View automatically jumps to Multiline Text Field - swiftui

Question

My SwiftUI View is kinda acting weird since i added a MultilineTextField. When pressing a item on the List, the view kind jumps back and forth and then it jumps automatically to the last text field in the view as seen in this video. This just happened after i added a MultilineTextField at the end.
MultilineTextField definition:
import Foundation
import SwiftUI
import UIKit
fileprivate struct UITextViewWrapper: UIViewRepresentable {
typealias UIViewType = UITextView
#Binding var text: String
#Binding var calculatedHeight: CGFloat
var onDone: (() -> Void)?
func makeUIView(context: UIViewRepresentableContext<UITextViewWrapper>) -> UITextView {
let textField = UITextView()
textField.delegate = context.coordinator
textField.isEditable = true
textField.font = UIFont.preferredFont(forTextStyle: .body)
textField.isSelectable = true
textField.isUserInteractionEnabled = true
textField.isScrollEnabled = false
textField.backgroundColor = UIColor.clear
if nil != onDone {
textField.returnKeyType = .done
}
textField.setContentCompressionResistancePriority(.defaultLow, for: .horizontal)
return textField
}
func updateUIView(_ uiView: UITextView, context: UIViewRepresentableContext<UITextViewWrapper>) {
if uiView.text != self.text {
uiView.text = self.text
}
if uiView.window != nil, !uiView.isFirstResponder {
uiView.becomeFirstResponder()
}
UITextViewWrapper.recalculateHeight(view: uiView, result: $calculatedHeight)
}
fileprivate static func recalculateHeight(view: UIView, result: Binding<CGFloat>) {
let newSize = view.sizeThatFits(CGSize(width: view.frame.size.width, height: CGFloat.greatestFiniteMagnitude))
if result.wrappedValue != newSize.height {
DispatchQueue.main.async {
result.wrappedValue = newSize.height // !! must be called asynchronously
}
}
}
func makeCoordinator() -> Coordinator {
return Coordinator(text: $text, height: $calculatedHeight, onDone: onDone)
}
final class Coordinator: NSObject, UITextViewDelegate {
var text: Binding<String>
var calculatedHeight: Binding<CGFloat>
var onDone: (() -> Void)?
init(text: Binding<String>, height: Binding<CGFloat>, onDone: (() -> Void)? = nil) {
self.text = text
self.calculatedHeight = height
self.onDone = onDone
}
func textViewDidChange(_ uiView: UITextView) {
text.wrappedValue = uiView.text
UITextViewWrapper.recalculateHeight(view: uiView, result: calculatedHeight)
}
func textView(_ textView: UITextView, shouldChangeTextIn range: NSRange, replacementText text: String) -> Bool {
if let onDone = self.onDone, text == "\n" {
textView.resignFirstResponder()
onDone()
return false
}
return true
}
}
}
struct MultilineTextField: View {
private var placeholder: String
private var onCommit: (() -> Void)?
#Binding private var text: String
private var internalText: Binding<String> {
Binding<String>(get: { self.text } ) {
self.text = $0
self.showingPlaceholder = $0.isEmpty
}
}
#State private var dynamicHeight: CGFloat = 100
#State private var showingPlaceholder = false
init (_ placeholder: String = "", text: Binding<String>, onCommit: (() -> Void)? = nil) {
self.placeholder = placeholder
self.onCommit = onCommit
self._text = text
self._showingPlaceholder = State<Bool>(initialValue: self.text.isEmpty)
}
var body: some View {
UITextViewWrapper(text: self.internalText, calculatedHeight: $dynamicHeight, onDone: onCommit)
.frame(minHeight: dynamicHeight, maxHeight: dynamicHeight)
.background(placeholderView, alignment: .topLeading)
}
var placeholderView: some View {
Group {
if showingPlaceholder {
Text(placeholder).foregroundColor(.gray)
.padding(.leading, 4)
.padding(.top, 8)
}
}
}
}
#if DEBUG
struct MultilineTextField_Previews: PreviewProvider {
static var test:String = ""//some very very very long description string to be initially wider than screen"
static var testBinding = Binding<String>(get: { test }, set: {
// print("New value: \($0)")
test = $0 } )
static var previews: some View {
VStack(alignment: .leading) {
Text("Description:")
MultilineTextField("Enter some text here", text: testBinding, onCommit: {
print("Final text: \(test)")
})
.overlay(RoundedRectangle(cornerRadius: 4).stroke(Color.black))
Text("Something static here...")
Spacer()
}
.padding()
}
}
#endif
Code:
struct DetailZwei : View {
#State var data : dataTypeZwei
#State var viewModel = GerätEditieren()
#Environment(\.presentationMode) var presentationMode
#State private var showingAlert = false
var body : some View {
NavigationView {
ScrollView {
VStack {
Group {
Section(header: Text("")) {
Text("Seriennummer")
TextField("Seriennummer", text: $data.sn).textFieldStyle(RoundedBorderTextFieldStyle())
Text("Objekt")
TextField("Objekt", text: $data.objekt).textFieldStyle(RoundedBorderTextFieldStyle())
Text("Gerätetyp")
TextField("Gerätetyp", text: $data.typ).textFieldStyle(RoundedBorderTextFieldStyle())
Text("Geräteposition")
TextField("Geräteposition", text: $data.pos).textFieldStyle(RoundedBorderTextFieldStyle())
}
Group {
Text("Installationsdatum")
TextField("Installationsdatum", text: $data.ida).textFieldStyle(RoundedBorderTextFieldStyle())
Text("Leasing oder Gekauft?")
TextField("Leasing oder Gekauft?", text: $data.lg).textFieldStyle(RoundedBorderTextFieldStyle())
Text("Ablaufdatum Leasing")
TextField("Ablaufdatum Leasing", text: $data.la).textFieldStyle(RoundedBorderTextFieldStyle())
Text("Ablaufdatum Garantie")
TextField("Ablaufdatum Garantie", text: $data.ga).textFieldStyle(RoundedBorderTextFieldStyle())
}
Section(header: Text("")) {
Text("Strasse")
TextField("Strasse", text: $data.str).textFieldStyle(RoundedBorderTextFieldStyle())
Text("Hausnummer")
TextField("Hausnummer", text: $data.nr).textFieldStyle(RoundedBorderTextFieldStyle())
Text("Postleitzahl")
TextField("Postleitzahl", text: $data.plz).textFieldStyle(RoundedBorderTextFieldStyle())
Text("Ort")
TextField("Ort", text: $data.ort).textFieldStyle(RoundedBorderTextFieldStyle())
}
Section(header: Text("")) {
Text("Ansprechperson")
TextField("Ansprechperson", text: $data.vp).textFieldStyle(RoundedBorderTextFieldStyle())
Text("Telefonnummer")
TextField("Telefonnummer", text: $data.tel).textFieldStyle(RoundedBorderTextFieldStyle())
}
Section(header: Text("VDS").bold()) {
Text("Eingetragen durch")
TextField("Eingetragen durch", text: $data.ed).textFieldStyle(RoundedBorderTextFieldStyle())
Text("Lieferdatum VDS")
TextField("Lieferdatum VDS", text: $data.ldvds).textFieldStyle(RoundedBorderTextFieldStyle())
}
// This is the Text Field
Section(header: Text("")) {
Text("Zusätzliche Informationen")
MultilineTextField("Zusätzliche Informationen", text: $data.zusatz).overlay(RoundedRectangle(cornerRadius: 4).stroke(Color.black))
}
}.padding()
.navigationBarTitle("Gerät bearbeiten", displayMode: .inline)
.navigationBarItems(leading: Button(action: { self.handleCancelTapped() }, label: {
Text("Abbrechen")
}),
trailing: Button(action: { self.handleDoneTapped() }, label: {
Text("Speichern")
})
// .disabled(!viewModel.modified)
)
}.alert(isPresented: $showingAlert) {
Alert(title: Text("Änderungen gespeichert"), message: Text("Die Änderungen vom Gerät \(data.sn) wurden erfolgreich gespeichert!"), dismissButton: .default(Text("Zurück").bold()){
self.handleCancelTapped()
})
}
}
}
}

Answer 1

When you opening the view, your Custom TextField calls firstResponders. Just remove calling firstResponder on load and your view will start at the beginning.
func updateUIView(_ uiView: UITextView, context: UIViewRepresentableContext<UITextViewWrapper>) {
if uiView.text != self.text {
uiView.text = self.text
}
if uiView.window != nil, !uiView.isFirstResponder {
//uiView.becomeFirstResponder() << Here calling firstResponder
}
UITextViewWrapper.recalculateHeight(view: uiView, result: $calculatedHeight)
}
SwiftUI TextFields do not support firstResponder yet, however with Representable and using UIKit it is possible, like in your solution, Grüezi