检查pickerView SwiftUi中的选择
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【中文标题】检查pickerView SwiftUi中的选择【英文标题】：Check selection in pickerView SwiftUi 【发布时间】：2021-04-21 14:05:34 【问题描述】：我是一个菜鸟，我正在学习 Swift 和 SwiftUI。 我想创建一个应用程序来组织笔记。 我有 2 个问题。
-
我想控制用户在按下按钮之前何时在选择器视图中选择了类别。如果未选择类别，则隐藏按钮保存。
在 ListView 中按类别对列表中的笔记进行排序。
//
// NewNoteView.swift
// List&Notes
//
// Created by Yoan on 18/04/2021.
//
import SwiftUI
struct NewNoteView: View
let coreDM: CoreDataManger
@State var category: [Category] = [Category]()
@State private var categorySelected = Category()
@State private var categoryField = String()
@State private var noteField: String = "Your note here"
@State private var noteTitleField = String()
@State private var showButton = false
private func emptyField()
categoryField = ""
noteField = ""
noteTitleField = ""
var body: some View
VStack
Form
Picker("Select your category", selection: $categorySelected)
ForEach(category, id: \.self) categorize in
Text(categorize.title ?? "no value")
TextField("titleNote", text: $noteTitleField)
.font(.title2)
.background(Color.white)
.cornerRadius(5)
.shadow(radius: 5)
TextEditor(text: $noteField)
.padding(.bottom)
.font(.body)
.background(Color.white)
.shadow(radius: 5)
.cornerRadius(8)
Button(action:
guard !noteTitleField.isEmpty && !noteField.isEmpty && categorySelected != nil else
print("Error")
return
coreDM.saveNote(noteData: noteField, noteTitle: noteTitleField,
noteDate: Date(), noteCategory: categorySelected)
emptyField()
, label:
Text("Save")
)
.frame(maxWidth: .infinity, maxHeight: 40.0 )
.background(Color.yellow)
.shadow(radius: 10)
.cornerRadius(10)
.navigationTitle("Create new note")
.onAppear(perform:
category = coreDM.getAllCategory()
)
struct NewNoteView_Previews: PreviewProvider
static var previews: some View
NavigationView
NewNoteView(coreDM: CoreDataManger())
//
// ListView.swift
// List&Notes
//
// Created by Yoan on 18/04/2021.
//
import SwiftUI
struct ListView: View
let coreDM: CoreDataManger
@State var notes: [Note] = [Note]()
@State var needsRefresh: Bool = false
@State var category: [Category] = [Category]()
private func updateListNote()
notes = coreDM.getAllNotes()
category = coreDM.getAllCategory()
var body: some View
List
ForEach(notes, id: \.self) notes in
NavigationLink(
destination: NoteDetailView(coreDM: coreDM, note: notes, needsRefresh: $needsRefresh),
label:
HStack
VStack
Text(notes.title ?? "no value")
.font(.title2)
.multilineTextAlignment(.leading)
.lineLimit(1)
Text(notes.dataNote ?? "No description")
.font(.subheadline)
.foregroundColor(.gray)
.multilineTextAlignment(.leading)
.lineLimit(2)
Spacer()
VStack
Text(notes.date!, style: .date)
Text(notes.date!, style: .time)
)
.onDelete(perform: indexSet in
indexSet.forEach index in
let note = notes[index]
coreDM.deleteNote(note: note)
updateListNote()
)
.listStyle(PlainListStyle())
.accentColor(needsRefresh ? .red: .blue)
.navigationTitle("Your notes")
.onAppear(perform:
updateListNote()
)
struct ListView_Previews: PreviewProvider
static var previews: some View
ListView(coreDM: CoreDataManger())
如果需要，可以在我的 GitHub 中找到我的项目。 https://github.com/yoan8306/List-Notes.git
对不起，我是法国人，我的英语不是很好。 我希望这是我的问题，很清楚。
【问题讨论】：
【参考方案1】：对于您的第一个查询，在您的代码中更改以下内容：
将categorySelected 设为可选
@State private var categorySelected: Category? = nil
在 VStack 中添加 if 条件以显示按钮
if let category = categorySelected
Button(action:
guard !noteTitleField.isEmpty && !noteField.isEmpty else
print("Error")
return
coreDM.saveNote(noteData: noteField, noteTitle: noteTitleField, noteDate: Date(), noteCategory: categorySelected)
emptyField()
, label:
Text("Save")
)
.frame(maxWidth: .infinity, maxHeight: 40.0 )
.background(Color.yellow)
.shadow(radius: 10)
.cornerRadius(10)
对于您的第二个问题，请澄清 - 您是否需要根据类别或其他内容在部分中显示数据。
【讨论】：
我，谢谢您的回复。按钮是隐藏的。用你的方法。但我无法在选择器中选择类别。对于我的第二个问题，我想按类别对我的笔记进行排序。他们的类别将在列表的标题中。排他们是笔记。 知道了，我会更新答案以包含您的第二点【参考方案2】：我修复了我的 1 个查询。就像说 udbhateja
将categorySelected 设为可选
@State private var categorySelected: Category? = nil
用于修复 pickerView 中的选择
我们需要添加
.tag((分类为类别？))
代码是
import SwiftUI
struct NewNoteView: View
let coreDM: CoreDataManger
@State var category: [Category] = [Category]()
@State private var categorySelected : Category? = nil
@State private var categoryField = String()
@State private var noteField: String = "Your note here"
@State private var noteTitleField = String()
@State private var showButton = false
@State private var presentAlert = false
@State private var saveSuccess = false
@State private var selection = Category()
private func emptyField()
categoryField = ""
noteField = ""
noteTitleField = ""
private func checkNoteIsOk() -> Bool
if !noteTitleField.isEmpty && !noteField.isEmpty && categorySelected != nil
return true
else
presentAlert = true
return false
var body: some View
VStack
Form
Picker("Select your category", selection: $categorySelected )
ForEach(category, id: \.self) categorize in
Text(categorize.title ?? "no value").tag((categorize as Category?))
TextField("titleNote", text: $noteTitleField)
.font(.title2)
.background(Color.white)
.cornerRadius(5)
.shadow(radius: 5)
TextEditor(text: $noteField)
.font(.body)
.background(Color.white)
.shadow(radius: 5)
.cornerRadius(8)
.padding(.bottom)
if let category = categorySelected
Button(action:
guard checkNoteIsOk() else
return
coreDM.saveNote(noteData: noteField, noteTitle: noteTitleField,
noteDate: Date(), noteCategory: categorySelected!)
emptyField()
saveSuccess = true
,
label:
Text("Save")
)
.frame(maxWidth: .infinity, maxHeight: 40.0 )
.background(Color.yellow)
.shadow(radius: 10)
.cornerRadius(10)
.navigationTitle("Create new note")
.onAppear(perform: category = coreDM.getAllCategory())
.alert(isPresented: $presentAlert)
Alert(title: Text("Error !"), message: Text("Not saved"),
dismissButton: .default(Text("OK")))
.alert(isPresented: $saveSuccess)
Alert(title: Text("Success !"), message: Text("Insert with success !"),
dismissButton: .default(Text("OK")))
struct NewNoteView_Previews: PreviewProvider
static var previews: some View
NavigationView
NewNoteView(coreDM: CoreDataManger())
但我有新问题。我认为这很简单。 我想发出 2 条警报消息。 第一个是保存成功，第二个是出现问题，例如一个字段为空或类别为空。
private func checkNoteIsOk() -> Bool
if !noteTitleField.isEmpty && !noteField.isEmpty && categorySelected != nil
return true
else
presentAlert = true
return false
.
Button(action:
guard checkNoteIsOk() else
// present alert here
return
coreDM.saveNote(noteData: noteField, noteTitle: noteTitleField,
noteDate: Date(), noteCategory: categorySelected!)
emptyField()
( ..present saveSuccess alert here..)
saveSuccess = true
,
label:
Text("Save")
) //end button
code ....
//end Vstak
.navigationTitle("Create new note")
.alert(isPresented: $presentAlert)
Alert(title: Text("Error !"), message: Text("Not saved"),
dismissButton: .default(Text("OK")))
.alert(isPresented: $saveSuccess)
Alert(title: Text("Success !"), message: Text("Insert with success !"),
dismissButton: .default(Text("OK")))
我认为这是因为它们是两条警报消息。并且只能显示最后一条消息警报。 感谢您的回答和帮助。
【讨论】：
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