Unity: Input.GetButtonDown is not reliably detected in Update? - unity3d

Question

I have a player script that I'm trying to implement jumping in. The problem is that Input.GetButtonDown("Jump") doesn't consistently fire in Update. I know this is a problem when it's in FixedUpdate. Here is my code.
Note: I put [SerializeField] on pressingJump and holdingJump so I could see what's happening. pressingJump is inconsistent (as expected) but holdingJump works perfectly.
using UnityEngine;
public class Player : MonoBehaviour
{
public float fallMultiplier = 15f;
public float lowJumpMultiplier = 10f;
public float walkSpeed = 20f;
public float jumpSpeed = 15f;
public bool canMove = true;
public bool canJump = true;
Rigidbody rb;
float horizontalInput;
bool doJump;
bool pressingJump;
bool holdingJump;
void Start()
{
rb = GetComponent<Rigidbody>();
}
void Update()
{
CaputureInput();
}
void CaputureInput()
{
if (canMove) {
horizontalInput = Input.GetAxisRaw("Horizontal");
}
pressingJump = Input.GetButtonDown ("Jump");
doJump = pressingJump && canJump;
holdingJump = Input.GetButton ("Jump") && canJump;
}
void FixedUpdate()
{
Move();
Jump();
}
void Move()
{
rb.velocity = new Vector2(horizontalInput * walkSpeed, rb.velocity.y);
}
void Jump()
{
if (doJump) {
rb.velocity += Vector3.up * jumpSpeed;
doJump = false;
}
if (rb.velocity.y < 0) {
rb.velocity += Vector3.up * Physics.gravity.y * (fallMultiplier - 1) * Time.deltaTime;
} else if (rb.velocity.y > 0 && !holdingJump) {
rb.velocity += Vector3.up * Physics.gravity.y * (lowJumpMultiplier - 1) * Time.deltaTime;
}
}
}

Answer 1

Ok found the solution here: https://www.reddit.com/r/Unity3D/comments/9nr2sd/inputgetbuttondown_and_getbuttonup_dont_work/e7ogta1?utm_source=share&utm_medium=web2x
This was the problem I was having.
Edit: Comment pointed out a link might not be accepted. Here is the relevant content from link. It points out why the issue is occurring and how to fix it.
What you end up with, with the code you've written, is essentially the
same as when you do input checking in FixedUpdate.
This is because Update runs several times in between every
FixedUpdate. Now, what this means for your code in this case is that
yes, you do capture the state of ButtonDown("Jump") during Update, but
think about this: what happens to button_down/up_jump if another
Update happens before a FixedUpdate? Both GetButtonDown and
GetButtonUp are functions that are true only for the one frame in
which the keypress/-release happened. In other words, this is
happening
Update runs -> button_down_jump is false
user presses "Jump".
Update runs -> button_down_jump is true
Update runs -> button_down_jump is false
FixedUpdate runs -> nothing happens, because of button_down_jump's
state
Now, you've actually had a few cases where you press/unpress "jump" at
just the right time to manage to get anything printed at all. This
will only happen given that the following happens:
User un-/press "jump"
Update runs (ONCE)
FixedUpdate runs
What you actually want to do is something like this:
void Update() {
if(Input.GetButtonDown("jump")) {
button_down_jump = true; //this captures the state of the boolean beyond the one frame, as it's only set whenever the input
event happens
}
if(Input.GetButtonUp("jump")) {
button_up_jump = true;
} }