如何在windows8应用中像c++一样处理文件？

Question

有这样一段c++代码：

#include "stdio.h"
int main(){
    FILE *in,*out;
    in=fopen("d:\\a.txt","r");
    out=fopen("d:\\b.txt","w");
    int a;
    fscanf(in,"%d",&a);
    fprintf(out,"%d",a);
}

请问如何在windows8应用（XAML）中实现打开文件d:\\a.txt和并进行读写？

（我曾经尝试直接写这段代码，结果in和out是NULL）

Answer 1

?????

Answer 2

首先先确认你有d盘读写权限

最好用"rb"

代码没什么问题，如果还是NULL，用GetLastError或者errno看看是什么错

---

0xDEADBEEF

Answer 3

那么如何通过文件选取器打开这个文件并读写？

Answer 4

Hi lxylxy123456,

一般来说你可以在MSDN上找到对应的例子。你的问题可以分解为两个步骤：

第一部分：如何通过文件读取器打开文件

原理： http://msdn.microsoft.com/zh-cn/library/windows/apps/xaml/hh771180.aspx 

具体实现方法：

FileOpenPicker^ openPicker = ref new FileOpenPicker(); 
openPicker->ViewMode = PickerViewMode::Thumbnail; 
openPicker->SuggestedStartLocation = PickerLocationId::PicturesLibrary; 
openPicker->FileTypeFilter->Append("*"); 
   
create_task(openPicker->PickSingleFileAsync()).then([this](StorageFile^ file) 
{
    if (file) 
    { 
        m_PickedFileName = file->Name; 
    } 
    else 
    { 
        // Operation cancelled.
    } 
});

例子：http://code.msdn.microsoft.com/windowsapps/File-picker-sample-9f294cba/

第二块：如何读写文件

原理：http://msdn.microsoft.com/zh-cn/library/windows/apps/xaml/hh758325.aspx

例子： http://code.msdn.microsoft.com/windowsapps/File-access-sample-d723e597

如还有疑问请提出来，ps这种问题可以到Windows Store App论坛提出来：）

--James

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Answer 5

你好：

根据你问题的描述，为了得到更好的回应，我把这个帖子移到Windows应用商店应用论坛。

感谢你的理解。

Answer 6

能不能将第二部分的C++代码给我？谢谢！

Answer 7

您可以去下载一下例子http://code.msdn.microsoft.com/windowsapps/File-access-sample-d723e597 帮助你更深入的理解 ：）

--James

---

<THE CONTENT IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND, WHETHER EXPRESS OR IMPLIED>
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Please remember to "Mark as Answer" the responses that resolved your issue. It is a common way to recognize those who have helped you, and makes it easier for other visitors to find the resolution later.

Answer 8

这个例子编译有问题，能不能把关键的代码写一下？

Answer 9

编译有问题是指？

StorageFile^ file = rootPage->SampleFile;
    if (file != nullptr)
    {
        String^ userContent = InputTextBox->Text;
        if (userContent != nullptr && !userContent->IsEmpty())
        {
            create_task(FileIO::WriteTextAsync(file, userContent)).then([this, file, userContent](task<void> task)
            {
                try
                {
                    task.get();
                    rootPage->NotifyUser("The following text was written to '" + file->Name + "':\n" + userContent, NotifyType::StatusMessage);
                }
                catch (COMException^ ex)
                {
                    rootPage->HandleFileNotFoundException(ex);
                }
            });
        }
        else
        {
            rootPage->NotifyUser("The text box is empty, please write something and then click 'Write' again.", NotifyType::ErrorMessage);
        }
    }
    else
    {
        rootPage->NotifyUserFileNotExist();
    }

--James

---

<THE CONTENT IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND, WHETHER EXPRESS OR IMPLIED>
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MSDN Community Support

Please remember to "Mark as Answer" the responses that resolved your issue. It is a common way to recognize those who have helped you, and makes it easier for other visitors to find the resolution later.

Answer 10

我用的是windows8.1，visual studio 2013，在打开项目前说需要单向升级，升级后似乎有一些不成功。编译后的错误：

错误 1 error C2039: “Scenario1”: 不是“SDKSample::FileAccess”的成员 c:\users\13691_000\downloads\c++\windows\generated files\xamltypeinfo.g.cpp 96
错误 2 error C2061: 语法错误: 标识符“Scenario1” c:\users\13691_000\downloads\c++\windows\generated files\xamltypeinfo.g.cpp 96
错误 3 error C2039: “Scenario3”: 不是“SDKSample::FileAccess”的成员 c:\users\13691_000\downloads\c++\windows\generated files\xamltypeinfo.g.cpp 108
错误 4 error C2061: 语法错误: 标识符“Scenario3” c:\users\13691_000\downloads\c++\windows\generated files\xamltypeinfo.g.cpp 108
错误 5 error C2039: “Scenario4”: 不是“SDKSample::FileAccess”的成员 c:\users\13691_000\downloads\c++\windows\generated files\xamltypeinfo.g.cpp 120
错误 6 error C2061: 语法错误: 标识符“Scenario4” c:\users\13691_000\downloads\c++\windows\generated files\xamltypeinfo.g.cpp 120
错误 7 error C2039: “Scenario5”: 不是“SDKSample::FileAccess”的成员 c:\users\13691_000\downloads\c++\windows\generated files\xamltypeinfo.g.cpp 132
错误 8 error C2061: 语法错误: 标识符“Scenario5” c:\users\13691_000\downloads\c++\windows\generated files\xamltypeinfo.g.cpp 132
错误 9 error C2039: “Scenario6”: 不是“SDKSample::FileAccess”的成员 c:\users\13691_000\downloads\c++\windows\generated files\xamltypeinfo.g.cpp 144
错误 10 error C2061: 语法错误: 标识符“Scenario6” c:\users\13691_000\downloads\c++\windows\generated files\xamltypeinfo.g.cpp 144
错误 11 error C2039: “Scenario7”: 不是“SDKSample::FileAccess”的成员 c:\users\13691_000\downloads\c++\windows\generated files\xamltypeinfo.g.cpp 156
错误 12 error C2061: 语法错误: 标识符“Scenario7” c:\users\13691_000\downloads\c++\windows\generated files\xamltypeinfo.g.cpp 156
错误 13 error C2039: “Scenario8”: 不是“SDKSample::FileAccess”的成员 c:\users\13691_000\downloads\c++\windows\generated files\xamltypeinfo.g.cpp 168
错误 14 error C2061: 语法错误: 标识符“Scenario8” c:\users\13691_000\downloads\c++\windows\generated files\xamltypeinfo.g.cpp 168
错误 15 error C2039: “Scenario10”: 不是“SDKSample::FileAccess”的成员 c:\users\13691_000\downloads\c++\windows\generated files\xamltypeinfo.g.cpp 180
错误 16 error C2061: 语法错误: 标识符“Scenario10” c:\users\13691_000\downloads\c++\windows\generated files\xamltypeinfo.g.cpp 180

Answer 11

能不能把读文件的代码也写一下？或者看一看这个代码为什么错了？

auto openPicker = ref new Windows::Storage::Pickers::FileOpenPicker();
openPicker->FileTypeFilter->Append("*");
create_task(openPicker->PickSingleFileAsync()).then([this](Windows::Storage::StorageFile^ file)
{
	if (file != nullptr){
		auto userContent = Windows::Storage::FileIO::ReadTextAsync(file);
		text->Text = userContent->ToString();
	}
});

还有，如何在已有文件的后面写？