QFile不会打开文件 [英] QFile won't open the file

问题描述

我有一个程序，我基本上从Qt网站偷了，试图获取一个文件打开。程序拒绝打开任何我困惑为什么。我已经查找了很多文档，但发现没有什么可以解释为什么它不工作。

I have a program that I basically stole from the Qt website to try to get a file to open. The program refuses to open anything I am confused as to why. I have looked for lots of documentation but found nothing can you please explain why it does not work.

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QFile>
#include <QTextStream>
#include <QString>
MainWindow::MainWindow(QWidget *parent) :
    QWidget(parent)
{
    QFile file("C:/n.txt");
    if (!file.open(QIODevice::ReadOnly | QIODevice::Text))
             return;
    QTextStream in(&file);
    QString f=in.readLine();
    lab =new QLabel("error",this);
    lab->setGeometry(100,100,100,100);
    lab->setText(f);

}

推荐答案

该文件，你可以随时检查existense：

Before opening the file, you can always check the existense:

QFile file("myfile.txt");
if (!file.exists()) {
    // react
}

如果文件存在但没有打开，您可以得到错误状态和消息：

If file exists but does not open, you can get the error state and message:

QString errMsg;
QFileDevice::FileError err = QFileDevice::NoError;
if (!file.open(QIODevice::ReadOnly)) {
    errMsg = file.errorString();
    err = file.error();
}

并且始终：如果文件是openend，那么请记住关闭它。在您的示例中，您没有：

And always: if the file was openend, then remember to close it. In your example you didn't:

file.close();

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