Created
April 15, 2022 11:42
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Difference in recomposition when using offset modfier in Jetpack Compose
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@HiltViewModel | |
class UpdatingViewModel @Inject constructor() : ViewModel() { | |
val offset = mutableStateOf(Offset(0f, 0f)) | |
init { | |
viewModelScope.launch { | |
while(isActive) { | |
delay(50) | |
offset.value = offset.value.copy(x = offset.value.x + 1) | |
} | |
} | |
} | |
} | |
@Composable | |
fun OffsetsSample( | |
vm: UpdatingViewModel = hiltViewModel() | |
) { | |
Column( | |
modifier = Modifier.systemBarsPadding(), | |
) { | |
RecomposingOffset(offset = vm.offset) | |
NonRecomposingOffset(offset = vm.offset) | |
} | |
} | |
@Composable | |
private fun RecomposingOffset( | |
modifier: Modifier = Modifier, | |
offset: State<Offset> | |
) { | |
LogRecompose(composableTag = "Recomposing") | |
Text( | |
text = "Recomposing", | |
modifier = modifier.fillMaxWidth().offset( | |
x = with(LocalDensity.current) { offset.value.x.toDp() }, | |
y = with(LocalDensity.current) { offset.value.y.toDp() }, | |
) | |
) | |
} | |
@Composable | |
private fun NonRecomposingOffset( | |
modifier: Modifier = Modifier, | |
offset: State<Offset> | |
) { | |
LogRecompose(composableTag = "NonRecomposing") | |
Text( | |
text = "NonRecomposing", | |
modifier = modifier.fillMaxWidth().offset { | |
IntOffset( | |
offset.value.x.roundToInt(), | |
offset.value.y.roundToInt() | |
) | |
} | |
) | |
} | |
class Ref(var value: Int) | |
@Composable | |
inline fun LogRecompose(composableTag: String) { | |
val ref = remember { Ref(0) } | |
SideEffect { ref.value++ } | |
Log.d(composableTag, "recomposed ${ref.value} times") | |
} |
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