Android Kotlin Room database. Query fails when called from ViewModel. Passes from App Inspection win-CodePudding

I have an app that use fragments, navigation and viewModels. I cannot call a query "getCustomerById" from my view model (CustomerViewModel.kt). More details: I am selecting customer from CustomerFragment which opens CustomerDetailFragment and display details about customer. I am using a common ViewModel for both fragments. Most of the things work, but I cannot get my query (getCustmoerbyID) to work from CustomerDetailsFragment. I have a compiler error. The code looks like this.

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)
    val customer = customerViewModel.geCustomerById("11")
    Log.i(Constants.LOG_TAG, "Customer details fragment. ${customer.first().firstName}.  Done ** onViewCreated. **")
}

The error is in the log statement, for method first(). "Suspend function 'first' should be called only from a coroutine or another suspend function"

Same issue with "getCustomerCount". I have spent hours or days on it, because of my lack of knowledge of Coroutines. I cannot put code from original app, so I have put a simplified app on github. The link is as follows.

CodePudding user response：

You need to launch a coroutine to call suspend function Flow.first(). In Activity or Fragment you can use lifecycleScope, in ViewModel - viewModelScope to launch a coroutine. Example:

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)
    lifecycleScope.launch {
        val customer = customerViewModel.geCustomerById("11")
        val name = customer.first()?.firstName;
        // ... use name
    }
}