常用的三种布局方法：

水平布局类QHBoxLayout
垂直布局类QVBoxLayout
网格布局类QGridLayout

头文件：

include <QHBoxLayout>
include <QVBoxLayout>
include <QGridLayout>

水平布局：

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    QWidget *w = new QWidget;
    QPushButton* button00 = new QPushButton("0");
    QPushButton* button01 = new QPushButton("1");
    QPushButton* button02 = new QPushButton("2");
    QPushButton* button03 = new QPushButton("3");
    QPushButton* button04 = new QPushButton("4");
    QHBoxLayout* layout = new QHBoxLayout();

    layout->addWidget(button00);
    layout->addWidget(button01);
    layout->addWidget(button02);
    layout->addWidget(button03);
    layout->addWidget(button04);

    w->setLayout(layout);
    w->show();
    
    return a.exec();
}

效果图：

1.jpg

垂直布局：

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    QWidget *w = new QWidget;
    QPushButton* button00 = new QPushButton("0");
    QPushButton* button01 = new QPushButton("1");
    QPushButton* button02 = new QPushButton("2");
    QPushButton* button03 = new QPushButton("3");
    QPushButton* button04 = new QPushButton("4");
    QVBoxLayout* layout = new QVBoxLayout();

    layout->addWidget(button00);
    layout->addWidget(button01);
    layout->addWidget(button02);
    layout->addWidget(button03);
    layout->addWidget(button04);

    w->setLayout(layout);
    w->show();
    
    return a.exec();
}

效果图：

2.jpg

网格布局：

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    QWidget *w = new QWidget;
    QPushButton* button00 = new QPushButton("0");
    QPushButton* button01 = new QPushButton("1");
    QPushButton* button02 = new QPushButton("2");
    QPushButton* button03 = new QPushButton("3");
    QPushButton* button04 = new QPushButton("4");
    QPushButton* button05 = new QPushButton("5");
    QPushButton* button06 = new QPushButton("6");
    QPushButton* button07 = new QPushButton("7");
    QPushButton* button08 = new QPushButton("8");
    QPushButton* button09 = new QPushButton("9");

    QGridLayout* layout = new QGridLayout();

    //QGridLayout需指定控件位置,以0开始
    layout->addWidget(button00, 0, 0);
    layout->addWidget(button01, 0, 1);
    layout->addWidget(button02, 0, 2);
    layout->addWidget(button03, 1, 0);
    layout->addWidget(button04, 1, 1);
    layout->addWidget(button05, 1, 2);
    layout->addWidget(button06, 2, 0);
    layout->addWidget(button07, 2, 1);
    layout->addWidget(button08, 2, 2);
    //addWidget的重载,可理解成：从第4行第一位开始，占用3个位置
    layout->addWidget(button09, 3, 0, 3, 3);

    w->setLayout(layout);
    w->show();

    return a.exec();
}

效果图：

3.jpg

嵌套布局：

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    QWidget *w = new QWidget;
    QPushButton* button00 = new QPushButton("0");
    QPushButton* button01 = new QPushButton("1");
    QPushButton* button02 = new QPushButton("2");
    QPushButton* button03 = new QPushButton("3");
    QPushButton* button04 = new QPushButton("4");
    QPushButton* button05 = new QPushButton("5");
    QPushButton* button06 = new QPushButton("6");

    QHBoxLayout* layoutH = new QHBoxLayout();
    QVBoxLayout* layoutV = new QVBoxLayout();

    layoutH->addWidget(button00);
    layoutH->addWidget(button01);
    layoutH->addWidget(button02);
    layoutH->addWidget(button03);

    layoutV->addWidget(button04);
    layoutV->addWidget(button05);
    layoutV->addWidget(button06);

    //将纵向布局layoutV加入到横向布局layoutH中
    layoutH->addLayout(layoutV);
    
    w->setLayout(layoutH);
    w->show();

    return a.exec();
}

效果图：

4.png

当改变顺序时：

    layoutH->addWidget(button00);
    layoutH->addWidget(button01);
    layoutH->addLayout(layoutV); //改变了插入的位置
    layoutH->addWidget(button02);
    layoutH->addWidget(button03);

    layoutV->addWidget(button04);
    layoutV->addWidget(button05);
    layoutV->addWidget(button06);

效果图：

5.jpg

构建子控件时不需指定parent，布局自动指定parent with QWidget::setParent()
布局中的控件是安装此布局的界面的子空间，控件只能以控件作为parent