How not to duplicate server request in Android?

I have several pages (Activities, Fragments) that list some posts. To receive these posts, I request them via Retrofit. To receive fresh posts, I call a method that requests them from the server whenever I open a new page.

Help me find best practices or solutions like pattern or architecture.

This is my pseudo code:

Activity

class Activity {
  fun onCreate () {
    viewModel.data.observe { state->
      loader.isVisible = state is State.Loading
      when(state) {
         State.Data -> adapter.submitList(state.data)
         State.Error -> showError(state.error)
      }
    }
  }
}

ViewModel

class ViewModel(val loader: PostsLoader) {
   val data get = loader.data.also {
     loader.execute()
   }
}

Loader (it is singleton?)

class PostsLoader(val repository: PostRepository) {

  val data get(): LiveData<DataWrapper<List<Post>> = _data 
   
  private val _data = MutableLiveData<DataWrapper<List<Post>>()

  fun execute() {
    if (_data.value == null || _data.value == DataWrapper.Loading) return

    _data.value = DataWrapper.Loading

    try {
      _data.value = DataWrapper.Success(repository.getPosts())
    } catch(error: Throwable) {
      _data.value = DataWrapper.Error(error)
    }
  }
}

Repository

class PostRepository(val api: Api) {
  fun getPosts(): List<Post> {
    return api.getPosts()
  }
}