Handling keypad input on the Game Boy Advance

Firstly, like all Butano features, you’ll need to include the proper header file. For input, you’ll really only need to include

#include <bn_keypad.h>

After that, all of the functions you need are in the “bn::keypad” namespace. You can find the documentation for this namespace here: Butano Docs – bn::keypad namespace.

Easy Keypad Functions in Butano

Butano has easy functions for common button operations:

bn::keypad::<button>_pressed
bn::keypad::<button>_released
bn::keypad::<button>_held

Where <button> is one of these values:

up
down
left
right
start
select
a
b
l
r

Here are some Examples:

if(bn::keypad::a_pressed())DoSomething();
if(bn::keypad::b_pressed())DoSomething();
if(bn::keypad::start_released())DoSomething();
if(bn::keypad::select_released())DoSomething();
if(bn::keypad::left_held())DoSomething();
if(bn::keypad::right_held())DoSomething();

Butano also has three easy catch-all functions:

if(bn::keypad::any_pressed())DoSomething();
if(bn::keypad::any_released())DoSomething();
if(bn::keypad::any_held())DoSomething();

Parametrized Keypad functions

In addition to those easy functions, you can use the “bn::keypad::key_type” enumeration as an argument for parametrized versions of the above functionality:

if(bn::keypad::held(bn::keypad::key_type::LEFT))DoSomething();
if(bn::keypad::pressed(bn::keypad::key_type::A))DoSomething();
if(bn::keypad::released(bn::keypad::key_type::B))DoSomething();

Here Are the full values for the “bn::keypad::key_type” enumeration:

bn::keypad::key_type::LEFT
bn::keypad::key_type::RIGHT
bn::keypad::key_type::DOWN
bn::keypad::key_type::UP
bn::keypad::key_type::A
bn::keypad::key_type::B
bn::keypad::key_type::R
bn::keypad::key_type::L
bn::keypad::key_type::START
bn::keypad::key_type::SELECT

Here’s an example of controlling a sprite. If you dont know how to use sprites in butano, see my tutorial here: Drawing sprites on the Game Boy Advance. We’ll use the directional buttons to move the sprites position.

#include <bn_core.h>
#include <bn_keypad.h>
#include <bn_sprite_ptr.h>
#include "bn_sprite_items_testplayer.h"

int main()
{
    bn::core::init();

    // Create a basic sprite in the center of the screen
    bn::sprite_ptr playersprite = bn::sprite_items::testplayer.create_sprite(0,0);
    

    // When this part of the code is reached, the clouds background has gone out of scope and will be removed
    while(true)
    {
        bn::core::update();

        if(bn::keypad::left_held()){

            // Decease the x position to move it to the left
            playersprite.set_x(playersprite.x()-bn::fixed(2));

        }else if(bn::keypad::right_held()){

            // Increase the x position to move it to the right
            playersprite.set_x(playersprite.x()+bn::fixed(2));
        }


        if(bn::keypad::up_held()){

            // Decrease the y  position to move it upwards
            playersprite.set_y(playersprite.y()-bn::fixed(2));
        }else if(bn::keypad::down_held()){

            // Increase the y  position to move it downwards
            playersprite.set_y(playersprite.y()+bn::fixed(2));
        }

    }
}

The end result is this:

butano keypad input gif using arrow keys

That’s everything you need to know about keypad input. if you want to see more documentation, check out:

Butano Docs – bn::keypad namespace
Butano Docs – bn::keypad::key_type enumeration
Butano Keypad Example (included in your Butano installation)

THANKS FOR READING!

If you have any suggestions, and/or are confused about anything: feel free to leave a comment, send me a email, or a message on social media. Constructive criticism will help the gameyard, and others like yourself. If you learned something from this tutorial, and are looking for more content, check other these other tutorials.