英文:
Correct way to remove item from the LazyColumn in jetpack compose
问题
I want to remove item from the LazyColumn. I have a bunch of item in the list i.e. 200+ item. When I removed item it little bit slow. I don't understand what is the problem in my code. I am adding basic sample what I did try on my code.
RemoveItem
@Composable
fun RemoveItem(viewModel: RemovedItemViewModel) {
var newList = viewModel.itemList
LaunchedEffect(key1 = viewModel.itemList) {
newList = viewModel.itemList
}
LazyColumn {
items(newList) {
Text(text = "$it")
}
}
}
RemovedItemViewModel
class RemovedItemViewModel : BaseViewModel() {
val itemList = mutableStateListOf<MovieItem>()
init {
repeat(10) {
itemList.add(MovieItem("$it cast", "Movie $it"))
}
}
fun removeItem() {
val random = (0..10).random()
itemList.removeAt(random)
}
}
MovieItem
data class MovieItem(val number: String, val name: String)
Is there any better way to remove item?
英文:
I want to remove item from the LazyColumn. I have a bunch of item in the list i.e. 200+ item. When I removed item it little bit slow. I don't understand what is the problem in my code. I am adding basic sample what I did try on my code.
RemoveItem
@Composable
fun RemoveItem(viewModel: RemovedItemViewModel) {
var newList = viewModel.itemList
LaunchedEffect(key1 = viewModel.itemList) {
newList = viewModel.itemList
}
LazyColumn {
items(newList) {
Text(text = "$it")
}
}
}
RemovedItemViewModel
class RemovedItemViewModel : BaseViewModel() {
val itemList = mutableStateListOf<MovieItem>()
init {
repeat(10) {
itemList.add(MovieItem("$it cast", "Movie $it"))
}
}
fun removeItem() {
val random = (0..10).random()
itemList.removeAt(random)
}
}
MovieItem
data class MovieItem(val number: String, val name: String)
Is there any better way to remove item?
答案1
得分: 1
以下是翻译好的内容：
你可能会出现性能问题，有几个原因造成这种情况。
第一个原因是你在使用项目时没有提供唯一的键。为了使列表项目操作更加优化，你需要使用唯一的键。如果不唯一，你将会遇到运行时异常，所以请小心。
第二个问题是不必要的LaunchedEffect，正如评论中已经指出的那样。
另外，为了确定你是否真的存在性能问题，我建议你首先在你的 build.gradle 文件中将 isDebuggable = false，然后使用启用了 R8 的发布版本进行检查。在使用Compose时，调试模式和发布模式之间存在很大差异，可以在这里了解更多信息。
如果尽管我上面列出的一切你仍然遇到性能问题，那么我建议你安装最新的 Android Studio Hedgehog 预览版本。在其中，你可以通过调试组合状态来查找为什么会发生不必要的重组。
英文:
You can have performance problems for several reasons.
The first reason is that you are using items without a key. In order for list item operations to be more optimized you need to use a unique key. If it is not unique, you will get a runtime exception, so be careful.
The second issue is the unnecessary LaunchedEffect as already noticed on the comments
Also, in order to determine if you really have problems with performance, I would recommend that you first to check your app with isDebuggable = false in your build.gradle file as well as the using release build with enabled R8. Here is a very big difference between debug and release modes when we're using compose, read more here.
If despite everything that I have listed above you still encounter performance problems, then I would recommend that you install a latest preview version of Android Studio Hedgehog. In it you can check why unnecessary recompositions happen by debugging the composition state
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