SwiftUI onDelete cannot detect tap when onTapGesture is added - ios

I am developing an iOS app with list by SwiftUI. I am implementing .onDelete to enable user to delete the rows. However, I have found that when I add a .onTapGesture to the VStack View containing the List, the onDelete function is not called when the user tapped the "Delete" button after slide the row left. However, it stills works when the user slide the row to the left side to delete this. It seems that the .onTapGesture blocks .onDelete to receive user input. How to solve this?
NavigationView {
VStack(alignment: .leading) {
List {
ForEach(things) { thing in
Text(thing)
}
.onDelete(perform: { indexSet in
things.remove(atOffsets: indexSet)
})
}
.listStyle(SidebarListStyle())
}
.onTapGesture {
}
}
Here is some code that can show my problem.

This is probably useless and very hacky but... If you must have an area that is tappable, you could place everything in a ZStack and put a random view over the List and make that tappable. Then you could set a good amount of padding to free the area where the delete button would be tapped, like this:
NavigationView {
ZStack {
List {
ForEach(things, id: \.self) { thing in
Text(thing)
}
.onDelete(perform: { indexSet in
things.remove(atOffsets: indexSet)
})
}
.zIndex(2)
.listStyle(SidebarListStyle())
Rectangle()
.zIndex(3)
.fill(Color.red)
.padding(.trailing, 80)
.allowsHitTesting(true)
.onTapGesture {
print("Blocking you")
}
}
}
I put the color in so you can see exactly where you are working, the code above would give you a look like this:
Tappable Rectangle on List
When you're happy with the area that the rectangle covers, you can just set the Opacity to a very small amount, just by replacing the color with
.opacity(0.000001)
or something. Unfortunately taps don't work with Color.clear or hidden() modifiers.

Related

TextField(_:text:axis:) breaks keyboard avoidance inside ScrollView in iOS 16

Automatic keyboard avoidance seems to work fine if it's a regular TextField (i.e. one that doesn't expand on an axis), whether or not it is contained in a ScrollView
Keyboard avoidance also seems to work with the new TextField(_:text:axis) introduced in iOS 16 if it's simply placed in a VStack without being wrapped in a ScrollView. It will even continue to avoid the keyboard correctly as the height expands with more text.
But I can't seem to get keyboard avoidance to work with TextField(_:text:axis) if it is placed inside a ScrollView
I can employ the hacky method of using a ScrollViewReader combined with DispatchQueue.main.asyncAfter(deadline: .now() + .milliseconds(400)) to wrap the proxy.scrollTo() when the TextField is focused. This sort of works when you first focus the field, but I can't seem to get the ScrollView to continue to adjust its position as the TextField expands.
Here is an example:
struct KeyboardAvoidingView: View {
#State var text = ""
var body: some View {
ScrollViewReader { proxy in
ScrollView {
VStack {
Color.red
.frame(height: 400)
Color.blue
.frame(height: 400)
TextField("Name", text: $text, axis: .vertical)
.padding(.vertical)
.onTapGesture {
DispatchQueue.main.asyncAfter(deadline: .now() + .milliseconds(400)) {
withAnimation(.default) {
proxy.scrollTo(0)
}
}
}
.onChange(of: text) { newValue in
proxy.scrollTo(0) // This doesn't seem to do anything
}
Spacer()
.frame(height: 0)
.id(0)
}
}
}
}
}
I guess I'm wondering whether this is expected behavior, or a bug. And regardless if it's one or the other, I'm wondering if I can have an auto-expanding text field inside a scroll view that I can make avoid the keyboard even as the height of the field expands?
UPDATE: It turns out, the issue was with placing the TextField inside a VStack instead of a LazyVStack. I assume ScrollView doesn't know what to do with just a regular VStack in certain situations. If I replace the VStack with a LazyVStack in my example, everything works as expected!
I answered the question with the update posted above. The issue was with using VStack instead of LazyVStack
This is a long time known bug in the TextField component, but you may achieve the desired behavior by using an anchor: .bottom in the proxy.scrollTo call of your onChange.
it'll look like this:
// ...
TextField("Name", text: $text, axis: .vertical)
.padding(.vertical)
.onTapGesture {
DispatchQueue.main.asyncAfter(deadline: .now() + .milliseconds(400)) {
withAnimation(.default) {
proxy.scrollTo(0)
}
}
}
.onChange(of: text) { newValue in
// This will always scroll to the bottom of the text editor,
// just make sure to pass the right value in the first parameter
// that will identify your TextEditor
proxy.scrollTo(MyTextEditorId, anchor: .bottom)
}
// ...
You may need some additional work to handle the editing of upper parts of the text editor when it's taller than your screen

ScrollView touch works despite all other touch is disabled

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))

How to align and anchor SwiftUI horizontal list at right edge of view?

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)
}
}
}
}

How to have 1 column in a multiple column list be of the same width w/out using a frame modifier of width so to retain flexibility

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. they’re 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 don’t believe the solution is optimised to consider the user’s 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("12°")
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("13°")
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, I’m 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: "12°", percent: "25%")
CustomRow(timeText: "10am", systemIcon: nil, centerText: nil, temperature: "13°", percent: "25%")
}
VStack {
CustomRow(timeText: "9am", systemIcon: "cloud.drizzle", centerText: "Summary", temperature: "12°", percent: "25%")
CustomRow(timeText: "10am", systemIcon: nil, centerText: nil, temperature: "13°", 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 each’s 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. We’ll get back to that clear background part in a moment, but first: there are several ways to set preferences, here, we’re using anchorPreference. Why?
Well, anchorPreference has “No Overview Available” so I don’t 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 doesn’t give you the value directly, you have to cash it in with a GeometryProxy to get the actual value, so, that’s what we did — 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). It’s 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 that’s 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) – 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 I’m 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.
It’s 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 that’s 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)
}
}
}

What is the correct way to pass touches through a view to those below it?

I have a SwiftUI view that is displayed over other views, and have found that using Color.clear like this below seems to allow touch interactions to pass through to anything under it:
var body: some View {
VStack {
Spacer()
HStack {
Spacer()
SomeCustomContent()
Spacer()
}
.overlay(GeometryReader { proxy in
Color.clear.preference(key: MyCustomHeightPreferenceKey.self, value: proxy.size.height)
})
}
}
Is this the correct way to make touches pass through to the views below, or it this just a coincidental quirk/bug in SwiftUI behaviour that Apple might fix/change as swiftui matures?
If not, what is the correct way to pass the touches through?
You can pass through touch events without use a clear color like this:
var body: some View {
Rectangle()
.overlay(
Circle()
.fill(.blue)
.allowsHitTesting(false) // <--- Passes through gestures
)
}
Asperi mentioned this solution in a comment above, and you can also find a good blog about this topic here: https://www.hackingwithswift.com/books/ios-swiftui/disabling-user-interactivity-with-allowshittesting

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