QTextStream文本流

用法

QTextStream()  
QTextStream(QIODevice *device)  
QTextStream(FILE *fileHandle, 
            QIODevice::OpenMode openMode = QIODevice::ReadWrite)  
QTextStream(QString *string, 
            QIODevice::OpenMode openMode = QIODevice::ReadWrite)  
QTextStream(QByteArray *array,
            QIODevice::OpenMode openMode = QIODevice::ReadWrite)  
QTextStream(const QByteArray &array,
            QIODevice::OpenMode openMode = QIODevice::ReadOnly)  

例子：

QFile data("output.txt");
if (data.open(QFile::WriteOnly | QFile::Truncate)) {
    QTextStream out(&data);
    out << "Result: " << qSetFieldWidth(10) << left << 3.14 << 2.7;
    // writes "Result: 3.14      2.7       "
}

需要格外注意的是，如果使用了运算符重载<<进行数据写入，需要用.flush()方法来刷新缓存才能成功写入。