Qt---为窗体添加滚动条：QScrollArea

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include 
#include 

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    //滚动区域
    QScrollArea *s = new QScrollArea(this);
    s->setGeometry(0, 0, 200, 200);
    //垂直滚动条不可见，只能通过鼠标滑动
    s->setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);

    //窗体1，其父窗体为滚动区域
    QWidget *w = new QWidget(s);
    //设置滚动区域的窗体
    s->setWidget(w);
    w->setGeometry(0, 0, 300, 300);

    //在窗体1上添加按钮
    QPushButton *btn = new QPushButton(w);
    btn->setText("123");
    btn->move(230, 130);
}

MainWindow::~MainWindow()
{
    delete ui;
}