Develop Reference

KOTLIN/FIREBASE Error when I try get data from firebase database - Client is offline

When i try get user information by his uid which is same like in firebase database this error is shown.
uid is passed in right way I have checked it. Route to database is good and I have checked this too.
Here is my code and this probably don't have any mistakes because everything work and only Firebase had some problems.
class Profil : AppCompatActivity() {
private var fAuth: FirebaseAuth?=null
private var database: DatabaseReference?=null
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_profil)
fAuth= FirebaseAuth.getInstance()
// ✋ Here I checked with uid and uid.toString()
var userCheck = fAuth!!.currentUser?.uid.toString()
getData(userCheck)
// ✋ Here I checked that good uid is get
//tv_firsName.text = userCheck
}
private fun getData(userCheck: String) {
database = FirebaseDatabase.getInstance().getReference("Users")
database!!.child(userCheck).get().addOnSuccessListener{
if(it.exists()){
val firstName = it.child("firstName").value
val lastName = it.child("lastName").value
val position = it.child("position").value
val email = it.child("email").value
tv_Imie.text = firstName.toString()
tv_Nazwisko.text = lastName.toString()
tv_Stanowisko.text = position.toString()
tv_Email.text = email.toString()
}else{
Toast.makeText(this, "User does not exist", Toast.LENGTH_SHORT).show()
}
}.addOnFailureListener{
Toast.makeText(this, "Failed", Toast.LENGTH_SHORT).show()
Log.e("firebase", "Error getting data", it)
}
}
}
Here is my database structure
I checked some ways to solve this problem.
I have seen some people propose a solution with addValueEventListener, but then the list is fetched. I want single user information to be included in my textViews. I read that the problem may be related to a bug in Firebase and not in the code.

Ok, problem was with Firebase not my application. I don't know why but when I started app in every try Firebase closed my connection with database. I tried add to google.services.json some links to database and change some settings but this didn't work. After all I removed app from firebase and delete file google.services.json. I added app again on website then I connect app with firebase and new google.services.json was set. That's all everything is working thanks for help.

How to use the keyword also in kotlin android

Am learning android kotlin follow this:
https://developer.android.com/topic/libraries/architecture/viewmodel#kotlin
class MyViewModel : ViewModel() {
private val users: MutableLiveData<List<User>> by lazy {
MutableLiveData<List<User>>().also {
loadUsers(it)
}
}
fun getUsers(): LiveData<List<User>> {
return users
}
private fun loadUsers() {
// Do an asynchronous operation to fetch users.
}
}
Dont know how to write the fun loadUsers()
Here is my User:
class User {
constructor(name: String?) {
this.name = name
}
var name:String? = null
}
If dont use the keyword 'also' , i know how to do it.
But if use 'also' , it seems not work.
Here is how i try to write the fun loadUsers:
private fun loadUsers( it: MutableLiveData<List<User>>){
val users: MutableList<User> = ArrayList()
for (i in 0..9) {
users.add(User("name$i"))
}
it = MutableLiveData<List<User>>(users)
}
Error tips near it : Val cant be ressigned

Part 1: According to the Kotlin documentation, also provides the object in question to the function block as a this parameter. So, every function call and property object you access is implied to refer to your MutableLiveData<List<User>>() object. also returns this from the function block when you are done.
Thus, another way of writing your MutableLiveData<> would be like this:
val users = MutableLiveData<List<User>>()
users.loadUsers()
Part 2: As far as how to implement loadUsers(), that is a separate issue (your question is not clear). You can use Retrofit + RxJava to load the data asynchronously, and that operation is totally outside of the realm of ViewModel or also.
Part 3: With your approach, you have conflicting things going on. Instead of doing a loadUsers() from your lazy {} operation, I would remove your lazy {} operation and create a MutableLiveData<> directly. Then, you can load users later on and update the users property any time new data is loaded. Here is a similar example I worked on a while ago. It uses state flows, but the idea is similar. Also use a data class to model the User instead of a regular class. Another example.

It is solved change to code:
private fun loadUsers( it: MutableLiveData<List<User>>){
val users: MutableList<User> = ArrayList()
for (i in 0..9) {
users.add(User("name$i"))
}
it.value = users
}
it can't be reassigned , but it.value could .

Need help Kotlin Coroutines, Architecture Component and Retrofit

I'm trying to wrap my head around the mentioned components and I can't get it right. I want to do something very simple: Fetch data from the network and present it to the user. Currently am not yet caching it as am still learning new Coroutine features in Architecture components. Every time app loads I get an empty model posted, which seems weird.
My API is get hit fine and response is 200 which is OK.
Below is what I have attempted:
POJO
data class Profile(#SerializedName("fullname") val fullName : String.....)
Repository
class UserRepo(val context: Context, val api: Api) {
suspend fun getProfile(): Profile
{
val accessToken = ....
return api.getUserProfile(accessToken)
}
}
API
interface GatewayApi {
#GET("users/profile")
suspend fun getUserProfile(#Query("access-token") accessToken: String?): Profile
}
ViewModel
class UserViewModel(application: Application) : AndroidViewModel(application) {
private val usersRepo = UserRepo(application.applicationContext, Apifactory.Api)
val userProfileData = liveData{
emit(usersRepo.getProfile())
}
fun getProfile() = viewModelScope.launch {
usersRepo.getProfile()
}
}
Finally my fragment's relevant code
val viewModel = ViewModelProviders.of(activity!!).get(UserViewModel::class.java)
viewModel.userProfileData.observe(this, Observer<UserProfile> {
//it is having nulls
})
//trigger change
viewModel.getProfile()

So I added HTTP requests and responses (thanks to #CommonsWare for pointing that out) and it happened I had used a different model than I was supposed to use. The correct model that mapped the JSON response was ProfileResponse and as you can see in my posted code, I used Profile instead. So all fields were empty as Gson could not correctly serialize JSON into Profile object.
All the credit goes to #CommonsWare for pointing that out in comment.

Saving a class to internal storage on android/kotlin

I'm trying to save user data via a Player class as seen below:
class Player(name: String, age: Int, gender: String) {
}
and I'm wondering what the best way to save the class instances is. I think internal storage fits best as it's internal app data that the user doesn't need to directly access.
However there are not many resources that explain saving class instances - I only see examples of saving key-value pairs.
Code:
import kotlinx.android.synthetic.main.activity_player_details.*
class PlayerDetails : AppCompatActivity(), View.OnClickListener {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_player_details)
val intent = getIntent()
val players = intent.getIntExtra("number_of_players", 1)
println(players)
next_details.setOnClickListener(this)
}
override fun onClick(v: View?) {
val name: String = player_name.text.toString()
val age = if (player_age.text.toString().isNotEmpty()) player_age.text.toString().toInt() else 0
val genderId: Int = gender.checkedRadioButtonId
val gender: String = if (genderId > 0) resources.getResourceEntryName(genderId) else ""
if (name.isNotEmpty() && genderId > 0 && age > 0 ){
println(name)
println(age)
println(gender)
val player = Player(name, age, gender) // I WANT TO SAVE THIS INSTANCE
} else {
blankFields()
}
}
private fun blankFields() {
blank_fields_error.visibility = View.VISIBLE
}
}
Any advice appreciated.

Basically what you're asking is called "serialization".
In Android you have several ways to serialize an object for storage:
Use Java standard serialization (not recommended). Note that this requires a binary storage (e.g. database BLOB) or be converted to Base64 to store in a text format.
Use a serialization library, e.g. JSON, YAML, etc... This is going to be several magnitudes slower that a binary serialization (Android's Parcelable or Java's Serializable), and also slower than binary + Base64, so in my opinion not really a valid option unless you absolutely want the data stored to be human-readable.
Note that Parcelable is not suitable for consitent storage, so it is not an option.
Note that however, in my experience, I tested a lot of serialization methods (mainly for for IPC) and Serializable was fast enough without adding all the bloated code to use Parcelable. Parcelable only provided a negligible speed gain not worth the hassle of implementing and correctly maintaining Parcelable classes.

Read CSV line-by-line in Kotlin

I'm writing a simple import application and need to read a CSV file, show result in a grid and show corrupted lines of the CSV file in another grid.
Is there any built-in lib for it or any easy pythonic-like way?
I'm doing it on android.

[Edit October 2019] A couple of months after I wrote this answer, Koyama Kenta wrote a Kotlin targeted library which can be found at https://github.com/doyaaaaaken/kotlin-csv and which looks much better to me than opencsv.
Example usage: (for more info see the github page mentioned)
import com.github.doyaaaaaken.kotlincsv.dsl.csvReader
fun main() {
csvReader().open("src/main/resources/test.csv") {
readAllAsSequence().forEach { row ->
//Do something
println(row) //[a, b, c]
}
}
}
For a complete minimal project with this example, see https://github.com/PHPirates/kotlin-csv-reader-example
Old answer using opencsv:
As suggested, it is convenient to use opencsv. Here is a somewhat minimal example:
// You can of course remove the .withCSVParser part if you use the default separator instead of ;
val csvReader = CSVReaderBuilder(FileReader("filename.csv"))
.withCSVParser(CSVParserBuilder().withSeparator(';').build())
.build()
// Maybe do something with the header if there is one
val header = csvReader.readNext()
// Read the rest
var line: Array<String>? = csvReader.readNext()
while (line != null) {
// Do something with the data
println(line[0])
line = csvReader.readNext()
}
As seen in the docs when you do not need to process every line separately you can get the result in the form of a Map:
import com.opencsv.CSVReaderHeaderAware
import java.io.FileReader
fun main() {
val reader = CSVReaderHeaderAware(FileReader("test.csv"))
val resultList = mutableListOf<Map<String, String>>()
var line = reader.readMap()
while (line != null) {
resultList.add(line)
line = reader.readMap()
}
println(resultList)
// Line 2, by column name
println(resultList[1]["my column name"])
}
Dependency for Gradle: compile 'com.opencsv:opencsv:4.6' or for Gradle Kotlin DSL: compile("com.opencsv:opencsv:4.6") (as always, check for latest version in docs).

In terms of easiness, kotlin written csv library is better.
For example, you can write code in DSL like way with below library that I created:
https://github.com/doyaaaaaken/kotlin-csv
csvReader().open("test.csv") {
readAllAsSequence().forEach { row ->
//Do something with the data
println(row)
}
}

Use opencsv.
This is gonna work like a charm for reading a CSV file.
As far as logging the corrupted lines is concerned you can do it using this logic.
while(input.hasNextLine())
{
try
{
//execute commands by reading them using input.nextLine()
}
catch (ex: UserDefinedException)
{
//catch/log the exceptions you're throwing
// log the corrupted line the continue to next iteration
}
}
Hope this helps.

I used net.sourceforge.javacsv with my Kotlin code for parsing CSV files. It is a "java" library but within kotlin it is fairly straightforward to work with it like
val reader = CsvReader("/path/to/file.csv").apply {
trimWhitespace = true
skipEmptyRecords = true
readHeaders()
}
while (reader.readRecord()) {
// do whatever
}

Frankly speaking, it is quite easy to make a simple reader in Kotlin using modern Java features, check this (REMEMBER to handle BOM :-)):
fun processLineByLine(csv: File, processor: (Map<String, String>) -> Unit) {
val BOM = "\uFEFF"
val header = csv.useLines { it.firstOrNull()?.replace(BOM, "")?.split(",") }
?: throw Exception("This file does not contain a valid header")
csv.useLines { linesSequence ->
linesSequence
.drop(1)
.map { it.split(",") }
.map { header.zip(it).toMap() }
.forEach(processor)
}
}
Than you can use it as follows (depends on your file structure):
processLineByLine(File("./my-file.csv")) { row ->
println("UserId: ${row["userId"]}")
println("Email: ${row["email"]}")
}

If you prefer to use your own data class for each row you should have a look at my solution https://github.com/gmuth/ipp-client-kotlin/blob/master/src/main/kotlin/de/gmuth/csv/CSVTable.kt
data class User(
val name: String,
val phone: String,
val email: String
) {
constructor(columns: List<String>) : this(
name = columns[0],
phone = columns[1],
email = columns[2]
)
}
CSVTable.print(FileInputStream("users.csv"))
val userList = CSVTable(FileInputStream("users.csv"), ::User).rows

I know i'm a bit late, but I recently had problems with parsing CSV and there seemed to be no library good enough for what I was looking for, so I created my own called Kotlin CSV stream.
This library is special because it doesn't throw exceptions on an invalid input, but returns in the result instead, which might be useful in some cases.
Here is an example of how easy it is to use
val reader = CsvReader()
.readerForType<CsvPerson>()
val people = reader.read(csv).map { it.getResultOrThrow() }.toList()

For version of commons-csv version 1.9.0, have implemented below code to get results.
It uses CSVBuilder and CSVFormat to get records with skip headers and auto-identify headers on basis of first row.
fun csvReader(file: MultipartFile): ResultListObject? {
var result = ResultListObject()
var csvFormat=CSVFormat.Builder.create().setHeader().setSkipHeaderRecord(true).build()
var csvRecords = CSVParser(file.inputStream.bufferedReader(), csvFormat)
csvRecords.forEach{csvRecords->
rowRecord.field1=records.get("field1")
rowRecord.field2=records.get("field2")
...
...
result.add(rowRecord)
}
return result
}