Qt入门-文件读写

转自：http://blog.csdn.net/xgbing/article/details/7772953  非常感谢原作者！

二进制文件的读写文件可以使用QFile类、QStream

文本文件的读写建议使用QTextStream类，它操作文件更加方便。

打开文件时，需要参数指定打开文件的模式：

 Constant        Value   Description
 QIODevice::NotOpen  0x0000  The device is not open.
 QIODevice::ReadOnly 0x0001  The device is open for reading.
 QIODevice::WriteOnly    0x0002  The device is open for writing.
 QIODevice::ReadWrite    ReadOnly | WriteOnly    The device is open for reading and writing.
 QIODevice::Append   0x0004  The device is opened in append mode, so that all data is written to the end of the file.
 QIODevice::Truncate 0x0008  If possible, the device is truncated before it is opened. All earlier contents of the device are lost.
 QIODevice::Text 0x0010  When reading, the end-of-line terminators are translated to '\n'. When writing, the end-of-line terminators are translated to the local encoding, for example '\r\n' for Win32.
 QIODevice::Unbuffered   0x0020  Any buffer in the device is bypassed.

QIODevice::Text在读写文本文件时使用，这样可以自动转化换行符为本地换行符。

(1)写入文本文件

 QFile f("c:\\test.txt");
 if(!f.open(QIODevice::WriteOnly | QIODevice::Text))
 {
     cout << "Open failed." << endl;
     return -1;
 }

 QTextStream txtOutput(&f);
 QString s1("123");
 quint32 n1(123);

 txtOutput << s1 << endl;
 txtOutput << n1 << endl;

 f.close();

写入的文件内容为：

123

123

(2)读取文本文件

 QFile f("c:\\test.txt");
 if(!f.open(QIODevice::ReadOnly | QIODevice::Text))
 {
     cout << "Open failed." << endl;
     return -1;
 }

 QTextStream txtInput(&f);
 QString lineStr;
 while(!txtInput.atEnd())
 {
     lineStr = txtInput.readLine();
     cout << lineStr << endl;
 }

 f.close();

屏蔽打印的内容为：

123

123