I'm trying to instanciate a Room database in my main activity in Android Studio, following codelabs and tutorials, but my app always crash. Here's a part of the code:
My database (AppDatabase.kt):
#Database(entities = [Device::class], version = 1, exportSchema = false)
abstract class AppDatabase : RoomDatabase() {
abstract fun deviceDao(): DeviceDao
companion object {
#Volatile
private var INSTANCE: AppDatabase? = null
fun getDatabase(context: Context): AppDatabase {
return INSTANCE ?: synchronized(this) {
val instance = Room.databaseBuilder(
context.applicationContext,
AppDatabase::class.java,
"item_database"
)
.fallbackToDestructiveMigration()
.build() // <---- The crash occurs here
INSTANCE = instance
return instance
}
}
}
}
And here's the activity from which I'm trying to instantiate it:
class NavigationActivity() : AppCompatActivity() {
private lateinit var binding: ActivityNavigationBinding
private val db by lazy { AppDatabase.getDatabase(this) }
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding = ActivityNavigationBinding.inflate(layoutInflater)
setContentView(binding.root)
Log.d("instantiation", "$db") // <----- Called from here
val navView: BottomNavigationView = binding.navView
val navController = findNavController(R.id.nav_host_fragment_activity_navigation)
val appBarConfiguration = AppBarConfiguration(
setOf(
R.id.navigation_devices, R.id.navigation_logs, R.id.navigation_settings
)
)
setupActionBarWithNavController(navController, appBarConfiguration)
navView.setupWithNavController(navController)
}
}
Finally, here's the error message, which doesn't helps me much:
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.Package.getName()' on a null object reference
at androidx.room.Room.getGeneratedImplementation(Room.java:82)
at androidx.room.RoomDatabase$Builder.build(RoomDatabase.java:1486)
at AppDatabase$Companion.getDatabase(AppDatabase.kt:24)
I tried a lot of things, including ViewModel, Repository and more, but got the crash systematically, at the same point.
Here's also the part of my build.gradle file where I import Room, maybe I'm wrong in some version or whatever...
plugins {
id 'com.android.application'
id 'org.jetbrains.kotlin.android'
id 'kotlin-android'
id 'kotlin-kapt'
}
[...]
def roomVersion = "2.4.2"
implementation("androidx.room:room-runtime:$roomVersion")
kapt("androidx.room:room-compiler:$roomVersion")
implementation "androidx.room:room-ktx:$roomVersion"
Make sure package declaration on top of the class is declared, for example:
package com.macrosystems.clean.ui.core.view
import android.content.Context
import android.content.Intent
import android.graphics.Color
etc...
Related
I am just trying to set up a spinner configured as a dropdown menu, but I can't even test my app to see if it works because every time I run it, it immediately crashes. I know that my issue is related to a null object reference at line 21 in my MainActivity.kt file. Here is the problem code:
val spinner: Spinner = findViewById<Spinner>(R.id.locations)
The id of the spinner is locations, so I'm not sure why this is coming back as a null value.
Here is also the full code for the file:
import android.app.Activity
import android.support.v7.app.AppCompatActivity
import android.os.Bundle
import android.view.View
import android.widget.Spinner
import android.widget.ArrayAdapter
import android.widget.AdapterView
private var userLocation: Any = ""
private var userDestination: Any = ""
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
}
val spinner: Spinner = findViewById<Spinner>(R.id.locations)
val locationsAdapter: ArrayAdapter<CharSequence> = ArrayAdapter.createFromResource(
this,
R.array.rooms,
android.R.layout.simple_spinner_item
).also { adapter ->
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item)
spinner.adapter = adapter
}
}
class SpinnerActivity : Activity(), AdapterView.OnItemSelectedListener {
override fun onItemSelected(parent: AdapterView<*>, view: View?, pos: Int, id:Long) {
userLocation = parent.getItemAtPosition(pos)
val spinner: Spinner = findViewById(R.id.locations)
spinner.onItemSelectedListener = this
}
override fun onNothingSelected(parent: AdapterView<*>) = Unit
}
Declare spinner global for MainActivity:
private lateinit var spinner: Spinner
On the method onCreate initialise the spinner and set its adapter, I would recommend you to set the array adapter as follows:
spinner = findViewById<Spinner>(R.id.locations)
spinner.adapter = ArrayAdapter(this, R.layout.drop_down_generic_item, resources.getStringArray(R.array.rooms))
I don't really understand the SpinnerActivity you showed in the question, sorry. But in MainActivity you can set the spinner.onItemSelectedLister() as follows:
spinner.onItemSelectedListener = object : AdapterView.OnItemSelectedListener {
override fun onItemSelected(adapterView: AdapterView<*>?, view: View?, position: Int, p3: Long) {
val selectedRoom = adapterView?.getItemAtPosition(position)
}
override fun onNothingSelected(p0: AdapterView<*>?) {
}
}
I don't want to confuse you, but have a look at a TextInputLayout with an AutoCompleteTextView, just as a hint. :D
I am struggling to use Live data on an MVVM pattern. The app is supposed to:
Fetch data from an API (which it does correctly)
Store that data in the Live data object from the ViewModel
Then the fragment calls the Observer method to fill the recyclerView.
The problem comes in point 3, it does nothing, and I cannot find the solution.
Here is the relevant code. (If I'm missing something, I will try to answer as quickly as possible)
Main Activity:
class MainActivity : AppCompatActivity() {
private lateinit var binding: ActivityMainBinding
private val viewModel: SharedViewModel by viewModels()
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding = ActivityMainBinding.inflate(layoutInflater)
setContentView(binding.root)
// Custom button to fetch data from api and log the Live Data value.
binding.refreshFab.setOnClickListener {
viewModel.fetchPlayerData()
Log.d("gabs", "${viewModel.livePlayerlist.value}")
}
}
}
ViewModel:
class SharedViewModel(app: Application): AndroidViewModel(app) {
// val playerDao = LaRojaDB.getDatabase(app).playerDao()
lateinit var playerList: Players
val livePlayerlist: MutableLiveData<MutableList<Players.PlayersItem>> by lazy {
MutableLiveData<MutableList<Players.PlayersItem>>()
}
fun fetchPlayerData() {
CoroutineScope(Dispatchers.IO).launch {
val response = MyService.getLaRojaService().getAllPlayers()
withContext(Dispatchers.Main) {
if (response.isSuccessful) {
val body = response.body()
if(!body.isNullOrEmpty()){
playerList = body
val playerArrayList = mutableListOf<Players.PlayersItem>()
playerList.forEach {
playerArrayList.add(it)
}
livePlayerlist.value = playerList
}
}
}
}
}
}
The fragment that displays the recycler view: (Fragment is already showing, I set up a textView as a title to make sure since I'm new using fragments as well.)
class PlayerListFragment : Fragment() {
private var _binding: FragmentPlayerListBinding? = null
private val binding get() = _binding!!
private val model: SharedViewModel by viewModels()
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
_binding = FragmentPlayerListBinding.inflate(inflater, container, false)
binding.rvPlayerList.layoutManager = LinearLayoutManager(activity)
----> // This is the observer that does not update the UI** <----
model.livePlayerlist.observe( viewLifecycleOwner, {
binding.rvPlayerList.adapter = PlayerAdapter(it)
})
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_player_list, container, false)
}
}
Thank you all in advance, hope I can finally learn what is causing the issue!
I think you don't need to switch Coroutine contexts. A few changes I'd expect if I were reviewing this code:
This should all be in the same IO context. You then postValue to your liveData.
fun fetchPlayerData() {
viewModelScope.launch(Dispatchers.IO) {
val xx = api.fetch()
...
_playerState.postValue(xx) //see below
}
}
Additionally, it's preferred not to expose mutable state, so your ViewModel should not expose the MutableLiveData (which shouldn't really be lazy). But it's also better to encapsulate the state in a sealed class:
//delete this
val livePlayerlist: MutableLiveData<MutableList<Players.PlayersItem>> by lazy {
MutableLiveData<MutableList<Players.PlayersItem>>()
}
Should be: (names are just pseudo code, I have no idea what this code is about)
sealed class PlayerDataState {
data class ListAvailable(data: List<Players.PlayersItem>>): PlayerDataState
object Loading(): PlayerDataState
}
And your new LiveData:
private val _playerState = MutableLiveData<PlayerDataState>()
val playerState: LiveData<PlayerDataState>() get() = _playerState
Finally when observing from the UI, you just...
model.playerState.observe(viewLifecycleOwner, {
when (it) {
is Loading -> ...
is ListAvailable -> binding.rvPlayerList.adapter = PlayerAdapter(it.data)
}
}
I am new with MVVM in kotlin, I want to fetch some data using retrofit and show this in textview but I can't fetch this. In this app first time, I am using the android jetpack component. I tried a lot of times but I can't solve this error. My code in below
MainActivity.kt
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
val repository = Repository()
val viewModelFactory = MainViewModelFactory(repository)
viewModel = ViewModelProvider(this, viewModelFactory).get(MainViewModel::class.java)
viewModel.getEmployeeData()
viewModel.repoResponse.observe(this, Observer { response ->
if (response.isSuccessful) {
Log.d("Response", response.body()?.employee_id.toString())
Log.d("Response", response.body()?.employee_name.toString())
Log.d("Response", response.body()?.employee_age.toString())
Log.d("Response", response.body()?.employee_salary.toString())
name.text = response.body()?.employee_name!!
} else {
Log.d("Response", response.errorBody().toString())
name.text = response.code().toString()
}
})
}
MainViewModelFactory.kt
class MainViewModelFactory(private val repository: Repository):ViewModelProvider.Factory {
override fun <T : ViewModel?> create(modelClass: Class<T>): T {
return MainViewModel(repository) as T
}
MainViewModel.kt
class MainViewModel(private val repository: Repository):ViewModel() {
val repoResponse:MutableLiveData<Response<Employee>> = MutableLiveData()
fun getEmployeeData(){
viewModelScope.launch {
val response = repository.getEmployeeData()
repoResponse.value = response
}
}
ApiClient.kt
object ApiClient {
private val retrofit by lazy{
Retrofit.Builder()
.baseUrl(BASE_URL)
.addConverterFactory(GsonConverterFactory.create())
.build()
}
val api:Api by lazy {
retrofit.create(Api::class.java)
}
Api.kt
public interface Api {
#GET("api/v1/employee/1")
suspend fun getEmployeeData():Response<Employee>
}
Repository.kt
class Repository {
suspend fun getEmployeeData():Response<Employee>{
return ApiClient.api.getEmployeeData()
}
Employee.kt
data class Employee(
#SerializedName("id")
var employee_id: Int,
#SerializedName("employee_name")
var employee_name: String,
#SerializedName("employee_age")
var employee_age: Int,
#SerializedName("employee_salary")
var employee_salary: Int
)
Constants.kt
class Constants {
companion object{
const val BASE_URL = "http://dummy.restapiexample.com"
}
Error image
How can i solve this? please help me. Thank you
Retrofit only supports suspend keyword since 2.6.4, so using 2.3.0 won't work.
You should update to a newer version of Retrofit. The current latest version at the time of writing is 2.9.0.
I am working on Android Application in Which I am getting specific Data from Room Database by specific path in the Storage. My App Got Crashes as It does not have Any Data in the Storage and the Logcat gives me this..
java.lang.IllegalStateException: Room cannot verify the data integrity. Looks like you've changed schema but forgot to update the version number. You can simply fix this by increasing the version number.
at androidx.room.RoomOpenHelper.checkIdentity(RoomOpenHelper.java:154)
at androidx.room.RoomOpenHelper.onOpen(RoomOpenHelper.java:135)
at androidx.sqlite.db.framework.FrameworkSQLiteOpenHelper$OpenHelper.onOpen(FrameworkSQLiteOpenHelper.java:195)
at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:428)
at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:317)
at androidx.sqlite.db.framework.FrameworkSQLiteOpenHelper$OpenHelper.getWritableSupportDatabase(FrameworkSQLiteOpenHelper.java:145)
at androidx.sqlite.db.framework.FrameworkSQLiteOpenHelper.getWritableDatabase(FrameworkSQLiteOpenHelper.java:106)
at androidx.room.RoomDatabase.inTransaction(RoomDatabase.java:476)
at androidx.room.RoomDatabase.assertNotSuspendingTransaction(RoomDatabase.java:281)
at com.maximus.technologies.views.activities.scanneddatabase.TodoDaoScanned_Impl.getAllScan(TodoDaoScanned_Impl.java:152)
at com.maximus.technologies.views.fragments.scanhistorypackage.QRRetrievingScanClassPresenter$getAllDatFromDatabase$1.invokeSuspend(QRRetrievingScanClassPresenter.kt:29)
at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
at kotlinx.coroutines.DispatchedTask.run(Dispatched.kt:241)
at kotlinx.coroutines.scheduling.CoroutineScheduler.runSafely(CoroutineScheduler.kt:594)
The Above Error or crash Only occurs as the app dont have any data in Storage. But as I put a Data the Crash Problem Get Resolved.
I am not able to Understand what the Problem actually is...
Here is My Room Database Class..
#Database(
entities = [TodoEntity::class,TodoEntityScanned::class],
version = 1)
abstract class AppDatabase : RoomDatabase() {
abstract fun TodoDao(): TodoDao
abstract fun TodoDaoScanned(): TodoDaoScanned
object DatabaseBuilder {
private var INSTANCE: AppDatabase? = null
fun getInstance(context: Context): AppDatabase {
if (INSTANCE == null) {
synchronized(AppDatabase::class) {
INSTANCE = buildRoomDB(context)
}
}
return INSTANCE!!
}
private fun buildRoomDB(context: Context) =
Room.databaseBuilder(
context.applicationContext,
AppDatabase::class.java,
"mindorks-example-coroutines"
).build()
}
}
Room Database Retrieving Interface where app Crashes on getall()
override fun getAllDatFromDatabase(appDatabasescanned: AppDatabase) {
var list = listOf<TodoEntityScanned>()
try {
GlobalScope.launch(Dispatchers.Default) {
list = appDatabasescanned.TodoDaoScanned().getAllScan()
Log.d("hello","hello")
mView.showAllData(list)
}
}
catch (e:Exception){
Log.d("get hello",e.toString())
}
}
The getAll lies in Dao Class
interface TodoDao {
#Query("SELECT * FROM tablefilepaths")
fun getAll(): List<TodoEntity>
#Query("SELECT * FROM tablefilepaths WHERE imagespath LIKE :title")
fun findByTitle(title: String): TodoEntity
#Insert
fun insertpaths(todo: TodoEntity)
#Delete
fun deletepaths(todo: TodoEntity)
#Query("DELETE FROM tablefilepaths WHERE id = :noteId")
fun deleteNoteById(noteId: Int)
#Update
fun updateTodo(vararg todos: TodoEntity)}
Here is My Fragment Class Where I am Setting data in RecyclerView
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
recyclerviewcreatehistory?.layoutManager = LinearLayoutManager(context)
recyclerviewcreatehistory?.setHasFixedSize(true)
filefetch()
customAdaptercreatehistory = CustomAdapterCreateHistory(this.context ?: return, charItemcreate!!,this)
recyclerviewcreatehistory?.adapter = customAdaptercreatehistory
}
fun filefetch() {
val noteDatabase: AppDatabase = AppDatabase.DatabaseBuilder.getInstance(requireContext())
retrivingpresenter = QRRetrievingClassPresenter(this)
retrivingpresenter!!.getAllDatFromDatabase(noteDatabase)
}
override fun showAllData(note_list: List<TodoEntity>) {
if (note_list is ArrayList<*>) {
val arraylist = note_list as ArrayList<TodoEntity>
charItemcreate=arraylist
}
if (charItemcreate.isEmpty()){
}else{
customAdaptercreatehistory?.updateUsers(note_list as ArrayList<TodoEntity>)
customAdaptercreatehistory?.notifyDataSetChanged()
// Log.d("hello", note_list[0].imagesPathData)
}
}
You have to do some checks in your getAllDatFromDatabase() inside your coroutine. I guess list variable equals null or something like that. You should check if there are any files and if not you need to put there something else.
I'm using the Realm database in my kotlin project.
I use MVVM architecture so I created a repository class which contains codes bellow:
class DatabaseRepository {
private val database = Realm.getDefaultInstance()
fun addOrUpdateUser(user: JSONObject) {
database.executeTransactionAsync{
database.createOrUpdateObjectFromJson(UserModel::class.java, user)
}
}
}
also, I have created my ViewModel class like this:
class DatabaseViewModel(private val database:DatabaseRepository) : ViewModel() {
fun addUser(information: JSONObject) {
database.addOrUpdateUser(information)
}
}
and my View ModelFactory class is like this:
class ViewModelFactory(private val databaseRepository:DatabaseRepository):ViewModelProvider.Factory {
override fun <T : ViewModel?> create(modelClass: Class<T>): T {
return modelClass.getConstructor(DatabaseRepository::class.java).newInstance(databaseRepository)
}
}
so I create the instance of them in my MainActivity like this:
val databaseRepo=DatabaseRepository()
val factory=ViewModelFactory(databaseRepo)
database = ViewModelProviders.of(this,factory).get(DatabaseViewModel::class.java)
the problem is that while I'm trying to add some data to Database using 'addUser' function in ViewModel class I get this error:
Realm objects can only be accessed on the thread they were created.
what have I done wrong?
the only problem was because of executeTransactionAsync, so I changed from:
executeTransactionAsync
to
executeTransaction
and it worked!