QFile Problem~ "Unknow error" in "open(QIODevice::ReadWrite)"

[fengtian.we]

My Code:

#include <QtGui/QApplication>
#include <QMessageBox>
 
int main(int argc, char *argv[])
{
	QApplication *app=new QApplication(argc, argv);
	QString localFileName="file.text";
	QFile *file=new QFile(localFileName);
	if(file->open(QIODevice::ReadWrite))
	{
		QMessageBox::information(0,"Error: Cannot open["+file->fileName()+"] "+file->errorString());
		return 0;
	}
	return app->exec();
}

#include <QtGui/QApplication>
#include <QMessageBox>

int main(int argc, char *argv[])
{
	QApplication *app=new QApplication(argc, argv);
	QString localFileName="file.text";
	QFile *file=new QFile(localFileName);
	if(file->open(QIODevice::ReadWrite))
	{
		QMessageBox::information(0,"Error: Cannot open["+file->fileName()+"] "+file->errorString());
		return 0;
	}
	return app->exec();
}

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this will output:Error: Cannot open[file.text] Unknow error.

?????? why??