Qt 实现多文档

//mainwindow.h
#include 

private:
    QMdiArea *mdiArea;

//mainwindow.cpp

#include 
MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    mdiArea=new QMdiArea();
    setCentralWidget(mdiArea);
}
MainWindow::~MainWindow()
{
    delete ui;
}
void MainWindow::on_actionA_triggered()
{
    QDialog *dlg=new QDialog();
    mdiArea->addSubWindow(dlg);
    dlg->show();
}