The Problem
In our brand new SwiftUI project (Multiplatform app for iPhone, iPad and Mac) we are using a ScrollView with both .horizontal and .vertical axes enabled. In the end it all looks like a spreadsheet.
Inside of ScrollView we are using LazyVStack with pinnedViews: [.sectionHeaders, .sectionFooters]. All Footer, Header and the content cells are wrapped into a LazyHStack each. The lazy stacks are needed due to performance reasones when rows and columns are growing.
And this exactly seems to be the problem. ScrollView produces a real layout mess when scrolling in both axes at the same time.
Tested Remedies
I tried several workarounds with no success.
We built our own lazy loading horizontal stack view which shows only the cells whose indexes are in the visible frame of the scrollview, and which sets dynamic calculated leading and trailing padding.
I tried the Introspect for SwiftUI packacke to set usesPredominantAxisScrolling for macOS and isDirectionalLockEnabled for iOS. None of this works as expected.
I also tried a workaround to manually lock one axis when the other one is scrolling. This works fine on iOS but it doesn't on macOS due to extreme poor performance (I think it's caused by the missing NSScrollViewDelegate and scroll events are being propagated via NotificationCenter).
How does it look?
To give you a better idea of what I mean, I have screenshots for both iOS and macOS.
Here you can watch short screen recording for both iOS and macOS.
Example Code
And this is the sample code used for the screenshots. So you can just create a new Multiplatform project and paste the code below in the ContentView.swift file. That's all.
import SwiftUI
let numberOfColums: Int = 150
let numberOfRows: Int = 350
struct ContentView: View {
var items: [[Item]] = {
var items: [[Item]] = [[]]
for rowIndex in 0..<numberOfRows {
var row: [Item] = []
for columnIndex in 0..<numberOfColums {
row.append(Item(column: columnIndex, row: rowIndex))
}
items.append(row)
}
return items
}()
var body: some View {
Group {
ScrollView([.horizontal, .vertical]) {
LazyVStack(alignment: .leading, spacing: 1, pinnedViews: [.sectionHeaders, .sectionFooters]) {
Section(header: Header()) {
ForEach(0..<items.count, id: \.self) { rowIndex in
let row = items[rowIndex]
LazyHStack(spacing: 1) {
ForEach(0..<row.count, id: \.self) { columnIndex in
Text("\(columnIndex):\(rowIndex)")
.frame(width: 100)
.padding()
.background(Color.gray.opacity(0.2))
}
}
}
}
}
}
.edgesIgnoringSafeArea([.top])
}
.padding(.top, 1)
}
}
struct Header: View {
var body: some View {
LazyHStack(spacing: 1) {
ForEach(0..<numberOfColums, id: \.self) { idx in
Text("Col \(idx)")
.frame(width: 100)
.padding()
.background(Color.gray)
}
Spacer()
}
}
}
struct Item: Hashable {
let id: String = UUID().uuidString
var column: Int
var row: Int
}
Can You Help?
Okay, long story short...
Does anybody know a real working solution for this issue?
Is it a known SwiftUI ScrollView bug?
If there were a way to lock one scrolling direction while the other one is being scrolled, then I could deal with that. But at the moment, unfortunately, it is not usable for us.
So any solution is highly appreciated! š
Is there any reason you don't want to use a Grid for this layout?
Here is the article I would suggest you read to solve this problem:
https://swiftui-lab.com/impossible-grids/
So my goal is to disable touch events for everything on screen and I don't want to use .disable on every view or to use Color.black.opacity(0.00001) because of the code smell. I want it to be a block that isn't visible for the user like if I would overlay Color.clear over the whole view. And I want it to behave like if I were to use Color.black.opacity(0.1) with it disabling touch events on every view underneath.
If I for example use a ZStack with:
Color.black.opacity(0.2) every view underneath will no longer register touch events. (I want this, but it should be transparent)
Color.black.opacity(0) every view underneath will register touch events.
Color.black.opacity(0).contentShape(Rectangle()), some events will register, some won't, for example buttons won't work though scrolling in a ScrollView, or using a toggle will still work.
Here is some example code
struct ContentView: View {
#State var numberOfRows: Int = 10
var body: some View {
ZStack {
Color.white
ScrollView {
VStack {
ForEach(0..<numberOfRows, id: \.self) { (call: Int) in
Text(String(call))
.frame(maxWidth: .infinity)
}
}
}
Button(action: {
numberOfRows += 1
}) {
Color.blue
.frame(width: 300, height: 300)
}
Color.black.opacity(0) // <- change this to 0.x to disable all touch
.contentShape(Rectangle()) // <- Remove this line to make blue button work (opacity needs to be 0)
}
}
}
Why is scrollview still receiving touch events and why is buttons not?
Is there a way to make my touch events for every view underneath, disabled?
Use instead (tested with Xcode 13.4 / iOS 15.5)
Color.clear
// .ignoresSafeArea(.all) // << if need all screen space
.contentShape(Rectangle())
.highPriorityGesture(DragGesture(minimumDistance: 0))
I am looking for how to align items in a list horizontally, where the items start at the last item, or on the right edge, and go left from there.
For example, with a list of 1-20, I'd be looking to show items 1-5 off the left edge of the screen, with item 20 being the right-most item, right on the edge of the screen. An image of this can be shown below (it is not the solution running, but rather a contrived image to show the desired effect).
How can I do this in SwiftUI?
An HStack will simply center itself horizontally. HStack doesn't seem to have a horizontal alignment that I can control.
An HStack in a scrollview allows me to reach the right-most item, but still starts at the first item, or the left-most edge of the list.
import SwiftUI
struct ContentView: View {
var body: some View {
VStack {
Divider()
// the HStack just tries to fit everything within the width of the view,
// without anything going "offscreen"
HStack(spacing: 10) {
ForEach(1..<21) { index in
Text("\(index)")
}
Spacer()
}
Divider()
// placing the HStack within a ScrollView does allow elements to go offscreen,
// but the list starts at 1 and goes offscreen at 16 on the right
// I am looking for how to "anchor" the list on the right edge instead,
// with elements 1 through 5 being displayed off the left edge of the screen,
// and the right-most element being 20, directly on the right edge of the screen
ScrollView(.horizontal) {
HStack(spacing: 10) {
ForEach(1..<21) { index in
Text("\(index)")
}
}
}
.frame(height: 100)
Divider()
// are there any other ways to achieve my desired effect?
}
}
}
If I properly understand question looks like you need ScrollViewReader:
// Define array for your label
var entries = Array(0...20)
ScrollView(.horizontal) {
ScrollViewReader { reader in
HStack(spacing: 10) {
ForEach(entries, id: \.self) { index in
Text("\(index)")
}.onAppear {
// Here on appear scroll go to last element
reader.scrollTo(entries.count - 1)
}
}
}
}
I have a list of entries that consist of multiple columns of UI with all except the first free to be uniquely sized horizontally (i.e. theyāre as short/long as their content demands). I know with the first consistently sized column I can set a frame modifier width to achieve this, but I was hoping there is a better and more flexible way to get the desired behaviour. The reason being I donāt believe the solution is optimised to consider the userās display size nor the actual max content width of the columns. That is, the width set will either not be wide enough when the display size is set to the largest, or, if it is, then it will be unnecessarily wide on a smaller/regular display size.
This is my current best attempt:
GeometryReader { geometry in
VStack {
HStack {
HStack {
Text("9am")
Image(systemName: "cloud.drizzle").font(Font.title2)
.offset(y: 4)
}.padding(.all)
.background(Color.blue.opacity(0.2))
.cornerRadius(16)
VStack {
HStack {
Text("Summary")
.padding(.trailing, 4)
.background(Color.white)
.layoutPriority(1)
VStack {
Spacer()
Divider()
Spacer()
}
VStack {
Text("12Ā°")
Text("25%")
.foregroundColor(Color.black)
.background(Color.white)
}.offset(y: -6)
Spacer()
}.frame(width: geometry.size.width/1.5)
}
Spacer()
}
HStack {
HStack {
Text("10am")
.customFont(.subheadline)
Image(systemName: "cloud.drizzle").font(Font.title2)
.offset(y: 4)
.opacity(0)
}
.padding(.horizontal)
.padding(.vertical,4)
.background(Color.blue.opacity(0.2))
.cornerRadius(16)
VStack {
HStack {
ZStack {
Text("Mostly cloudy")
.customFont(.body)
.padding(.trailing, 4)
.background(Color.white)
.opacity(0)
VStack {
Spacer()
Divider()
Spacer()
}
}
VStack {
Text("13Ā°")
Text("25%")
.foregroundColor(Color.black)
.background(Color.white)
}.offset(y: -6)
Spacer()
}.frame(width: geometry.size.width/1.75)
}
Spacer()
}
}
}
For me, this looks like:
As you can tell, 10 am is slightly wider than 9 am. To keep them as closely sized as possible, Iām including a cloud icon in it too, albeit with zero opacity. Ideally, 10 am would be sized the same as 9 am without needing a transparent cloud icon. More generally speaking, what would make sense is the widest HStack in this column is identified and then whatever its width is will be applied to all other columns. Keep in mind, my code above is static for demo purposes. It will be a view that is rendered iterating through a collection of rows.
You can use dynamic frame modifiers, such as frame(.maxWidth: .infinity) modifier to extend views so that they fill up the entire frame, even if the frame is dynamic. Here is an example that should help you get going:
struct CustomContent: View {
var body: some View {
VStack {
VStack {
CustomRow(timeText: "9am", systemIcon: "cloud.drizzle", centerText: "Summary", temperature: "12Ā°", percent: "25%")
CustomRow(timeText: "10am", systemIcon: nil, centerText: nil, temperature: "13Ā°", percent: "25%")
}
VStack {
CustomRow(timeText: "9am", systemIcon: "cloud.drizzle", centerText: "Summary", temperature: "12Ā°", percent: "25%")
CustomRow(timeText: "10am", systemIcon: nil, centerText: nil, temperature: "13Ā°", percent: "25%")
}
.frame(width: 300)
}
}
}
struct CustomContent_Previews: PreviewProvider {
static var previews: some View {
CustomContent()
}
}
struct CustomRow: View {
let timeText: String
let systemIcon: String?
let centerText: String?
let temperature: String
let percent: String
var body: some View {
HStack {
//Left column
HStack(alignment: .center) {
Text(timeText)
if let icon = systemIcon {
Image(systemName: icon)
.font(.title2)
}
}
.padding(.all)
.frame(width: 105, height: 60)
.background(Color.blue.opacity(0.2))
.cornerRadius(16)
// Center column
ZStack(alignment: .leading) {
Capsule()
.fill(Color.black.opacity(0.3))
.frame(height: 0.5)
if let text = centerText {
Text(text)
.lineLimit(1)
.background(Color.white)
}
}
// Right column
VStack {
Text(temperature)
Text(percent)
.foregroundColor(Color.black)
}
}
}
}
Guided by https://www.wooji-juice.com/blog/stupid-swiftui-tricks-equal-sizes.html, I accomplished this.
This is the piece of UI I want to make sure is horizontally sized equally across all rows with the width set to whatever is the highest:
HStack {
VStack {
Spacer()
Text("9am")
Spacer()
}
}.frame(minWidth: self.maximumSubViewWidth)
.overlay(DetermineWidth())
The stack the above is contained in has an OnPreferenceChange modifier:
.onPreferenceChange(DetermineWidth.Key.self) {
if $0 > maximumSubViewWidth {
maximumSubViewWidth = $0
}
}
The magic happens here:
struct MaximumWidthPreferenceKey: PreferenceKey
{
static var defaultValue: CGFloat = 0
static func reduce(value: inout CGFloat, nextValue: () -> CGFloat)
{
value = max(value, nextValue())
}
}
struct DetermineWidth: View
{
typealias Key = MaximumWidthPreferenceKey
var body: some View
{
GeometryReader
{
proxy in
Color.clear
.anchorPreference(key: Key.self, value: .bounds)
{
anchor in proxy[anchor].size.width
}
}
}
}
The link at the top best describes eachās purpose.
MaximumWidthPreferenceKey
This defines a new key, sets the default to zero, and as new values get added, takes the widest
DetermineWidth
This view is just an empty (Color.clear) background, but with our new preference set to its width. Weāll get back to that clear background part in a moment, but first: there are several ways to set preferences, here, weāre using anchorPreference. Why?
Well, anchorPreference has āNo Overview Availableā so I donāt actually have a good answer for that, other than it seems to be more reliable in practice. Yeah, cargo-cult code. Whee! I have a hunch that, what with it taking a block and all, SwiftUI can re-run that block to get an updated value when there are changes that affect layout.
Another hope I have is that this stuff will get better documented, so that we can better understand how these different types are intended to be used and new SwiftUI developers can get on board without spending all their time on Stack Overflow or reading blog posts like this one.
Anyway, an anchor is a token that represents a dimension or location in a view, but it doesnāt give you the value directly, you have to cash it in with a GeometryProxy to get the actual value, so, thatās what we did ā to get the value, you subscript a proxy with it, so proxy[anchor].size.width gets us what we want, when anchor is .bounds (which is the value we passed in to the anchorPreference call). Itās kind of twisted, but it gets the job done.
maximumSubViewWidth is a binding variable passed in from the parent view to ensure the maximumSubViewWidth each subview refers to is always the the up-to-date maximum.
ForEach(self.items) { item, in
ItemSubview(maximumSubViewWidth: $maximumSubViewWidth, item: item)
}
The one issue with this was there was an undesired subtle but still noticeable animation on the entire row with any UI that gets resized to the max width. What I did to work around this is add an animation modifier to the parent container thatās nil to start with that switches back to .default after an explicit trigger.
.animation(self.initialised ? .default : nil)
I set self.initialised to be true after the user explicitly interacts with the row (In my case, they tap on a row to expand to show additional info) ā this ensured the initial animation doesn't incorrectly happen but animations go back to normal after that. My original attempt toggled initialised's state in the .onAppear modifier so that the change is automatic but that didn't work because Iām assuming resizing can occur after the initial appearance.
The other thing to note (which possibly suggests although this solution works that it isn't the best method) is I'm seeing this message in the console repeated for either every item, or just the ones that needed to be resized (unclear but the total number of warnings = number of items):
Bound preference MaximumWidthPreferenceKey tried to update multiple
times per frame.
If anyone can think of a way to achieve the above whilst avoiding this warning then great!
UPDATE: I figured the above out.
Itās actually an important change because without addressing this I was seeing the column keep getting wider on subsequent visits to the screen.
The view has a new widthDetermined #State variable thatās set to false, and becomes true inside .onAppeared.
I then only determine the width for the view IF widthDetermined is false i.e. not set. I do this by using the conditional modifier proposed at https://fivestars.blog/swiftui/conditional-modifiers.html:
func `if`<Content: View>(_ conditional: Bool, content: (Self) -> Content) -> TupleView<(Self?, Content?)> {
if conditional { return TupleView((nil, content(self))) }
else { return TupleView((self, nil)) }
}
and in the view:
.if(!self.widthDetermined) {
$0.overlay(DetermineWidth())
}
I had similar issue. My text in one of the label in a row was varying from 2 characters to 20 characters. It messes up the horizontal alignment as you have seen. I was looking to make this column in row as fixed width. I came up with something very simple. And it worked for me.
var body: some View { // view for each row in list
VStack(){
HStack {
Text(wire.labelValueDate)
.
.
.foregroundColor(wire.labelColor)
.fixedSize(horizontal: true, vertical: false)
.frame(width: 110.0, alignment: .trailing)
}
}
}
I am developing an app based on a Tabview with three TabItems. Each TabItem is a List and I would be able to show a kind of modal view over those Lists. The problem becomes when I can not call a Sheet as modal view because Sheets are almost full windowed. I need some kind of bottom modal view, so I create a View that I present over a List with higher ZIndex. It seems to work until you click in the tabbar and select another TabItem having deployed the "modal" view. The error is:
[TableView] Warning once only: UITableView was told to layout its
visible cells and other contents without being in the view hierarchy
(the table view or one of its superviews has not been added to a
window). This may cause bugs by forcing views inside the table view to
load and perform layout without accurate information (e.g. table view
bounds, trait collection, layout margins, safe area insets, etc), and
will also cause unnecessary performance overhead due to extra layout
passes.
So, I would like as solution to restrict the tappable area to the "modal" view area. ĀæIs there a way to achieve this?
Probably you have some condition state depending on which you present your "modal-like" view, so depending on the same condition you can disable below TabView, like below
TabView {
// ... tabs content here
}.disabled(showingModal)
Update: Here is a demo of approach that I meant (tested with Xcode 11.3+)
struct TestTabViewModal: View {
#State private var selectedTab = 0
#State private var modalShown = false
var body: some View {
ZStack {
TabView(selection: $selectedTab) {
VStack {
Button("Show Modal") { self.modalShown = true }
.padding(.top, 40)
Spacer()
}
.tabItem {
Image(systemName: "1.circle")
}.tag(0)
Text("2").tabItem {
Image(systemName: "1.circle")
}.tag(1)
}.disabled(modalShown)
if modalShown {
RoundedRectangle(cornerRadius: 10)
.fill(Color.yellow)
.frame(width: 320, height: 240)
.overlay(Button("CloseMe") { self.modalShown = false })
}
}
}
}