QT Layout中增删widget与切换界面

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:

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。

->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 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

​​.h​​文件

#ifndef MAINWINDOW_H#define#include #include #include #include #include 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

​​cpp​​文件：

#include "mainwindow.h"#include "ui_mainwindow.h"#include 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"); }}

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