CODEWITHSUNDEEP
c++winapikeyboardkeypress
user3793107
user3793107

Reputation: 135

GetKeyState function returning a wrong value

After I press the directional arrow ON, why does the function GetKeyState continue to give me a value greater than 0?

#include <iostream>
#include <windows.h>
using namespace std;

int main()
{
    for(int i = 0; i < 1000; ++i)
    {
        if(GetKeyState(VK_UP))
        {
            cout << "UP pressed" << endl;
        }
        else
            cout << "UP not pressed" << endl;
            
        Sleep(150);
    }
    
    return 0;
}

Upvotes: 4

Views: 12046

Answers (3)

Hyunsang_Shim
Hyunsang_Shim

Reputation: 11

and also, GetKeyState() function, can be used for normal character keys like 'a' ~ 'Z'. (it's not case sensitive)

    if (GetKeyState('A' & 0x8000)
    {
        // code for Pressed
    }
    else
    {
        // code for Not Pressed
    }

Upvotes: 0

David Heffernan
David Heffernan

Reputation: 613572

From the documentation:

The key status returned from this function changes as a thread reads key messages from its message queue. The status does not reflect the interrupt-level state associated with the hardware. Use the GetAsyncKeyState function to retrieve that information.

Since you are not processing messages, you'll want to call GetAsyncKeyState instead.

Test for the key being pressed like this:

if (GetAsyncKeyState(VK_UP) < 0)
    // key is pressed

Upvotes: 6

Strigidis
Strigidis

Reputation: 108

GetKeyState doesn't return a "boolean-like". Take a look at the documentation :

http://msdn.microsoft.com/en-us/library/windows/desktop/ms646301(v=vs.85).aspx

It seems that you need to do :

if (GetKeyState(VK_UP) & 0x8000)
{
  //Your code
}
else
{
  // Not pressed
}

0x8000 if the result is a short or -127/-128 if the result is a char. Check the "return value" section of the documentation to see what you want

Upvotes: 1

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