Especially if the list scrolls slow and sometimes even without scrolling. But in your example and in your issue, we want SwiftUI renders only the changed View, for this goal the down code works well without issue, but as you can see I used VStack, if we change VStack to LazyVStack, SwiftUI would renders some extra view due its undercover codes, and if you scroll to down and then to up, it would forget all rendered. Hello guys I started this channel talking about stacks in SwiftUI, today we will talk about another stack: LazyVStack. ContentView.swift // LazyVStackIssue // Created by Vishwanath. In VStack, all views are rendered and loaded in memory as soon as view is initialized and appears on screen. When you have a VStack with a View and a LazyVStack and scroll though the list, sometimes the buttons will trigger even through the top view above the LazyVStack.Įxample Code -> Scroll the List and click e.g. LazyVStack not refreshing content size correctly for child list container view in SwiftUI. ‘Lazy’ keyword distinguishes LazyVStack from VStack. When you have a LazyVStack with buttons and scroll through it, you can sometimes click the button even it's behind a pinned view. I like to work with List in my apps as it provides some more functionality than just a ScrollView with a stack of content inside. It seems like in a LazyStack, every child needs to be some sort of fixed size or a purely SwiftUI view to work.I found an unexpected behavior with the pinnedViews (header, footer) in LazyVStack. LazyStacks In SwiftUI (SwiftUI LazyHStack, SwiftUI LazyVStack, LazyStacks For Beginners)In this video, we're going to look at lazystacks in SwiftUI. There is LazyVStack to work with a large amount of content inside a ScrollView and ensure good scrolling performance. As soon as I add a UIViewRepresentable of variable height, it starts to stutter again. If I add fixedSize(horizontal: false, vertical: true) to the Text element it seems to stop stuttering. I ripped everything out in my view and built it back up one by one - the LazyVStack begins to stutter as soon as I put a VStack/HStack/ZStack around a simple Text element. In the video below, notice the behavior of the scrollbar and the stuttering when we get to the bottom: This is still happening in iOS 15, Version 13.0 beta (13A5155e). A VStack is a free-form StackView that contains arbitrary combinations of other views and manages their layout and organization. Note: Stutter only happens at the top of the scroll view It does lazy loading of cells but brings with it a lot of baggage and limitations that stem from the TableView need for delegates, and from the underlying cell-based table view structure. With iOS 14, Apple gives you the ability to use lazy stacks. I'm wondering if anyone else has encountered this? Is this a bug in SwiftUI? I've reliably reproduced this for months across different projects and end up resorting to not using Lazy stacks which I wish I could. Get better scroll performance by using LazyHStack and LazyVStack instead of HStack and VStack. My theory is that due to using a Lazy stack, when a view goes off the screen it gets removed from the view hierarchy, creating a stutter. Because all views are built lazily, there are no other views above that one and therefore, there's nothing to focus and I cannot scroll up and I'm stuck. the functionality when using an Array versus when using CoreData. However, from time to time the LazyVStack scrolls its content in such a way that the panel containing the call to action button is at the top edge of the screen. Observed behavior: It stops and jitters when it reaches the edge, but doesn't bounce List with ScrollView and ForEach (4:09) LazyVStack (4:50) Lesson 9: SwiftUI Picker. Scenario 2 - Scroll fast to the edge so that it has to bounce Scenario 1 - Pull the scrollview beyond the bounds (as if you were pulling to refresh)Įxpected behavior: It behaves as expected where the scrollview stays under your finger
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