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#compose
Title
# compose
a
amar_1995
01/31/2020, 10:22 AMPurpose and difference of Key and Pivotal ?
m
Manuel Wrage
01/31/2020, 10:24 AMPivotal is the mechanism which is used to implement the key function.
a
amar_1995
01/31/2020, 10:26 AMI am making infinite scrolling view.
After making to the end of verticalScroller. I am calling api to load more data and store it in a local db.
I am observing the local db and as change happen i recieved a new list of data(with old data also).
Now the problem is that scroller is recomposing the whole view. I only want the data to load with new ids.
Is using
KeyPivotalI don't want to recompose the whole ui.
m
Manuel Wrage
01/31/2020, 10:29 AMIs every parameter of your item composable stable?
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amar_1995
01/31/2020, 10:32 AMI am getting list of livedata which is observed inside a below function
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fun <T> observer(data: LiveData<T>) = effectOf<T?> {
var result = +state<T?> { data.value }
val observer = +memo { Observer<T> { result.value = it } }
+onCommit(data) {
data.observeForever(observer)
onDispose { data.removeObserver(observer) }
}
result.value
}m
Manuel Wrage
01/31/2020, 10:32 AMCan you show me code were you compose the VerticalScroller?
a
amar_1995
01/31/2020, 10:33 AM Copy code
var internationalState = +observer(newArticleModel.internationalHeadline)
Surface(color = (+MaterialTheme.colors()).surface, modifier = Expanded) {
if (internationalState == null) {
ShowLoading()
} else if (internationalState.isEmpty()) {
NoContentMore()
} else {
val scrollerPosition: ScrollerPosition = +memo { ScrollerPosition(0f) }
println("MainActivity data here : " + internationalState)
Observe {
+onCommit(scrollerPosition.isAtEndOfList) {
println("Is commit entered")
if(scrollerPosition.isAtEndOfList)
newArticleModel.loadMoreData()
}
}
VerticalScroller(scrollerPosition = scrollerPosition) {
Column(Expanded) {
println("Page rendering size " + PageSize.topHeadlineInternationalPageNo)
internationalState!!.forEach {
Ripple(bounded = true) {
Clickable() {
ArticleTicket(
backgroundColor = (+MaterialTheme.colors()).background,
article = it
)
}
}
}
}
}
}
}m
Manuel Wrage
01/31/2020, 10:37 AM1. Extract the logic inside the forEach to a function that accepts your article class as a parameter
2. Annotate the article with @Pivotal
3. Annotate the article class with @Immutable, @Stable or @Model depending on what is applicable. I guess it's @Immutable in this case
a
amar_1995
01/31/2020, 10:41 AMGetting this error
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java.lang.IllegalStateException: Expected a group start
at androidx.compose.SlotTableKt.getAsGroupStart(SlotTable.kt:641)
at androidx.compose.SlotTableKt.access$getAsGroupStart$p(SlotTable.kt:1)m
Manuel Wrage
01/31/2020, 10:43 AMYou have to use the latest version of compose
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amar_1995
01/31/2020, 10:44 AMOkay, let me try after updating the compose
After changing from dev03 to dev04, I am getting this error
java.lang.ClassCastException: androidx.compose.GroupStart cannot be cast to androidx.ui.foundation.ScrollerPosition5 Views