Tukukkk

I have converted RAVI TAMADA's RxJava tutorial from Java into Kotlin Android RxJava Networking with Retrofit, Gson – Notes App. On testing of the application just on the first network call I receive a HTTP 500 Internal Error (com.jakewharton.retrofit2.adapter.rxjava2.HttpException: HTTP 500 Internal Server Error). This is for the first network call registerUsers As far as conversion is concerned I have done everything by the book.

I have included the code base for the following classes

MainActivity

class MainActivity : AppCompatActivity()

{



    lateinit var apiService: ApiService

    var disposable = CompositeDisposable()

    lateinit var mAdapter: NotesAdapter

    var noteList = ArrayList<Note>()



    companion object

    {

        val TAG = MainActivity::class.java.simpleName;



    }



    @BindView(R.id.coordinator_layout) var coordinatorLayout: CoordinatorLayout? = null



    @BindView(R.id.recycler_view)  var recyclerView: RecyclerView? = null



    @BindView(R.id.txt_empty_notes_view) var noNotesView: TextView? = null



    override fun onCreate(savedInstanceState: Bundle?)

    {

        super.onCreate(savedInstanceState)



        getWindow().getDecorView().setSystemUiVisibility(View.SYSTEM_UI_FLAG_LIGHT_STATUS_BAR);

        setContentView(R.layout.activity_main);

        ButterKnife.bind(this);



        val toolbar = findViewById<Toolbar>(R.id.toolbar)

        toolbar.setTitle(getString(R.string.activity_title_home))

        setSupportActionBar(toolbar)



        fab.setOnClickListener { view ->



            showNoteDialog(false, null, -1);



        }



        // white background notification bar

        whiteNotificationBar(fab);



        apiService = ApiClient.getClient(getApplicationContext())?.create(ApiService::class.java)!!



        mAdapter = NotesAdapter(this, noteList)

        var mLayoutManager = LinearLayoutManager(getApplicationContext());

        recyclerView?.setLayoutManager(mLayoutManager);

        recyclerView?.setItemAnimator(DefaultItemAnimator());

        recyclerView?.addItemDecoration(MyDividerItemDecoration(this, LinearLayoutManager.VERTICAL, 16));

        recyclerView?.setAdapter(mAdapter);



        /**

         * On long press on RecyclerView item, open alert dialog

         * with options to choose

         * Edit and Delete

         * */

        recyclerView?.addOnItemTouchListener(RecyclerTouchListener(this, recyclerView!!, object : RecyclerTouchListener.ClickListener

        {



            override fun onClick(view: View, position: Int)

            {

            }



            override fun onLongClick(view: View, position: Int)

            {

                showActionsDialog(position);

            }

        }))



        /**

         * Check for stored Api Key in shared preferences

         * If not present, make api call to register the user

         * This will be executed when app is installed for the first time

         * or data is cleared from settings

         * */



        var test = PrefUtils.getApiKey(this)

        if (TextUtils.isEmpty(PrefUtils?.getApiKey(this)))

        {

            registerUser();

        } else

        {

            // user is already registered, fetch all notes

            fetchAllNotes();

        }

    }



    override fun onCreateOptionsMenu(menu: Menu): Boolean

    {

        // Inflate the menu; this adds items to the action bar if it is present.

        menuInflater.inflate(R.menu.menu_main, menu)

        return true

    }



    override fun onOptionsItemSelected(item: MenuItem): Boolean

    {

        // Handle action bar item clicks here. The action bar will

        // automatically handle clicks on the Home/Up button, so long

        // as you specify a parent activity in AndroidManifest.xml.

        return when (item.itemId)

        {

            R.id.action_settings -> true

            else -> super.onOptionsItemSelected(item)

        }

    }





    /**

     * Registering new user

     * sending unique id as device identification

     * https://developer.android.com/training/articles/user-data-ids.html

     */

    private fun registerUser()

    {

        // unique id to identify the device

        val uniqueId = UUID.randomUUID().toString()



        disposable

            .add(apiService.register(uniqueId)

                .subscribeOn(Schedulers.io())

                .observeOn(AndroidSchedulers.mainThread())

                .subscribeWith(

            object : DisposableSingleObserver<User>()

            {

                override fun onSuccess(user: User)

                {

                    // Storing user API Key in preferences

                    user.apiKey?.let { PrefUtils.storeApiKey(applicationContext, it) }



                    Toast.makeText(applicationContext,

                        "Device is registered successfully! ApiKey: " + PrefUtils.getApiKey(applicationContext),

                        Toast.LENGTH_LONG).show()

                }



                override fun onError(e: Throwable)

                {

                    Log.e(TAG, "onError: " + e.message)

                    showError(e)

                }

            }))

    }



    /**

     * Fetching all notes from api

     * The received items will be in random order

     * map() operator is used to sort the items in descending order by Id

     */

    fun fetchAllNotes()

    {

        disposable.add(apiService.fetchAllNotes().subscribeOn(Schedulers.io()).observeOn(AndroidSchedulers.mainThread()).map(

            object : io.reactivex.functions.Function<List<Note>, List<Note>>

            {

                override fun apply(notes: List<Note>): List<Note>

                {

                    Collections.sort(notes, object : Comparator<Note>

                    {

                        override fun compare(n1: Note?, n2: Note?): Int

                        {

                            return n2!!.id - n1!!.id;



                        }

                    })

                    return notes

                }

            }).subscribeWith(object : DisposableSingleObserver<List<Note>>()

        {

            override fun onSuccess(notes: List<Note>)

            {

                noteList.clear();

                noteList.addAll(notes);

                mAdapter.notifyDataSetChanged();



                toggleEmptyNotes();

            }



            override fun onError(e: Throwable)

            {

                Log.e(TAG, "onError: " + e.message);

                showError(e);





            }

        }))

    }





    /**

     * Creating new note

     */

    private fun createNote(note: String)

    {

        disposable.add(apiService.createNote(note)

            .subscribeOn(Schedulers.io())

            .observeOn(AndroidSchedulers.mainThread())

            .subscribeWith(

            object : DisposableSingleObserver<Note>()

            {



                override fun onSuccess(note: Note)

                {

                    if (!TextUtils.isEmpty(note.error))

                    {

                        Toast.makeText(applicationContext, note.error, Toast.LENGTH_LONG).show()

                        return

                    }



                    Log.d(TAG, "new note created: " + note.id + ", " + note.note + ", " + note.timestamp)



                    // Add new item and notify adapter

                    noteList.add(0, note)

                    mAdapter.notifyItemInserted(0)



                    toggleEmptyNotes()

                }



                override fun onError(e: Throwable)

                {

                    Log.e(TAG, "onError: " + e.message)

                    showError(e)

                }

            }))

    }



    /**

     * Updating a note

     */

    private fun updateNote(noteId: Int, note: String, position: Int)

    {

        disposable

            .add(apiService.updateNote(noteId,

            note)

                .subscribeOn(Schedulers.io())

                .observeOn(AndroidSchedulers.mainThread())

                .subscribeWith(object :

            DisposableCompletableObserver()

        {

            override fun onComplete()

            {

                Log.d(TAG, "Note updated!")



                val n = noteList.get(position)

                n.note = (note)



                // Update item and notify adapter

                noteList.set(position, n)

                mAdapter.notifyItemChanged(position)

            }



            override fun onError(e: Throwable)

            {

                Log.e(TAG, "onError: " + e.message)

                showError(e)

            }

        }))

    }



    /**

     * Deleting a note

     */

    private fun deleteNote(noteId: Int, position: Int)

    {

        Log.e(TAG, "deleteNote: $noteId, $position")

        disposable

            .add(apiService.deleteNote(noteId)

                .subscribeOn(Schedulers.io())

                .observeOn(AndroidSchedulers.mainThread())

                .subscribeWith(

            object : DisposableCompletableObserver()

            {

                override fun onComplete()

                {

                    Log.d(TAG, "Note deleted! $noteId")



                    // Remove and notify adapter about item deletion

                    noteList.removeAt(position)

                    mAdapter.notifyItemRemoved(position)



                    Toast.makeText(this@MainActivity, "Note deleted!", Toast.LENGTH_SHORT).show()



                    toggleEmptyNotes()

                }



                override fun onError(e: Throwable)

                {

                    Log.e(TAG, "onError: " + e.message)

                    showError(e)

                }

            }))

    }



    /**

     * Shows alert dialog with EditText options to enter / edit

     * a note.

     * when shouldUpdate=true, it automatically displays old note and changes the

     * button text to UPDATE

     */

    private fun showNoteDialog(shouldUpdate: Boolean, note: Note?, position: Int)

    {

        val layoutInflaterAndroid = LayoutInflater.from(applicationContext)

        val view = layoutInflaterAndroid.inflate(R.layout.note_dialog, null)



        val alertDialogBuilderUserInput = AlertDialog.Builder(this@MainActivity)

        alertDialogBuilderUserInput.setView(view)



        val inputNote = view.findViewById<EditText>(R.id.note)

        val dialogTitle = view.findViewById<TextView>(R.id.dialog_title)

        dialogTitle.setText(if (!shouldUpdate) getString(R.string.lbl_new_note_title) else getString(R.string.lbl_edit_note_title))



        if (shouldUpdate && note != null)

        {

            inputNote.setText(note.note)

        }

        alertDialogBuilderUserInput.setCancelable(false).setPositiveButton(if (shouldUpdate) "update" else "save",

            DialogInterface.OnClickListener { dialogBox, id -> })

            .setNegativeButton("cancel", DialogInterface.OnClickListener { dialogBox, id -> dialogBox.cancel() })



        val alertDialog = alertDialogBuilderUserInput.create()

        alertDialog.show()



        alertDialog.getButton(AlertDialog.BUTTON_POSITIVE).setOnClickListener(View.OnClickListener {

            // Show toast message when no text is entered

            if (TextUtils.isEmpty(inputNote.text.toString()))

            {

                Toast.makeText(this@MainActivity, "Enter note!", Toast.LENGTH_SHORT).show()

                return@OnClickListener

            } else

            {

                alertDialog.dismiss()

            }



            // check if user updating note

            if (shouldUpdate && note != null)

            {

                // update note by it's id

                updateNote(note.id, inputNote.text.toString(), position)

            } else

            {

                // create new note

                createNote(inputNote.text.toString())

            }

        })

    }



    /**

     * Opens dialog with Edit - Delete options

     * Edit - 0

     * Delete - 0

     */

    private fun showActionsDialog(position: Int)

    {

        val colors = arrayOf<CharSequence>("Edit", "Delete")



        val builder = AlertDialog.Builder(this)

        builder.setTitle("Choose option")

        builder.setItems(colors) { dialog, which ->

            if (which == 0)

            {

                showNoteDialog(true, noteList.get(position), position)

            } else

            {

                deleteNote(noteList.get(position).id, position)

            }

        }

        builder.show()

    }



    private fun toggleEmptyNotes()

    {

        if (noteList.size > 0)

        {

            noNotesView?.setVisibility(View.GONE)

        } else

        {

            noNotesView?.setVisibility(View.VISIBLE)

        }

    }





    /**

     * Showing a Snackbar with error message

     * The error body will be in json format

     * {"error": "Error message!"}

     */

    fun showError(e: Throwable)

    {

        var message = ""

        try

        {

            if (e is IOException)

            {

                message = "No internet connection!"

            }

            else (e is HttpException)

            run {

                var error = e as HttpException

                var errorBody = error.response().errorBody().toString()

                var jObj = JSONObject(errorBody)

                message = jObj.getString("error")







            }



        }

        catch (e1: IOException)

        {

            e1.printStackTrace()

        }

        catch (e1: JSONException)

        {

            e1.printStackTrace()

        }

        catch (e1: Exception)

        {

            e1.printStackTrace()

        }



        if (TextUtils.isEmpty(message))

        {

            message = "Unknown error occurred! Check LogCat."

        }



        val snackbar = coordinatorLayout?.let { Snackbar.make(it, message, Snackbar.LENGTH_LONG) }



        val sbView = snackbar?.getView()

        val textView = sbView?.findViewById<TextView>(android.support.design.R.id.snackbar_text)

        textView?.setTextColor(Color.YELLOW)

        snackbar?.show()

    }



    fun whiteNotificationBar(view: View)

    {

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M)

        {

            var flags = view.getSystemUiVisibility()

            flags = View.SYSTEM_UI_FLAG_LIGHT_STATUS_BAR

            view.setSystemUiVisibility(flags)

            getWindow().setStatusBarColor(Color.WHITE)

        }

    }



    override fun onDestroy()

    {

        super.onDestroy()

        disposable.dispose()

    }

}

ApiService Interface

interface  ApiService

{

    // Register new user

    @FormUrlEncoded

    @POST("notes/user/register")

    fun register(@Field("device_id") deviceId: String): Single<User>

    //    Single<User> register(@Field("device_id") String deviceId)



    // Create note

    @FormUrlEncoded

    @POST("notes/new")

    fun createNote(@Field("note") note: String): Single<Note>



    // Fetch all notes

    @GET("notes/all") fun fetchAllNotes(): Single<List<Note>>



    // Update single note

    @FormUrlEncoded

    @PUT("notes/{id}")

    fun updateNote(@Path("id") noteId: Int, @Field("note") note: String): Completable



    // Delete note

    @DELETE("notes/{id}")

    fun deleteNote(@Path("id") noteId: Int): Completable

    }

ApiClient Class

class ApiClient

{

    companion object

    {

        var retrofit: Retrofit? = null

        var REQUEST_TIMEOUT = 60

        var okHttpClient: OkHttpClient? = null



        fun getClient(context: Context): Retrofit?

        {

            if (okHttpClient == null)

                initOkHttp(context)



            if (retrofit == null)

            {

                retrofit = Retrofit.Builder().baseUrl(BASE_URL).client(okHttpClient)

                    .addCallAdapterFactory(RxJava2CallAdapterFactory.create())

                    .addConverterFactory(GsonConverterFactory.create()).build()

            }

            return retrofit

        }



        fun initOkHttp(context: Context)

        {

            val httpClient = OkHttpClient().newBuilder().connectTimeout(REQUEST_TIMEOUT.toLong(), TimeUnit.SECONDS)

                .readTimeout(REQUEST_TIMEOUT.toLong(), TimeUnit.SECONDS)

                .writeTimeout(REQUEST_TIMEOUT.toLong(), TimeUnit.SECONDS)



            val interceptor = HttpLoggingInterceptor()

            interceptor.level = HttpLoggingInterceptor.Level.BODY



            httpClient.addInterceptor(interceptor)



            httpClient.addInterceptor(object : Interceptor

            {

                override fun intercept(chain: Interceptor.Chain): Response

                {

                    var original = chain.request()

                    var requestBuilder = original.newBuilder()



                        .addHeader("Accept", "application/json").addHeader("Content-Type", "application/json");



                    // Adding Authorization token (API Key)

                    // Requests will be denied without API key

                    if (!TextUtils.isEmpty(PrefUtils.getApiKey(context)))

                    {

                        requestBuilder.addHeader("Authorization", PrefUtils.getApiKey(context));

                    }



                    var request = requestBuilder.build();



                    return chain.proceed(request)

                }





            })



            okHttpClient = httpClient.build()

        }

    }

}

PrefUtils Class

 class PrefUtils

{

    /**

     * Storing API Key in shared preferences to

     * add it in header part of every retrofit request

     */





    companion object

    {



        fun getSharedPreferences(context: Context): SharedPreferences

        {

            return context.getSharedPreferences("APP_PREF", Context.MODE_PRIVATE)

        }



        fun storeApiKey(context: Context, apiKey: String)

        {

            val editor = getSharedPreferences(context).edit()

            editor.putString("API_KEY", apiKey)

            editor.commit()

        }



        fun getApiKey(context: Context): String?

        {

            return getSharedPreferences(context).getString("API_KEY", null)

        }

    }

}