SharedViewModel.kt

private val cartHashMap = MutableLiveData<HashMap<String,Cart>>()
private var sharedHashMap = HashMap<String,Cart>() 

fun setProductSelectedHashMap(productId:String,productSelected:Cart){
        sharedHashMap[productId] = productSelected
        cartHashMap.value = sharedHashMap
    }

    fun removeSelectedProduct(productId:String){
        sharedHashMap.remove(productId)
        cartHashMap.value = sharedHashMap
    }

    fun updateProductQuantity(productId:String, quantity:Int){
        val productoCartSelected = sharedHashMap[productId]
        productoCartSelected?.cantidad = quantity
        sharedHashMap[productId] = productoCartSelected!!
        cartHashMap.value = sharedHashMap
    }