条件检查后，可以在Unity中协同运行协程

Question

I'm new to Unity and I was just creating a simple galaxy shooter game where I want the enemies to be spawned only when the the player comes to existence. So I have created a coroutine that checks for the playerExists condition, if it turns out to be true , it should further proceed in spawning the enemies every 5 seconds. But for some reason, it spawns just one enemy. Am I missing anything here ? Below is my SpawnManager where the spawning behaviour is controlled.

public class SpawnManager : MonoBehaviour {

[SerializeField]
private GameObject _enemyShipPrefab;
[SerializeField]
private GameObject[] _powerUp;
UIManager _uimanager;


// Use this for initialization
void Start () {
    _uimanager = GameObject.Find("Canvas").GetComponent<UIManager>();
    StartCoroutine(SpawnPowerUps());
    StartCoroutine(SpawnEnemy());

}

IEnumerator SpawnEnemy(){
    while (_uimanager.playerExists == true)
    {
            Vector3 position = new Vector3(Random.Range(-8.23f, 8.23f), 5.7f, 0.0f);
            Instantiate(_enemyShipPrefab, position, Quaternion.identity);
            yield return new WaitForSeconds(5.0f);
    }

}

}

Below is my UIManager where i control the existence of the player.

public class UIManager : MonoBehaviour {

// Use this for initialization
public bool playerExists = false; 
public int playerScores = 0; 
public Sprite[] lives;
public Image playerLivesImagesToBeShown;
public Text playerScoreToBeShown;
public Image titleImage;
public GameObject playerPrefab;
void Start()
{

}

void Update()
{

        if (Input.GetKeyDown(KeyCode.Space) && playerExists == false){
            titleImage.gameObject.SetActive(false);
            Instantiate(playerPrefab, new Vector3(0, 0, 0), Quaternion.identity);
            playerScores = 0;
            playerScoreToBeShown.text = "Score : 0";
            playerExists = true;
        }


}


public void updateLives(int livesToView ){
    playerLivesImagesToBeShown.sprite = lives[livesToView];
            if(livesToView == 0){
                playerExists = false;
                titleImage.gameObject.SetActive(true);
            }
}

Answer 1

At the first glace of your code (and the described problem) i would say, your SpawnEnemy() Coroutine runs through and exit afterwards. You have to lock it in some loop, like this:

IEnumerator SpawnEnemy ()
{
    while (true) // Keep checking
    {
        if(_uimanager.playerExists == true)
        {
            Vector3 position = new Vector3(Random.Range(-8.23f, 8.23f), 5.7f, 0.0f);
            Instantiate(_enemyShipPrefab, position, Quaternion.identity);            
            yield return new WaitForSeconds (5.0f);  // After spawning waits 5secs
        }
        yield return null; // Starts loop with next frame.
    }
}