I want to get the selected item from a Picker to update some data on the Firebase Database, but when i use the onTapGesture is not working
Note: The items inside the picker are Strings
My Code:
Picker(selection: $numUnitIndex, label: Text("Numerical Unit: \(numUnit)")) {
ForEach(0 ..< units.count) {
Text(self.units[$0]).tag($0).foregroundColor(.blue)
.onTapGesture {
//updateUnit(newUnit: self.units[numUnitIndex])
print("selected \(numUnitIndex)")
}
}
}.pickerStyle(MenuPickerStyle())
Here is a simple example of right way of doing this, no need onTapGesture here:
struct ContentView: View {
let units: [String] = ["😀", "😎", "🥶", "😡", "😍"]
#State private var selectedUnit: Int = 0
var body: some View {
Picker(selection: $selectedUnit, label: Text("You selected: \(units[selectedUnit])")) {
ForEach(units.indices, id: \.self) { unitIndex in Text(units[unitIndex]) }
}
.pickerStyle(MenuPickerStyle())
.onChange(of: selectedUnit, perform: { newValue in print("Selected Unit: \(units[newValue])", "Selected Index: \(newValue)")})
}
}
You shouldn't use indices but the objects in the array in your ForEach and there is no need for onTapGesture, the variable passed to selection will hold the selected value.
Something like this
let units: [String] = ["a", "b", "c"]
#State private var selectedUnit: String
init() {
selectedUnit = units.first ?? ""
}
var body: some View {
VStack {
Picker("Units", selection: $selectedUnit) {
ForEach(units, id: \.self) { unit in
Text(unit)
.foregroundColor(.blue)
.font(.largeTitle)
}
}.pickerStyle(MenuPickerStyle())
Text("Selected unit is \(selectedUnit)")
}
}
Related
I just want to simply navigate to a detail page from a List if press any cell. I have a list like this:
When I click cell c it gets d or others. Rather than this page.
Here is my code:
struct ContentView: View {
var items = ["a", "b", "c", "d"]
#State var isCellSelected = false
var body: some View {
NavigationView {
List {
ForEach(items.indices, id: \.self) { index in
NavigationLink(
destination: Text("\(items[index])"),
isActive: $isCellSelected,
label: {
RowView(text: items[index])
})
}
}
}
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
struct RowView: View {
var text: String
var body: some View {
VStack {
Text(text)
}
}
}
If I remove isActive: $isCellSelected then it works as expected. I need to use isCellSelected to pop back to root view. Not sure how to fix this issue.
Any help? thanks!
EDIT
Update removed isActive and try set selection = nil
truct DetailView: View {
var text: String
#Binding var isCellSelected: Int?
var body: some View {
VStack {
Text(text)
Button("Back") {
isCellSelected = nil
}
}
}
}
struct ContentView: View {
var items = ["a", "b", "c", "d"]
#State var selectedTag: Int? = nil
var body: some View {
NavigationView {
List {
ForEach(items.indices, id: \.self) { index in
NavigationLink(
destination: DetailView(text: "\(items[index])", isCellSelected: $selectedTag),
tag: index,
selection: $selectedTag,
label: {
RowView(text: items[index])
})
}
}
}
}
}
When press Back button, doesn't go back.
It is not recommended to share a single isActive state among multiple NavigationLinks.
Why don't you use selection instead of isActive?
struct ContentView: View {
var items = ["a", "b", "c", "d"]
#State var selectedTag: Int? = nil //<-
var body: some View {
NavigationView {
List {
ForEach(items.indices, id: \.self) { index in
NavigationLink(
destination: Text("\(items[index])"),
tag: index, //<-
selection: $selectedTag, //<-
label: {
RowView(text: items[index])
})
}
}
}
}
}
You can set nil to selectedTag to pop back. Seems NavigationLink in List does not work as I expect. Searching for workarounds and update if found.
A dirty workaround:
(Tested with Xcode 12.3/iPhone simulator 14.3. Please do not expect this to work on other versions of iOS including future versions.)
struct DetailView: View {
var text: String
#Binding var isCellSelected: Bool
var body: some View {
VStack {
Text(text)
Button("Back") {
isCellSelected = false
}
}
}
}
struct Item {
var text: String
var isActive: Bool = false
}
struct ContentView: View {
#State var items = ["a", "b", "c", "d"].map {Item(text: $0)}
#State var listId: Bool = false //<-
var body: some View {
// Text(items.description) // for debugging
NavigationView {
List {
ForEach(items.indices) { index in
NavigationLink(
destination:
DetailView(text: "\(items[index].text)",
isCellSelected: $items[index].isActive)
.onAppear{ listId.toggle() } //<-
,
isActive: $items[index].isActive,
label: {
RowView(text: items[index].text)
})
}
}
.id(listId) //<-
}
}
}
Another workaround:
struct DetailView: View {
var text: String
#Binding var isCellSelected: Int?
var body: some View {
VStack {
Text(text)
Button("Back") {
isCellSelected = nil
}
}
}
}
struct ContentView: View {
var items = ["a", "b", "c", "d"]
#State var selectedTag: Int? = nil
var body: some View {
NavigationView {
ZStack {
ForEach(items.indices) { index in
NavigationLink(
destination:
DetailView(text: "\(items[index])",
isCellSelected: $selectedTag),
tag: index,
selection: $selectedTag,
label: {
EmptyView()
})
}
List {
ForEach(items.indices) { index in
Button(action: {
selectedTag = index
}) {
HStack {
RowView(text: items[index])
Spacer()
Image(systemName: "chevron.right")
.foregroundColor(Color.secondary)
}
}
}
}
}
}
}
}
I get this error every time I launch a secondary picker.
The first picker works okay.
However when I switch pickers & scroll, I get the following:
Here is my entire code (written as a test of this problem):
import SwiftUI
struct ContentView: View {
#State private var selectedItem = 0
#State private var isMainPickerHidden = false
#State private var isSecondaryPickerHidden = true
var colors = ["Red", "Green", "Blue", "Tartan"]
var sizes = ["Tiny", "Small", "Medium", "Large", "Super Size"]
var body: some View {
ZStack {
Color.yellow.edgesIgnoringSafeArea(.all)
ZStack {
VStack {
Picker(selection: $selectedItem, label: Text("Please choose a color")) {
ForEach(colors.indices, id: \.self) {
Text(self.colors[$0])
}
}.hiddenConditionally(isHidden: isMainPickerHidden)
Text("You selected: \(colors[selectedItem])")
.hiddenConditionally(isHidden: isMainPickerHidden)
}
VStack {
Picker(selection: $selectedItem, label: Text("Please choose a size")) {
ForEach(sizes.indices, id: \.self) {
Text(self.sizes[$0])
}
}.hiddenConditionally(isHidden: isSecondaryPickerHidden)
Text("You selected: \(sizes[selectedItem])")
.hiddenConditionally(isHidden: isSecondaryPickerHidden)
Spacer()
Button(action: {
isSecondaryPickerHidden = !isSecondaryPickerHidden
isMainPickerHidden = !isMainPickerHidden
}) {
Text("Switch Pickers")
}.padding()
}
}
}
}
}
// =========================================================================================================
extension View {
func hiddenConditionally(isHidden: Bool) -> some View {
isHidden ? AnyView(hidden()) : AnyView(self)
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
What is the correct syntax for the ForEach{} to avoid this problem?
This is because you use the same selectedItem for both pickers.
If in the second picker you select the last item (index 4) and then you switch to the first picker (max index = 3), then in this line:
Text("You selected: \(colors[selectedItem])")
you'll try accessing the index which is out of range.
To fix this you can use a separate #State variable for each picker:
struct ContentView: View {
#State private var selectedColorIndex = 0
#State private var selectedSizeIndex = 0
Picker(selection: $selectedColorIndex, label: Text("Please choose a color")) {
Picker(selection: $selectedSizeIndex, label: Text("Please choose a size")) {
The following code creates new controls every time a button is pressed at runtime, the problem is that the picker selection is set to the same state.
How can I create new controls with different state variables so they can operate separately ?
struct ContentView: View {
#State private var numberOfControlls = 0
#State var selection: String="1"
var body: some View {
VStack {
Button(action: {
self.numberOfControlls += 1
}) {
Text("Tap to add")
}
ForEach(0 ..< numberOfControlls, id: \.self) { _ in
Picker(selection: self.$selection, label:
Text("Picker") {
Text("1").tag(1)
Text("2").tag(2)
}
}
}
}
}
How can I create new controls with different state variables so they can operate separately ?
Separate control into standalone view with own state (or view model if/when needed).
Here is a demo:
struct ContentView: View {
#State private var numberOfControlls = 0
var body: some View {
VStack {
Button(action: {
self.numberOfControlls += 1
}) {
Text("Tap to add")
}
ForEach(0 ..< numberOfControlls, id: \.self) { _ in
ControlView()
}
}
}
}
struct ControlView: View {
#State var selection: String="1"
var body: some View {
Picker(selection: self.$selection, label:
Text("Picker")) {
Text("1").tag(1)
Text("2").tag(2)
}
}
}
I want a list with rows, with each row having 2 Textfields inside of it. Those rows should be saved in an array, so that I can use the data in an other view for further functions. If the text in the Textfield is changed, the text should be saved inside the right entry in the array.
You also can add new rows to the list via a button, which should also change the array for the rows.
The goal is to have a list of key value pairs, each one editable and those entries getting saved with the current text.
Could someone help me and/or give me hint for fixing this problem?
So far I have tried something like this:
// the array of list entries
#State var list: [KeyValue] = [KeyValue()]
// the List inside of a VStack
List(list) { entry in
KeyValueRow(list.$key, list.$value)
}
// the single item
struct KeyValue: Identifiable {
var id = UUID()
#State var key = ""
#State var value = ""
}
// one row in the list with view elements
struct KeyValueRow: View {
var keyBinding: Binding<String>
var valueBinding: Binding<String>
init(_ keyBinding: Binding<String>, _ valueBinding: Binding<String>){
self.keyBinding = keyBinding
self.valueBinding = valueBinding
}
var body: some View {
HStack() {
TextField("key", text: keyBinding)
Spacer()
TextField("value", text: valueBinding)
Spacer()
}
}
}
Also, about the button for adding new entries.
Problem is that if I do the following, my list in the view goes blank and everything is empty again
(maybe related: SwiftUI TextField inside ListView goes blank after filtering list items ?)
Button("Add", action: {
self.list.append(KeyValue())
})
I am not sure what the best practice is keep a view up to date with state in an array like this, but here is one approach to make it work.
For the models, I added a list class that conforms to Observable object, and each KeyValue item alerts it on changes:
class KeyValueList: ObservableObject {
#Published var items = [KeyValue]()
func update() {
self.objectWillChange.send()
}
func addItem() {
self.items.append(KeyValue(parent: self))
}
}
class KeyValue: Identifiable {
init(parent: KeyValueList) {
self.parent = parent
}
let id = UUID()
private let parent: KeyValueList
var key = "" {
didSet { self.parent.update() }
}
var value = "" {
didSet { self.parent.update() }
}
}
Then I was able to simply the row view to just keep a single piece of state:
struct KeyValueRow: View {
#State var item: KeyValue
var body: some View {
HStack() {
TextField("key", text: $item.key)
Spacer()
TextField("value", text: $item.value)
Spacer()
}
}
}
And for the list view:
struct TextFieldList: View {
#ObservedObject var list = KeyValueList()
var body: some View {
VStack {
List(list.items) { item in
HStack {
KeyValueRow(item: item)
Text(item.key)
}
}
Button("Add", action: {
self.list.addItem()
})
}
}
}
I just threw an extra Text in there for testing to see it update live.
I did not run into the Add button blanking the view as you described. Does this solve that issue for you as well?
Working code example for iOS 15
In SwiftUI, Apple recommends passing the binding directly into the List constructor and using a #Binding in the ViewBuilder block to iterate through with each element.
Apple recommends this approach over using the Indices to iterate over the collection since this doesn't reload the whole list every time a TextField value changes (better efficiency).
The new syntax is also back-deployable to previous releases of SwiftUI apps.
struct ContentView: View {
#State var directions: [Direction] = [
Direction(symbol: "car", color: .mint, text: "Drive to SFO"),
Direction(symbol: "airplane", color: .blue, text: "Fly to SJC"),
Direction(symbol: "tram", color: .purple, text: "Ride to Cupertino"),
Direction(symbol: "bicycle", color: .orange, text: "Bike to Apple Park"),
Direction(symbol: "figure.walk", color: .green, text: "Walk to pond"),
Direction(symbol: "lifepreserver", color: .blue, text: "Swim to the center"),
Direction(symbol: "drop", color: .indigo, text: "Dive to secret airlock"),
Direction(symbol: "tram.tunnel.fill", color: .brown, text: "Ride through underground tunnels"),
Direction(symbol: "key", color: .red, text: "Enter door code:"),
]
var body: some View {
NavigationView {
List($directions) { $direction in
Label {
TextField("Instructions", text: $direction.text)
}
}
.listStyle(.sidebar)
.navigationTitle("Secret Hideout")
}
}
}
struct Direction: Identifiable {
var id = UUID()
var symbol: String
var color: Color
var text: String
}
No need to mess up with classes, Observable, Identifiable. You can do it all with structs.
Note, that version below will do fine for insertions, but fail if you try to delete array elements:
import SwiftUI
// the single item
struct KeyValue {
var key: String
var value: String
}
struct ContentView: View {
#State var boolArr: [KeyValue] = [KeyValue(key: "key1", value: "Value1"), KeyValue(key: "key2", value: "Value2"), KeyValue(key: "key3", value: "Value3"), KeyValue(key: "key4", value: "Value4")]
var body: some View {
NavigationView {
// id: \.self is obligatory if you need to insert
List(boolArr.indices, id: \.self) { idx in
HStack() {
TextField("key", text: self.$boolArr[idx].key)
Spacer()
TextField("value", text: self.$boolArr[idx].value)
Spacer()
}
}
.navigationBarItems(leading:
Button(action: {
self.boolArr.append(KeyValue(key: "key\(UInt.random(in: 0...100))", value: "value\(UInt.random(in: 0...100))"))
print(self.boolArr)
})
{ Text("Add") }
, trailing:
Button(action: {
self.boolArr.removeLast() // causes "Index out of range" error
print(self.boolArr)
})
{ Text("Remove") })
}
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
Update:
A little trick to make it work with deletions as well.
import SwiftUI
// the single item
struct KeyValue {
var key: String
var value: String
}
struct KeyValueView: View {
#Binding var model: KeyValue
var body: some View {
HStack() {
TextField("Key", text: $model.key)
Spacer()
TextField("Value", text: $model.value)
Spacer()
}
}
}
struct ContentView: View {
#State var kvArr: [KeyValue] = [KeyValue(key: "key1", value: "Value1"), KeyValue(key: "key2", value: "Value2"), KeyValue(key: "key3", value: "Value3"), KeyValue(key: "key4", value: "Value4")]
var body: some View {
NavigationView {
List(kvArr.indices, id: \.self) { i in
KeyValueView(model: Binding(
get: {
return self.kvArr[i]
},
set: { (newValue) in
self.kvArr[i] = newValue
}))
}
.navigationBarItems(leading:
Button(action: {
self.kvArr.append(KeyValue(key: "key\(UInt.random(in: 0...100))", value: "value\(UInt.random(in: 0...100))"))
print(self.kvArr)
})
{ Text("Add") }
, trailing:
Button(action: {
self.kvArr.removeLast() // Works like a charm
print(self.kvArr)
})
{ Text("Remove") })
}
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
Swift 5.5
This version of swift enables one line code for this by passing the bindable item directly from the array.
struct DirectionsList: View {
#Binding var directions: [Direction]
var body: some View {
List($directions) { $direction in
Label {
TextField("Instructions", text: $direction.text)
} icon: {
DirectionsIcon(direction)
}
}
}
}
I can't find how to add some element in a picker view in SwiftUI, in my sample, I want add "Z" value in picker when I click the button.
struct ContentView: View {
#State var values: [String] = ["A", "B", "C"]
#State private var selectedValue = 0
var body: some View {
NavigationView {
Form {
Section {
Picker(selection: $selectedValue, label: Text("Value")) {
ForEach(0 ..< values.count) {
Text(self.values[$0])
}
}
}
Button(action: {
self.values.append("Z")
}, label: {
Text("Add")
})
}.navigationBarTitle("Select a value")
}
}
When I click on the button, Z is added to "values" array but Picker is not refreshed.
Thank you :)
You must identify values by id for SwiftUI to make it's changes detectable:
ForEach(0 ..< self.values.count, id: \.self) {
Text(self.values[$0])
}
This way SwiftIU knowns it should rebuild the picker on change.
Tip: You can use elements directly like this:
ForEach(values, id: \.self) {
Text($0)
}
Don't forget to change the selectedValue type and value to match with the dataSource IF you followed the tip above:
#State private var selectedValue = "A"
Change selectedValue from int to String
#State private var selectedValue = "A"
add the parameter id and the tag modifier
Picker(selection: $selectedValue, label: Text("Value")) {
ForEach(values, id: \.self) {
Text($0).tag(String($0))
}
}