如何将数据写入多个 QFiles

问题描述

我每次接收数据时都试图在文件中添加一行，如果行数超过 10 行，则创建新文件来存储数据，直到创建 5 个文件，但我遇到了一个问题，那就是应用程序将在第 56 行崩溃：QTextStream stream(current_record_file); ，代码为：

ma​​inwindow.cpp：

#include "mainwindow.h"
#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent),ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    simulateReceiveData();
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::simulateReceiveData()
{
    while(file_count < 5){
        qDebug()<<"on recording ...";
        if(file_count == 1 && msg_line_count == -1){
            //create the very first new file
            record_file_name_prefix = "D:/Project/MessageRecording";
            QString record_file_name = record_file_name_prefix + "(1).asc";
            qDebug()<<"record_file_name is"<<record_file_name;
            QFile file(record_file_name);
            if (!file.open(QFile::writeonly | QFile::Truncate)){
                qDebug()<<QString("Fail to open file : %1").arg(record_file_name);
                return;
            }

            //write the header
            current_record_file = &file;
            QTextStream stream(current_record_file);
            stream << "START\r\n";
            msg_line_count = 0;

        }else if(msg_line_count == 10){
            //write footer to privIoUs file
            QTextStream stream(current_record_file);
            stream << "END";
            stream.flush();
            current_record_file->close();

            //create next new file
            file_count++;
            QString record_file_name = record_file_name_prefix + QString("(%1).%2").arg(file_count).arg("asc");
            QFile file(record_file_name);
            if (!file.open(QFile::writeonly | QFile::Truncate))
                return;
            current_record_file = &file;  //redirect to the new created file
            msg_line_count = 0;
        }else{
            //write the main body
            QTextStream stream(current_record_file); // CRASH HERE !
            stream <<"0.0000 0 Rx 00 00 00 00 00 00 00 00\r\n";
            msg_line_count++;
        }
    }
}

ma​​inwindow.h :

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QFile>
#include <QDateTime>
#include <QTextStream>
#include <QDebug>

QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();

private:
    Ui::MainWindow *ui;

    void simulateReceiveData();
    int file_count = 1;//number of files
    int msg_line_count = -1;//number of lines in one file
    QString record_file_name_prefix;
    QFile* current_record_file = nullptr;//point to currently written file
};
#endif // MAINWINDOW_H

解决方法

正如 chehrlic 的评论所述，您正在访问一个（悬空）指针，该指针指向已超出范围的对象。

存在两种解决方案：

1. 在每次写入时重新打开文件（可能与 QFile::Truncate 不兼容且效率较低）
2. 使用 QFile current_record_file 作为成员，而不是 QFile* current_record_file。在我看来，这似乎是最好的方法。

,

谢谢大家的回复，我尝试了m7913d的第二种方案，现在可以创建多个QFile了！神奇的一点是，当你关闭最后一个 QFile current_record_file，并通过 current_record_file.setFileName(record_file_name); 重置其文件名后，programm 将帮助我们自动创建新文件。新的可用代码是：

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QThread>

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent),ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    simulateReceiveData();
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::simulateReceiveData()
{
    while(file_count < 5){
        qDebug()<<"on recording ...";

        if(file_count == 1 && msg_line_count == -1){
            //create the very first new file
            record_file_name_prefix = "D:/Project/MessageRecording";
            QString record_file_name = record_file_name_prefix + QString::number(file_count) + ".asc";
            current_record_file.setFileName(record_file_name);
            if (!current_record_file.open(QFile::WriteOnly | QFile::Truncate)){
                qDebug()<<QString("Fail to open file : %1").arg(record_file_name);
                return;
            }

            //write the header
            QTextStream stream(&current_record_file);
            stream << "START\r\n";
            msg_line_count = 0;

        }else if(msg_line_count == 10){
            //write footer to privious file
            QTextStream stream(&current_record_file);
            stream << "END";
            stream.flush();
            current_record_file.close();

            file_count++;
            QString record_file_name = record_file_name_prefix + QString::number(file_count) +  ".asc";
            qDebug()<<"new record file is"<<record_file_name;
            current_record_file.setFileName(record_file_name);
            if (!current_record_file.open(QFile::WriteOnly | QFile::Truncate)){
                qDebug()<<QString("Fail to open file : %1").arg(record_file_name);
                return;
            }

            QTextStream stream2(&current_record_file);
            stream2 << "START\r\n";
            msg_line_count = 0;

        }else{
            //write the main body
            QTextStream stream(&current_record_file); // CRASH HERE !
            stream <<file_count<<" 0.0000 0 Rx 00 00 00 00 00 00 00 00\r\n";
            msg_line_count++;
            QThread::sleep(1);
        }
    }
}

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QFile>
#include <QDateTime>
#include <QTextStream>
#include <QDebug>

QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();

private:
    Ui::MainWindow *ui;

    void simulateReceiveData();
    int file_count = 1;//number of files
    int msg_line_count = -1;//number of lines in one file
    QString record_file_name_prefix;
    QFile current_record_file;
};
#endif // MAINWINDOW_H