C++ QFile 不会打开文件
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QFile won't open the file
提问by Ville Lukka
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.
我有一个程序，我基本上是从 Qt 网站上偷来的，试图打开一个文件。该程序拒绝打开任何我不知道为什么的东西。我已经寻找了很多文档，但没有找到任何你能解释为什么它不起作用的东西。
#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);
}
回答by Ville Lukka
Before opening the file, you can always check the existense:
在打开文件之前，您可以随时检查是否存在：
QFile file("myfile.txt");
if (!file.exists()) {
// react
}
If file exists but does not open, you can get the error state and message:
如果文件存在但未打开，您可以获得错误状态和消息：
QString errMsg;
QFileDevice::FileError err = QFileDevice::NoError;
if (!file.open(QIODevice::ReadOnly)) {
errMsg = file.errorString();
err = file.error();
}
And always: if the file was openend, then remember to close it. In your example you didn't:
并且总是：如果文件是开放式的，那么记得关闭它。在您的示例中，您没有：
file.close();
回答by arun_vj
FileError QFile::error() const Returns the file error status. The I/O device status returns an error code. For example, if open() returns false, or a read/write operation returns -1, this function can be called to find out the reason why the operation failed. See also unsetError().
FileError QFile::error() const 返回文件错误状态。I/O 设备状态返回错误代码。例如，如果 open() 返回 false，或者读/写操作返回 -1，则可以调用此函数来查找操作失败的原因。另见 unsetError()。
Post the error code. Isn't it supposed to be QFile file("C:\n.txt"); \ not / in windows?
贴出错误代码。不应该是QFile file("C:\n.txt"); \ 不是 / 在 Windows 中？
