LiveData onChanged在使用FirebaseAuth时多次调用相同的数据

Question

我有一个登录活动，该活动使用电子邮件和密码实施Firebase身份验证。它的作用是将用户输入的电子邮件和密码发送给FirebaseAuth函数，并通过LiveData检索响应，然后观察它。

问题是，当登录失败或凭据无效时，它应该祝酒一条消息，但是真正发生的是它祝酒了​​多次，也许超过了4次（这使祝酒显示了很长时间）。] >

LoginActivity

    private fun signInWithEmailAndPassword(email: String, password: String){
        val authResult = viewModel.authWithEmailPassword(email, password)
        handleAuthenticationResult(authResult)
    }

    private fun handleAuthenticationResult(authResult: LiveData<Resource<AuthResult>>){
        authResult.observe(this, object : Observer<Resource<AuthResult>>{
            override fun onChanged(it: Resource<AuthResult>?) {
                when(it){
                    is Resource.Loading -> {
                        toggleLoadingIndicator(true)
                    }
                    is Resource.Success -> {
                        toggleLoadingIndicator(false)

                        val isNewUser = it.data.additionalUserInfo?.isNewUser ?: true

                        if(isNewUser) gotoIntroActivity()
                        else gotoMainActivity()
                    }
                    is Resource.Failure -> {
                        toggleLoadingIndicator(false)

                        when(it.throwable){
                            is FirebaseAuthException -> Toast.makeText(this@LoginActivity, getString(R.string.error_credentials_invalid), Toast.LENGTH_SHORT).show()
                            else -> Toast.makeText(this@LoginActivity, getString(R.string.error_login_failed), Toast.LENGTH_SHORT).show()
                        }
                    }
                }
            }
        })
    }
ViewModel

    fun authWithEmailPassword(email: String, password: String): LiveData<Resource<AuthResult>>{
        return AuthRepository.signInWithEmailAndPassword(email, password)
    }
FirebaseAuth

    private var authResult: MutableLiveData<Resource<AuthResult>> = MutableLiveData()

    fun signInWithEmailAndPassword(email: String, password: String): LiveData<Resource<AuthResult>>{
        authResult.value = Resource.Loading()

        mAuth.signInWithEmailAndPassword(email, password)
                .addOnCompleteListener{
                    if(it.isSuccessful) authResult.value = Resource.Success(it.result!!)
                    else authResult.value = Resource.Failure(it.exception!!)
                }

        return authResult
    }
资源

sealed class Resource<out T> {
    class Loading<out T> : Resource<T>()
    data class Success<out T>(val data: T) : Resource<T>()
    data class Failure<out T>(val throwable: Throwable) : Resource<T>()
}
为什么会这样，如何解决？我应该在每次触发Resource.Failure时都删除观察者吗？

我有一个登录活动，该活动使用电子邮件和密码实施Firebase身份验证。它的作用是将用户输入的电子邮件和密码发送给FirebaseAuth函数并检索响应...

Answer 1

LiveData是您创建并只能订阅一次的东西。就您而言，您每次获得身份验证结果时都会订阅它，因此会发生多个重复事件。