具体代码示例如下 ：

    QHBoxLayout* hLayout = new QHBoxLayout;
    hLayout->addWidget(new QLabel("444"));
    hLayout->addWidget(new QLineEdit("444"));
    hLayout->addWidget(new QPushButton("444"));

    layout->addLayout(hLayout);

    QHBoxLayout* hLayout2 = new QHBoxLayout;
    hLayout2->addWidget(new QLabel("123"));
    hLayout2->addWidget(new QLineEdit("123"));
    hLayout2->addWidget(new QPushButton("123"));

    layout->addLayout(hLayout2);

    ui->widget->setLayout(layout);

    QHBoxLayout* deleteHLayout = dynamic_cast<QHBoxLayout*>(layout->itemAt(0)->layout());
    if(!deleteHLayout)
        return;

    QLayoutItem* child;
    while((child = deleteHLayout->takeAt(0)) != nullptr)
    {
        delete child->widget(); // 删除对象
        delete child;   // 删除布局
    }

   delete deleteHLayout;

运行效果展示：

完整效果：

删除第一个布局之后效果：