QT Layout中增删widget与切换界面

背景：以QGroupBox为father widget，用VBoxLayout的布局排版多个checkBox。接下来解决三个问题：
（1）在VBoxLayout中增添checkBox并显示
（2）从VBoxLayout中删除checkBox
（3）切换groupBox中的界面

在QGroupBox中以VBoxLayout添加子widget （checkBox）

失败的案例：

code:

    ui->setupUi(this);    QVBoxLayout layout;    QCheckBox box1("box1");    QCheckBox box2("box2");    QCheckBox box3("box3");    layout.addStretch(1);    layout.addWidget(&box1);    layout.addStretch(1);    layout.addWidget(&box2);    layout.addStretch(1);    layout.addWidget(&box3);    layout.addStretch(1);    wui->groupBox->setLayout(&layout);

关键点：
（1）需要在groupBox中加上一个father widget: widget
（2）设置widget的几何形状和groupBox保持一致，需注意的是widget设置geometry的时候QRect是相对于groupBox而言的。
（3）在widget中以VBoxLayout的方式添加子widget: checkBox ，且要注明checkBox的father widget是widget。
（4）最后要将widget show出来。

    ui->setupUi(this);    QVBoxLayout layout;    QWidget *widget = new QWidget(ui->groupBox);    QRect rect = ui->groupBox->geometry();    rect.setX(0);   // X and Y is related to parent widget    rect.setY(0);    widget->setGeometry(rect);    widget->setWindowTitle("hello");    QCheckBox *box1 = new QCheckBox("box1",widget);     //set box's father is widget    QCheckBox *box2 = new QCheckBox("box2",widget);    QCheckBox *box3 = new QCheckBox("box3",widget);    layout.addStretch(1);    layout.addWidget(box1);     // addStrech means allocate extra space base on factor param    layout.addStretch(2);    layout.addWidget(box2);    layout.addStretch(2);    layout.addWidget(box3);    layout.addStretch(2);    widget->setLayout(&layout);    widget->show(); // show means update layout

checkBox和groupBox的父子关系决定了check能否显示出来，Layout则规定了checbBox显示布局。

从VBoxLayout中删除子widget（checkBox）

在QLayout中有这样一个方法：void QLayout::removeWidget(QWidget * widget)
不过，这只能确保子widget和Layout没有了关系，子widget和父widget还存在关系。所以单纯使用removeWidget不能删除父widget中的子widget，哪怕将Layout删除也不行。如果要删除子widget，必须将子widget从layout和父widget都删除才行。

#include "mainwindow.h"#include "ui_mainwindow.h"#include <QMessageBox>MainWindow::MainWindow(QWidget *parent) :    QMainWindow(parent),    ui(new Ui::MainWindow){   // ...}MainWindow::~MainWindow(){    delete ui;}void MainWindow::on_pushButton_clicked(bool checked){    if(checked){        layout->removeWidget(box1);        layout->removeWidget(box2);        layout->removeWidget(box3);        delete layout;        layout = NULL;        delete box1;        delete box2;        delete box3;    }    else {        layout = new QVBoxLayout();        box1 = new QCheckBox("box1",widget);    //set box's father is widget        box2 = new QCheckBox("box2",widget);        box3 = new QCheckBox("box3",widget);        layout->addStretch(1);        layout->addWidget(box1);    // addStrech means allocate extra space base on factor param        layout->addStretch(2);        layout->addWidget(box2);        layout->addStretch(2);        layout->addWidget(box3);        layout->addStretch(2);        widget->setLayout(layout);    }}

切换groupBox中的界面

还是以上面的例子做说明，假设点击button切换两个checkBox列表，我想保存checkBox的勾选状态并再次显示出来，这应该怎么做呢？
可以做两个父widget，将checkBox放进不同的widget中。再在button的click(bool)事件中通过hide()，show()切换这两个页面。

.h文件

#ifndef MAINWINDOW_H#define MAINWINDOW_H#include <QMainWindow>#include <QCheckBox>#include <QVBoxLayout>#include <QCheckBox>#include <QWidget>namespace Ui {class MainWindow;}class MainWindow : public QMainWindow{    Q_OBJECT    QWidget *widget;    QWidget *widget2;    QCheckBox *box1;    QCheckBox *box2;    QCheckBox *box3;    QCheckBox *box2_1;    QCheckBox *box2_2;    QCheckBox *box2_3;    QVBoxLayout *layout;    QVBoxLayout *layout2;public:    explicit MainWindow(QWidget *parent = 0);    ~MainWindow();    void widget1_init();    void widget2_init();private slots:    void on_pushButton_clicked(bool checked);private:    Ui::MainWindow *ui;};#endif // MAINWINDOW_H

cpp文件：

#include "mainwindow.h"#include "ui_mainwindow.h"#include <QMessageBox>MainWindow::MainWindow(QWidget *parent) :    QMainWindow(parent),    ui(new Ui::MainWindow){    ui->setupUi(this);    layout = new QVBoxLayout();    layout2 = new QVBoxLayout();    widget1_init();    widget2_init();    ui->pushButton->setCheckable(true);}MainWindow::~MainWindow(){    delete ui;}void MainWindow::widget1_init(){    widget = new QWidget();    QRect rect = ui->groupBox->geometry();    rect.setX(0);  // X and Y is related to parent widget    rect.setY(0);    widget->setGeometry(rect);    box1 = new QCheckBox("box1",widget);    //set box's father is widget    box2 = new QCheckBox("box2",widget);    box3 = new QCheckBox("box3",widget);    layout->addStretch(1);    layout->addWidget(box1);    // addStrech means allocate extra space base on factor param    layout->addStretch(2);    layout->addWidget(box2);    layout->addStretch(2);    layout->addWidget(box3);    layout->addStretch(2);    widget->setLayout(layout);}void MainWindow::widget2_init(){    widget2 = new QWidget();    QRect rect = ui->groupBox->geometry();    rect.setX(0);  // X and Y is related to parent widget2    rect.setY(0);    widget2->setGeometry(rect);    box2_1 = new QCheckBox("box2_1",widget2);    //set box's father is widget2    box2_2 = new QCheckBox("box2_2",widget2);    box2_3 = new QCheckBox("box2_3",widget2);    layout2->addStretch(1);    layout2->addWidget(box2_1);    // addStrech means allocate extra space base on factor param    layout2->addStretch(2);    layout2->addWidget(box2_2);    layout2->addStretch(2);    layout2->addWidget(box2_3);    layout2->addStretch(2);    widget2->setLayout(layout2);}void MainWindow::on_pushButton_clicked(bool checked){    if(checked){        widget->setParent(ui->groupBox);        widget->show();        widget2->hide();        ui->groupBox->setTitle("widget");    }    else {        widget->hide();        widget2->setParent(ui->groupBox);        widget2->show();        ui->groupBox->setTitle("widget2");    }}