调用广播接收器时流程未更新

Question

我是 kotlin 新手，正在尝试制作一个课程药物提醒应用程序。 当我的 AlarmReceiver 将新名称添加到当前警报流中时，我的虚拟机没有做出反应。

“正在执行某事”的唯一时间是应用程序启动时，而不是名称添加到 currentAlerts 时。是否可以以这种方式使用流程或者我误解了它们？

medicineViewModel.kt

class MedicineViewModel(
    private val dao: DatabaseDAO,
    private val alarmScheduler: AlarmScheduler,
    alarmReceiver: AlarmReceiver,
    private val userPreferencesRepository: UserPreferencesRepository,
) : ViewModel() {
    
    private val _currentAlerts = alarmReceiver.currentAlertsFlow

    private val _medicines = combine(dao.getMedicinesByName(), _currentAlerts) { medicines, currentAlerts ->
        Log.d("medicineViewModel", "${currentAlerts.size}")
        medicines.map { medicine ->
            Log.d("medicineViewMode", "doing something! ${medicine.name}")
            Log.d("medicineViewModel", "${medicine.name}, ${medicine.name in currentAlerts}")
            medicine.copy(isAlerting = medicine.name in currentAlerts)
        }
    }.stateIn(viewModelScope, SharingStarted.WhileSubscribed(), emptyList())

    private val _preferences = userPreferencesRepository.getActivated().stateIn(
        viewModelScope,
        SharingStarted.WhileSubscribed(),
        UserPreferences(activated = false)
    )

    //_state håller koll på allt som visas på skärmen.
    private val _state =
        MutableStateFlow(MedicineState()) // Starta ett nytt flow utifrån MedicineState (börjar tomt)

    // _state är allting som visas på skärmen. Man hämtar medicinerna via DAO och stoppar in det i "medicines" i state.
    // Allting innan .stateIn är instruktioner för när man börjar löpande hämta data. MedicineState() i stateIn är
    // utgångspunkten, alltså en tom skärm.
    val state = combine(_state, _medicines, _preferences) { state, medicines, preferences ->
        state.copy(
            medicines = medicines,
            preferences = preferences,
        )
    }.stateIn(viewModelScope, SharingStarted.WhileSubscribed(5000), MedicineState())

        fun onEvent(event: MedicineEvent) {
            when (event) {
               ...
           }
        }

    fun calculateAlarms() {
        for (medicine in state.value.medicines) {

            val alarmItem = AlarmItem(
                medicineName = medicine.name,
                time = LocalDateTime.now()
                    .plusMinutes(medicine.interval.toLong())
            )

            alarmItem.let(alarmScheduler::schedule)

        }
    }
}

alarmReceiver.kt

package com.example.myapplication.model.alarm

import android.content.BroadcastReceiver
import android.content.Context
import android.content.Intent
import android.util.Log
import kotlinx.coroutines.flow.MutableStateFlow
import kotlinx.coroutines.flow.StateFlow

class AlarmReceiver : BroadcastReceiver() {

    // MutableStateFlow to hold the latest list of alerts
    private val _currentAlertsFlow = MutableStateFlow(mutableListOf<String>())
    val currentAlertsFlow: StateFlow<MutableList<String>> get() = _currentAlertsFlow

    override fun onReceive(context: Context, intent: Intent?) {
        Log.d("AlarmReceiver", "alarm triggered!")
        val message = intent?.getStringExtra("medicineName") ?: return
        Log.d("AlarmReceiver", "Alarm triggered: $message")

        // Update the alerts list and emit the new list
//        val updatedAlerts = _currentAlertsFlow.value.toMutableList()
//        updatedAlerts.add(message)
//        _currentAlertsFlow.value = updatedAlerts
        _currentAlertsFlow.value.add(message)
    }
}

感谢您的阅读！

Answer 1

你所做的基本上是正确的。只有一个主要问题：StateFlow 仅在设置“new”值时通知其观察者。但这不是你所做的：

_currentAlertsFlow.value.add(message)

这只会

修改

已经存在的值。在这种情况下，最佳实践应该首先阻止此错误的出现：使您的状态对象

不可变。 _currentAlertsFlow 的内容应为 List<String>

 类型，而不是 

MutableList<String>

。

AlarmReceiver 应该看起来像这样：

class AlarmReceiver : BroadcastReceiver() {
    private val _currentAlertsFlow = MutableStateFlow(emptyList<String>())
    val currentAlertsFlow: StateFlow<List<String>> get() = _currentAlertsFlow

    override fun onReceive() {
        // ..
        _currentAlertsFlow.update { it + message }
    }
}