QT新建文件、打开文件、保存文件

    private slots:
    void calcSlot();
    //新建文件
    void createNewFile();
    //打开文件
    void openFileSlot();
    //保存文件

//新建文件
void MainWindow::createNewFile(){
    //如果当前文档的内容已经改变了
    if(ui->textAreaInput->document()->isModified()){
        qDebug()<<"is aready";
        return;
    }else{
        //qDebug()<<"is null for ecit";
        ui->textAreaInput->clear();
        this->setWindowTitle("新文档.txt");
    }
}

//打开文件
void MainWindow::openFileSlot(){
    QString fileName = QFileDialog::getOpenFileName(this,"Open File",QDir::currentPath());
    //qDebug()<<"文件名是："<<fileName;
    if(fileName.isEmpty()){
        QMessageBox::information(this,"错误消息","请选择一个文件");
        return;
    }
    QFile *file = new QFile;
    file->setFileName(fileName);
    bool openFileOk = file->open(QIODevice::ReadOnly);
    if(openFileOk){
        //文件与文本流相关联
        QTextStream in(file);
        ui->textAreaInput->setText(in.readAll());
        file->close();
        delete file;
    }else{
        QMessageBox::information(this,"错误提示","打开文件失败："+file->errorString());
        return;
    }
}

QObject::connect(ui->equalButton,SIGNAL(clicked()),this,SLOT(calcSlot()));
QObject::connect(ui->createNewAction,SIGNAL(triggered()),this,SLOT(createNewFile()));
QObject::connect(ui->openAction,SIGNAL(triggered()),this,SLOT(openFileSlot()));