Controls

using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Input;

namespace WindowsGame4
{
    class Controls
    {
        KeyboardState previousKeyState;
        KeyboardState currentKeyState;

        float player_speed = 4.0f;
        Vector2 gravity = new Vector2(0, 2.0f);
        Vector2 jumpVector = new Vector2(0, -16.0f);

        public void Update(PlayerObject player)
        {
            //If we were on the ground, but the Yvelocity became higher than 0, then apperantly we are not on the ground anymore
            if (player.PositionState == PositionState.onGround && player.Velocity.Y > 0)
                player.PositionState = PositionState.inAir;

            previousKeyState = currentKeyState;
            currentKeyState = Keyboard.GetState();

            int direction_x = 0;
            int direction_y = 0;

            if (currentKeyState.IsKeyDown(Keys.Left))
                direction_x = -1;
            if (currentKeyState.IsKeyDown(Keys.Right))
                direction_x = 1;

            //only in space we have free movement in all directions
            if (player.PositionState == PositionState.inSpace)
            {
                if (currentKeyState.IsKeyDown(Keys.Up))
                    direction_y = -1;
                if (currentKeyState.IsKeyDown(Keys.Down))
                    direction_y = 1;
            }

            Vector2 previousVelocity = player.Velocity;
            player.Velocity = new Vector2(direction_x, direction_y) * player_speed;

            //When we aren't in space, we apply gravity
            if (player.PositionState != PositionState.inSpace)
            {
                player.Velocity += gravity;
                player.VelocityY += previousVelocity.Y;
            }

            //You can only jump if you are on the ground
            if (player.PositionState == PositionState.onGround)
            {
                if (currentKeyState.IsKeyDown(Keys.Up) && previousKeyState.IsKeyUp(Keys.Up))
                {
                    player.Velocity += jumpVector;
                    player.PositionState = PositionState.inAir;
                }
            }

            //Max falling speed, to avoid falling though tiles
            if (player.Velocity.Y > 16)
                player.VelocityY = 16;
        }
    }
}