LiveData observation won't update - kotlin

Question

I want to send some data to the server and show its response to the user.
I'm using MVVM so I created a repository like this:
class Repository {
fun getData(context: Context, word: String): LiveData<String> {
val result = MutableLiveData<String>()
val request = object : StringRequest(
Method.POST,
"https://.......",
Response.Listener {
result.value = it.toString()
},
Response.ErrorListener {
result.value = it.toString()
}) {
#Throws(AuthFailureError::class)
override fun getParams(): MutableMap<String, String> {
val params = HashMap<String, String>()
params["word"] = word
return params
}
}
val queue = Volley.newRequestQueue(context)
queue.add(request)
return result
}
}
which just sends 'word' to the server and get its response.
my view model class contains just a mutableLiveData and a function. it is like this:
class ViewModel(application: Application) : AndroidViewModel(application) {
var result = MutableLiveData<String>()
fun getData(word: String): LiveData<String> {
val repository = Repository()
result = repository.getData(getApplication(), word) as MutableLiveData<String>
return result
}
}
I set an observation for result in my main Activity, therefore it is my MainActivity codes:
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
val model = ViewModelProviders.of(this).get(ViewModel::class.java)
submit.setOnClickListener {
model.getData(search_txt.text.toString())
}
model.result.observe(this, Observer {
Log.i("Log", "observe is :$it")
text.text = it
})
}
but it doesn't work! I get the user's input using an edit text and after pressing a button, I call getData function which is in my View Model class. but it returns always null and observation won't work.
I try to put observe the method in my button listener, in this way I get the result but it seems it's not a correct way because after I rotate my phone, all data ware gone and I need to fetch data from the server again while it shouldn't.