Qt QScrollArea and layout in code

一、参考文档：

    . Qt 第六章 QScrollArea类给QWidget添加滚动条

        http://blog.csdn.net/commshare/article/details/6753978

    . 24小时学会QT编程──窗口的缩放和滚动条的使用

        http://blog.163.com/vic_kk/blog/static/4947052420083308325238/

    . QWidget::setLayout: Attempting to set QLayout "" on MainWindow "", which already has a layout

        http://blog.csdn.net/zhuyingqingfen/article/details/6562246

    . QWidget::setLayout: Attempting to set QLayout "" on MainWindow "", which already has a layout

        http://yebaoshan.blog.163.com/blog/static/20423116720126267524060/

二、cat main.cpp

    #include "mainwindow.h"

    #include <QApplication>

    #include <QScrollArea>

    int main(int argc, char *argv[])

    {

        QApplication a(argc, argv);

        MainWindow mainWindow;

        // 加入滚动条

        QScrollArea scrollArea;

        scrollArea.setWidget(&mainWindow);

        scrollArea.show();

        return a.exec();

    }

三、cat mainwindow.cpp

    #include "mainwindow.h"

    #include <QSize>

    #include <QPushButton>

    #include <QHBoxLayout>

    #include <QTextEdit>

    #include <QWidget>

    MainWindow::MainWindow(QWidget *parent)

        : QMainWindow(parent)

    {

        // 设置大小

        this->setMinimumSize(QSize(, ));

        this->setMaximumSize(QSize(, ));

        // 设置标题

        this->setWindowTitle("About");

        QPushButton *button    = new QPushButton("zengjf");

        QTextEdit   *leftEdit  = new QTextEdit(this);

        QTextEdit   *rightEdit = new QTextEdit(this);

        QHBoxLayout *layout    = new QHBoxLayout(this);

        layout->addWidget(leftEdit);

        layout->addWidget(button);

        layout->addWidget(rightEdit);

        QWidget *widget = new QWidget(this);

        widget->setLayout(layout);

        setCentralWidget(widget);

    }

    MainWindow::~MainWindow()

    {

    }