如何在 ViewModel 中使用 Strings.xml 而不在 Android 中使用上下文？

Question

We have existing app, we need to add Multiple Language Support for that app. All the strings which are accessed with String.xml are translating. but we have a constants (which are strings), which we are accessing in VewModel. these constant are not getting translate.code structure is like below

Constant.kt file

    class Constants private constructor() {

companion object {

    const val NAME= "Name"
    const val LAST_NAME= "Last name"
    
}

ViewModel looks like this

VewModel.kt

 class VewModel() : ViewModel() {
    fun getStrings():String{
        return NAME+LAST_NAME
    }
}

In Activity calling method like this

viewmodel.getStrings()

and there are relevant strings of Name and Last_Name in all multiple Strings.xml file.

I am not getting How do i convert those constant strings to multiple languages. I cant use context in viewmodel and constants(Architecture restrictions). any help.

Answer 1

Either you use binding expression in your xml layout, for example the text:

android:text="@{@string/name_label + `: ` + viewModel.name}"    //not single quote, be careful

Or use AndroidViewModel :

class StudentViewModel(private val application: Application) : AndroidViewModel(application) {
    val name = "Sam"

    fun getNameText() = "${application.getString(R.string.name_label): $name}"

---

The way you pass arguement to ViewModel is through the ViewModelFactory , just boilerplate code:

class StudentViewModelFactory(private val application: Application) : ViewModelProvider.Factory {
    override fun <T : ViewModel?> create(modelClass: Class<T>): T {
        if (modelClass.isAssignableFrom(StudentViewModel::class.java)) {
            return StudentViewModel(application) as T
        }

        throw IllegalArgumentException("Unknown ViewModel class")
    }
}

And setup both in your fragment :

viewModelFactory = StudentViewModelFactory( requireActivity().application)
viewModel = ViewModelProvider(this, viewModelFactory).get(StudentViewModel::class.java)