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 

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::_pressed
• bn::keypad::_released
• bn::keypad::_held

Where 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 
#include 
#include 
#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:

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)