C++: GetKeyState() has to run once

Question

I need to listen keyboard key states for my tiny application.

#include <windows.h>
#include <fstream>
#include <iostream>

using namespace std;

int main()
{
    while(1)
    {
        if(GetKeyState(VK_SPACE) & 0x80)
        {
            cout << "Space pressed.\r\n";
            DoSpaceKeyTask();
        }

        if(GetKeyState(OTHER_KEY) & 0x80)
        {
            cout << "Other key pressed.\r\n";
            DoOtherKeyTask();
        }
    }
    return 0;
}

Once I click some keys from my keyboard, these functions has to run once. They're just some tiny tasks for my applications, which is not related in this topic.

My problem is, when I press a key, it executes the functions few times, due to while(1) looping few times during key press. I cannot use Sleep() in this case, because it still won't be effective.

I'm looking for a solution like this.

1. I press SPACE key.
2. DoSpaceKeyTask() executes "once."
3. I press OTHER key.
4. DoOtherKeyTask() executes "once."

I have like 5 keys that I will be using. Could anyone help me on this case?

Ps. If GetKeyState() function isn't useful on this task, feel free to suggest yours. My function knowledge is pretty limited on C++.

Answer 1

Your functions are called multiple times because of the duration time the button stays pressed. The system is very sensitive. So this is a workaround.

You could do something like this (set a flag that will assign a value when the key is down, and then reasign it when the key is up).

int k=0;//Flag
while(1){
    //check if the key was pressed (key_down)
    if((GetAsyncKeyState('0') & 0x8000) && (k == 0)){k=1; cout<<"'0' PRESSED."<<k<<endl;}//do your stuff here
    //check if the key was released (key up)
    else if(GetAsyncKeyState('0') == 0) k = 0;//reset the flag
}