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How to synchonize executing http requests (kotlin, android)?

I am debugging an application that communicates with an IoT device via http.
In response to commands, the device sends information in xml format.
An application can also receive binary data on a GET request.
In the functionality of the application, filling the RecyclerView from the list and loading images to fill the RecyclerView and executing individual commands to change modes.
The problem is that the device does not have the most powerful processor, and when a large number of http commands are received, the service cannot cope and hangs for a long time until the WiFi channel fails.
I can’t figure out how to organize interaction so that each next command waits for the previous one to complete. The solution is complicated by the fact that populating the RecyclerView, loading images, and executing commands are in different parts of the code, and each is executed asynchronously.
Populating RecyclerView:
private fun initViewModel(filter: String) {
val st = Storage(requireContext())
val cache = "${st.externalCacheDir}/$filter/"
val viewModel = ViewModelProvider(this).get(DeviceListViewModel::class.java)
viewModel.getRecycerListObserver().observe(requireActivity(), Observer<ResponseData> {
if (it != null) {
val media = it.mediaData?.filter { it.mediaData?.fPath!!.contains(filter, false) }
mediaList = arrayListOf()
if (media != null) {
for (i in media.sortedByDescending { it.mediaData?.fTimeCode }) {
i.mediaData?.let { it1 -> mediaList.add(it1) }
}
}
viewModel.recyclerListLiveData = MutableLiveData()
ThumbDownloader(dataAdapter, mediaList, cache, swipeLayout).execute()
} else {
Toast.makeText(activity, "Error in getting data", Toast.LENGTH_SHORT).show()
}
})
viewLifecycleOwner.lifecycleScope.launch {
viewModel.makeApiCall()
}
}
ViewModel:
class DeviceListViewModel : ViewModel() {
var recyclerListLiveData: MutableLiveData<ResponseData>
init {
recyclerListLiveData = MutableLiveData()
}
fun getRecycerListObserver(): MutableLiveData<ResponseData> {
return recyclerListLiveData
}
fun makeApiCall() {
viewModelScope.launch(Dispatchers.IO) {
try {
val retroInstance =
RetroInstance.getRetroInstance(MainActivity.BaseUrl).create(RetroService::class.java)
val response = retroInstance.getDataFromApi(1, Cmd.WIFIAPP_CMD_FILELIST)
recyclerListLiveData.postValue(response)
} catch (e: Exception) {
var response: ResponseData? = null
when (e) {
is ConnectException -> {
recyclerListLiveData.postValue(response)
}
is SocketTimeoutException -> {
recyclerListLiveData.postValue(response)
}
}
}
}
}
}
Service to make a command (processing results in the Handler):
class DeviceService {
private val handler: Handler
private var mJob: Job? = null
constructor(handler: Handler) {
this.handler = handler
}
fun sendCommand(cmd: Int) {
val service = RetroInstance.buildService(MainActivity.BaseUrl, RetroService::class.java)
mJob = CoroutineScope(Dispatchers.IO).launch {
val response = when (cmd) {
Cmd.WIFIAPP_CMD_MOVIE_GET_LIVEVIEW_FMT -> {
try {
service.getLinkFromApi(1, cmd)
} catch (e: Exception) {
handler.obtainMessage(Msg.MESSAGE_TOAST, "Error in getting data").sendToTarget()
mJob?.cancel()
}
}
else -> {
try {
service.makeCommand(1, cmd)
} catch (e: Exception) {
handler.obtainMessage(Msg.MESSAGE_TOAST, "Error in getting data").sendToTarget()
mJob?.cancel()
}
}
}
withContext(Dispatchers.Main) {
try {
when (cmd) {
Cmd.WIFIAPP_CMD_MOVIE_GET_LIVEVIEW_FMT -> {
handler.obtainMessage(Msg.MESSAGE_LINK_FORMAT, response).sendToTarget()
}
else -> {
handler.obtainMessage(Msg.MESSAGE_PAR_FUNCTION, response).sendToTarget()
}
}
} catch (e: Exception) {
when (e) {
is ConnectException -> {
handler.obtainMessage(Msg.MESSAGE_TOAST, "Connection lost").sendToTarget()
}
is SocketTimeoutException -> {
handler.obtainMessage(Msg.MESSAGE_TOAST, "Connection lost").sendToTarget()
}
}
}
mJob?.cancelAndJoin()
}
}
}
}
Downloading a images:
class ThumbDownloader(dataAdapter: DeviceAdapter, data: ArrayList<MediaData>, file_path: String, swipe: SwipeRefreshLayout) : CoroutineScope {
private var job: Job = Job()
private var file_path: String
private var dataAdapter: DeviceAdapter
private var data: ArrayList<MediaData>
private var swipe: SwipeRefreshLayout
init {
this.data = data
this.file_path = file_path
this.dataAdapter = dataAdapter
this.swipe = swipe
}
override val coroutineContext: CoroutineContext
get() = Dispatchers.Main + job
fun cancel() {
job.cancel()
}
fun execute() = async {
var item: File? = null
for (i in data) {
val task = async(Dispatchers.IO) {
val url = i.fPath!!
val real_url = "${MainActivity.BaseUrl}$url"
item = NetworkUtil.downloadFile(real_url, file_path, false)
}
task.await()
if (item != null) {
dataAdapter.insertItem(i)
}
}
cancel()
swipe.isRefreshing = false
}
}
Any ideas how to come up with their synchronization while waiting for the previous commands to complete?

Making a generic network adapter using livedata, retrofit, mvvm and repository pattern

I am new to android architecture components and I am trying to use LiveData and ViewModels with mvvm, repository pattern and retrofit. Referred to GitHubSample google gave in its architecture guide but want to simplify it little bit for my needs. Below is the code which I had so far but having below problems in completing it.
onActive() method in LiveDataCallAdapter is not invoking at all
Not able to figure out how I can get the response as a LiveData(I get this as null always) in SettingsData class? Ideally here I just want to have success and failure listener and I should get the data inside these blocks. All the generic network errors should already be handled before coming to this class. I am not able to figure out how to do this.
3.I do not want to call.enqueue in this SettingsData class which many examples shows
Any help is greatly appreciated. Thanks in advance
//Activity
private fun loadApplicationSettings() {
val settingsViewModel = ViewModelProviders.of(this).get(SettingsViewModel::class.java)
settingsViewModel.userApplicationSettings.observe(this, Observer<UserApplicationSettings> { userApplicationSettingsResult ->
Log.d("UserApplicationSettings", userApplicationSettingsResult.toString())
userSettingsTextView.text = userApplicationSettingsResult.isPushNotificationEnabled
})
}
//ViewModel
class SettingsViewModel : ViewModel() {
private var settingsRepository: SettingsRepository
lateinit var userApplicationSettings: LiveData<UserApplicationSettings>
init {
settingsRepository = SettingsRepository()
loadUserApplicationSettings()
}
private fun loadUserApplicationSettings() {
userApplicationSettings = settingsRepository.loadUserApplicationSettings()
}
}
//Repository
class SettingsRepository {
val settingsService = SettingsData()
fun loadUserApplicationSettings(): LiveData<UserApplicationSettings> {
return settingsService.getUserApplicationSettings()
}
}
//I do not want to do the network calls in repository, so created a seperate class gets the data from network call
class SettingsData {
val apiBaseProvider = ApiBaseProvider()
fun getUserApplicationSettings(): MutableLiveData<UserApplicationSettings> {
val userApplicationSettingsNetworkCall = apiBaseProvider.create().getApplicationSettings()
//Not sure how to get the data from userApplicationSettingsNetworkCall and convert it to livedata to give to repository
// deally here I just want to have success and failure listener and I should get the data inside these blocks. All the generic network errors should already be handled before coming to this class. I am not able to figure out how to do this.
val userApplicationSettingsData: LiveData<ApiResponse<UserApplicationSettings>> = userApplicationSettingsNetworkCall
//Thinking of having a success and fail block here and create a LiveData object to give to repository. Not sure how to do this
return userApplicationSettingsData
}
}
//Settings Service for retrofit
interface SettingsService {
#GET("url")
fun getApplicationSettings(): LiveData<ApiResponse<UserApplicationSettings>>
}
//Base provider of retrofit
class ApiBaseProvider {
fun create(): SettingsService {
val gson = GsonBuilder().setLenient().create()
val okHttpClient = createOkHttpClient()
val retrofit = Retrofit.Builder()
.addCallAdapterFactory(LiveDataCallAdapterFactory())
.addConverterFactory(GsonConverterFactory.create(gson))
.baseUrl("url")
.build()
return retrofit.create(SettingsService::class.java)
}
}
//
class LiveDataCallAdapterFactory : Factory() {
override fun get(
returnType: Type,
annotations: Array<Annotation>,
retrofit: Retrofit
): CallAdapter<*, *>? {
if (getRawType(returnType) != LiveData::class.java) {
return null
}
val observableType = getParameterUpperBound(0, returnType as ParameterizedType)
val rawObservableType = getRawType(observableType)
if (rawObservableType != ApiResponse::class.java) {
throw IllegalArgumentException("type must be a resource")
}
if (observableType !is ParameterizedType) {
throw IllegalArgumentException("resource must be parameterized")
}
val bodyType = getParameterUpperBound(0, observableType)
return LiveDataCallAdapter<Any>(bodyType)
}
}
//Custom adapter that does the network call
class LiveDataCallAdapter<T>(private val responseType: Type) : CallAdapter<T, LiveData<ApiResponse<T>>> {
override fun responseType(): Type {
return responseType
}
override fun adapt(call: Call<T>): LiveData<ApiResponse<T>> {
return object : LiveData<ApiResponse<T>>() {
override fun onActive() {
super.onActive()
call.enqueue(object : Callback<T> {
override fun onResponse(call: Call<T>, response: Response<T>) {
println("testing response: " + response.body())
postValue(ApiResponse.create(response))
}
override fun onFailure(call: Call<T>, throwable: Throwable) {
postValue(ApiResponse.create(throwable))
}
})
}
}
}
}
//I want to make this class as a generic class to do all the network success and error handling and then pass the final response back
/**
* Common class used by API responses.
* #param <T> the type of the response object
</T> */
sealed class ApiResponse<T> {
companion object {
fun <T> create(error: Throwable): ApiErrorResponse<T> {
return ApiErrorResponse(error.message ?: "unknown error")
}
fun <T> create(response: Response<T>): ApiResponse<T> {
println("testing api response in create")
return if (response.isSuccessful) {
val body = response.body()
if (body == null || response.code() == 204) {
ApiEmptyResponse()
} else {
ApiSuccessResponse(
body = body
)
}
} else {
val msg = response.errorBody()?.string()
val errorMsg = if (msg.isNullOrEmpty()) {
response.message()
} else {
msg
}
ApiErrorResponse(errorMsg ?: "unknown error")
}
}
}
}
/**
* separate class for HTTP 204 responses so that we can make ApiSuccessResponse's body non-null.
*/
class ApiEmptyResponse<T> : ApiResponse<T>()
data class ApiErrorResponse<T>(val errorMessage: String) : ApiResponse<T>()
data class ApiSuccessResponse<T>(
val body: T
) : ApiResponse<T>() {
}

We can connect Activity/Fragment and ViewModel as below:
Firstly, we have to create our ApiResource which will handle the retrofit response.
public class ApiResource<T> {
#NonNull
private final Status status;
#Nullable
private final T data;
#Nullable
private final ErrorResponse errorResponse;
#Nullable
private final String errorMessage;
private ApiResource(Status status, #Nullable T data, #Nullable ErrorResponse errorResponse, #Nullable String errorMessage) {
this.status = status;
this.data = data;
this.errorResponse = errorResponse;
this.errorMessage = errorMessage;
}
public static <T> ApiResource<T> create(Response<T> response) {
if (!response.isSuccessful()) {
try {
JSONObject jsonObject = new JSONObject(response.errorBody().string());
ErrorResponse errorResponse = new Gson()
.fromJson(jsonObject.toString(), ErrorResponse.class);
return new ApiResource<>(Status.ERROR, null, errorResponse, "Something went wrong.");
} catch (IOException | JSONException e) {
return new ApiResource<>(Status.ERROR, null, null, "Response Unreachable");
}
}
return new ApiResource<>(Status.SUCCESS, response.body(), null, null);
}
public static <T> ApiResource<T> failure(String error) {
return new ApiResource<>(Status.ERROR, null, null, error);
}
public static <T> ApiResource<T> loading() {
return new ApiResource<>(Status.LOADING, null, null, null);
}
#NonNull
public Status getStatus() {
return status;
}
#Nullable
public T getData() {
return data;
}
#Nullable
public ErrorResponse getErrorResponse() {
return errorResponse;
}
#Nullable
public String getErrorMessage() {
return errorMessage;
}
}
The Status is just an Enum class as below:
public enum Status {
SUCCESS, ERROR, LOADING
}
The ErrorResponse class must be created in such a way that the getter and setter can handle the error.
RetrofitLiveData class
public class RetrofitLiveData<T> extends LiveData<ApiResource<T>> {
private Call<T> call;
public RetrofitLiveData(Call<T> call) {
this.call = call;
setValue(ApiResource.loading());
}
Callback<T> callback = new Callback<T>() {
#Override
public void onResponse(Call<T> call, Response<T> response) {
setValue(ApiResource.create(response));
}
#Override
public void onFailure(Call<T> call, Throwable t) {
setValue(ApiResource.failure(t.getMessage()));
}
};
#Override
protected void onActive() {
super.onActive();
call.enqueue(callback);
}
#Override
protected void onInactive() {
super.onInactive();
if (!hasActiveObservers()) {
if (!call.isCanceled()) {
call.cancel();
}
}
}
}
Repository class
public class Repository {
public LiveData<ApiResource<JunoBalanceResponse>> getJunoBalanceResponse(Map<String, String> headers) {
return new RetrofitLiveData<>(ApiClient.getJunoApi(ApiClient.BASE_URL.BASE).getJunoBalance(headers));
}
}
JunoBalanceResponse contains the objects and its getters and setters that I am waiting as a response of my retrofit request.
below is an example for the api interface.
public interface JunoApi {
#Headers({"X-API-Version: 2"})
#GET("balance")
Call<JunoBalanceResponse> getJunoBalance(#HeaderMap Map<String, String> headers);
}
ApiClient class
public class ApiClient {
public enum BASE_URL {
AUTH, BASE
}
private static Retrofit retrofit;
private static final String JUNO_SANDBOX_AUTH_URL = "https://sandbox.boletobancario.com/authorization-server/";
private static final String JUNO_SANDBOX_BASE_URL = "https://sandbox.boletobancario.com/api-integration/";
private static Retrofit getRetrofit(String baseUrl) {
OkHttpClient okHttpClient = new OkHttpClient().newBuilder()
.connectTimeout(90, TimeUnit.SECONDS)
.readTimeout(90, TimeUnit.SECONDS)
.writeTimeout(90, TimeUnit.SECONDS)
.build();
retrofit = new Retrofit.Builder()
.baseUrl(baseUrl)
.client(okHttpClient)
.addConverterFactory(GsonConverterFactory.create())
.build();
return retrofit;
}
public static JunoApi getJunoApi(BASE_URL targetPath) {
switch (targetPath) {
case AUTH: return getRetrofit(JUNO_SANDBOX_AUTH_URL).create(JunoApi.class);
case BASE: return getRetrofit(JUNO_SANDBOX_BASE_URL).create(JunoApi.class);
default: return getRetrofit(JUNO_SANDBOX_BASE_URL).create(JunoApi.class);
}
}
}
Now we can connect our Repository and ApiViewModel.
public class ApiViewModel extends ViewModel {
private Repository repository = new Repository();
public LiveData<ApiResource<JunoBalanceResponse>> getJunoBalanceResponse(Map<String, String> headers) {
return repository.getJunoBalanceResponse(headers);
}
}
And finally, we can observe the retrofit response in our Activity/Fragment
apiViewModel = ViewModelProviders.of(requireActivity()).get(ApiViewModel.class);
apiViewModel.getJunoBalanceResponse(headers).observe(getViewLifecycleOwner(), new Observer<ApiResource<JunoBalanceResponse>>() {
#Override
public void onChanged(ApiResource<JunoBalanceResponse> response) {
switch (response.getStatus()) {
case LOADING:
Log.i(TAG, "onChanged: BALANCE LOADING");
break;
case SUCCESS:
Log.i(TAG, "onChanged: BALANCE SUCCESS");
break;
case ERROR:
Log.i(TAG, "onChanged: BALANCE ERROR");
break;
}
}
});

Unable to read data via bluetooth successfully

I'm trying to create an App which can receive data and send data to the microcontroller (ESP32). But for some reason, I'm unable to receive data from microcontroller successfully.
The app is written in Kotlin, and I already tried some examples mentioned on StackOverflow, but none of them actually works on my code.
I can successfully send data to the microcontroller via Bluetooth, but I can't receive data from Bluetooth. (The method I used in the microcontroller is just simply "ESP_BT.println("Check");"
In the code snippet, the function relates to my receiving data is called "receiveBluetooth"
class ControlActivity: AppCompatActivity() {
companion object {
val myUUID: UUID = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB")
var myBluetoothSocket: BluetoothSocket? = null
lateinit var myProgress: ProgressDialog
lateinit var myBluetoothAdapter: BluetoothAdapter
var myIsConnected: Boolean = false
lateinit var myAddress: String
val mmInStream: InputStream? = null
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.control_layout)
myAddress = intent.getStringExtra(SelectDeviceActivity.EXTRA_ADDRESS)
ConnectToDevice(this).execute()
val btnShow = findViewById<Button>(R.id.btnShow)
var inputRPM: String
//Read in value and store it as String
btnShow.setOnClickListener{
inputRPM = receiveInput()
sendCommand(inputRPM)
}
//Read RPM from microcontroller (bluetooth)
val showCountTextView = findViewById<TextView>(R.id.textView)
btnRefresh.setOnClickListener {
//showCountTextView.text = receiveBluetooth()
receiveBluetooth(showCountTextView)
}
control_disconnect.setOnClickListener{
disconnect()
}
}
private fun receiveInput(): String {
val input = findViewById<EditText>(R.id.editText)
return input.text.toString()
}
private fun sendCommand(input: String) {
if (myBluetoothSocket != null) {
try{
myBluetoothSocket!!.outputStream.write(input.toByteArray())
} catch (e: IOException) {
e.printStackTrace()
}
}
}
private fun receiveBluetooth(input: TextView) {
val buffer = ByteArray(256)
val bytes:Int
var tmpIn: InputStream? = null
if (myBluetoothSocket != null) {
try {
tmpIn = myBluetoothSocket!!.inputStream
val mmInStream = DataInputStream(tmpIn)
bytes = mmInStream.read(buffer)
val readMessage = String(buffer, 0, bytes)
input.text = readMessage
//input.text="123"
} catch (e:IOException) {
e.printStackTrace()
}
}
}
private fun disconnect() {
if (myBluetoothSocket != null) {
try {
myBluetoothSocket!!.close()
myBluetoothSocket = null
myIsConnected = false
} catch (e: IOException) {
e.printStackTrace()
}
}
finish()
}
private class ConnectToDevice(c: Context) : AsyncTask<Void, Void, String> () {
private var connectSuccess: Boolean = true
private val context: Context
init {
this.context = c
}
override fun onPreExecute() {
super.onPreExecute()
myProgress = ProgressDialog.show(context, "Connecting", "Please wait")
}
override fun doInBackground(vararg params: Void?): String? {
try {
if (myBluetoothSocket == null || !myIsConnected) {
myBluetoothAdapter = BluetoothAdapter.getDefaultAdapter()
val device: BluetoothDevice = myBluetoothAdapter.getRemoteDevice(myAddress)
myBluetoothSocket = device.createInsecureRfcommSocketToServiceRecord(myUUID)
BluetoothAdapter.getDefaultAdapter().cancelDiscovery()
myBluetoothSocket!!.connect()
}
} catch (e: IOException) {
connectSuccess = false
e.printStackTrace()
}
//Needs be fixed
return null
}
override fun onPostExecute(result: String?) {
super.onPostExecute(result)
if (!connectSuccess) {
Log.i("data", "couldn't connect")
} else {
myIsConnected = true
}
myProgress.dismiss()
}
}
}
I expect the text will show exactly "Check", but instead, my text will only show the initial value that I assigned.

Maybe you should use a library. For me works fine RxAndroidBle library:
Gradle:
implementation "com.polidea.rxandroidble2:rxandroidble:1.8.1"
Implementation:
In my project with Android Java and ESP32 too, I read some characteristics or values with simple implementations, for example:
public void setupNotification() {
if (isConnected()) {
final Disposable disposable = connectionObservable
.flatMap(rxBleConnection -> rxBleConnection.setupNotification(charactSensorDataUuid))
.doOnNext(notificationObservable -> { notificationHasBeenSetUp(); })
.flatMap(notificationObservable -> notificationObservable)
.observeOn(AndroidSchedulers.mainThread())
.subscribe(this::onNotificationReceived, this::onNotificationSetupFailure);
compositeDisposable.add(disposable);
}
}
public void readSensorConfig(){
if (isConnected()) {
final Disposable disposable = connectionObservable
.firstOrError()
.flatMap(rxBleConnection -> rxBleConnection.readCharacteristic(charactConfigUuid))
.observeOn(AndroidSchedulers.mainThread())
.subscribe(this::onSensorConfigRead, this::onReadFailure);
compositeDisposable.add(disposable);
}
}
public void readSensorData(){
if (isConnected()) {
final Disposable disposable = connectionObservable
.firstOrError()
.flatMap(rxBleConnection -> rxBleConnection.readCharacteristic(charactSensorDataUuid))
.observeOn(AndroidSchedulers.mainThread())
.subscribe(this::onSensorDataRead, this::onReadFailure);
compositeDisposable.add(disposable);
}
}
The complete Java implementation is here:
https://github.com/kike-canaries/android-hpma115s0/blob/master/app/src/main/java/hpsaturn/pollutionreporter/common/BLEHandler.java
The migration to Kotlin should be simple, also on this library the main target is Bluetooth BLE, and they have many samples on Kotlin

NetworkBoundResource helper class without Room

When I tried to implements the NetworkBoundResource and Resource helper class for the Room Db and Retrofit, it works perfect. However, I need to implement the Search Result from RESTful using Retrofit only without Room. The Resources class is good and I dont need to change it. What I want to do is try to remove db source inside this class.
public abstract class NetworkBoundResource<ResultType, RequestType> {
private final AppExecutors appExecutors;
private final MediatorLiveData<Resource<ResultType>> result = new MediatorLiveData<>();
#MainThread
public NetworkBoundResource(AppExecutors appExecutors) {
this.appExecutors = appExecutors;
result.setValue(Resource.loading(null));
LiveData<ResultType> dbSource = loadFromDb();
result.addSource(dbSource, data -> {
result.removeSource(dbSource);
if (shouldFetch(data)) {
fetchFromNetwork(dbSource);
} else {
result.addSource(dbSource, newData -> setValue(Resource.success(newData)));
}
});
}
#MainThread
private void setValue(Resource<ResultType> newValue) {
if (!Objects.equals(result.getValue(), newValue)) {
result.setValue(newValue);
}
}
private void fetchFromNetwork(final LiveData<ResultType> dbSource) {
LiveData<ApiResponse<RequestType>> apiResponse = createCall();
// we re-attach dbSource as a new source, it will dispatch its latest value quickly
result.addSource(dbSource, newData -> setValue(Resource.loading(newData)));
result.addSource(apiResponse, response -> {
result.removeSource(apiResponse);
result.removeSource(dbSource);
//noinspection ConstantConditions
if (response.isSuccessful()) {
appExecutors.diskIO().execute(() -> {
saveCallResult(processResponse(response));
appExecutors.mainThread().execute(() ->
// we specially request a new live data,
// otherwise we will get immediately last cached value,
// which may not be updated with latest results received from network.
result.addSource(loadFromDb(),
newData -> setValue(Resource.success(newData)))
);
});
} else {
onFetchFailed();
result.addSource(dbSource,
newData -> setValue(Resource.error(response.errorMessage, newData)));
}
});
}
protected void onFetchFailed() {
}
public LiveData<Resource<ResultType>> asLiveData() {
return result;
}
#WorkerThread
protected RequestType processResponse(ApiResponse<RequestType> response) {
return response.body;
}
#WorkerThread
protected abstract void saveCallResult(#NonNull RequestType item);
#MainThread
protected abstract boolean shouldFetch(#Nullable ResultType data);
#NonNull
#MainThread
protected abstract LiveData<ResultType> loadFromDb();
#NonNull
#MainThread
protected abstract LiveData<ApiResponse<RequestType>> createCall();
}

The problem is that any loaded data have to go through the database first, then loading it from the database to the UI, as NetworkBoundResource does. Consequently, What I did is to decouple the persistent database and create a temporary field to load from.
For example if I wanted to edit the original search method, I would suggest:
public LiveData<Resource<List<Repo>>> search(String query) {
return new NetworkBoundResource<List<Repo>, RepoSearchResponse>(appExecutors) {
// Temp ResultType
private List<Repo> resultsDb;
#Override
protected void saveCallResult(#NonNull RepoSearchResponse item) {
// if you don't care about order
resultsDb = item.getItems();
}
#Override
protected boolean shouldFetch(#Nullable List<Repo> data) {
// always fetch.
return true;
}
#NonNull
#Override
protected LiveData<List<Repo>> loadFromDb() {
if (resultsDb == null) {
return AbsentLiveData.create();
}else {
return new LiveData<List<Repo>>() {
#Override
protected void onActive() {
super.onActive();
setValue(resultsDb);
}
};
}
}
#NonNull
#Override
protected LiveData<ApiResponse<RepoSearchResponse>> createCall() {
return githubService.searchRepos(query);
}
#Override
protected RepoSearchResponse processResponse(ApiResponse<RepoSearchResponse> response) {
RepoSearchResponse body = response.body;
if (body != null) {
body.setNextPage(response.getNextPage());
}
return body;
}
}.asLiveData();
}
I ran it and it works.
Edit:
I made another simpler class to handle that (There is another answer here by Daniel Wilson has more feature and is updated).
However, this class has no dependencies and is converted to the basics to make fetch response only:
abstract class NetworkBoundResource<RequestType> {
private val result = MediatorLiveData<Resource<RequestType>>()
init {
setValue(Resource.loading(null))
fetchFromNetwork()
}
#MainThread
private fun setValue(newValue: Resource<RequestType>) {
if (result.value != newValue) {
result.value = newValue
}
}
private fun fetchFromNetwork() {
val apiResponse = createCall()
result.addSource(apiResponse) { response ->
result.removeSource(apiResponse)
when (response) {
is ApiSuccessResponse -> {
setValue(Resource.success(processResponse(response)))
}
is ApiErrorResponse -> {
onFetchFailed()
setValue(Resource.error(response.errorMessage, null))
}
}
}
}
protected fun onFetchFailed() {
}
fun asLiveData() = result as LiveData<Resource<RequestType>>
#WorkerThread
protected open fun processResponse(response: ApiSuccessResponse<RequestType>) = response.body
#MainThread
protected abstract fun createCall(): LiveData<ApiResponse<RequestType>>
}
So when using it, only one method could be implemented createCall():
fun login(email: String, password: String) = object : NetworkBoundResource<Envelope<User>>() {
override fun createCall() = api.login(email, password)
}.asLiveData()

Here is my attempt after a long while!
abstract class NetworkOnlyResource<ResultType, RequestType>
#MainThread constructor(private val appExecutors: AppExecutors) {
private val result = MediatorLiveData<Resource<ResultType>>() //List<Repo>
private val request = MediatorLiveData<Resource<RequestType>>() //RepoSearchResponse
init {
result.value = Resource.loading(null)
fetchFromNetwork()
}
#MainThread
private fun setResultValue(newValue: Resource<ResultType>) {
if (result.value != newValue) {
result.value = newValue
}
}
private fun fetchFromNetwork() {
val apiResponse = createCall()
result.addSource(apiResponse) { response ->
result.removeSource(apiResponse)
response?.let {
if (response.isSuccessful) {
appExecutors.diskIO().execute({
val requestType = processResponse(response)
val resultType = processResult(requestType)
appExecutors.mainThread().execute({
setResultValue(Resource.success(resultType))
}
)
})
} else {
val errorMessage = when (response.errorThrowable) {
is HttpException -> "An error has occurred: ${response.errorThrowable.code()} Please try again."
is SocketTimeoutException -> "A timeout error has occurred, please check your internet connection and try again"
is IOException -> "An IO error has occurred, most likely a network issue. Please check your internet connection and try again"
is UnauthorizedCredentialsException -> "This user name or password is not recognized"
else -> {
response.errorMessage
}
}
Timber.e(errorMessage)
errorMessage?.let {
val requestType = processResponse(response)
val resultType = processResult(requestType)
setResultValue(Resource.error(errorMessage, resultType, response.errorThrowable))
}
onFetchFailed()
}
}
}
}
protected open fun onFetchFailed() {}
fun asLiveData() = result as LiveData<Resource<ResultType>>
#WorkerThread
protected open fun processResponse(response: ApiResponse<RequestType>) = response.body
#WorkerThread
protected abstract fun processResult(item: RequestType?): ResultType?
#MainThread
protected abstract fun createCall(): LiveData<ApiResponse<RequestType>>
}
The processResult() function allows you to transform a successful RequestType into a ResultType. It seems to work for me but would love any feedback from someone that knows what they are doing :)
Fyi Yigit has since updated the NetworkBoundResource with better error handling which should also work here in the not-successful 'else' statement.

Here's my version which I wrote sometime back:
import android.arch.lifecycle.LiveData
import android.arch.lifecycle.MediatorLiveData
import android.support.annotation.MainThread
/**
* A generic class to send loading event up-stream when fetching data
* only from network.
*
* #param <RequestType>
</RequestType></ResultType> */
abstract class NetworkResource<RequestType> #MainThread constructor() {
/**
* The final result LiveData
*/
private val result = MediatorLiveData<Resource<RequestType>>()
init {
// Send loading state to UI
result.value = Resource.loading()
fetchFromNetwork()
}
/**
* Fetch the data from network and then send it upstream to UI.
*/
private fun fetchFromNetwork() {
val apiResponse = createCall()
// Make the network call
result.addSource(apiResponse) { response ->
result.removeSource(apiResponse)
// Dispatch the result
response?.apply {
when {
status.isSuccessful() -> setValue(this)
else -> setValue(Resource.error(errorMessage))
}
}
}
}
#MainThread
private fun setValue(newValue: Resource<RequestType>) {
if (result.value != newValue) result.value = newValue
}
fun asLiveData(): LiveData<Resource<RequestType>> {
return result
}
#MainThread
protected abstract fun createCall(): LiveData<Resource<RequestType>>
}

This for database operation only in case you needed it (with kotlin coroutine
import androidx.lifecycle.LiveData
import androidx.lifecycle.MediatorLiveData
/**
* A generic class that can provide a resource backed by the sqlite database.
*
*
* #param <ResultType>
</ResultType> */
abstract class DatabaseResource<ResultType> {
private val result = MediatorLiveData<Resource<ResultType>>()
init {
result.value = Resource.loading(null)
GlobalScope.launch(Dispatchers.IO) {
val dbSource = performDbOperation()
GlobalScope.launch(Dispatchers.Main) {
result.addSource(dbSource) { data ->
result.removeSource(dbSource)
result.addSource(dbSource) { newData ->
setValue(Resource.success(newData))
}
}
}
}
}
private fun setValue(newValue: Resource<ResultType>) {
if (result.value != newValue) {
result.value = newValue
}
}
fun asLiveData() = result as LiveData<Resource<ResultType>>
protected abstract fun performDbOperation(): LiveData<ResultType>
}

For future Kotlin users, make it simple as:
1. Resource class:
sealed class Resource<T>(
val data: T? = null,
val error: Throwable? = null
) {
class Success<T>(data: T) : Resource<T>(data)
class Loading<T>(data: T? = null) : Resource<T>(data)
class Error<T>(throwable: Throwable, data: T? = null) : Resource<T>(data, throwable)
}
2. NetworkBoundResource:
inline fun <T> networkBoundResource(
crossinline fetch : suspend () -> Response<T>
) = flow {
emit(Resource.Loading(null))
try {
emit(Resource.Success(fetch().body()))
}catch(throwable : Throwable){
emit(Resource.Error(throwable, null))
}
}

android retrofit download progress

I'm new to retrofit. I've searched but didn't found a simple answer. I want to know how can I show progress of download in Notification bar or at least show a progress dialog which specifies the percent of process and size of downloading file.
Here is my code:
public interface ServerAPI {
#GET
Call<ResponseBody> downlload(#Url String fileUrl);
Retrofit retrofit =
new Retrofit.Builder()
.baseUrl("http://192.168.43.135/retro/")
.addConverterFactory(GsonConverterFactory.create())
.build();
}
public void download(){
ServerAPI api = ServerAPI.retrofit.create(ServerAPI.class);
api.downlload("https://www.google.com/images/branding/googlelogo/2x/googlelogo_color_120x44dp.png").enqueue(new Callback<ResponseBody>() {
#Override
public void onResponse(Call<ResponseBody> call, Response<ResponseBody> response) {
try {
File path = Environment.getExternalStorageDirectory();
File file = new File(path, "file_name.jpg");
FileOutputStream fileOutputStream = new FileOutputStream(file);
IOUtils.write(response.body().bytes(), fileOutputStream);
}
catch (Exception ex){
}
}
#Override
public void onFailure(Call<ResponseBody> call, Throwable t) {
}
});
}
please guide me if you can.
thanks

You need to create a specific OkHttp client which will intercept the network requests and send updates. This client should only be used for downloads.
First you are going to need an interface, like this one:
public interface OnAttachmentDownloadListener {
void onAttachmentDownloadedSuccess();
void onAttachmentDownloadedError();
void onAttachmentDownloadedFinished();
void onAttachmentDownloadUpdate(int percent);
}
Your download call should return a ResponseBody, which we will extend from to be able to get the download progress.
private static class ProgressResponseBody extends ResponseBody {
private final ResponseBody responseBody;
private final OnAttachmentDownloadListener progressListener;
private BufferedSource bufferedSource;
public ProgressResponseBody(ResponseBody responseBody, OnAttachmentDownloadListener progressListener) {
this.responseBody = responseBody;
this.progressListener = progressListener;
}
#Override public MediaType contentType() {
return responseBody.contentType();
}
#Override public long contentLength() {
return responseBody.contentLength();
}
#Override public BufferedSource source() {
if (bufferedSource == null) {
bufferedSource = Okio.buffer(source(responseBody.source()));
}
return bufferedSource;
}
private Source source(Source source) {
return new ForwardingSource(source) {
long totalBytesRead = 0L;
#Override public long read(Buffer sink, long byteCount) throws IOException {
long bytesRead = super.read(sink, byteCount);
totalBytesRead += bytesRead != -1 ? bytesRead : 0;
float percent = bytesRead == -1 ? 100f : (((float)totalBytesRead / (float) responseBody.contentLength()) * 100);
if(progressListener != null)
progressListener.onAttachmentDownloadUpdate((int)percent);
return bytesRead;
}
};
}
}
Then you will need to create your OkHttpClient like this
public OkHttpClient.Builder getOkHttpDownloadClientBuilder(OnAttachmentDownloadListener progressListener) {
OkHttpClient.Builder httpClientBuilder = new OkHttpClient.Builder();
// You might want to increase the timeout
httpClientBuilder.connectTimeout(20, TimeUnit.SECONDS);
httpClientBuilder.writeTimeout(0, TimeUnit.SECONDS);
httpClientBuilder.readTimeout(5, TimeUnit.MINUTES);
httpClientBuilder.addInterceptor(new Interceptor() {
#Override
public Response intercept(Chain chain) throws IOException {
if(progressListener == null) return chain.proceed(chain.request());
Response originalResponse = chain.proceed(chain.request());
return originalResponse.newBuilder()
.body(new ProgressResponseBody(originalResponse.body(), progressListener))
.build();
}
});
return httpClientBuilder;
}
Finally you only have to create your Retrofit client a different way, by passing your new OkHttp client. Based on your code, you can use something like this:
public Retrofit getDownloadRetrofit(OnAttachmentDownloadListener listener) {
return new Retrofit.Builder()
.baseUrl("http://192.168.43.135/retro/")
.addConverterFactory(GsonConverterFactory.create())
.client(getOkHttpDownloadClientBuilder(listener).build())
.build();
}
Your listener will handle the creation of your notification or whatever else you want.

Here is another Kotlin solution using Flow
interface MyService {
#Streaming // allows streaming data directly to fs without holding all contents in ram
#GET
suspend fun getUrl(#Url url: String): ResponseBody
}
sealed class Download {
data class Progress(val percent: Int) : Download()
data class Finished(val file: File) : Download()
}
fun ResponseBody.downloadToFileWithProgress(directory: File, filename: String): Flow<Download> =
flow {
emit(Download.Progress(0))
// flag to delete file if download errors or is cancelled
var deleteFile = true
val file = File(directory, "${filename}.${contentType()?.subtype}")
try {
byteStream().use { inputStream ->
file.outputStream().use { outputStream ->
val totalBytes = contentLength()
val data = ByteArray(8_192)
var progressBytes = 0L
while (true) {
val bytes = inputStream.read(data)
if (bytes == -1) {
break
}
outputStream.write(data, 0, bytes)
progressBytes += bytes
emit(Download.Progress(percent = ((progressBytes * 100) / totalBytes).toInt()))
}
when {
progressBytes < totalBytes ->
throw Exception("missing bytes")
progressBytes > totalBytes ->
throw Exception("too many bytes")
else ->
deleteFile = false
}
}
}
emit(Download.Finished(file))
} finally {
// check if download was successful
if (deleteFile) {
file.delete()
}
}
}
.flowOn(Dispatchers.IO)
.distinctUntilChanged()
suspend fun Context.usage() {
coroutineScope {
myService.getUrl("https://www.google.com")
.downloadToFileWithProgress(
externalCacheDir!!,
"my_file",
)
.collect { download ->
when (download) {
is Download.Progress -> {
// update ui with progress
}
is Download.Finished -> {
// update ui with file
}
}
}
}
}

Here is my variant with Kotlin's coroutines
Specify API interface. We need #Streaming annotation to say Retrofit that we want to handle the response body manually. Otherwise, retrofit will try to write your file straight into RAM
interface Api {
#Streaming
#GET("get-zip-ulr/{id}")
fun getZip(#Path("id") id: Int): Call<ResponseBody>
}
Create DataSource which will control downloading process
class FilesDataSource(private val parentFolder: File, private val api: Api) {
suspend fun downloadZip(id: Int, processCallback: (Long, Long) -> Unit): File {
val response = api.getZip(id).awaitResponse()// returns the response, but it's content will be later
val body = response.body()
if (response.isSuccessful && body != null) {
val file = File(parentFolder, "$id")
body.byteStream().use { inputStream ->
FileOutputStream(file).use { outputStream ->
val data = ByteArray(8192)
var read: Int
var progress = 0L
val fileSize = body.contentLength()
while (inputStream.read(data).also { read = it } != -1) {
outputStream.write(data, 0, read)
progress += read
publishProgress(processCallback, progress, fileSize)
}
publishProgress(processCallback, fileSize, fileSize)
}
}
return file
} else {
throw HttpException(response)
}
}
private suspend fun publishProgress(
callback: (Long, Long) -> Unit,
progress: Long, //bytes
fileSize: Long //bytes
) {
withContext(Dispatchers.Main) { // invoke callback in UI thtread
callback(progress, fileSize)
}
}
}
Now you can execute downloadZip() method in your ViewModel or Presenter and give it a callback which will be linked to some ProgerssBar. After download completion, you will receive the downloaded file.

None of provided answers works correctly, here is a working solution which combine both approach correctly.
First create new retrofit object for download, this retrofit object shouldn't contain any log interceptor because this will cause java.lang.IllegalStateException: closed
fun interface ResponseBodyListener {
fun update(responseBody: ResponseBody)
}
fun getDownloaderRetrofit(listener: ResponseBodyListener): Retrofit = Retrofit.Builder()
.baseUrl("https://example.com")// <-- this is just a placeholder, we will not use it either way in the request.
.client(initHttpDownloadListenerClient(listener))
.build()
private fun initHttpDownloadListenerClient(listener: ResponseBodyListener): OkHttpClient {
return OkHttpClient.Builder()
.connectTimeout(20, TimeUnit.SECONDS)
.readTimeout(5, TimeUnit.MINUTES)
.writeTimeout(0, TimeUnit.SECONDS)
.addNetworkInterceptor { chain ->
chain.proceed(chain.request()).also { originalResponse ->
originalResponse.body?.let { listener.update(it) }
}
}
.build()
}
in addNetworkInterceptor we get the response body as soon as it becomes available so that we track the actual download progress. It has stream of data being downloaded data from server.
Here is api interface
interface DownloadFilesApi {
#GET
#Streaming
suspend fun downloadFile(#Url url: String): ResponseBody
}
Here is the request itself
#OptIn(ExperimentalCoroutinesApi::class)
override suspend fun downloadFile(url: String, directory: File, fileName: String): Flow<DownloadFileState> =
callbackFlow {
val listener = ResponseBodyListener { responseBody: ResponseBody ->
this.launch {
responseBody.downloadToFileWithProgress(directory, fileName).collect {
trySend(it)
}
}
}
getDownloaderRetrofit(listener).create(DownloadFilesApi::class.java).downloadFile(url)
awaitClose()
}
Notice that downloadFile is suspend this suspends the coroutine until it finishes download.
here callbackFlow is used to work as bridge between the normal callback and flow result.
finally downloadToFileWithProgress is the same as written by #Robert the difference is that here it shows progress of downloading the file instead of showing progress of writing the file on desk after the actual download finishes.
for reference here it's RetrofitExtentions.kt
fun ResponseBody.downloadToFileWithProgress(directory: File, filename: String): Flow<DownloadFileState> = flow {
emit(DownloadFileState.Progress(0))
// flag to delete file if download errors or is cancelled
var deleteFile = true
val file = File(directory, filename)
try {
byteStream().use { inputStream ->
file.outputStream().use { outputStream ->
val totalBytes = contentLength()
val data = ByteArray(8_192)
var progressBytes = 0L
while (true) {
val bytes = inputStream.read(data)
if (bytes == -1) {
break
}
outputStream.write(data, 0, bytes)
progressBytes += bytes
val progress = ((progressBytes * 100) / totalBytes).toInt()
emit(DownloadFileState.Progress(percent = progress))
}
when {
progressBytes < totalBytes ->
throw Exception("missing bytes")
progressBytes > totalBytes ->
throw Exception("too many bytes")
else ->
deleteFile = false
}
}
}
emit(DownloadFileState.Finished(file))
} finally {
if (deleteFile) {
file.delete()
}
}
}
For completness here is how to get root folder in which you are going to save the video
fun videosRootFolder(context: Context): File {
return File(
Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_MOVIES),
APP_DIRECTORY_NAME
).run {
if (exists()) {
this
} else {
this.mkdir()
this
}
}
}

you can take a look here, you dont have to implement it by yourself ,the idea behind is to take the content-length of the request and when you write on the buffer just calculate your progress