如何使用C ++ / CX在UWP应用中查找当前用户的名称？

Question

Unlike C#, there does not appear to be a straight forward way to get the currently logged in user's name in a UWP application in C++. One of the Xbox Live certification requirements involves getting this information and displaying it on the main menu, and this game was written in C++ before Windows 10 was even a thing so this is one of the challenges I'm experiencing while porting it over.

This is the function that I have attempted to write in order to accomplish the task. What I get is an empty string.

int get_user_name( char* username )
{
    auto users = User::FindAllAsync();
    auto event1 = CreateEventEx( NULL, NULL, 0, EVENT_MODIFY_STATE | SYNCHRONIZE );

    /* Wait for asynchronous procedure to finish */
    for(;;)
    {
        if( users->Status == Windows::Foundation::AsyncStatus::Completed )
            break;

        WaitForSingleObjectEx( event1, 100, FALSE );
    }

    CloseHandle( event1 );

    auto results = users->GetResults();
    if( results->Size < 1 )
    {
        strcpy( username, "Nil" );
        return 1;
    }

    for( int i = 0; i < results->Size; i++ )
    {
        User^ user = results->GetAt(i);
        auto name = user->GetPropertyAsync( KnownUserProperties::DisplayName );

        auto event2 = CreateEventEx( NULL, NULL, 0, EVENT_MODIFY_STATE | SYNCHRONIZE );
        for(;;)
        {
            if( name->Status == Windows::Foundation::AsyncStatus::Completed )
                break;

            WaitForSingleObjectEx( event2, 100, FALSE );
        }
        CloseHandle( event2 );

        Platform::Object^ object = name->GetResults();
        std::wstring wstr = object->ToString()->Data();

        //setup converter
        typedef std::codecvt_utf8<wchar_t> convert_type;
        std::wstring_convert<convert_type, wchar_t> converter;

        //use converter (.to_bytes: wstr->str, .from_bytes: str->wstr)
        std::string converted_str = converter.to_bytes( wstr );

        strcpy( username, converted_str.c_str() );
    }

    return 1;
}

Now, I'm aware that this isn't the most well written function, but the main thing is getting it working for the time being.

This is the absolute best I could come up with, and countless days of googling hasn't yielded anything helpful so far, minus a very complicated C++ sample I found on GitHub here (all the asynchronous stuff makes it more confusing for me): https://github.com/Microsoft/Windows-universal-samples/blob/master/Samples/UserInfo/cpp/Scenario1_FindUsers.xaml.cpp#L33

Any ideas? Thanks.

Answer 1

To understand the whole scenario. There are two things that you can try.

You can learn from this page https://docs.microsoft.com/en-us/windows/uwp/threading-async/asynchronous-programming-in-cpp-universal-windows-platform-apps#creating-a-chain-of-tasks to understand how to use lambda and task chain to create the async action If it is too complex, you can consider "co_await" as the alternative way. Here are some related info:

1. https://blogs.msdn.microsoft.com/vcblog/2016/04/04/using-c-coroutines-to-simplify-async-uwp-code/

2. https://channel9.msdn.com/Events/Build/2016/P489

I've created a simple test code to simplify the whole screnario:

Step 1: Add the following header file(Then add /await to compile command):

#include <pplawait.h>
#include <experimental\resumable>

Step 2: Chick to choose "User Account Information" from Capbility tap in packagemanifest

Step 3: Write the following test code in cpp:

task<void> FindUserCPlusTest::MainPage::test()
{
IVectorView<Windows::System::User ^> ^users = co_await User::FindAllAsync();
auto user = users->GetAt(0);
auto name = co_await user->GetPropertyAsync(KnownUserProperties::DisplayName);
auto displayname=safe_cast<String^>(name);
}

Step 4:Write the following code in .h

concurrency::task<void> test();

Step 5:Put your method in any place and debug it When debugging you will be able to see the default user's display name. You can get started from this simple test.