仿记事本；QFile

 widget.cpp

#include "widget.h"
#include "ui_widget.h"
#include "filedialog.h"
#include <QFile>
#include <QDateTime>

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

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


void Widget::on_pushButton_clicked()
{
    //创建文件；
    QFile file;
    file.setFileName(QDateTime::currentDateTime().toString("MMddhhmmss")+".txt");
    
    file.open(QIODevice::ReadWrite);
    
    FileDialog filedialog;
    filedialog.resize(this->size());//设置窗口大小
    filedialog.show();
    filedialog.setModal(true);//不能点击父界面
    filedialog.exec();//让界面一直存在；
    
    //写入文件内容；
    file.write(filedialog.getTextEditContent().toUtf8());
    file.close();
    //判断有没有内容；
    if(filedialog.getTextEditContent().length() == 0)
        file.remove();
    
}

filedialog.cpp

#include "filedialog.h"
#include "ui_filedialog.h"

FileDialog::FileDialog(QWidget *parent) :
    QDialog(parent),
    ui(new Ui::FileDialog)
{

    ui->setupUi(this);
    this->setLayout(ui->verticalLayout);

}

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

QString FileDialog::getTextEditContent()
{
    return ui->textEdit->toPlainText();
}

void FileDialog::on_pushButton_clicked()
{
    this->close();//关闭窗口；
}