Failed getStringExtra Kotlin mvvm - android

I want to move from one Activity which displays a RecyclerView to another Activity (detail). But when I added data transmission via Intent, the data always failed to be taken in the Activity detail.
This is the error:
My MainDetail:
private lateinit var viewModel: MainDetailModel
var idAnime: String = "34134"
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main_detail)
idAnime = intent.getStringExtra("idAnime")
println("idanime $idAnime")
setupFragment()
setupViewModel()
}
}
ViewModel:
class MainViewModel(context: Application, private val appRepository: AppRepository, private val contexts: Context) : AndroidViewModel(context), MainItemClickAction {
override fun onItemClicked(detailModel: DetailModel) {
var intent = Intent(contexts, MainDetailActivity::class.java)
intent.putExtra("idAnime",detailModel.mal_id )
contexts.startActivity(intent)
}
}

Check if your field "detailModel.mal_id" mal_id in that case is string, because you're requesting string in details activity. If it's string check also if this "mal_id" is null. Other issues from code you provided can't be seen.

Check your value idAnime, it exists or not, I think is better check all value is empty or not before putting into listView or another view.

Related

ViewModel not initializing or problem design with my viewModel

I've been reading some questions, answers and blogs about MVVM pattern in Android, and I've implemented it in my application.
My application consists of a MainActivity with 3 Tabs. Content of each tab is a fragment.
One of these fragments, is a List of Users stored on Room DB, which is where I've implemented the MVVM (implementing User object, ViewModel, Repository and Adapter with RecycleView).
In this same fragment, I have an "add User" button at the end that leads to a new activity where a formulary is presented to add a new user. In this activity I want to be sure that the full name of user not exists in my DB before saving it.
I was trying to use the same ViewModel to get full UserNames full name, but it seems that ViewModel is never initialized and I dont' know why.
I've read some questions about that viewmodel can't be used in different activities (I use it in MainActivity also in AddUser activity
This is my ViewModel:
class UserViewModel : ViewModel() {
val allUsersLiveData: LiveData<List<User>>
private val repository: UserRepository
init {
Timber.i("Initializing UserViewModel")
repository = UserRepository(UserTrackerApplication.database!!.databaseDao())
allUsersLiveData = repository.getAllUsers()
}
fun getAllUsersFullName(): List<String> {
return allUsersLiveData.value!!.map { it.fullname}
}
And my AddUser activity:
class AddUser : AppCompatActivity() {
private lateinit var userList:List<String>
private lateinit var binding: ActivityAddUserBinding
private val userViewModel: UserViewModel by viewModels()
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_add_user)
Timber.i("Add User OnCreate")
binding = ActivityAddUserBinding.inflate(layoutInflater)
setContentView(binding.root)
}
fun addUserClick(v : View){
//someCode
val userName = binding.constraintLayoutAddUser.etUserName!!.text.toString()
if(checkUserExistance(userName)) {
val text: String = String.format(
resources.getString(R.string.repeated_user_name),
userName
Snackbar.make(v, text, Snackbar.LENGTH_LONG).show()
{
else
{
lifecycleScope.launch {
UserTrackerApplication.database!!.databaseDao()
.insertUser(user)
Timber.i("User added!")
}
finish()
}
}
Debugging, I see the log "Initializing UserViewModel" when the fragment of MainActivity is started, but I can't see it when AddUser activity is called. So it seems it's not initializing correctly.
So the questions:
Is this a good approach? I'm making some design mistake?
Why the VM isn't initializing?
EDIT
I forgot to add this function. Calling userViewModel here is where I get the error:
private fun checkUserExistance(userName: String): Boolean {
var result = false
userList = userViewModel.getAllUsersNames()
for (usr in userList)
{
if(usr.uppercase() == userName.uppercase())
{
result = true
break
}
}
return result
}
EDIT 2
I added this on my "onCreate" function and started to work:
userViewModel.allUsersLiveData.observe(this, Observer<List<User>>{
it?.let {
// updates the list.
Timber.i("Updating User Names")
userList =userViewModel.getAllUsersNames()
}
})
if you take a look at by viewModels delegate you will see it's lazy it means it will initialize when it is first time accessed
#MainThread
public inline fun <reified VM : ViewModel> ComponentActivity.viewModels(
noinline factoryProducer: (() -> Factory)? = null
): Lazy<VM> {
val factoryPromise = factoryProducer ?: {
defaultViewModelProviderFactory
}
return ViewModelLazy(VM::class, { viewModelStore }, factoryPromise)
}

Can't get search data from ViewModel to Activity Kotlin

I'm trying to get my data from my ViewModel to my MainActivity.
I know that what I'm doing in my MainActivity is very wrong, but I can't seem to configure it in a way that will get the data into the MainActivity. It's just a simple string.
ViewModel
class MovieSearchViewModel : ViewModel() {
var searchTerm = ""
fun getSearchTerm(query: String) {
searchTerm = query
}
}
MainActivity
open class MainActivity : AppCompatActivity() {
private val viewModel: MovieSearchViewModel by viewModels()
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
var searchTerm = viewModel.searchTerm
}
}
View Model
you can use LiveData to always get the latest data in Activity
var searchTerm = MutableLiveData("")
fun setSearchTerm(query: String){
searchTerm.value = query
}
MainActivity
in observe it will always run every time there is a data change
viewModel.searchTerm.observe(this){
Log.e("tag", it)
}
or
if you want get the data manually without observe you can do like this
var data = viewModel.searchTerm.value

How to build a live data based on lateinit property?

I have a property with late initialization.
Now I want to provide a live data which does not emit anything until the property is initialized completely.
How to do this in proper Kotlin way?
class SomeConnection {
val data: Flow<SomeData>
...
class MyViewModel {
private lateinit var _connection: SomeConnection
// private val _connection: CompletableDeferred<SomeConnection>()
val data = _coonection.ensureInitilized().data.toLiveData()
fun connect(){
viewModelScope.launch {
val conn = establishConnection()
// Here I have to do something for the call ensureInitilized to proceed
}
}
private suspend fun establishConnection(){
...
}
Declare a MutableLiveData emitting values of type SomeConnection and a corresponding LiveData.
private val _connectionLiveData = MutableLiveData<SomeConnection>()
val connectionLiveData: LiveData<SomeConnection> = _connectionLiveData
Then assign value to _connectionLiveData when _connection is initialized:
if (::_connection.isInitialized()) _connectionLiveData.value = _connection
(or _connectionLiveData.postValue(_connection) if your code works concurrently)
Now observe this LiveData in another place in code, I'll use fragment here for the sake of example:
override fun firstOnViewCreated(view: View, savedInstanceState: Bundle?) {
viewModel.connectionLiveData.observe(this, ::sendData)
}
Then send the desired data via the corresponding view model method

Access private variable in Kotlin [duplicate]

This question already has an answer here:
Kotlin - How can we access private property with getter and setter? Is access methods are calling internally? [duplicate]
(1 answer)
Closed 2 years ago.
So, im trying to develop an Android app with Kotlin as an Pen and Paper RPG companion. Right now I want to make a mob class like
class Mob(name: String, health: Int, armor: Int) {
private val name: String
get() = field
private var health: Int = 0
get() = field
set(value) {
field = value
}
private val armor: Int
get() = field
}
In another activity I want to display this information like
class MeinMonster : AppCompatActivity() {
private lateinit var monster: Mob
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_mein_monster)
monster = Mob(
intent.getStringExtra("Name"),
intent.getIntExtra("Health", 20),
intent.getIntExtra("Armor", 0)
)
print()
}
private fun print() {
try {
tvName.text = monster.name
tvHealth.text = "LeP: ${monster.health}"
tvArmor.text = "RS: ${monster.armor}"
} catch (ex:Exception) {
val goBack = Intent(this, MainActivity::class.java)
startActivity(goBack)
}
}
}
Android studio is constantly telling me Cannot access 'name': It is private in 'Mob', though. I thought that's what I got the get() for?
Maybe someone with more Kotlin experience can help. Thank you in advance.
you can try to change your class for data class like these:
data class Mob(val name: String, var health: Int, val armor: Int)
When you use "val" your variable will be to get, when you use "var" your variable will be to get and set.

Receiving data in incorrect order on Querying database

Activity receiving intent
class AddNoteActivity : AppCompatActivity() {
private lateinit var addViewModel: NoteViewModel
private lateinit var titleEditText: TextInputEditText
private lateinit var contentEditText: TextInputEditText
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_add_note_activty)
setSupportActionBar(toolbar)
addViewModel = ViewModelProviders.of(this).get(NoteViewModel::class.java)
titleEditText = findViewById(R.id.itemTitle)
contentEditText = findViewById(R.id.itemNote)
val extra = intent.extras
if (extra != null) {
val uuid = extra.getLong("UUID")
val note: Notes? = addViewModel.getNote(uuid)
titleEditText.setText(note!!.title)
contentEditText.setText(note.note)
}
}
}
NoteViewModel class
class NoteViewModel(application: Application) : AndroidViewModel(application) {
companion object {
private var note: Notes = Notes(0, "", "test title", "test ontent")
}
fun getNote(uuid: Long?): Notes {
val job = async(CommonPool) {
getNoteAsyncTask(notesDatabase).execute(uuid)
}
runBlocking { job.await() }
return note
}
class getNoteAsyncTask(database: NotesDatabase) : AsyncTask<Long, Unit, Unit>() {
private val db: NotesDatabase = database
override fun doInBackground(vararg params: Long?) {
note = db.notesDataDao().getNote(params[0])
}
}
}
If I pass an intent to get a Note object from the database with a uuid and set that received data in titleEditText and contentEditText, the data set in the Note was from previous intent invoked when we clicked on the Note item in RecyclerView. On clicking the Note item for the first time, I get the default value which I have set "test title" and "test content".
Aforementioned is the behavior most of the time. Sometimes the data set in titleEditText and contentEditText is of the correct Note object.
Can someone please tell me what I have done wrong? How can I correct my apps behavior?
Unfortunately, there is a big mistake in how you use a view model to provide a data to your view(AddNoteActivity).
Basically, your view never has a chance to wait for the data to be fetched as it always receives a default value. This happens because the AsyncTask runs on its own thread pool so the coroutine completes immediately and returns a default value.
You should consider using LiveData to post a new object to your view and refactor your view model.
So, you need to make a query to the database synchronous and observe changes to a note rather than have a getter for it. Of course, in a real life scenario it might be a good idea to have different kind of states to be able to show a spinner while a user is waiting. But this is another big question. So to keep things simple consider changing your view model to something like that:
class NoteViewModel(private val database: NotesDatabase) : ViewModel { // you do not need an application class here
private val _notes = MutableLiveData<Notes>()
val notes: LiveData<Notes> = _notes
fun loadNotes(uuid: Long) {
launch(CommonPool) {
val notes = database.notesDataDao().getNote(uuid)
_notes.setValue(notes)
}
}
}
Then, you can observe changes to the note field in your activity.
class AddNoteActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
// ...
val noteViewModel = ViewModelProviders.of(this).get(NoteViewModel::class.java)
noteViewModel.notes.observe(this, Observer {
title.text = it.title
content.text = it.note
})
}
}
Also you need to use a ViewModelProvider.Factory to create your view model and properly inject dependencies into it. Try to avoid having a context there as it makes it much harder to test.

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