My app uses camera2 and I map the CameraCharacteristics for the camera currently in use, in a Flow t...

# compose

[Chris Fillmore]

My app uses camera2 and I map the CameraCharacteristics for the camera currently in use, in a Flow that I collect in a screen in my app. I am routinely getting this exception (in 🧵 )

[Chris Fillmore]

E  java.lang.IllegalStateException: Reading a state that was created after the snapshot was taken or in a snapshot that has not yet been applied
E      at androidx.compose.runtime.snapshots.SnapshotKt.readError(Snapshot.kt:1791)
E      at androidx.compose.runtime.snapshots.SnapshotKt.readable(Snapshot.kt:1786)
E      at androidx.compose.runtime.snapshots.SnapshotKt.readable(Snapshot.kt:1777)
E      at androidx.compose.runtime.SnapshotMutableStateImpl.getValue(SnapshotState.kt:130)
E      at com.example.android.camera.LiveLiterals$CameraCharacteristicsExtKt.Boolean$arg-1$call-EQEQ$fun-$get-hasFlashUnit$$get$val-hasFlashUnit(Unk
  nown Source:27)
E      at com.example.android.camera.CameraCharacteristicsExtKt.getHasFlashUnit(CameraCharacteristicsExt.kt:68)

(stack trace edited to remove my package name)

[Chris Fillmore]

This occurs when calling this extension property

val CameraCharacteristics.hasFlashUnit: Boolean get() {
  return get(CameraCharacteristics.FLASH_INFO_AVAILABLE) == true
}

[Chris Fillmore]

My composable screen is roughly

@Composable
fun CameraScreen(
  ...
  currentCameraCharacteristics: CameraCharacteristics,
) {
  if (currentCameraCharacteristics.hasFlashUnit) {
    // show an icon to enable the torch
  }
}

[Chris Fillmore]

Called like so

val currentCameraCharacteristics by cameraOwner.currentCameraCharacteristics.collectAsState()
CameraScreen(
  ...,
  currentCameraCharacteristics = currentCameraCharacteristics,
)

[Chris Fillmore]

There are about a dozen other flows collected and shown in this screen; but I occasionally get this exception for this exact situation. And I only get it for this

[Chris Fillmore]

I would guess it happens maybe 1 in 50 times I run the app. Possibly less frequently

[Chris Fillmore]

I’m disturbed somewhat by the presence of LiveLiterals in this stack trace

LiveLiterals$CameraCharacteristicsExtKt.Boolean$arg-1$call-EQEQ$fun-$get-hasFlashUnit$$get$val-hasFlashUnit(Unk
  nown Source:27)

[Chris Fillmore]

Is this only happening when I’m editing code while running the app?

[Chris Fillmore]

Thanks for any help!

[Colton Idle]

Maybe disable live literals and see if that's the culprit?

[Chris Fillmore]

Yeah that seems a good place to start. It occurs so infrequently I’m not sure I’ll notice though

[Colton Idle]

I guess LiveLiterals is going away in favor of Live Edit anyway. So you can try that?

[Chris Fillmore]

Ooh thanks for the tip. I’ll check it out

[Colton Idle]

im also in electric eel though, so you may not see those options (they unfortunately dont show when you search for them using the intellij action search)

[Colton Idle]

but you should still be able to disable live literals in stable or beta.