Xamarin 应用异常："Objective-C exception thrown. Name: NSInvalidArgumentException"

Question

我尝试构建一个简单的Xamarin Forms应用程序，该应用程序对联系人列表进行分组。 在这种情况下，我只有两个联系人来保持简单。在iOS模拟器或我的iPhone 6s(iOS 12(上启动应用程序时，出现错误，指出：

"{Foundation.MonoTouchException： Objective-C exception thrown. 名字： NSInvalidArgumentException Reason： *** -[NSPlaceholderString initWithUTF8String：]： NULL cString Native stack trace： 0
核心基金会0x00000001068e56fb __exceptionPrepr...}">

C#

namespace Lists{
    public partial class MainPage : ContentPage
    {
        public MainPage()
        {
            InitializeComponent();
            listView.ItemsSource = new List<ContactGroup> {
                new ContactGroup("P", "P")
                {
                    new Contact { Name = "Peter Parker", Status = "Nice to meet you!" }
                },
                new ContactGroup("J", "J")
                {
                    new Contact { Name = "John Smith", Status = "Hey, let's talk!" }
                }
            };
        }
    }
    public class Contact
    {
        public string Name { get; set; }
        public string Status { get; set; }
    }
    public class ContactGroup : List<Contact>
    {
        public string Title { get; set; }
        public string ShortTitle { get; set; }
        public ContactGroup(string title, string shortTitle)
        {
            Title = title;
            ShortTitle = shortTitle; 
        }
    }
}

XAML

<?xml version="1.0" encoding="utf-8"?>
<ContentPage
    Padding="0, 20, 0, 0"
    xmlns="http://xamarin.com/schemas/2014/forms" 
    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" 
    xmlns:local="clr-namespace:Lists" x:Class="Lists.MainPage">
    <ListView x:Name="listView"
              IsGroupingEnabled="true" 
              GroupDisplayBinding="{Binding Title}"
              GroupShortNameBinding="{Binding shortTitle}">
        <ListView.ItemTemplate>
            <DataTemplate>
                <TextCell Text="{Binding Name}" Detail="{Binding Status}"/>
            </DataTemplate>
        </ListView.ItemTemplate>
    </ListView>
</ContentPage>

Answer 1

在行中：

  GroupShortNameBinding="{Binding shortTitle}">

应将绑定设置为">短标题"而不是"shortTitle"。

这是一个带有代码的演示，您可以检查它：grouped-listView