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Title
# compose
r

reactormonk

09/20/2023, 3:31 PM
Any reason why
Copy code
var done by remember(mediaItems) { mutableStateOf(false) }

<inside callback>
  done = true
doesn't trigger a recompose? the 
done = true
is getting invoked, println debugging.
v

vide

09/20/2023, 3:46 PM
you only get recomposition in the scopes you read the value of 
done
in
r

reactormonk

09/20/2023, 3:47 PM
At the end of the function defining it, I got
Copy code
Box(
        modifier = Modifier.fillMaxWidth(),
        contentAlignment = Alignment.Center,
    ) {
        if (!done) {
            VideoPlayer(exoPlayer)
        } else {
            ErrorTemplate(message = stringResource(R.string.end_of_playlist))
        }
    }
And I'm wondering why the 
ErrorTemplate
isn't being displayed
v

vide

09/20/2023, 3:47 PM
are you changing 
mediaItems
?
you will lose the previous instance of the state because you create a new one when 
mediaItems
changes
r

reactormonk

09/20/2023, 3:48 PM
No, added a log statement in the 
remember
block, no recreation
v

vide

09/20/2023, 3:49 PM
can you post a bit more context?
r

reactormonk

09/20/2023, 3:51 PM
Sure.
Copy code
var done by remember(mediaItems) { Log.d(TAG, "Recreating done."); mutableStateOf(false) }
    var started = false
    val listener = object : Player.Listener {
        override fun onEvents(player: Player, events: Player.Events) {
            if (events.contains(Player.EVENT_PLAYBACK_STATE_CHANGED)) {
                if (player.playbackState == Player.STATE_ENDED && started) {
                    done = true
                    Log.d(TAG, "Done.")
                }
            }
        }

        override fun onIsPlayingChanged(isPlaying: Boolean) {
            if (isPlaying) {
                started = true
            }
        }
    }

    val exoPlayer = remember(context) {
        val mediaSourceFactory = DefaultMediaSourceFactory(context).setLoadErrorHandlingPolicy(
            DefaultLoadErrorHandlingPolicy()
        )
        val player = ExoPlayer.Builder(context).setMediaSourceFactory(mediaSourceFactory).build()
        player.addListener(listener)
//        player.addAnalyticsListener(EventLogger())
        player.repeatMode = REPEAT_MODE_OFF

        player
    }
    if (exoPlayer.availableCommands.contains(Player.COMMAND_CHANGE_MEDIA_ITEMS)) {
        exoPlayer.setMediaItems(mediaItems)
        exoPlayer.prepare()
        exoPlayer.playWhenReady = true
    } else {
        Log.e(TAG, "Can't change media items!?!")
    }

    if (mediaItemIndex > -1) {
        exoPlayer.seekTo(mediaItemIndex, position)
    }

    Box(
        modifier = Modifier.fillMaxWidth(),
        contentAlignment = Alignment.Center,
    ) {
        if (!done) {
            VideoPlayer(exoPlayer)
        } else {
            ErrorTemplate(message = stringResource(R.string.end_of_playlist))
        }
    }
... and a bit more lifecycle stuff to clean up things.
v

vide

09/20/2023, 3:56 PM
this seems like you're calling 
exoPlayer.setMediaItems(mediaItems)
exoPlayer.prepare()
exoPlayer.seekTo(mediaItemIndex, position)
on every recomposition
you're also creating a new var 
started
and a new 
listener
on every recomposition
r

reactormonk

09/20/2023, 3:58 PM
Thanks, moved things inside 
remember
blocks
v

vide

09/20/2023, 3:58 PM
you're probably seeing 
started
update correctly because the player is memoized in the remember block for creating the exoplayer instance 🤔
r

reactormonk

09/20/2023, 3:59 PM
Huh, I can't used remember blocks with 
Unit
as return?
v

vide

09/20/2023, 3:59 PM
you need to have something to remember, right? 😅 what are you trying to do?
r

reactormonk

09/20/2023, 4:00 PM
Copy code
remember(mediaItems) {

        if (exoPlayer.availableCommands.contains(Player.COMMAND_CHANGE_MEDIA_ITEMS)) {
            exoPlayer.setMediaItems(mediaItems)
            exoPlayer.prepare()
            exoPlayer.playWhenReady = true
        } else {
            Log.e(TAG, "Can't change media items!?!")
        }
}
v

vide

09/20/2023, 4:02 PM
It looks like you could use a 
LaunchedEffect
here? https://developer.android.com/jetpack/compose/side-effects#launchedeffect
r

reactormonk

09/20/2023, 4:02 PM
Yup, exactly.
Nope, still not recomposing as it should 😭
v

vide

09/20/2023, 4:14 PM
Can you post your updated source? I can try to to take a look again simple smile
r

reactormonk

09/20/2023, 4:14 PM
ChatGPT tells me I shouldn't update 
MutableState
from non-main-threads
v

vide

09/20/2023, 4:23 PM
what kind of logs do you get by running that?
r

reactormonk

09/20/2023, 4:24 PM
Copy code
MediaItems: []
Recreating done.
Exo player: androidx.media3.exoplayer.ExoPlayerImpl@fef39da
currentMediaItem: null
Done: false
MediaItems: [androidx.media3.common.MediaItem@1db4b9bf]
Recreating done.
Exo player: androidx.media3.exoplayer.ExoPlayerImpl@fef39da
currentMediaItem: null
Done: false
Done.
The second 
Recreating done.
is fine, I'm changing the MediaItems, so it's expected. The final 
Done.
is where I'm changing the 
done
variable.
v

vide

09/20/2023, 4:27 PM
Ah, so you are changing your 
mediaItems
. That is a problem, can you see why?
❤️ 1
r

reactormonk

09/20/2023, 4:28 PM
This one should go in there certainly:
Copy code
var started = false
    
    LaunchedEffect(mediaItems) {
        started = false
    }
... but that's not the exact issue here 🤔
v

vide

09/20/2023, 4:30 PM
The issue is that your 
listener
contains a reference to the first 
done
state. You change 
mediaItems
after it has captured it in the closure, and it creates a new state, which always stays in 
false
. Because your listener is actually updating the first instance.
r

reactormonk

09/20/2023, 4:32 PM
🤦 , moved it inside a 
DisposableEffect
to change out the listener
v

vide

09/20/2023, 4:34 PM
I would suggest considering using a state holder class since managing complex state inside composables can be quite hard.
➕ 1
r

reactormonk

09/20/2023, 4:34 PM
Aka shoving things into a 
data class
?
Sorry, my background is FP, not OOP, so I'm not sure what a "state holder class" is 😅
s

Stylianos Gakis

09/20/2023, 4:35 PM
Are you using 
rememberPagerState
anywhere in your app? 
PagerState
is an example of such a class
v

vide

09/20/2023, 4:36 PM
It doesn't have to be 
data
, but it can also be that. You can just use a regular class too. The main point is to separate your state and mutation logic from the UI code
s

Stylianos Gakis

09/20/2023, 4:36 PM
r

reactormonk

09/20/2023, 4:37 PM
Tried doing so already, but because the state depends a whole lot on callbacks because of the ExoPlayer API, I'm not sure which state I can push outside of the composable 🤔
Good think about the 
LaunchedEffect
and recomposing, had similar bugs in other parts of the code 😅
v

vide

09/20/2023, 4:44 PM
I don't have too much time to think about the architecture, but you could for example move creating the exoplayer object to a class, and have a method for changing the active index. Then you could just use state exposed by the class to drive your UI
f

Filip Wiesner

09/20/2023, 7:02 PM
Ah, so you are changing your 
mediaItems
. That is a problem, can you see why?
I love this ❤️ I wish someone gave me code reviews like this ☺️
😅 1
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