Qt程序，从外部的文本读取汉字存进QString，如何让其转换成unicode：报错

QByteArray text = LoadTxt.readAll();
QTextCodec *codec = QTextCodec::codecForName("GB2312");
QString in = codec->toUnicode(text);

#include <QtCore/QCoreApplication>
#include <QtCore/QFile>
#include <QtCore/QTextStream>
#include <QtCore/QTextCodec>
#include <iostream>
#include <QDebug>
using namespace std;

int main(int argc, char *argv[])
{
	QCoreApplication a(argc, argv);
	QFile file("test.txt");
	if (!file.open(QIODevice::ReadOnly | QIODevice::Text))
	{
		cout << "open error" << endl;
		return -1;
	}
	QTextStream textInput(&file);
	QString lineStr;
	while (!textInput.atEnd())
	{
		textInput.setCodec("utf-8");
		lineStr = textInput.readLine();
		//cout << lineStr.toStdString() << endl;
		qDebug() << lineStr << endl;
	}
	file.close();
	return a.exec();
}

QTextStream::setCodec