在循环中获取 LiveData 转换 android

Question

I am getting all categories from a different endpoint, different repository. That is giving me all categories. Now i want to run this categories in loop and write observer to get all the items of each category. In other words - I want to get FeedItems of all categories one by one because i have to fire separate endpoint to each category. I have list of all categories.

I am able to get single category's items by writing below code, but do not know how to get multiple.

In viewModal i am doing below code for to single category Observer

  val categoryByIdItems: LiveData<Resource<List<FeedItem>>> = Transformations
        .switchMap(categoryByIdParam) { input ->
            input.ifExists { catId, shouldFetch ->
                feedRepository.loadCategoryByIdFeed(catId.toString(), shouldFetch)
            }
        }

if i use above code it will give me feedItems of one category by calling load function

fun load(categories:List<Category>,shouldFetch:Boolean = false){
    setCategoryByIdRequest(categories[0].id, shouldFetch)
}

I want to run setCategoryByIdRequest in loop based on categories, i can do that. I am using this code to get first category items in fragment file

viewModel.categoryByIdItems.observe(this, Observer { resource ->
})

if i run the loop for viewModel.categoryByIdItems.observe than layout adds in fragment but because of same observer all are same.

But i am not sure how can i get categoryByIdItems in loop as observe in fragment. as categoryByIdItems i am defining in view-modal first and using that in fragment but i want that dynamic based on number of categories.

Sorry for my writing as i do not know how to explain more to tell you what i want. I am new with LiveData and Transformations. I am not using DB, using apis to get data. let me know if you want to find more code about repository, view modal or fragment, i'll provide you.

Answer 1

I would advise you to get all category in a list first from DB and then using kotlin filter to fetch by ID like this

DAO

@Query("SELECT * FROM categories_table") fun getAll(): LiveData<List>

VIEWMODEL

private val _categories = DAO.getAll()

val categories : LiveData<Category>
   get() = _categories

ACTIVITY/ FRAGMENT

viewModel.categories .observe(viewLifecycleOwner, Observer { it ->

if(it!=null){

//filter your data
})