我希望在文本框中有一个不能被删除的“+”符号。用户应该能够在其后输入值,如果按回退键,它只能删除用户输入的值。当我输入其他数字时,它将自动在输入值的开头添加一个“+”。
例如:我想在文本框中添加国家代码,因此只要用户开始输入国家代码,就会自动在字段开头添加“+”。
例如:我想在文本框中添加国家代码,因此只要用户开始输入国家代码,就会自动在字段开头添加“+”。
ObservableObject
来处理值的变化。以下是示例代码:import SwiftUI
import Combine
struct ContentView: View {
class ViewModel: ObservableObject {
@Published var text = "" {
didSet {
if text.prefix(1) != "+" {
text = "+" + text
}
}
}
}
@ObservedObject var viewModel = ViewModel()
var body: some View {
TextField("Placeholder", text:$viewModel.text)
}
}
尝试用我的“千克”替换“+”
func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
var amountTypedString = myTF.text
if string.count > 0 {
if amountTypedString?.count ?? 0 > 2 {
amountTypedString = String((amountTypedString?.dropLast(2))!)
}
amountTypedString! += string
let newString = amountTypedString! + "kg"
myTF.text = newString
} else {
amountTypedString = String((amountTypedString?.dropLast(3))!)
if (amountTypedString?.count)! > 0 {
let newString = amountTypedString! + "kg"
myTF.text = newString
} else {
myTF.text = ""
}
}
return false
}
我在我的应用程序中需要相同的功能(用户需要输入国家代码,以便我可以验证号码),并且我使用自定义绑定实现了类似于您想要的功能:
struct PrefixedTextField: View {
@State private var countryCode = "+"
var body: some View {
let countryCodeCustomBinding =
Binding(
get: { self.countryCode },
set: {
self.countryCode = $0
if self.countryCode.isEmpty { self.countryCode = "+" }
})
return TextField("+91", text: countryCodeCustomBinding).keyboardType(.numberPad)
}
}
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
let textField = UITextField(frame: CGRect(x: 100, y: 100, width: 200, height: 20))
view.addSubview(textField)
textField.addTarget(self, action: #selector(textFieldDidChange(_:)), for: UIControl.Event.editingChanged)
textField.layer.borderColor = UIColor.red.cgColor
textField.layer.borderWidth = 2
}
@objc func textFieldDidChange(_ textField: UITextField) {
if textField.text?.prefix(1) != "+" {
textField.text = "+" + textField.text!
}
}
import SwiftUI
struct ContentView: View {
@State var userName : String = ""
var body: some View {
VStack {
HStack{
Image(systemName: "plus")
TextField("placeholder",text:$userName)
}
.padding(5)
.foregroundColor(.white)
.background(Capsule().fill(Color.gray))
Spacer()
}.padding(5)
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
我认为这是一种更好的方法,可以添加“+”号,这样当您访问 userName 时就不会收到 + 号了。
import SwiftUI import Combine
class ViewModel: ObservableObject {
@Published var text = "" {
didSet {
if text.prefix(1) != "+"{
if text.count == 1{
text = "+" + amount
}
}
if text.prefix(0) == "+" && text.prefix(1) == ""{
text = ""
}
}
}
@ObservedObject var viewModel = ViewModel()
var body: some View {
TextField("Placeholder", text:$viewModel.text)
}