如何在每次API请求时显示加载图标？二次请求加载图标不显示如何解决？

问题根源 #

你当前的逻辑是通过MessageCad的message字段是否为空判断是否展示加载图标，第一次请求完成后，_resultado已经被赋值为携带内容的MessageCad实例，后续再次发起请求时没有重置这个状态，因此value.message.isEmpty()的判断一直为false，自然不会触发加载图标的展示。

方案1：快速修复 #

修改ViewModel的create方法，每次发起请求前先重置_resultado为空的MessageCad实例，触发加载状态，同时补充异常场景的状态赋值，避免加载动画一直展示：

fun create(nome: String,email: String,cpf:String,telefone:String,
           celular:String,senha:String,endereco:String,bairro:String,numero:String,
           complemento:String,cidade:String
){
    viewModelScope.launch {
        try {
            // 新增：请求发起前先重置状态，触发加载
            _resultado.value = MessageCad()
            val r = cadastroRepository.createUser(nome,email,cpf,telefone,celular,senha,endereco,bairro,
                    numero,complemento,cidade)
            _resultado.value = r
        } catch (e:Exception) {
            Log.d("Service error",e.toString())
            // 新增：异常场景也赋值状态，避免一直显示加载
            _resultado.value = MessageCad(message = "请求出错：${e.message?:"未知错误"}")
        }
    }
}

方案2：更规范的状态管理（推荐） #

用密封类拆分UI状态，明确区分初始、加载、成功、失败四种状态，避免靠业务字段判断状态的歧义问题：

1. 首先定义UI状态密封类

sealed interface CadastroUiState {
    object Idle: CadastroUiState // 初始状态
    object Loading: CadastroUiState // 加载中
    data class Success(val data: MessageCad): CadastroUiState // 请求成功
    data class Error(val errMsg: String): CadastroUiState // 请求失败
}

2. 修改ViewModel的状态定义与请求逻辑

class CadastroViewModel:ViewModel() {
    private val cadastroRepository= CadastroRepository()

    private val _uiState: MutableStateFlow<CadastroUiState> = MutableStateFlow(CadastroUiState.Idle)
    val uiState: StateFlow<CadastroUiState> = _uiState.asStateFlow()

    fun create(nome: String,email: String,cpf:String,telefone:String,
               celular:String,senha:String,endereco:String,bairro:String,numero:String,
               complemento:String,cidade:String
    ){
        viewModelScope.launch {
            try {
                // 置为加载状态
                _uiState.value = CadastroUiState.Loading
                val r = cadastroRepository.createUser(nome,email,cpf,telefone,celular,senha,endereco,bairro,
                        numero,complemento,cidade)
                _uiState.value = CadastroUiState.Success(r)
            } catch (e:Exception) {
                Log.d("Service error",e.toString())
                _uiState.value = CadastroUiState.Error("请求失败：${e.localizedMessage?:"未知错误"}")
            }
        }
    }
}

3. 修改Compose层的调用逻辑

val uiState: CadastroUiState by model.uiState.collectAsState()
    
when(uiState) {
    CadastroUiState.Loading -> CircularProgressIndicator(modifier = Modifier.wrapContentWidth(Alignment.CenterHorizontally))
    is CadastroUiState.Success -> {
        val messageCad = (uiState as CadastroUiState.Success).data
        // 替换为你自己的成功逻辑，比如提示请求结果
        Text(text = messageCad.message)
    }
    is CadastroUiState.Error -> {
        val errMsg = (uiState as CadastroUiState.Error).errMsg
        // 替换为你自己的错误提示逻辑
        Text(text = errMsg, color = Color.Red)
    }
    CadastroUiState.Idle -> {
        // 初始状态展示，比如表单输入界面
    }
}

内容的提问来源于stack exchange，提问作者Rafael Souza