooling::getInstance(9);
    return a.exec();
}

#ifndef OBJECTPOOLING_H
#define OBJECTPOOLING_H
#include <QObject>
#include <QWidget>
#include <QVector>
class ObjectPooling:public QObject
{
    Q_OBJECT
private:
    ObjectPooling(qint32 num);
    ObjectPooling(const ObjectPooling &) = delete;
    ObjectPooling& operator=(const ObjectPooling&)=delete;
public:
    static ObjectPooling *getInstance(qint32 num);
    ~ObjectPooling();
    QWidget* takeOut();
    void putIn(QWidget *pWidget);
    int getSize()const;
private:
    QVector<QWidget*> m_vecWidget;
};
#endif // OBJECTPOOLING_H

#include "objectpooling.h"
#include <qDebug>
ObjectPooling::ObjectPooling(qint32 num):QObject() {
    for(int i = 0; i < num;++i){
        QWidget *pWidget = new QWidget;
        if(pWidget){
            pWidget->setStyleSheet("background-color:back;");
            m_vecWidget.push_back(pWidget);
        }
    }
}
ObjectPooling *ObjectPooling::getInstance(qint32 num)
{
    static ObjectPooling instance(num);
    return &instance;
}
ObjectPooling::~ObjectPooling()
{
    if(m_vecWidget.size()<1)
        return;
    for(auto it = m_vecWidget.begin();it != m_vecWidget.end();++it){
        if(*it){
            delete *it;
            (*it) = nullptr;
        }
    }
    m_vecWidget.clear();
}
QWidget *ObjectPooling::takeOut()
{
    if(m_vecWidget.size()){
       QWidget*pWidget = m_vecWidget.back();
//        qDebug()<<"takeOut-befor : "<<m_vecWidget.size();
        m_vecWidget.pop_back();
//       qDebug()<<"takeOut-back : "<<m_vecWidget.size();
       return pWidget;
    }
    qDebug()<<"对象池没有对象了！！";
    return nullptr;
}
void ObjectPooling::putIn(QWidget *pWidget)
{
    m_vecWidget.push_back(pWidget);
}
int ObjectPooling::getSize() const
{
    return m_vecWidget.size();
}

#ifndef MANULLAYOUTDIALOG_H
#define MANULLAYOUTDIALOG_H
#include <QDialog>
#include "objectpooling.h"
QT_BEGIN_NAMESPACE
namespace Ui {
class ManulLayoutDialog;
}
QT_END_NAMESPACE
class ManulLayoutDialog : public QDialog
{
    Q_OBJECT
public:
    ManulLayoutDialog(QWidget *parent = nullptr);
    ~ManulLayoutDialog();
private:
    void initLayout();
    void clearLastLayout(int n);//n——新的布局中窗口的总数
    void threeColumnLayout(int r,int c);//r——行数，c——列数
private slots:
    void on_pushButton_clicked();
    void on_pushButton_2_clicked();
    void on_pushButton_3_clicked();
    void on_pushButton_4_clicked();
    void on_pushButton_5_clicked();
private:
    Ui::ManulLayoutDialog *ui;
    qint32 m_n;//布局中窗口的总个数
    QVector<QWidget*> m_vecWidget;//保存布局中的窗口
    ObjectPooling* m_pool;
};
#endif // MANULLAYOUTDIALOG_H

#include "manullayoutdialog.h"
#include "ui_manullayoutdialog.h"
#include <QDebug>
ManulLayoutDialog::ManulLayoutDialog(QWidget *parent)
    : QDialog(parent)
    , ui(new Ui::ManulLayoutDialog)
{
    ui->setupUi(this);
    initLayout();
}
ManulLayoutDialog::~ManulLayoutDialog()
{
    for(QWidget *pWidget:m_vecWidget){
        pWidget->setParent(nullptr);//不设置被回收的窗口父对象为空，会被再次释放
        ObjectPooling::getInstance(9)->putIn(pWidget);
    }
    m_vecWidget.clear();
    delete ui;//若被回收的窗口没有设置父对象为空，这里会析构该窗口，回收到对象池后会再次析构
}
void ManulLayoutDialog::initLayout()
{
    QHBoxLayout *pHLayout = new QHBoxLayout(ui->widget);
    pHLayout->setContentsMargins(0,0,0,0);
    QWidget *pWidget = ObjectPooling::getInstance(9)->takeOut();
    pHLayout->addWidget(pWidget);
    m_n = 1;
    m_vecWidget.push_back(pWidget);
    m_pool = ObjectPooling::getInstance(9);
}
void ManulLayoutDialog::clearLastLayout(int n)
{
    QLayout *pLayout = ui->widget->layout();
//    qDebug()<<"移除前的窗口数m_vecWidget: "<<m_vecWidget.size();
    if(m_n>n){
        for(int i =0; i <m_n -n;++i){//趟数
            //移除窗口中的控件，回收到对象池
            QWidget *pWidget = m_vecWidget.back();
            if(pLayout && pWidget){
                qDebug()<<"准备移除窗口===";
                pLayout->removeWidget(pWidget);
                pWidget->setParent(nullptr);
                m_vecWidget.pop_back();
            }
            // if(pLayout){qDebug()<<"布局不为空 ";}
            // if(pWidget){qDebug()<<"窗口不为空 ";}
            // QWidget *fWidget = pWidget->parentWidget();
            ObjectPooling::getInstance(9)->putIn(pWidget);
            // qDebug()<<"对象池窗口数m_vecWidget： "<<ObjectPooling::getInstance(9)->getSize();
            // qDebug()<<"移除后的窗口数m_vecWidget： "<<m_vecWidget.size();
        }
    }else if(m_n <n){
        //为了防止二次重设父对象，先将上一次的父对象清空
        for(auto it = m_vecWidget.begin();it != m_vecWidget.end();++it){
            if(*it){
                (*it)->setParent(nullptr);
            }
        }
        for(int i = 0; i < n-m_n;++i){
            m_vecWidget.push_back(ObjectPooling::getInstance(9)->takeOut());
        }
    }
    //删除窗口原本的布局
    delete pLayout;
    //    ui->widget->setLayout(nullptr);
}
void ManulLayoutDialog::threeColumnLayout(int r, int c)
{
    int total = r*c;
    if(m_n == total){
        return ;
    }
    clearLastLayout(total);
    QGridLayout *pGridLayout = new QGridLayout(ui->widget);
    pGridLayout->setContentsMargins(0,0,0,0);
    for(int i = 0; i < r;++i){
        for(int j = 0; j < c; ++j){
            pGridLayout->addWidget(m_vecWidget[i+j+2*i],i,j);//找下标对应的位置与元素之间的关系
        }
    }
    m_n = total;
}
void ManulLayoutDialog::on_pushButton_clicked()
{
    if(m_n == 1){
        return ;
    }else{
        clearLastLayout(1);
    }
    QHBoxLayout *pHLayout = new QHBoxLayout(ui->widget);
    pHLayout->setContentsMargins(0,0,0,0);
    // qDebug()<<"布局1中的窗口数m_vecWidget： "<<m_vecWidget.size();
    pHLayout->addWidget(m_vecWidget.back());
    m_n = 1;
}
void ManulLayoutDialog::on_pushButton_2_clicked()
{
    if(m_n == 2){
        return ;
    }else if(m_n > 2){
        clearLastLayout(2);
        QHBoxLayout *pLayout = new QHBoxLayout(ui->widget);
        pLayout->setContentsMargins(0,0,0,0);
        for(auto it = m_vecWidget.begin();it != m_vecWidget.end();++it){
            pLayout->addWidget(*it);
        }
    }else{
        QLayout *pLayout = ui->widget->layout();
        QWidget *pWidget = ObjectPooling::getInstance(9)->takeOut();
        pLayout->addWidget(pWidget);
        m_vecWidget.push_back(pWidget);
    }
    m_n = 2;
    // qDebug()<<"布局2中的窗口数m_vecWidget: "<<m_vecWidget.size();
}
void ManulLayoutDialog::on_pushButton_3_clicked()
{
    if(m_n == 4){
        return ;
    }
    clearLastLayout(4);//只能先清理之前的布局，不能与下面的新布局互换位置
    QGridLayout *pGridLayout = new QGridLayout(ui->widget);
    pGridLayout->setContentsMargins(0,0,0,0);
    for(int i = 0; i < 2;++i){
        for(int j = 0; j < 2; ++j){
            pGridLayout->addWidget(m_vecWidget[i+j+i],i,j);//找下标对应的位置与元素之间的关系
        }
    }
    m_n = 4;
}
void ManulLayoutDialog::on_pushButton_4_clicked()
{
    threeColumnLayout(2,3);
}
void ManulLayoutDialog::on_pushButton_5_clicked()
{
    threeColumnLayout(3,3);
}