NullReferenceException

Unity Engine
,
1

Hi everyone, I’ve encountered a problem that I can’t understand: NullReferenceException. I’m making a simple sound player, and I want to change the name on the interface according to the name of the song and synchronize the playback progress of the song to the progress bar.
My code is following the video tutorial exactly, but it still gives an error.

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

public class SoundManager : MonoBehaviour
{
public AudioClip[ ] AudioClips;
AudioSource audioSource;
public int CurrentTrack = 0;
bool isPlaying = false;
public Text SongName;
public Slider ProgressBar;
// Start is called before the first frame update
void Start()
{
audioSource = GetComponent<AudioSource>();
audioSource.clip = AudioClips[CurrentTrack];
}

// Update is called once per frame
void Update()
{
SongName.text = AudioClips[CurrentTrack].name;
ProgressBar.maxvalue = AudioClips[CurrentTrack].length;
ProgressBar.value = audioSource.time;
}

void Play()
{
audioSource.Play();
isPlaying = true;
}

void Pause()
{
audioSource.Pause();
isPlaying = false;
}

void Stop ()
{
audioSource.Stop();
}
void Mute()
{
audioSource.mute = true;
}

void UnMute()
{
audioSource.mute = false;
}

void Next()
{
Stop();
if (CurrentTrack == AudioClips.Length - 1)
CurrentTrack = 0;

else 
CurrentTrack++;
audioSource.clip = AudioClips[CurrentTrack];
if(isPlaying)
Play();
}

void Previous()
{
Stop();
if (CurrentTrack == 0)
CurrentTrack = AudioClips.Length - 1;

else
CurrentTrack--;
audioSource.clip = AudioClips[CurrentTrack];
if (isPlaying)
Play();
}
}
2

Do you know where the error occurs? Either looking at the error log or by step debugging you should be able to identify the culprit variable. NullReferenceException means that a class that you are using refers to an object that has not been initialized with newor simply has a value of null. This happens quite frequently, and it is also why I’m always writing if(something == null) return someError; everywhere in my code.

In your case I would always make sure that AudioClips[...] has valid content before doing any operation on the presumed AudioClip. Your AudioSource might also be in cause. You could add [RequireComponent(typeof(AudioSource))] on top of your class to force an automatic check on your GameObject to validate it owns an AudioSource.

I hope this helps!

3

Also I think your referring to an inexistent member: ProgressBar.maxvalue is probably missing a capital V (maxValue).