当我尝试这样做时它崩溃了:
我想要异步获取用户数据,如果我不使用异步任务,它会返回 null
public class Database : MonoBehaviour
{
private DatabaseReference m_database;
private const string DATA_URL = "hidden";
public static Database singleton;
void Awake ()
{
FirebaseApp.DefaultInstance.SetEditorDatabaseUrl(DATA_URL);
m_database = FirebaseDatabase.DefaultInstance.RootReference;
DontDestroyOnLoad(this);
singleton = this;
}
void Start ()
{
User user = new User();
user = GetUserAsync("213asdasd").Result;
Debug.Log(user.email);
}
public void RegisterNewUser (User user)
{
string jsonData = JsonUtility.ToJson(user);
m_database.Child("Users").Child(user.id).SetRawJsonValueAsync(jsonData);
m_database.Child("Users").Child(user.id).Child("id").SetValueAsync(user.id);
m_database.Child("Users").Child(user.id).Child("email").SetValueAsync(user.email);
}
public async Task<User> GetUserAsync (string id)
{
User user = new User();
await FirebaseDatabase.DefaultInstance.GetReference("Users").Child(id)
.GetValueAsync().ContinueWith(task =>
{
if (task.IsFaulted)
{
// Handle the error...
}
else if (task.IsCompleted)
{
DataSnapshot snapshot = task.Result;
string rawUserData = snapshot.GetRawJsonValue();
Debug.Log(rawUserData);
user = JsonUtility.FromJson<User>(rawUserData);
}
});
return user;
}
}
混合使用异步等待和阻塞调用可能会导致问题。
参考Async/Await - 异步编程的最佳实践 https://msdn.microsoft.com/en-us/magazine/jj991977.aspx
如果代码无法完全重构为异步,请使用异步事件处理程序
void Start () {
started += onStarted;
started(this, EventArgs.Empty);
}
event EventHandler started = delegate { }
private async void onStarted(object sender, EventArgs args) {
started -= onStarted;
User user = await GetUserAsync("213asdasd");
Debug.Log(user.email);
}
另外,代码应该遵循异步模式
public async Task<User> GetUserAsync (string id) {
User user = new User();
try {
DataSnapshot snapshot = await FirebaseDatabase.DefaultInstance
.GetReference("Users").Child(id).GetValueAsync();
string rawUserData = snapshot.GetRawJsonValue();
Debug.Log(rawUserData);
user = JsonUtility.FromJson<User>(rawUserData);
} catch(Exception ex) {
// Handle the error...
}
return user;
}
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