QTDesigner的QVBoxLayout自动随窗口拉伸

在MainWindow的构造函数中添加如下代码：
//设置Ui
ui.setupUi(this);

//使Ui可自适应父窗口大小
QVBoxLayout* mainLayout = new QVBoxLayout;
mainLayout->addWidget(ui.verticalLayoutWidget);
setLayout(mainLayout);

或

MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
QVBoxLayout* mainLayout = new QVBoxLayout;
mainLayout->addWidget(ui->verticalLayoutWidget);
ui->centralWidget->setLayout(mainLayout);
}
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