//获取保存路径
    QString savepath = QFileDialog::getSaveFileName(this);
    //创建文件对象
    QFile file(savepath);
    if(!file.open(QIODevice::ReadWrite))    //读写方式打开
    {
        ui->statusBar->showMessage("打开文件失败");
        return;
    }
    QString msg = ui->textEdit->toPlainText();
    //写文件
    file.write(msg.toUtf8());
    file.close();

6-Qt文件操作-读写_哔哩哔哩_bilibili