Develop Reference

How to delay in fragment and cancel in onPause

I just want to delay a task in a fragment and if the app goes to the background while the delay is running the scope should never resume when the app comes to the foreground:
With following 2 approaches both will execute once the app comes back again, but I want that this never returns once the app was in the background. How to achieve that?
lifecycleScope.launch {
lifecycle.whenResumed {
Timber.d("before delay 1")
delay(15000)
Timber.d("after delay 1")
}
}
lifecycleScope.launch {
viewLifecycleOwner.repeatOnLifecycle(Lifecycle.State.RESUMED) {
Timber.d("before delay 2")
delay(15000)
Timber.d("after delay 2")
}
}
kotlinx.coroutines.delay()

A Job launched by lifecycleScope will not be canceled until lifecycle destroy
https://developer.android.com/reference/kotlin/androidx/lifecycle/LifecycleCoroutineScope
If you need to run it once you have to write something like this
private var delayedJob: Job? = null
override fun onResume() {
if(delayedJob == null) {
delayedJob = lifecycleScope.launch {
Timber.d("before delay")
delay(15000)
Timber.d("after delay")
}
}
}
override fun onPause() {
delayedJob?.cancel()
}

Integer Value increase with TextView after Ad Show

ok I am working on concept idea my dad has pitched to me. I have an app that runs AdMobs. On the interstitial ads based off button. The idea of the app is you press the start button and you watch an ad. However, when the ad is closed out, the value should increase in the Ads Watched Field.
I have created a function that increases the TextView no problem. My issue is with AdMob functions, when I call the function in AdDismissed, it does not change the value. I can plug the function into the Start Button and it increases value, but when the Ad is dismissed it zeros out the textView.
I am showing the demo portion of the app, this is still experimental, but also learning with Admobs and the coding on functions. Any advice would be appreciated. Also the adCounter is in the stop button, that was just to make sure the increments where firing. Which it does work perfectly. My thing is when the ad ends keeping the value.
SO in example the Ads Watched: 167,897,256 should increment by one when the ad is dismissed. However placing adCount() in the dismissed section of the ad does not work it just zeros out that textView.
MainActivity
import android.content.Intent
import android.os.Bundle
import android.widget.Button
import android.widget.TextView
import androidx.appcompat.app.AppCompatActivity
import com.google.android.gms.ads.*
import com.google.android.gms.ads.interstitial.InterstitialAd
import com.google.android.gms.ads.interstitial.InterstitialAdLoadCallback
class MainActivity : AppCompatActivity() {
lateinit var mAdView : AdView
private var mInterstitialAd: InterstitialAd? = null
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
loadBanner()
loadInterAd()
val interAdBtnStart : Button = findViewById(R.id.btnStartAds)
val interAdBtnStop : Button = findViewById(R.id.btnStopAds)
interAdBtnStart.setOnClickListener {
showInterAd()
}
interAdBtnStop.setOnClickListener {
adCountInc()
}
}
fun adCountInc(){
val tvAdsAmount : TextView = findViewById(R.id.tvAdsAmount)
var i : Int = tvAdsAmount.text.toString().toInt()
tvAdsAmount.text = "${++i}"
}
private fun showInterAd() {
if (mInterstitialAd != null)
{
mInterstitialAd?.fullScreenContentCallback = object : FullScreenContentCallback(){
override fun onAdClicked() {
super.onAdClicked()
}
override fun onAdDismissedFullScreenContent() {
super.onAdDismissedFullScreenContent()
val intent = Intent(this#MainActivity, MainActivity::class.java)
startActivity(intent)
}
override fun onAdFailedToShowFullScreenContent(p0: AdError) {
super.onAdFailedToShowFullScreenContent(p0)
}
override fun onAdImpression() {
super.onAdImpression()
}
override fun onAdShowedFullScreenContent() {
super.onAdShowedFullScreenContent()
}
}
mInterstitialAd?.show(this)
}
else
{
val intent = Intent(this, MainActivity::class.java)
startActivity(intent)
}
}
private fun loadInterAd() {
var adRequest = AdRequest.Builder().build()
InterstitialAd.load(this,"ca-app-pub-3940256099942544/1033173712", adRequest, object : InterstitialAdLoadCallback() {
override fun onAdFailedToLoad(adError: LoadAdError) {
mInterstitialAd = null
}
override fun onAdLoaded(interstitialAd: InterstitialAd) {
mInterstitialAd = interstitialAd
}
})
}
private fun loadBanner() {
MobileAds.initialize(this) {}
mAdView = findViewById(R.id.adView)
val adRequest = AdRequest.Builder().build()
mAdView.loadAd(adRequest)
mAdView.adListener = object: AdListener() {
override fun onAdLoaded() {
// Code to be executed when an ad finishes loading.
}
override fun onAdFailedToLoad(adError : LoadAdError) {
// Code to be executed when an ad request fails.
}
override fun onAdOpened() {
// Code to be executed when an ad opens an overlay that
// covers the screen.
}
override fun onAdClicked() {
// Code to be executed when the user clicks on an ad.
}
override fun onAdClosed() {
// Code to be executed when the user is about to return
// to the app after tapping on an ad.
}
}
}
}
this is the full code to the app so far. Any advice will help. If i place the adCounter() anywhere in the ads section it will not update the textfield at all. Even after the textfield shows 1 then an ad is displayed it will always zero out the text field.

The value is not updated because you are opening the same Activity (MainActivity) on onAdDismissedFullScreenContent again.
First create a global TextView variable like:
private lateinit var tvAdsAmount : TextView`\
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
tvAdsAmount = findViewById(R.id.tvAdsAmount)
// Other things...
}
Then simply use:
override fun onAdDismissedFullScreenContent() {
val value = tvAdsAmount.text.toString().toInt()
// make sure that value is an Integer.
val updateValue = value++
tvAdsAmount.text = "$updatedValue"
}

Some points you should learn:
Every time you start a new Activity, you're getting a new TextView that has no memory of what was in a TextView of some previous Activity.
You should never use a UI component like TextView to store application state. It's just not reliable. UI components are intended to be a bridge between your application state and the user. They aren't supposed to be the application state themselves. This is the programming principle of separation of concerns.
Since you're not finishing the previous Activity, you're building up a large stack of duplicate Activities. The user will be surprised when they push the back button to see an outdated copy of the Activity, one after another.
Whenever there's a configuration change (such as a screen rotation, or the user changing some setting in the Android settings like the device language), Android destroys all of the Activities that you have open and creates new instances of them. So any application state you were holding in them is going to be lost. This is why there is a ViewModel class for holding state that will survive configuration changes.
To fix your app:
Change your logic so you aren't starting new Activities. Keep everything in the same Activity instance. If you want to load a new ad, just call the function that loads ads rather than creating a brand new Activity.
Create a ViewModel to hold your application state. In this case, it will just need a LiveData<Int> to hold your count. You can observe this LiveData in your Activity and update the value of the TextView in the observer function. Your ViewModel can have an increment function that increases the LiveData's integer value, and you'll call this after ads are dismissed.
Long term, you can consider backing up this value with SharedPreferences, so the value will persist between sessions of your app.
Points 2 and 3 have many tutorials online and questions on this site about them, so I'm not going to explain them in detail.

How can I stop the execution of FixedRateTimer() in Kotlin using a button?

I need some help to achieve something that is maybe simple. My code is like this :
class HomeActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
repeatAction()
val stoprepeat = findViewById(R.id.btn) as Button
stoprepeat.setOnClickListener{
// I need to completely stop the actions that are repeating from here
}
}
private fun repeatAction(){
var repeataction = FixedRateTimer("mytimer",false,2400,20000){
this#HomeActivity.runOnUiThread {
// Stuff to repeat (3 or 4 actions)
}
}
}
}
What I'm trying to do is to stop the FixedTimeRate tasks when I Click on the button.
Also, is there a way to prevent fixedRateTimer from crashing the app after maybe 10 minutes of running?

how about intruducing a var keepRunning: Boolean = true in HomeActivity that is checked every cycle by repeatAction() ie. while(keepRunning){ ... } and is set to false by stoprepeat.setOnClickListener?

Navigation controller gets called twice inside livedata observer

What I'm trying to do is to use the Navigation controller inside a LiveData observer, so when the user clicks an item from the list it notifies the ViewModel, then the ViewModel updates the data and when this happens the fragment observes this and navigates to the next.
My problem is that for some reason the observer gets called twice and the second time I get an exception saying that the destination is unknown to this NavController.
My Fragment onCLick:
override fun onClick(view: View?) {
viewModel.productSelected.observe(viewLifecycleOwner, Observer<ProductModel> {
try {
this.navigationController.navigate(R.id.action_product_list_to_product_detail)
} catch (e: IllegalArgumentException) { }
})
val itemPosition = view?.let { recyclerView.getChildLayoutPosition(it) }
viewModel.onProductSelected(listWithHeaders[itemPosition!!].id)
}
And in my ViewModel:
fun onProductSelected(productId: String) {
productSelected.value = getProductById(productId)
}

It's called twice because first you subscribe and so you get a default value back, then you change a value in your productSelected LiveData and so your observer gets notified again.
Thereof, start observing after onProductSelected is called as below:
override fun onClick(view: View?) {
val itemPosition = view?.let { recyclerView.getChildLayoutPosition(it) }
viewModel.onProductSelected(listWithHeaders[itemPosition!!].id)
viewModel.productSelected.observe(viewLifecycleOwner, Observer<ProductModel> {
try {
this.navigationController.navigate(R.id.action_product_list_to_product_detail)
} catch (e: IllegalArgumentException) { }
})
}
Once again, beware that once you start observing your LiveData it will get notified each time productSelected is changed. Is it what you want? If not, then you should remove the observer once it's used once.

Catching the exception may work, but it can also make you miss several other issues. It might be better to check the current layout with the destination to validate if the user is already there. Another alternative that I prefer is to check with the previous destination, something like:
fun Fragment.currentDestination() = findNavController().currentDestination
fun Fragment.previousDestination() = findNavController().previousBackStackEntry?.destination
fun NavDestination.getDestinationIdFromAction(#IdRes actionId: Int) = getAction(actionId)?.destinationId
private fun Fragment.isAlreadyAtDestination(#IdRes actionId: Int): Boolean {
val previousDestinationId = previousDestination()?.getDestinationIdFromAction(actionId)
val currentDestinationId = currentDestination()?.id
return previousDestinationId == currentDestinationId
}
fun Fragment.navigate(directions: NavDirections) {
if (!isAlreadyAtDestination(directions.actionId)) {
findNavController().navigate(directions)
}
}
Basically, here we validate that we are not already at the destination. This can be done by comparing the previous action destination with the current destination. Let me know if the code helps!

Refreshing MediaBrowserService subcription content

TL;DR: I have successfully created and coupled (via a subscription) an activity to a media browser service. This media browser service can continue running and play music in the background. I'd like to be able to refresh the content at some stage, either when the app comes to the foreground again or during a SwipeRefreshLayout event.
I have the following functionality I'd like to implement:
Start a MediaBrowserServiceCompat service.
From an activity, connect to and subscribe to the media browser service.
Allow the service to continue running and playing music while the app is closed.
At a later stage, or on a SwipeRefreshLayout event, reconnect and subscribe to the service to get fresh content.
The issue I am receiving is that within a MediaBrowserService (after a subscription has been created) you can only call sendResult() once from the onLoadChildren() method, so the next time you try to subscribe to the media browser service using the same root, you get the following exception when sendResult() is called for the second time:
E/UncaughtException: java.lang.IllegalStateException: sendResult() called when either sendResult() or sendError() had already been called for: MEDIA_ID_ROOT
at android.support.v4.media.MediaBrowserServiceCompat$Result.sendResult(MediaBrowserServiceCompat.java:602)
at com.roostermornings.android.service.MediaService.loadChildrenImpl(MediaService.kt:422)
at com.roostermornings.android.service.MediaService.access$loadChildrenImpl(MediaService.kt:50)
at com.roostermornings.android.service.MediaService$onLoadChildren$1$onSyncFinished$playerEventListener$1.onPlayerStateChanged(MediaService.kt:376)
at com.google.android.exoplayer2.ExoPlayerImpl.handleEvent(ExoPlayerImpl.java:422)
at com.google.android.exoplayer2.ExoPlayerImpl$1.handleMessage(ExoPlayerImpl.java:103)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:150)
at android.app.ActivityThread.main(ActivityThread.java:5665)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:822)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:712)
I call the following methods to connect to and disconnect from the media browser (again, everything runs smoothly on first connection, but on the second connection I'm not sure how to refresh the content via a subscription):
override fun onStart() {
super.onStart()
mMediaBrowser = MediaBrowserCompat(this, ComponentName(this, MediaService::class.java), connectionCallback, null)
if (!mMediaBrowser.isConnected)
mMediaBrowser.connect()
}
override fun onPause() {
super.onPause()
//Unsubscribe and unregister MediaControllerCompat callbacks
MediaControllerCompat.getMediaController(this#DiscoverFragmentActivity)?.unregisterCallback(mediaControllerCallback)
if (mMediaBrowser.isConnected) {
mMediaBrowser.unsubscribe(mMediaBrowser.root, subscriptionCallback)
mMediaBrowser.disconnect()
}
}
I unsubscribe and disconnect in onPause() instead of onDestroy() so that the subscription is recreated even if the activity is kept on the back-stack.
Actual method used for swipe refresh, in activity and service respectively:
Activity
if (mMediaBrowser.isConnected)
mMediaController?.sendCommand(MediaService.Companion.CustomCommand.REFRESH.toString(), null, null)
Service
inner class MediaPlaybackPreparer : MediaSessionConnector.PlaybackPreparer {
...
override fun onCommand(command: String?, extras: Bundle?, cb: ResultReceiver?) {
when(command) {
// Refresh media browser content and send result to subscribers
CustomCommand.REFRESH.toString() -> {
notifyChildrenChanged(MEDIA_ID_ROOT)
}
}
}}
Other research:
I have referred to the Google Samples code on Github, as well as...
https://github.com/googlesamples/android-MediaBrowserService
https://github.com/moondroid/UniversalMusicPlayer
Neither of the above repos seem to handle the issue of refreshing content after the media browser service has been created and the activity has subscribed at least once - I'd like to avoid restarting the service so that the music can continue playing in the background.
Possible related issues:
MediaBrowser.subscribe doesn't work after I get back to activity 1 from activity 2 (6.0.1 Android) --no effect on current issue

Calling you music service implementations notifyChildrenChanged(String parentId) will trigger the onLoadChildren and inside there, you can send a different result with result.sendResult().
What I did was that I added a BroadcastReceiver to my music service and inside it, I just called the notifyChildrenChanged(String parentId). And inside my Activity, I sent a broadcast when I changed the music list.

Optional (not Recommended) Quick fix
MusicService ->
companion object {
var musicServiceInstance:MusicService?=null
}
override fun onCreate() {
super.onCreate()
musicServiceInstance=this
}
//api call
fun fetchSongs(params:Int){
serviceScope.launch {
firebaseMusicSource.fetchMediaData(params)
//Edit Data or Change Data
notifyChildrenChanged(MEDIA_ROOT_ID)
}
}
ViewModel ->
fun fetchSongs(){
MusicService.musicServiceInstance?.let{
it.fetchSongs(params)
}
}
Optional (Recommended)
MusicPlaybackPreparer
class MusicPlaybackPreparer (
private val firebaseMusicSource: FirebaseMusicSource,
private val serviceScope: CoroutineScope,
private val exoPlayer: SimpleExoPlayer,
private val playerPrepared: (MediaMetadataCompat?) -> Unit
) : MediaSessionConnector.PlaybackPreparer {
override fun onCommand(player: Player, controlDispatcher: ControlDispatcher, command: String, extras: Bundle?, cb: ResultReceiver?
): Boolean {
when(command){
//edit data or fetch more data from api
"Add Songs"->{
serviceScope.launch {
firebaseMusicSource.fetchMediaData()
}
}
}
return false
}
override fun getSupportedPrepareActions(): Long {
return PlaybackStateCompat.ACTION_PREPARE_FROM_MEDIA_ID or
PlaybackStateCompat.ACTION_PLAY_FROM_MEDIA_ID
}
override fun onPrepare(playWhenReady: Boolean) = Unit
override fun onPrepareFromMediaId(mediaId: String, playWhenReady: Boolean, extras: Bundle?) {
firebaseMusicSource.whenReady {
val itemToPlay = firebaseMusicSource.songs.find { mediaId == it.description.mediaId }
playerPrepared(itemToPlay)
}
}
override fun onPrepareFromSearch(query: String, playWhenReady: Boolean, extras: Bundle?) = Unit
override fun onPrepareFromUri(uri: Uri, playWhenReady: Boolean, extras: Bundle?) = Unit
}
MusicServiceConnection
fun sendCommand(command: String, parameters: Bundle?) =
sendCommand(command, parameters) { _, _ -> }
private fun sendCommand(
command: String,
parameters: Bundle?,
resultCallback: ((Int, Bundle?) -> Unit)
) = if (mediaBrowser.isConnected) {
mediaController.sendCommand(command, parameters, object : ResultReceiver(Handler()) {
override fun onReceiveResult(resultCode: Int, resultData: Bundle?) {
resultCallback(resultCode, resultData)
}
})
true
} else {
false
}
ViewModel
fun fetchSongs(){
val args = Bundle()
args.putInt("nRecNo", 2)
musicServiceConnection.sendCommand("Add Songs", args )
}
MusicService ->
override fun onLoadChildren(
parentId: String,
result: Result<MutableList<MediaBrowserCompat.MediaItem>>
) {
when(parentId) {
MEDIA_ROOT_ID -> {
val resultsSent = firebaseMusicSource.whenReady { isInitialized ->
if(isInitialized) {
try {
result.sendResult(firebaseMusicSource.asMediaItems())
if(!isPlayerInitialized && firebaseMusicSource.songs.isNotEmpty()) {
preparePlayer(firebaseMusicSource.songs, firebaseMusicSource.songs[0], true)
isPlayerInitialized = true
}
}
catch (exception: Exception){
// not recommend to notify here , instead notify when you
// change existing list in MusicPlaybackPreparer onCommand()
notifyChildrenChanged(MEDIA_ROOT_ID)
}
} else {
result.sendResult(null)
}
}
if(!resultsSent) {
result.detach()
}
}
}
}

My issue was unrelated to the MediaBrowserServiceCompat class. The issue was coming about because I was calling result.detach() in order to implement some asynchronous data fetching, and the listener I was using had both the parentId and result variables from the onLoadChildren method passed in and assigned final val rather than var.
I still don't fully understand why this occurs, whether it's an underlying result of using a Player.EventListener within another asynchronous network call listener, but the solution was to create and assign a variable (and perhaps someone else can explain this phenomenon):
// Create variable
var currentResult: Result<List<MediaBrowserCompat.MediaItem>>? = null
override fun onLoadChildren(parentId: String, result: MediaBrowserServiceCompat.Result<List<MediaBrowserCompat.MediaItem>>) {
// Use result.detach to allow calling result.sendResult from another thread
result.detach()
// Assign returned result to temporary variable
currentResult = result
currentParentId = parentId
// Create listener for network call
ChannelManager.onFlagChannelManagerDataListener = object : ChannelManager.Companion.OnFlagChannelManagerDataListener {
override fun onSyncFinished() {
// Create a listener to determine when player is prepared
val playerEventListener = object : Player.EventListener {
override fun onPlayerStateChanged(playWhenReady: Boolean, playbackState: Int) {
when(playbackState) {
Player.STATE_READY -> {
if(mPlayerPreparing) {
// Prepare content to send to subscribed content
loadChildrenImpl(currentParentId, currentResult as MediaBrowserServiceCompat.Result<List<MediaBrowserCompat.MediaItem>>)
mPlayerPreparing = false
}
}
...
}
}
}
}