問題

在我看來，僅有的兩個值是FansNo和Description。我已經用盡了修復的嘗試。我確實注意到，當我在其中一個中更改值時Forms9Patch Label，XAML 熱多載會導致所有專案正確顯示。我尚未在 Xamarin.iOS 上對此進行測驗，但在 Xamarin.Android 上，這個特定頁面給我帶來了很多麻煩。我的目標是使用 C# 版本 8 的 .NET Standard 2.1。

任何幫助將不勝感激。

我最后的嘗試是卸載需要 .NET v2.1 的模塊并將目標降級到 v2.0。我會及時通知你這是否有效——不過我沒有太大希望。

除錯資訊

這些是從 ViewModel 中列印的控制臺中的一些行 - 這些證明資料被正確接收并且可系結值（例如Title）正在設定。拉動重繪（呼叫 PropertyChanged 事件）不會導致顯示值。

User Object: {"Artist":{"Name":"Matt Band","Description":"The best band in the area performing electronic stuffs","Genres":["Electro","D&B","Piano"],"MaxDistance":25,"MinNotice":3},"Venue":{"Name":null,"Description":null,"MinNotice":0},"FirstName":"Matthew","LastName":"Main","DOB":"2001-01-26T00:00:00.391Z","Followers":250,"Devices":["fgfafgadfgdafga"]}
Name: Matt Band

作業/非作業值

我已經使用 ViewModel 測驗了所有值，Console.WriteLine()并且它們都設定正確（參見上面的命令列塊）。

作業的價值觀是：

FansNo
Description
所有 CollectionView 模板值 (IE: AuthorID, Likes.Length, TimeStamp)
PostSpacing用于調整大小 (IE: ) 和命令 (IE: comm)的所有數值

不作業的有：

Title
NameGenre
Location

編碼

視圖模型：

using System;
using AV.Resources.Structures;
using System.Collections.ObjectModel;
using Xamarin.Essentials;
using Xamarin.Forms;
using Plugin.CloudFirestore;
using Newtonsoft.Json;
using System.ComponentModel;
using System.Threading.Tasks;
using System.Windows.Input;

namespace AV.ViewModels
{
    public class ProfilePage : INotifyPropertyChanged
    {

        public event PropertyChangedEventHandler PropertyChanged;

        public ObservableCollection<User> UsersList { get; set; }
        public ObservableCollection<Post> Posts { get; set; }

        public double RowWidth { get; set; }
        public double RowSpacing { get; set; }
        public double RowStart { get; set; }

        public double RowHeight { get; set; }
        public double PostSpacing { get; set; }
        public Thickness ContentPadding { get; set; }

        public double TopLayoutHeight { get; set; }

        public string Title { get; set; }
        public string NameGenre { get; set; }
        public string Location { get; set; }
        public int FansNo { get; set; }
        public int RatingNo { get; set; }
        public string Description { get; set; }

        public ICommand comm
        {
            get
            {
                return new Command(() =>
                {
                    Console.WriteLine("Property Changed! Title is: "   Title);
                    PropertyChanged.Invoke(this, new PropertyChangedEventArgs(null));
                });
            }
        }

        public ProfilePage(string userID)
        {

            Init();
            LoadProfile(userID);

        }

        void Init()
        {

            PostSpacing = (DeviceDisplay.MainDisplayInfo.Height / DeviceDisplay.MainDisplayInfo.Density) * 0.023758;
            RowHeight = (DeviceDisplay.MainDisplayInfo.Height / DeviceDisplay.MainDisplayInfo.Density) * 0.058315;
            ContentPadding = new Thickness((DeviceDisplay.MainDisplayInfo.Width / DeviceDisplay.MainDisplayInfo.Density) * 0.086449, 0, (DeviceDisplay.MainDisplayInfo.Width / DeviceDisplay.MainDisplayInfo.Density) * 0.037383, (DeviceDisplay.MainDisplayInfo.Height / DeviceDisplay.MainDisplayInfo.Density) * 0.017279);

            RowWidth = (DeviceDisplay.MainDisplayInfo.Width / DeviceDisplay.MainDisplayInfo.Density) * 0.189252;
            RowSpacing = (DeviceDisplay.MainDisplayInfo.Width / DeviceDisplay.MainDisplayInfo.Density) * 0.046729;
            RowStart = (DeviceDisplay.MainDisplayInfo.Width / DeviceDisplay.MainDisplayInfo.Density) * 0.086449;

            TopLayoutHeight = (DeviceDisplay.MainDisplayInfo.Height / DeviceDisplay.MainDisplayInfo.Density) * 0.763499;

            UsersList = new ObservableCollection<User>()
            {
                new User
                {
                    FirstName = "User"
                },
                new User
                {
                    FirstName = "User"
                },
                new User
                {
                    FirstName = "User"
                },
                new User
                {
                    FirstName = "User"
                },
                new User
                {
                    FirstName = "User"
                },
                new User
                {
                    FirstName = "User"
                }
            };

        }

        async void LoadProfile(string userID)
        {

            Console.WriteLine("UserID is: "   userID);

            Posts = new ObservableCollection<Post>();

            IDocumentSnapshot doc = await App.Firestore.Collection("users").Document(userID).GetAsync();
            User user = doc.ToObject<User>();

            Console.WriteLine("User Object: "   JsonConvert.SerializeObject(user));

            //IQuery relatedQuery;
            if (!user.Artist.Equals(default(User.artist)))
            {
                Console.WriteLine("This user is an artist");
                Title = user.Artist.Name;
                NameGenre = user.Artist.Genres[0];
                Location = "Location";
                FansNo = user.Followers;
                RatingNo = 5;
                Description = user.Artist.Description;
                Console.WriteLine("Name: "   Title);
                PropertyChanged.Invoke(this, new PropertyChangedEventArgs(null));
                //relatedQuery = App.Firestore.Collection("users").WhereArrayContainsAny("Artist.Genres", user.artist.Genres);
            }
            else if (!user.Venue.Equals(default(User.venue)))
            {
                Console.WriteLine("This user is a venue");
                Title = "Venue";
                NameGenre = user.Venue.Name;
                Location = "Location";
                FansNo = user.Followers;
                RatingNo = 5;
                Description = user.Venue.Description;
            }
            else
            {
                Console.WriteLine("This user is neither");
                Console.WriteLine("Name is: "   user.Artist.Name);
                //regular user
            }

            IQuerySnapshot posts = await App.Firestore.Collection("users").Document(userID).Collection("posts").OrderBy("TimeStamp").LimitTo(8).GetAsync();
            foreach(Post post in posts.ToObjects<Post>())
            {
                Posts.Add(post);
            }

            PropertyChanged.Invoke(this, new PropertyChangedEventArgs(null));

        }

    }
}

看法：

<?xml version="1.0" encoding="UTF-8" ?>
<ContentPage x:Name="contentPage" xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" xmlns:Forms9Patch="clr-namespace:Forms9Patch;assembly=Forms9Patch" xmlns:ViewModels="clr-namespace:AV.ViewModels" xmlns:ext="clr-namespace:AV.Resources.Extensions" x:Class="AV.ProfilePage" NavigationPage.HasNavigationBar="False">
    <ContentPage.Resources>

        <DataTemplate x:Key="textTemplate">

            <StackLayout BackgroundColor="#F7F7F7">

                <RelativeLayout HeightRequest="{Binding Source={x:Reference contentPage}, Path=BindingContext.RowHeight}">

                    <Image Source="logo2" Aspect="AspectFit" RelativeLayout.WidthConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.077}" RelativeLayout.HeightConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.077}" RelativeLayout.XConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.031}" RelativeLayout.YConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.231}" />
                    <Forms9Patch:Label Text="{Binding AuthorID}" FontFamily="AV.Resources.Fonts.Syne-Bold.otf" FontSize="100" Lines="0" AutoFit="Width" RelativeLayout.WidthConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.287}" RelativeLayout.HeightConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.333}" RelativeLayout.XConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.138}" RelativeLayout.YConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.276}" />
                    <Forms9Patch:Label Text="{Binding TimeStamp}" FontFamily="AV.Resources.Fonts.Syne-Bold.otf" FontSize="100" Lines="0" AutoFit="Width" RelativeLayout.WidthConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.098}" RelativeLayout.HeightConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.222}" RelativeLayout.XConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.138}" RelativeLayout.YConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.646}" />
                    <Forms9Patch:Label Text="{Binding Likes.Length}" FontSize="100" Lines="0" AutoFit="Width" RelativeLayout.WidthConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.047}" RelativeLayout.HeightConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.333}" RelativeLayout.XConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.847}" RelativeLayout.YConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.426}" />
                    <Image Source="LikeButton" RelativeLayout.WidthConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.037}" RelativeLayout.HeightConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.315}" RelativeLayout.XConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.925}" RelativeLayout.YConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.37}" />

                </RelativeLayout>
                <Label Text="{Binding Content}" FontFamily="Syne" Margin="{Binding Source={x:Reference contentPage}, Path=BindingContext.ContentPadding}" />

            </StackLayout>

        </DataTemplate>

        <DataTemplate x:Key="imageTemplate">

            <StackLayout BackgroundColor="#F7F7F7">

                <RelativeLayout HeightRequest="{Binding Source={x:Reference contentPage}, Path=BindingContext.RowHeight}">

                    <Image Source="logo2" Aspect="AspectFit" RelativeLayout.WidthConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.077}" RelativeLayout.HeightConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.077}" RelativeLayout.XConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.031}" RelativeLayout.YConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.231}" />
                    <Forms9Patch:Label Text="{Binding AuthorID}" FontFamily="AV.Resources.Fonts.Syne-Bold.otf" FontSize="100" Lines="0" AutoFit="Width" RelativeLayout.WidthConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.287}" RelativeLayout.HeightConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.333}" RelativeLayout.XConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.138}" RelativeLayout.YConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.276}" />
                    <Forms9Patch:Label Text="{Binding TimeStamp}" FontFamily="AV.Resources.Fonts.Syne-Bold.otf" FontSize="100" Lines="0" AutoFit="Width" RelativeLayout.WidthConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.098}" RelativeLayout.HeightConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.222}" RelativeLayout.XConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.138}" RelativeLayout.YConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.646}" />
                    <Forms9Patch:Label Text="{Binding Likes.Length}" FontSize="100" Lines="0" AutoFit="Width" RelativeLayout.WidthConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.047}" RelativeLayout.HeightConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.333}" RelativeLayout.XConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.847}" RelativeLayout.YConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.426}" />
                    <Image Source="LikeButton" RelativeLayout.WidthConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.037}" RelativeLayout.HeightConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.315}" RelativeLayout.XConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.925}" RelativeLayout.YConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.37}" />

                </RelativeLayout>
                <Label Text="{Binding Content}" FontFamily="Syne" Margin="{Binding Source={x:Reference contentPage}, Path=BindingContext.ContentPadding}" />
                <Image Source="SampleImage" Aspect="AspectFit" BackgroundColor="Red" HorizontalOptions="CenterAndExpand" />

            </StackLayout>

        </DataTemplate>

        <ext:RowTypeSelector x:Key="selector" TextTemplate="{StaticResource textTemplate}" ImageTemplate="{StaticResource imageTemplate}" />

    </ContentPage.Resources>

    <RefreshView Command="{Binding comm}">
        <ScrollView>
            <StackLayout BackgroundColor="White" Spacing="{Binding PostSpacing}">

                <RelativeLayout HeightRequest="{Binding TopLayoutHeight}">

                    <Image BackgroundColor="Red" Aspect="AspectFit" RelativeLayout.WidthConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=1.0}" RelativeLayout.HeightConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.402}" />
                    <Forms9Patch:Label Text="{Binding Path=BindingContext.Title, Source={x:Reference contentPage}}" TextColor="Black" FontSize="100" Lines="0" AutoFit="Width" RelativeLayout.WidthConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.43}" RelativeLayout.HeightConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.034}" RelativeLayout.XConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.086}" RelativeLayout.YConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.436}" />

                    <Forms9Patch:Label Text="Fans" TextColor="Black" FontFamily="AV.Resources.Fonts.Syne-Bold.otf" HorizontalTextAlignment="Center" FontSize="100" Lines="0" AutoFit="Width" RelativeLayout.WidthConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.189}" RelativeLayout.HeightConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.025}" RelativeLayout.XConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.512}" RelativeLayout.YConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.475}" />
                    <Forms9Patch:Label Text="{Binding FansNo}" TextColor="Black" FontSize="100" Lines="0" AutoFit="Width" HorizontalTextAlignment="Center" RelativeLayout.WidthConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.189}" RelativeLayout.HeightConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.025}" RelativeLayout.XConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.512}" RelativeLayout.YConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.443}" />
                    <Forms9Patch:Label Text="Rating" TextColor="Black" FontFamily="AV.Resources.Fonts.Syne-Bold.otf" HorizontalTextAlignment="Center" FontSize="100" Lines="0" AutoFit="Width" RelativeLayout.WidthConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.189}" RelativeLayout.HeightConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.025}" RelativeLayout.XConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.724}" RelativeLayout.YConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.475}" />

                    <Forms9Patch:Label Text="{Binding NameGenre}" TextColor="Black" FontFamily="AV.Resources.Fonts.Syne-Bold.otf" FontSize="100" Lines="0" AutoFit="Width" RelativeLayout.WidthConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.402}" RelativeLayout.HeightConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.025}" RelativeLayout.XConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.086}" RelativeLayout.YConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.501}" />
                    <Forms9Patch:Label Text="{Binding Location}" FontFamily="AV.Resources.Fonts.Syne-Bold.otf" FontSize="100" Lines="0" AutoFit="Width" RelativeLayout.WidthConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.827}" RelativeLayout.HeightConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.023}" RelativeLayout.XConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.086}" RelativeLayout.YConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.53}" />
                    <Label Text="{Binding Description}" TextColor="Black" FontFamily="Syne" RelativeLayout.WidthConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.827}" RelativeLayout.HeightConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.115}" RelativeLayout.XConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.086}" RelativeLayout.YConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.569}" />

                    <Frame BackgroundColor="Black" Padding="3" RelativeLayout.WidthConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.402}" RelativeLayout.HeightConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.048}" RelativeLayout.XConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.086}" RelativeLayout.YConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.69}">
                        <Frame BackgroundColor="White" Padding="1" CornerRadius="0" InputTransparent="True">
                            <Forms9Patch:Label Text="Follow" TextColor="Black" FontFamily="AV.Resources.Fonts.Syne-Bold.otf" InputTransparent="True" HorizontalTextAlignment="Center" VerticalTextAlignment="Center" Lines="0" AutoFit="Width" FontSize="100" />
                        </Frame>
                    </Frame>
                    <Frame BackgroundColor="Blue" Padding="4" CornerRadius="0" RelativeLayout.WidthConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.292}" RelativeLayout.HeightConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.048}" RelativeLayout.XConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.512}" RelativeLayout.YConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.69}">
                        <Forms9Patch:Label Text="Chat" TextColor="White" FontFamily="AV.Resources.Fonts.Syne-Bold.otf" InputTransparent="True" HorizontalTextAlignment="Center" VerticalTextAlignment="Center" Lines="0" AutoFit="Width" FontSize="100" />
                    </Frame>
                    <Frame BackgroundColor="Blue" Padding="6" CornerRadius="0" RelativeLayout.WidthConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.086}" RelativeLayout.HeightConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.048}" RelativeLayout.XConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.827}" RelativeLayout.YConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.69}">
                        <Image Source="CalendarIcon" Aspect="AspectFit" />
                    </Frame>

                    <BoxView BackgroundColor="Black" RelativeLayout.WidthConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.827}" RelativeLayout.HeightConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.004}" RelativeLayout.XConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.086}" RelativeLayout.YConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.766}" />

                    <Forms9Patch:Label Text="Artists" Lines="0" AutoFit="Width" FontSize="100" FontFamily="AV.Resources.Fonts.Syne-Bold.otf" RelativeLayout.WidthConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.827}" RelativeLayout.HeightConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.023}" RelativeLayout.XConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.086}" RelativeLayout.YConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.803}" />
                    <ScrollView Orientation="Horizontal" RelativeLayout.WidthConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=2}" RelativeLayout.HeightConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.16}" RelativeLayout.YConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.84}">

                        <CollectionView ItemsSource="{Binding UsersList}" TranslationX="{Binding RowStart}">

                            <CollectionView.ItemsLayout>

                                <LinearItemsLayout Orientation="Horizontal" ItemSpacing="{Binding Path=BindingContext.RowSpacing, Source={x:Reference contentPage}}" />

                            </CollectionView.ItemsLayout>

                            <CollectionView.ItemTemplate>

                                <DataTemplate>

                                    <RelativeLayout WidthRequest="{Binding Path=BindingContext.RowWidth, Source={x:Reference contentPage}}">

                                        <Image Source="logo2" Aspect="AspectFit" RelativeLayout.WidthConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=1.0}" RelativeLayout.HeightConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=1.0}" />
                                        <Forms9Patch:Label Text="{Binding FirstName}" BackgroundColor="White" FontFamily="AV.Resources.Fonts.Syne-Bold.otf" TextColor="Black" VerticalTextAlignment="Center" HorizontalTextAlignment="Center" Lines="0" AutoFit="Width" FontSize="100" RelativeLayout.WidthConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=1.0}" RelativeLayout.HeightConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.159}" RelativeLayout.YConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.841}" />

                                    </RelativeLayout>

                                </DataTemplate>

                            </CollectionView.ItemTemplate>

                        </CollectionView>

                    </ScrollView>

                </RelativeLayout>

                <RelativeLayout>

                    <CollectionView ItemsSource="{Binding Posts}" ItemTemplate="{StaticResource selector}">

                        <CollectionView.ItemsLayout>

                            <LinearItemsLayout Orientation="Vertical" ItemSpacing="{Binding PostSpacing}" />

                        </CollectionView.ItemsLayout>

                    </CollectionView>

                </RelativeLayout>

            </StackLayout>
        </ScrollView>
    </RefreshView>
</ContentPage>

uj5u.com熱心網友回復：

我看到您在 ViewModel 中定義了屬性，但是當它們的值設定時，它們并沒有引發屬性更改。

在您的視圖模型中，您可以定義完整的屬性詳細資訊并在更新時引發更改，如下例所示：

private string  _title;
    public string Title
    {
        get 
        { 
            return _title; 
        }
        set 
        { 
            _title = value;
            OnPropertyChanged("Title");}
        }

另外，我看到您從 INotifyPropertyChanged 繼承，確保您在 ViewModel 中正確實作了介面！例子：

 public void OnPropertyChanged(string propertyName)
 {
     if (PropertyChanged != null)
     {
         PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
     }
 }

PS：不確定這是否會解決您的問題。但至少這會讓你更容易開發！

uj5u.com熱心網友回復：

這行得通

<Forms9Patch:Label Text="{Binding FansNo}" ...

這不

<Forms9Patch:Label Text="{Binding Path=BindingContext.Title, Source={x:Reference contentPage}}" ...

這兩個屬性都定義在 VM 中的同一個位置，因此修改不作業的系結以匹配作業的系結將修復它是理所當然的

<Forms9Patch:Label Text="{Binding Title}" ...

uj5u.com熱心網友回復：

我得出的結論是，這是 Forms9Patch 庫的問題。當我將元素更改為常規標簽時，它們都顯示正常。

轉載請註明出處，本文鏈接：https://www.uj5u.com/ruanti/506325.html

標籤：C＃ xml xamarin.forms 数据绑定 xamarin.android

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盡管在ViewModel中設定了值，但標簽未顯示我的系結值

問題

除錯資訊

作業/非作業值

編碼

視圖模型：

看法：