SDL_GetKeyboardState not working - c

Question

I am trying to make a controller for a game with SDL 2(didn't want to ask on gamedev since it is not a game issue directly) I use SDL_GetKeyboardEvent to see if the navigation arrows are being pressed but it apparently doesn't work, it is supposed to print a value 1 or -1 if one of those keys is pressed but it doesn't it just prints 0 even if I hold the key down for several seconds, it is like it doesn't detect that the key is being pressed. I searched all over the internet and this is how they do it, but it doesn't work for me.
#define SDL_MAIN_HANDLED
#include <stdio.h>
#include "SDL.h"
/* I'll add some code later
so something that isn't used
might be initialized
*/
int main (void)
{
int a = 1;
int x;
int z;
SDL_Event quit;
const Uint8 *keys = SDL_GetKeyboardState(NULL);
SDL_Init(SDL_INIT_VIDEO);
while(a)
{
SDL_PollEvent(&quit);
if(quit.type == SDL_QUIT)
a = 0;
if(keys[SDL_SCANCODE_UP])
z = 1;
else if(keys[SDL_SCANCODE_DOWN])
z = -1;
else
z = 0;
if(keys[SDL_SCANCODE_LEFT])
x = -1;
else if(keys[SDL_SCANCODE_RIGHT])
x = 1;
else
x = 0;
printf("%d, %d\n", x, z);
//This is supposed to print
//x, z values so if up arrow is pressed it will print 0, 1 and if
//down arrow is pressed it will print 0, -1: the same with horizontal ones.
//1 or -1, 1 or -1
}
SDL_Quit();
return 0;
}

Answer 1

Read the documentation: wiki
Note: This function gives you the current state after all events have been processed, so if a key or button has been pressed and released before you process events, then the pressed state will never show up in the SDL_GetKeyboardState() calls
What it means is?
You need to process all events. How? Looping the PollEvent, after the loop (or if you want to check in the loop, check at the end), the SDL_GetKeyboardState is usable.
So, go through the loop, check for keyboards states. Do not forget to always go through the loop before checking for keys
e.g.
while (game)
{
/*! updates the array of keystates */
while ((SDL_PollEvent(&e)) != 0)
{
/*! request quit */
if (e.type == SDL_QUIT)
{
game = false;
}
}
if (keys[SDL_SCANCODE_RIGHT])
std::cout << "Right key";
}

Answer 2

You'll need to create a window with SDL_SetVideoMode to get mouse and keyboard events.

Answer 3

Here is my InputManager update function that updates the user input from the keyboard and mouse. Notice the const_cast needed to be able to update the class variable Uint8* keysArray;. This way, more than one event can be processed at once.
void update() {
SDL_PumpEvents();
// update keyboard state
keysArray = const_cast <Uint8*> (SDL_GetKeyboardState(NULL));
if (keysArray[SDL_SCANCODE_RETURN])
printf("MESSAGE: <RETURN> is pressed...\n");
if (keysArray[SDL_SCANCODE_RIGHT] && keysArray[SDL_SCANCODE_UP])
printf("MESSAGE: Right and Up arrows are pressed...\n");
// update mouse location and button states
SDL_GetMouseState(&x, &y);
getMouseButtonStates();
}