Develop Reference

Can't use SharedPreferences in intended activity

There are two classes MainActivity and PickTimeForNotif in my project. In MainActivity getSharedPreferences works just fine, i can save my data and get it back. In PickTimeForNotif, however, the same method seems to do nothing.
Here's my simplified MainActivity class:
class MainActivity : AppCompatActivity(), ChangeCupDialogFragment.StringListener {
#SuppressLint("SetTextI18n")
//this is variable i'm saving
private var drankToday = 0
//function in which i save my value to SharedPreferences
private fun saveWaterCountToInternalStorage(clickCounter: Int) {
val sharedPref = this.getSharedPreferences("something", Context.MODE_PRIVATE)
with (sharedPref.edit()){
putInt(getString(R.string.clickCount), clickCounter)
apply()
}
}
//and here i get it from there
private fun loadWaterCountToInternalStorage(): Int {
val sharedPref = this.getSharedPreferences("something", Context.MODE_PRIVATE)
return sharedPref.getInt(getString(R.string.clickCount), drankToday)
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.main_activity)
val setupNotifButton = findViewById<Button>(R.id.setupNotifButton)
setupNotifButton.setOnClickListener{
val notifIntent = Intent(applicationContext, PickTimeForNotif::class.java)
startActivity(notifIntent)
}
}
}
In setOnClickListener i intend my second activity PickTimeForNotif, here it is.
class PickTimeForNotif: AppCompatActivity(), TimePickerFragment.OnCompleteListener {
val APP_PREFERENCES = "settings"
private val SAVED_FROM_HOUR = "SetFromHour"
private var FROM_HOUR = 99
private fun saveTimeToInternalStorage(prefName1: String, Hour:Int) {
val sharedPref = this.getSharedPreferences(APP_PREFERENCES, MODE_PRIVATE)
with (sharedPref.edit()){
putInt(prefName1, Hour)
apply()
}
}
private fun loadTimeFromInternalStorage() {
val sharedPref = this.getSharedPreferences(APP_PREFERENCES, MODE_PRIVATE)
if (sharedPref.contains(APP_PREFERENCES)) {
sharedPref.getInt(SAVED_FROM_HOUR, FROM_HOUR)
}
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.pick_time_activity)
saveTimeToInternalStorage(SAVED_FROM_HOUR, 1)
loadTimeFromInternalStorage()
Toast.makeText(applicationContext,"$FROM_HOUR", Toast.LENGTH_SHORT).show()
}
}
In the code above i'm trying to set value (1 for example ) to a SAVED_FROM_HOUR key and then get it back and assign to FROM_HOUR variable. However, the Toast shows 99, which means that new data wasn't loaded properly. I tried putting all code from loadTimeFromInternalStorage and saveTimeToInternalStorage to onCreate, but the result is same.
I also tried checking if the Preferences file exists after i call getSharedPreferences with
if (sharedPref.contains(APP_PREFERENCES))
but it does not.
So i'm asking to explain what am i doing wrong and why i can save the data in my MainActivity, but not in the second one. Thanks alot to anyone in advance!!

In loadTimeFromInternalStorage(), you are fetching the value but not assigning to variable like this:
private fun loadTimeFromInternalStorage() {
val sharedPref = this.getSharedPreferences(APP_PREFERENCES, MODE_PRIVATE)
if (sharedPref.contains(APP_PREFERENCES)) {
FROM_HOUR = sharedPref.getInt(SAVED_FROM_HOUR, FROM_HOUR)
}
}
Also, in this line FROM_HOUR = sharedPref.getInt(SAVED_FROM_HOUR, FROM_HOUR), the last parameter in getInt() method is the default value so you should make another constant for it or supply it 0.

How to get SharedPreferences in KoinComponent?

I'm using SharedPreferences in SettingsFragment:
val myPrefs = activity?.getSharedPreferences("myPrefs", Context.MODE_PRIVATE) ?: return
val testEnvEnabled = myPrefs.getBoolean(getString(R.string.saved_test_env_key), false)
This is working just fine.
Then I need to ready those preferences in object Api : KoinComponent {
I cannot get there context or activity.
Is there some another way to get information from shared preferences?
For me it's important just to save one information, if test env. is on or off.
I'm saving that information in SettingsFragment over switch.
Thank you

You can use Like this;
class Api : KoinComponent {
private val sharedPreferences by inject<SharedPreferences> {
parametersOf("myPref")
}
fun test() {
sharedPreferences.edit().putInt("Test", 1).commit()
}
fun get(): Int {
return sharedPreferences.getInt("Test", -1)
}
}
val sharedPreferences = module {
factory { key ->
androidContext().getSharedPreferences(key.get<String>(0), Context.MODE_PRIVATE)
}
factory {
Api()
}
}
class App : Application() {
override fun onCreate() {
super.onCreate()
startKoin {
androidContext(this#App)
modules(sharedPreferences)
}
}
}
enter code here

How to use Android DataStore with multi users or files

I want to store some preferences using DataStore. But the problem is that my application can have multiple users and therefor needs to store these preferences in separate files. I got a working example using only one user but I'm struggling to support multiple users.
Here is an example of my code:
class DataStorageRepository(private val context: Context, private val userRepository: UserRepository) {
private object PreferencesKeys {
val SETTING_ONE = intPreferencesKey("setting_one")
}
// retrieve datastore for currently logged in user.
private val Context.dataStore: DataStore<Preferences> by preferencesDataStore(name = userRepository.currentRegistration().name)
val userPreferencesFlow: Flow<UserPreferences> = context.dataStore.data.map { preferences ->
val settingOne = preferences[PreferencesKeys.SETTING_ONE] ?: 0
UserPreferences(settingOne)
}
suspend fun storeSettingOne(settingOne: Int) {
context.dataStore.edit { preferences ->
preferences[PreferencesKeys.SETTING_ONE] = settingOne
}
}
data class UserPreferences(val lastUsedToAccountTab: Int)
}
I'm using Koin and I tried unloading the DataStorageRepository on logout and recreating it on login but the DataStore seems to stay alive until the app is killed and I get the following crash:
java.lang.IllegalStateException: There are multiple DataStores active
for the same file: [...] You should either maintain your DataStore as
a singleton or confirm that there is no two DataStore's active on the
same file (by confirming that the scope is cancelled).
I also tried to use a CoroutineScope and kill that when I log out, but after recreating the scope on login the DataStore doesn't seem to get recreated.
Does DataStore support a way to close the connection or to handle multiple files?

Put this line inside companion object { }
private val Context.dataStore: DataStore<Preferences> by preferencesDataStore(name = "settingPrefs")
My Code
class SettingPrefs(private val context: Context) {
companion object {
private val Context.dataStore: DataStore<Preferences> by preferencesDataStore(name = "settingPrefs")
private val soundKey = booleanPreferencesKey("sound")
private val vibrateKey = booleanPreferencesKey("vibrate")
}
val getSound: Flow<Boolean>
get() = context.dataStore.data.map {
it[soundKey] ?: true
}
suspend fun setSound(value: Boolean) {
context.dataStore.edit { it[soundKey] = value }
}
val getVibration: Flow<Boolean>
get() = context.dataStore.data.map {
it[vibrateKey] ?: true
}
suspend fun setVibration(value: Boolean) {
context.dataStore.edit { it[vibrateKey] = value }
}
}

You can use different key for different user or manual keep DataStore singleton.
For exception:
java.lang.IllegalStateException: There are multiple DataStores active for the same file: [...] You should either maintain your DataStore as a singleton or confirm that there is no two DataStore's active on the same file (by confirming that the scope is cancelled).
androidx.datastore:datastore-*:1.0.0-alpha07 is released.
Put this at the top level of your kotlin file so there is only one instance of it.
private val Context.dataStore by preferencesDataStore("settings")
class Xxx{
}
https://developer.android.com/jetpack/androidx/releases/datastore#1.0.0-alpha07.
The Context.createDataStore extension function has been removed and replaced with globalDataStore property delegate. Call globalDataStore once at the top level in your kotlin file. For example:
val Context.myDataStore by dataStore(...)
Put this at the top level of your kotlin file so there is only one instance of it. (I57215, b/173726702)

At the moment I was posting this question I found a solution to this problem. In order to solve my problem I needed to combine my previous two solutions. So on logout I unload the DataStorageRepository and on login I reload it again. I also needed to create a CoroutineScope that I cancel on logout.
My Module
val loggedInModule = module {
single { DataStorageRepository(get(), get()) }
}
I created a scope and passed it to the DataStore
var loggedInScope: CoroutineScope = CoroutineScope(Dispatchers.Default)
private val Context.dataStore: DataStore<Preferences> by preferencesDataStore(name = userRepository.currentRegistration().name, scope = loggedInScope)
On Login
loggedInScope = CoroutineScope(Dispatchers.Default)
loadKoinModules(loggedInModule)
On Logout
loggedInScope.cancel()
unloadKoinModules(loggedInModule)

Just put your declaration datastore out of your DataStorageRepository class
private val Context.dataStore: DataStore<Preferences> by preferencesDataStore(name="settings")
class DataStorageRepository(context: Context) {
private var appContext = context.applicationContext
val mData: Flow<String?> = appContext.dataStore.data.map { preferences ->
preferences[YOUR_KEY]
}
suspend fun insertData(value: String) {
appContext.dataStore.edit { preferences ->
preferences[YOUR_KEY] = authToken
}
}
companion object {
private val KEY = stringPreferencesKey("data")
}
}

This is what I'm using in my project:
private object UserIdBasedPrefDs {
val lock = Any()
#GuardedBy("lock")
#Volatile
var currentId: String = ""
#GuardedBy("lock")
#Volatile
var INSTANCE: DataStore<Preferences>? = null
}
fun Context.happyStore( // rename what ever you like.
userId: String,
// below 3 optional params are same as int the `preferencesDataStore`.
corruptionHandler: ReplaceFileCorruptionHandler<Preferences>? = null,
produceMigrations: (Context) -> List<DataMigration<Preferences>> =
{ listOf() },
scope: CoroutineScope = CoroutineScope(Dispatchers.IO + SupervisorJob())
): DataStore<Preferences> = UserIdBasedPrefDs.run {
// check if current user id has been changed.
if (userId != currentId && INSTANCE != null) {
synchronized(lock) {
// release previous saved.
INSTANCE = null
// reset new user id.
currentId = userId
}
}
// below is the same logic inside the `preferencesDataStore` delegate.
INSTANCE ?: synchronized(lock) {
if (INSTANCE == null) {
INSTANCE = PreferenceDataStoreFactory.create(
corruptionHandler = corruptionHandler,
migrations = produceMigrations(applicationContext),
scope = scope
) {
applicationContext.preferencesDataStoreFile(userId)
}
}
INSTANCE!!
}
}
Hope it can be helpful to you.

build own cache, in Kotlin

I have a list with four elements: created_at, text, name, screen_name. The first represent a date of creation, the second the texto of a tweet and the latest the name and screen name of user.
I want to storage this information with lifespan, a random lifespan. For this i thinking using the cache and the implementation of this link https://medium.com/#kezhenxu94/how-to-build-your-own-cache-in-kotlin-1b0e86005591.
My questions is:
use a map key-value and save in value a string with all information (created_at, text, name, screen_name)?
how add this information in map with this code?
Please, give me a sample example for storage this data. Or if there is another way to make what i want more correctly, tell me.
My code in the moment:
class ExpirableCache(private val delegate: Cache, private val flushInterval: Long = TimeUnit.MINUTES.toMillis(1000)) : Cache {
private val dataTweet: Map<Long, Long>? = null
private var lastFlushTime = System.nanoTime()
override val size: Int
get() = delegate.size
override fun set(key: Any, value: Any) {
delegate[key] = value
}
override fun remove(key: Any): Any? {
recycle()
return delegate.remove(key)
}
override fun get(key: Any): Any? {
recycle()
return delegate[key]
}
override fun add(key: Any, value: Any) {
dataTweet[0, value]
}
override fun clear() = delegate.clear()
private fun recycle() {
val shouldRecycle = System.nanoTime() - lastFlushTime >= TimeUnit.MILLISECONDS.toNanos(flushInterval)
if (!shouldRecycle) return
delegate.clear()
}
}

Kotlin Assign Delegate After Variable Declaration

So, basically I have a class:
class App : Application() {
lateinit var prefs: SharedPreferences
}
Now, I want to add a delegated property:
var isInitialized: Boolean by prefs.boolean()
The problem is that this, isInitialized property must be initialized lazily since I'm using Android Dagger2 framework, which performs injection after App creation (during calling onCreate() method):
class App : Application() {
lateinit var prefs: SharedPreferences
var isInitialized: Boolean = false
override fun onCreate() {
super.onCreate()
// how can I assign a delegate to isInitialized?
}
}
I would like it to be done either via:
lazy initialization during declaration (which is delegate in delegate - wondering whether this possible?)
lazy initialization during assignment
Is there any way of doing this?
Thanks!

You could do it with an indirection:
class DoubleDelegate<R, T>(var realDelegate: ReadWriteProperty<R, T> = /* some default */) : ReadWriteProperty<R, T> by realDelegate
then
val isInitializedDelegate = DoubleDelegate<App, Boolean>()
var isInitialized: Boolean by isInitializedDelegate
override fun onCreate() {
super.onCreate()
isInitializedDelegate.realDelegate = prefs.boolean()
}
Somehow I don't think this is actually a good idea.

Use Lazy
From the document Lazy Gets the lazily initialized value of the current Lazy instance. Once the value was initialized it must not change during the rest of lifetime of this Lazy instance.
Application class
val prefs: Prefs by lazy {
App.prefs!!
}
class App : Application() {
companion object {
var prefs: Prefs? = null
}
override fun onCreate() {
prefs = Prefs(applicationContext)
super.onCreate()
}
}
your data model class should be like this
class Prefs (context: Context) {
val PREFS_FILENAME = "com.teamtreehouse.colorsarefun.prefs"
val IsInitialized = "isInitialized"
val prefs: SharedPreferences = context.getSharedPreferences(PREFS_FILENAME, 0);
var initialized: Boolean
get() = prefs. getBoolean(IsInitialized, false)
set(value) = prefs.edit(). putBoolean(IsInitialized, value).apply()
}
then use Activity or fragment
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
val initialized = prefs.initialized //getvalue
selectvalue(false)// set value
}
private fun selectvalue(value: Boolean) {
prefs.initialized = value
}
}
more details refer this example SharedPreferences Easy with Kotlin