Can't access script from another scene in Unity

Question

I'm learning unity and I'm trying to change the volume of the background music when the game starts but can't access script where the sound is playing (game scene) from settings menu (settings scene).

There is always an error in settings scene line that says

"BGMusicScript = GameObject.FindGameObjectWithTag("BGMusic").GetComponent();" which says "Object reference not set to an instance of an object".

Settings scene:

public class SettingsMenuLogic : MonoBehaviour
{
    
    public TMP_Dropdown resolutionDropdown;
    Resolution[] resolutions;
    public Slider BGMusicSlider;
    public GameObject backgroundMusicGameObject;
    public BackgroundMusicScript BGMusicScript;
    

    void Start()
    {
        resolutions = Screen.resolutions;

        resolutionDropdown.ClearOptions();

        List<string> options = new List<string>();

        int currentResolutionIndex = 0;
        for(int i = 0; i < resolutions.Length; i++)
        {
            string option = resolutions[i].width + " x " + resolutions[i].width;
            options.Add(option);

            if (resolutions[i].width == Screen.currentResolution.width && resolutions[i].height == Screen.currentResolution.height)
            {
                currentResolutionIndex = i;
            }
        }

        resolutionDropdown.AddOptions(options);
        resolutionDropdown.value = currentResolutionIndex;
        resolutionDropdown.RefreshShownValue();


        BGMusicScript = GameObject.FindGameObjectWithTag("BGMusic").GetComponent<BackgroundMusicScript>();


        if (!PlayerPrefs.HasKey("BGMusicVolume"))
        {
            PlayerPrefs.SetFloat("BGMusicVolume", 1);
            loadBGVolume();
        } else
        {
            loadBGVolume();
        }
    }

    public void setResolution(int resolutionIndex)
    {
        Resolution resolution = resolutions[resolutionIndex];
        Screen.SetResolution(resolution.width, resolution.height, Screen.fullScreen);
    }

    public void changeBGVolume()
    {
        BGMusicScript.BGMusic.volume = BGMusicSlider.value;
        saveBGVolume();
    }

    public void saveBGVolume()
    {
        PlayerPrefs.SetFloat("BGMusicVolume", BGMusicSlider.value);
    }

    public void loadBGVolume()
    {
        BGMusicSlider.value = PlayerPrefs.GetFloat("BGMUsicVolume");
    }
    public void setQuality(int qualityIndex)
    {
        QualitySettings.SetQualityLevel(qualityIndex);
    }

    public void setFullscreen(bool isFullscreen)
    {
        Screen.fullScreen = isFullscreen;
    }
}

Script from game scene:

public class BackgroundMusicScript : MonoBehaviour
{
    public BirdScript bird;
    public AudioSource BGMusic;
    // Start is called before the first frame update
    void Start()
    {
        bird = GameObject.FindGameObjectWithTag("Bird").GetComponent<BirdScript>();
        BGMusic = GetComponent<AudioSource>();
        BGMusic.volume = PlayerPrefs.GetFloat("BGMusicVolume");
    }

    // Update is called once per frame
    void Update()
    {
        if(bird.birdIsAlive == false)
        {
            BGMusic.Stop();
        }
    }
}

Tried finding a tutorial on Google but to no avail, I hope someone here can help.

if it was in a scene, and you changed scenes the items in that scene not makred as dont delete are gone, therefore even if the new scene has one that to you is the same its a new instance. — BugFinder, Aug 15 '23 at 20:45

score 0 · Accepted Answer · answered Aug 15 '23 at 23:22

Use an Audio Mixer.

Basically, you can make the AudioSource for the background audio output its audio into an AudioMixer, and the settings menu can be used to set the output volume of aforementioned AudioMixer.

The AudioMixer does not belong to any scene (being accessible from all scenes), meaning that there will be no need for you to attempt referencing the BackgroundMusicScript within the SettingsMenuLogic.

And if you're wondering how to refactor your settings menu to adjust the audio mixer instead, this thread demonstrates how to adjust a mixer in your settings menu: https://stackoverflow.com/a/50940850/22296059

Can't access script from another scene in Unity

1 Answers1