unity3d - C# Unity GetKeyDown() not being detected properly

Question

So I've got a little sledding prototype going. I'm currently coding some controls to compliment the RigidBody physics I've applied. My goal is to apply a force in the opposite direction of the turn left or right in order to get a sort of skidding, edge catching effect, and then apply a force forward to compensate for the loss of momentum.

However I can't get that far, because for whatever ever reason I can't get the GetKeyDown() or GetKeyUp() functions to work. I've included the code below. Basically what happens is the "Button released." text gets output constantly, and then once in a while I will get a "Button pressed" output that happens only once before reverting back to the "Button released." outputs. Even this is rare. Usually I get no indication of any detection.

I'm sure I'm missing something miniscule, and I have looked for similar questions, but none of them seem to solve my problem. If anyone can give me any ideas I'd be very grateful. Also, any optimization tips would be appreciated. I'm still a little new to C# and Unity.

I'm in the middle of tweaking and experimenting so I apologize if I missed some un-necessary comments.

    using System.Collections;
    using System.Collections.Generic;
    using UnityEngine;

    public class PlayerController : MonoBehaviour
    {

    private Rigidbody rb;
    public bool sidePhysics;
    public bool keyPress;

    // Use this for initialization
    void Awake()
    {
        rb = GetComponent<Rigidbody>();

    }

    // Update is called once per frame
    void FixedUpdate()
    {
        var x = Input.GetAxis("Horizontal") * Time.deltaTime * 50.0f;
        // No vertical controlls for now.
        //var z = Input.GetAxis("Vertical") * Time.deltaTime * 40.0f;


        // Get axis against which to apply force
        var turnAngle = rb.transform.position.x;




        transform.Rotate(0, x, 0);
        //transform.Translate(0, 0, z);


        // Debug to test input detection
        keyPress = Input.GetKeyDown(KeyCode.A);
        Debug.Log("keyPress: " + keyPress);

        // On either right or left key input down, apply force
        // Later once keys are being detected - addForce forward too 
        if (Input.GetKeyDown(KeyCode.LeftArrow) || Input.GetKeyDown(KeyCode.LeftArrow)
           || Input.GetKeyDown(KeyCode.A) || Input.GetKeyDown(KeyCode.D))
        {
            Debug.Log("Button pressed. ");

            // Add opposing force proportionate to the degree of the turn
            rb.AddForce((turnAngle * (-x * 10)), 0, 0, ForceMode.Acceleration);
        }
        else
        {
            Debug.Log("Button released.");
        }



        //Debug.Log("RigidBody: " + rb +
        //          "   Rotation: " + x +
        //          "   turnAngle: " + turnAngle);


    }
}

Answer 1

If you want to continuously do stuff when key is held down, you use the Input.GetKey function. If you want to want to do something once when key is pressed, you use the Input.GetKeyDown function since that's would evaluate to true once only until the key is released and pressed again. It's important that you understand the difference between the two.

Now, to detect when button is released, don't use else statement after checking the Input.GetKey. You won't get the effect you are looking for. To detect when button is released use the Input.GetKeyUp function. Add another if statement there.

More like something like this:

if (Input.GetKeyDown(KeyCode.A))
{
    //KEY PRESSED
}

if (Input.GetKey(KeyCode.A))
{
    //KEY PRESSED AND HELD DOWN
}

if (Input.GetKeyUp(KeyCode.A))
{
    //KEY RELEASED
}

Finally, you should always check for input in the Update function instead of the FixedUpdate function.