Send a parameter to Kotlin retrofit call

Question

I am a beginner in Kotlin. I need to send a variable parameter from my Activity to a Retrofit call.

This is my call in on Create of Detail Activity

override fun onCreate(savedInstanceState: Bundle?) {
    //...
    val id = intent.getStringExtra("id")

    // Get the ViewMode
    val mModel = ViewModelProviders.of(this).get(myObjectViewModel::class.java)

    //Create the observer which updates the UI.
    val myObjectByIdObserver = Observer<MyObject> { myObject->
        //...
    }

    //Observe the LiveData, passing in this activity as the LifecycleOwner and the observer.
    mModel.getObjectById.observe(this, myObjectByIdObserver)
}

Here I insert value hardcode, I need the parameter received from the previous Activity.

class MyObjectViewModel : ViewModel() {

    //this is the data that we will fetch asynchronously 
    var myObject: MutableLiveData<MyObject>? = null

    val getMyObjectById: LiveData<MyObject>
        get() {
            if (myObject == null) {
                myObject = MutableLiveData()
                loadMyObjectById()
            }
        return myObject as MutableLiveData<MyObject>
    }

private fun loadMyObjectById() {
    val retrofit = Retrofit.Builder()
        .baseUrl(Api.BASE_URL)
        .addConverterFactory(GsonConverterFactory.create())
        .build()

    val api = retrofit.create(Api::class.java)
    val call = api.myObjectById(100)

    call.enqueue(object : Callback<MyObject> {
        override fun onResponse(call: Call<MyObject>, response: Response<MyObject>) {
            myObject!!.value = response.body()
        }
        override fun onFailure(call: Call<MyObject>, t: Throwable) {
            var tt = t
        }
    })
}

My API:

interface Api {
    companion object {
        const val BASE_URL = "https://.../"
    }

    @GET("myObjects/{id}")
    fun myObjectById(@Path("id") id: Int?): Call<MyObject>
}

taka · Accepted Answer · 2019-01-24T03:45:11.240

8

You can do this by ``@Query``` annotation.

interface Api {
    companion object {
        const val BASE_URL = "https://.../"
    }

    @GET("myObjects/{id}")
    fun myObjectById(@Path("id") id: Int?, @Query("a_param") aParam: String?): Call<MyObject>
}

Edited. I completely misread your intension.

What you need seems to be ViewModelProvider.NewInstanceFactory like

class MyObjectViewModel(val id: Int): ViewModel() {
    class Factory(val id: Int) : ViewModelProvider.NewInstanceFactory() {
        override fun <T : ViewModel?> create(modelClass: Class<T>): T {
            return MyObjectViewModel(id) as T
        }
    }
}

then

    val myViewModel = ViewModelProviders
        .of(this, MyObjectViewModel.Factory(id))
        .get(MyObjectViewModel::class.java)

edited Jan 24 '19 at 03:45

answered Jan 24 '19 at 03:15

taka

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1

My problem is HOW to send this parameter from the call in the onCreate of my Activity. Thanks!! – Andy Jan 24 '19 at 03:18
Create a function in the viewmodel class and pass the parameter in the function itself, then make the service call from that funciton. – Sarthak Gandhi Jan 24 '19 at 05:31
This answer work for me! I call yo my ViewModel in this way: val myViewModel = ViewModelProviders.of(this, MyObjectViewModelFactory(this.application, id)).get(MyObjectViewModel::class.java) – Andy Jan 24 '19 at 13:19

Send a parameter to Kotlin retrofit call

1 Answers1