我想在$(document).on("change", 'select#recordavailable', function(e)
{
var dateInquiry = $(this).val();
$.ajax
({
type: "GET",
data: 'dateInquiry='+dateInquiry,
url: 'getmysqldata',
dataType: 'JSON',
success: function(data)
{
var randomnumber = Math.floor((Math.random()*100)+1);
var winPrint = window.open('',"",'PopUp'+randomnumber+', "scrollbars=1,menubar=0,resizable=1"');
winPrint.document.write('<title>Display Record of '+dateInquiry+'</title><style>table{ border-collapse: collapse;border-spacing: 0;'+
'width: 100%;border: 1px solid #ddd;}table, td, th{border: 1px solid black;text-align:center;padding: 5px;}#stockname {text-align: left;}'+
'h3 {text-align:center;}#qty, #cost, #balance, #total {text-align: right;}</style><h3>'+dateInquiry+'</h3>');
winPrint.document.write(JSON.stringify(data));
}
});
});
被更改但没有@State
且无法将Picker
置于选择器状态时更改其他一些不相关的onChanged
变量那我还能怎么做呢?
答案 0 :(得分:55)
这就是我刚刚决定使用的... (部署目标iOS 13)
struct MyPicker: View {
@State private var favoriteColor = 0
var body: some View {
Picker(selection: $favoriteColor.onChange(colorChange), label: Text("Color")) {
Text("Red").tag(0)
Text("Green").tag(1)
Text("Blue").tag(2)
}
}
func colorChange(_ tag: Int) {
print("Color tag: \(tag)")
}
}
使用此助手
extension Binding {
func onChange(_ handler: @escaping (Value) -> Void) -> Binding<Value> {
return Binding(
get: { self.wrappedValue },
set: { selection in
self.wrappedValue = selection
handler(selection)
})
}
}
编辑:
如果您的部署目标设置为iOS 14或更高版本-苹果提供了onChange
的内置View
扩展名,可以这样使用(谢谢@杰里米):
Picker(selection: $favoriteColor, label: Text("Color")) {
// ..
}
.onChange(of: favoriteColor) { print("Color tag: \($0)") }
答案 1 :(得分:15)
我认为这是更简单的解决方案:
@State private var pickerIndex = 0
var yourData = ["Item 1", "Item 2", "Item 3"]
// USE this if needed to notify parent
@Binding var notifyParentOnChangeIndex: Int
var body: some View {
let pi = Binding<Int>(get: {
return self.pickerIndex
}, set: {
self.pickerIndex = $0
// TODO: DO YOUR STUFF HERE
// TODO: DO YOUR STUFF HERE
// TODO: DO YOUR STUFF HERE
// USE this if needed to notify parent
self.notifyParentOnChangeIndex = $0
})
return VStack{
Picker(selection: pi, label: Text("Yolo")) {
ForEach(self.yourData.indices) {
Text(self.yourData[$0])
}
}
.pickerStyle(WheelPickerStyle())
.padding()
}
}
答案 2 :(得分:6)
我知道这是一岁的帖子,但是我认为此解决方案可能会帮助其他需要解决方案的来访者。希望它可以帮助其他人。
import Foundation
import SwiftUI
struct MeasurementUnitView: View {
@State var selectedIndex = unitTypes.firstIndex(of: UserDefaults.standard.string(forKey: "Unit")!)!
var userSettings: UserSettings
var body: some View {
VStack {
Spacer(minLength: 15)
Form {
Section {
Picker(selection: self.$selectedIndex, label: Text("Current UnitType")) {
ForEach(0..<unitTypes.count, id: \.self) {
Text(unitTypes[$0])
}
}.onReceive([self.selectedIndex].publisher.first()) { (value) in
self.savePick()
}
.navigationBarTitle("Change Unit Type", displayMode: .inline)
}
}
}
}
func savePick() {
if (userSettings.unit != unitTypes[selectedIndex]) {
userSettings.unit = unitTypes[selectedIndex]
}
}
}
答案 3 :(得分:6)
首先,充分感谢ccwasden以获得最佳答案。我必须对其稍作修改以使其对我有用,所以我在回答这个问题,希望其他人也能找到它。
这就是我最终的结果(在iOS 14 GM和Xcode 12 GM上进行了测试)
struct SwiftUIView: View {
@State private var selection = 0
var body: some View {
Picker(selection: $selection, label: Text("Some Label")) {
ForEach(0 ..< 5) {
Text("Number \($0)") }
}.onChange(of: selection) { _ in
print(selection)
}
}
}
我需要包含“ _ in”。没有它,我收到错误消息“无法将类型'Int'的值转换为预期的参数类型'()'”
答案 4 :(得分:5)
我使用分段选择器,并且有类似的要求。在尝试了几件事之后,我只使用了一个同时具有ObservableObjectPublisher
和PassthroughSubject
发布者作为选择的对象。这让我很满意SwiftUI,并且使用onReceive()
也可以做其他事情。
// Selector for the base and radix
Picker("Radix", selection: $base.value) {
Text("Dec").tag(10)
Text("Hex").tag(16)
Text("Oct").tag(8)
}
.pickerStyle(SegmentedPickerStyle())
// receiver for changes in base
.onReceive(base.publisher, perform: { self.setRadices(base: $0) })
基地有一个objectWillChange
和一个PassthroughSubject<Int, Never>
的发布者,它们被形象地称为发布者。
class Observable<T>: ObservableObject, Identifiable {
let id = UUID()
let objectWillChange = ObservableObjectPublisher()
let publisher = PassthroughSubject<T, Never>()
var value: T {
willSet { objectWillChange.send() }
didSet { publisher.send(value) }
}
init(_ initValue: T) { self.value = initValue }
}
typealias ObservableInt = Observable<Int>
定义objectWillChange并不是绝对必要的,但是当我写这封信时,我想提醒自己它在那里。
答案 5 :(得分:2)
使用onReceive
和Just
:
import Combine
import SwiftUI
struct ContentView: View {
@State private var selection = 0
var body: some View {
Picker("Some Label", selection: $selection) {
ForEach(0 ..< 5, id: \.self) {
Text("Number \($0)")
}
}
.onReceive(Just(selection)) {
print("Selected: \($0)")
}
}
}
答案 6 :(得分:2)
对于必须同时支持iOS 13和14的用户,我添加了一个扩展名,该扩展名对这两者均适用。不要忘记导入Combine。
Extension View {
@ViewBuilder func onChangeBackwardsCompatible<T: Equatable>(of value: T, perform completion: @escaping (T) -> Void) -> some View {
if #available(iOS 14.0, *) {
self.onChange(of: value, perform: completion)
} else {
self.onReceive([value].publisher.first()) { (value) in
completion(value)
}
}
}
}
用法:
Picker(selection: $selectedIndex, label: Text("Color")) {
Text("Red").tag(0)
Text("Blue").tag(1)
}.onChangeBackwardsCompatible(of: selectedIndex) { (newIndex) in
print("Do something with \(newIndex)")
}
重要说明::如果要更改完成块中观察到的对象内的已发布属性,此解决方案将在iOS 13中引起无限循环。但是,通过添加检查可以很容易地解决此问题。 ,就像这样:
.onChangeBackwardsCompatible(of: showSheet, perform: { (shouldShowSheet) in
if shouldShowSheet {
self.router.currentSheet = .chosenSheet
showSheet = false
}
})
答案 7 :(得分:2)
我在尝试绑定到 CoreData 实体时遇到了这个问题,发现以下方法有效:
Picker("Level", selection: $contact.level) {
ForEach(levels) { (level: Level?) in
HStack {
Circle().fill(Color.green)
.frame(width: 8, height: 8)
Text("\(level?.name ?? "Unassigned")")
}
.tag(level)
}
}
.onChange(of: contact.level) { _ in savecontact() }
其中“联系人”是与“级别”有关系的实体。
Contact
类是一个 @ObservedObject var contact: Contact
saveContact
是一个 do-catch
函数,用于 try viewContext.save()
...
答案 8 :(得分:0)
非常重要的问题:我们必须将一些东西传递给 Picker 项目视图(在 ForEach 内部)的“标记”修饰符,以让它“识别”项目并触发选择更改事件。并且我们传递的值将通过 Picker 的“选择”返回到 Binding 变量中。
例如:
Picker(selection: $selected, label: Text("")){
ForEach(data){item in //data's item type must conform Identifiable
HStack{
//item view
}
.tag(item.property)
}
}
.onChange(of: selected, perform: { value in
//handle value of selected here (selected = item.property when user change selection)
})