从最后一个场景开始游戏Unity 3D

Question

After closing the game and reopening it, I want to load the last scene, so the player can continue from the level he reached. I've tried using PlayerPrefs as you see in the code bellow, but the game crash on startup.

GameManager Script:

    bool GameHasEnded = false;
    public float RestartDelay = 2f;
    public float NextLevelDelay = 5f;

    int level_index;

    private void Start()
    {

        level_index = PlayerPrefs.GetInt("Last_Level");
        SceneManager.LoadScene(level_index);


    }

    public void CompleteLevel()
    {
        Invoke("NextLevel", NextLevelDelay);
        level_index = level_index++;
        PlayerPrefs.SetInt("Last_Level", level_index);
    }

    public void EndGame()
    {
        if (GameHasEnded == false)
        {
            GameHasEnded = true;
            Invoke("Restart", RestartDelay);
        }
    }

    void NextLevel()
    {
        SceneManager.LoadScene(SceneManager.GetActiveScene().buildIndex +1);
    }

    void Restart()
    {
        SceneManager.LoadScene(SceneManager.GetActiveScene().path);
    }
}

All scenes are linked with GameManager , they all have the same code that load the next scene:

FindObjectOfType<GameManager>().CompleteLevel();

Answer 1

You need to specify a defaultValue for GetInt so that the first time it starts up, it can pick the appropriate scene to start at.

Also, you need to track whether or not you have already loaded at scene start, and only do this load if it hasn't yet happened. GameManager seems like it should be made into a singleton but since it's not, you can just make this loaded flag static, so that is common among all GameManager instances.

Altogether, this might look like this:

public readonly int defaultLastLevel = 1; // Set as appropriate
private static bool loaded = false;

void Start()
{
    if (!loaded) {
        loaded = true;
        level_index = PlayerPrefs.GetInt("Last_Level", defaultLastLevel);
        SceneManager.LoadScene(level_index);
    }
}

Also, your CompleteLevel has some very strange code where you post-increment and assign in the same line:

level_index = level_index++;

This is extremely hard to read and actually doesn't do what you want it to do . You can do level_index = SceneManager.GetActiveScene().buildIndex + 1; instead.

Also, you need to Save changes you make to PlayerPrefs with PlayerPrefs.Save();

Altogether, this makes your CompleteLevel look like this:

public void CompleteLevel()
{
    Invoke("NextLevel", NextLevelDelay);
    level_index = SceneManager.GetActiveScene().buildIndex + 1; // use this instead
    PlayerPrefs.SetInt("Last_Level", level_index);
    PlayerPrefs.Save();
}