将SDL2箭头/ WASD键转换为播放器移动的最佳/最可靠方法是什么？

Question

My question is what is the most solid way to implement directional input in SDL2.

The problem with my current code is that say you wanted to move the player to the left. Pressing a would decrease his x value and once you release the a key, it stops decreasing the x value. however, if you wanted to move to the left and then immediately move to the right, the player would just stop for a period of time and then continue moving right.

Any advice would be very helpful.

My keyboard function:

class KeyboardController : public Component {

public: 
TransformComponent* transform;

void init() override {
    transform = &entity->getComponent<TransformComponent>();
}

void update() override {

    if (MainGame::evnt.type == SDL_KEYDOWN) {
        switch (MainGame::evnt.key.keysym.sym)
        {
        case SDLK_w:
            transform->velocity.y = -1;

            break;
        case SDLK_a:
            transform->velocity.x = -1;

            break;
        case SDLK_s:
            transform->velocity.y = 1;

            break;
        case SDLK_d:
            transform->velocity.x = 1;

            break;
        }
    } 

    if (MainGame::evnt.type == SDL_KEYUP) {
        switch (MainGame::evnt.key.keysym.sym)
        {
        case SDLK_w:
            transform->velocity.y = 0;

            break;

        case SDLK_a:
            transform->velocity.x = 0;

            break;

        case SDLK_s:
            transform->velocity.y = 0;

            break;

        case SDLK_d:
            transform->velocity.x = 0;

            break;
        }
      }
   }
};

My velocity function:

/* class */

Vector2D position;
Vector2D velocity;

/* other code */

void update() override {
    position.x += velocity.x * speed; //speed = 3
    position.y += velocity.y * speed;
}

Answer 1

Instead of acting upon events to immediately change the velocity, consider adding additional state (an array) which remembers which keys are down at any given moment. Any time an input event is received, update the array and recalculate the velocity based on that.

For example, depending on what game you're making, you may want to make the player stop moving if both left and right are pressed at the same time. Alternatively, a keydown event for a direction key would make the player immediately start moving in that direction, but you'll still need to keep track of when no more buttons are held down to know when the player should stop moving.