Qt中文件写入和读取

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1.写入数据到文件

    //writetext    QFile file("./test.txt");    file.open( QIODevice::ReadWrite | QIODevice::Append);    QTextStream out(&file);    if(!ui->lineEdit->text().isEmpty() && !ui->lineEdit_2->text().isEmpty()){        out << ui->lineEdit->text();        out << ":";        out << ui->lineEdit_2->text();        out << "\n";    }    file.close();

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2.从文件中读取数据

    QFile file("./test.txt");    if(!file.open(QIODevice::ReadOnly))    {         return;    }    QTextStream in(&file);    while(!in.atEnd()){        QString onecount = in.readLine();        QStringList userpwd = onecount.split(':');        qDebug() << userpwd.at(0) << "--" << userpwd.at(1);    }    file.close();

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3.通过单个json对象形式写入

//头文件#include<QJsonArray>#include<QJsonObject>#include<QJsonDocument>#include<QByteArray>#include<QDebug>#include<QJsonParseError>//写入    QFile file("./test.txt");    file.open( QIODevice::ReadWrite | QIODevice::Append);    QTextStream out(&file);    if(!ui->lineEdit->text().isEmpty() && !ui->lineEdit_2->text().isEmpty()){        QJsonObject json;        json.insert("name",ui->lineEdit->text());        json.insert("pwd",ui->lineEdit_2->text());        QJsonDocument document1;        document1.setObject(json);        QByteArray byteArray = document1.toJson(QJsonDocument::Compact);        QString strJson(byteArray);        out << strJson;        out << "\n";    }    file.close();//读取    QFile file("./test.txt");    if(!file.open(QIODevice::ReadOnly))    {         return;    }    QTextStream in(&file);    while(!in.atEnd()){        QString onecount = in.readLine();        QByteArray byteArray = onecount.toLocal8Bit();        QJsonParseError jsonError;        QJsonDocument doucment = QJsonDocument::fromJson(byteArray,&jsonError);        if (!doucment.isNull() && (jsonError.error == QJsonParseError::NoError)){            if (doucment.isObject()) {                QJsonObject object = doucment.object();                if (object.contains("name")) {                    QJsonValue value = object.value("name");                    if (value.isString()){                        QString strName = value.toString();                        qDebug() << strName;                    }                }                if (object.contains("pwd")) {                    QJsonValue value = object.value("pwd");                    if (value.isString()){                        QString strName = value.toString();                        qDebug() << strName;                    }                }            }        }    }    file.close();

4.写入json数组

//写入    QJsonObject json;    json.insert("name","aaa");    json.insert("pwd","123");    QJsonObject json1;    json1.insert("name","bbb");    json1.insert("pwd","111");    QJsonArray arr;    arr.append(json);    arr.append(json1);    QJsonDocument document1;    document1.setArray(arr);    QByteArray byteArray = document1.toJson(QJsonDocument::Compact);    QString strJson(byteArray);//读取    QJsonParseError jsonError;    QJsonDocument doucment = QJsonDocument::fromJson(byteArray,&jsonError);    if (!doucment.isNull() && (jsonError.error == QJsonParseError::NoError)){        if(doucment.isArray()){            QJsonArray temp = doucment.array();            for(int i=0; i<temp.count(); i++){                QJsonValue tempvalue = temp.at(i);                if(tempvalue.isObject()){                    QJsonObject object = tempvalue.toObject();                    if (object.contains("name")) {                        QJsonValue value = object.value("name");                        if (value.isString()){                            QString strName = value.toString();                            qDebug() << strName;                        }                    }                }            }        }    }

5.从文件中读取内容

    QFile file("./textFile.txt");    if(file.open(QIODevice::ReadOnly))    {       char buffer[2048];       //读取所有内容       //QByteArray bytearr = file.readAll();       // qDebug()<<  "all" << bytearr;       //逐行读取内容       while(!file.atEnd()){           qint64 lineLen = file.readLine(buffer,sizeof(buffer));           qDebug()<< "b1" <<lineLen;           if(lineLen!=-1)           {               qDebug()<< "b1" <<buffer;           }       }    }    file.close();

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6.ini文件写入读取

#include <QSettings>QSettings *config = new QSettings("./test.ini", QSettings::IniFormat);void writeToFile(const QString groupName,const QString key,const QString value){    config->beginGroup(groupName);    config->setValue(key,value);    config->endGroup();}QString readFromFile(const QString groupName,const QString key){    QString filePath = groupName + "/" + key;    QString objectString = config->value(filePath).toString();    return objectString;}//写入config->writeToFile("ip","ip","192.168.1.1");config->writeToFile("next","nexus5","1999");//读取QString temp = config->readFromFile("ip","ip");

文件内容：
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