MvxBind:错误: 10.40视图绑定过程中抛出异常

Question

我正在尝试使用提供的代码创建一个简单的服务，但我不明白为什么绑定时会出现异常。

10-19 11:42:09.148 I/mono-stdout( 1622)：MvxBind:Error: 10.40视图绑定过程中抛出异常

MvxBindingLayoutInflatorFactory第133行！

我需要一些帮助:)

我的来源：

DataStore接口：

using Core.Models;
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using System.Text;

namespace Core.Interfaces
{
    public interface IDataStore
    {
        void UpdateFeed(FeedModel feedModel);
        void DeleteFeed(FeedModel feedModel);
        void CreateFeed(FeedModel feedModel);
        FeedModel GetFeed(Uri uri);
        ObservableCollection<FeedModel> Feeds { get; }
    }
}

DataStore类：

using System;
using System.Collections.Generic;
using System.Linq;

using Core.Interfaces;
using System.Collections.ObjectModel;
using Cirrious.MvvmCross.Interfaces.ServiceProvider;
using Cirrious.MvvmCross.Interfaces.Platform;
using Cirrious.MvvmCross.Interfaces.Localization;
using Cirrious.MvvmCross.ExtensionMethods;
using Core.Helpers;
using System.Xml.Serialization;
using System.Xml.Linq;
using System.IO;

namespace Core.Models
{
    public class DataStore
        : IDataStore
        , IMvxServiceConsumer<IMvxSimpleFileStoreService>
        , IMvxServiceConsumer<IMvxResourceLoader>
    {
        public DataStore()
        {
            Load();
        }

        public void UpdateFeed(FeedModel feedModel)
        {
            var toUpdate = this.m_feeds.First(feed => feed.Url == feedModel.Url);
            toUpdate.CloneFrom(feedModel);
            Save();
        }

        public void DeleteFeed(FeedModel feedModel)
        {
            this.m_feeds.Remove(this.m_feeds.First(feed => feed.Url == feedModel.Url));
            Save();
        }

        public void CreateFeed(FeedModel feedModel)
        {
            this.m_feeds.Add(feedModel);
            Save();
        }

        public FeedModel GetFeed(Uri uri)
        {
            return this.m_feeds.First(feed => feed.Url == uri);
        }

        private void Load()
        {
            var fileService = this.GetService<IMvxSimpleFileStoreService>();
            if (!fileService.TryReadBinaryFile(LocationDataService.StoreFileName, LoadFrom))
            {
                var resourceLoader = this.GetService<IMvxResourceLoader>();
                resourceLoader.GetResourceStream(LocationDataService.ResourceFileName, (inputStream) => LoadFrom(inputStream));
            }
        }

        private bool LoadFrom(Stream inputStream)
        {
            try
            {
                var loadedData = XDocument.Load(inputStream);
                if (loadedData.Root == null)
                    return false;

                using (var reader = loadedData.Root.CreateReader())
                {
                    var list = (List<FeedModel>)new XmlSerializer(typeof(List<FeedModel>)).Deserialize(reader);
                    this.m_feeds = new ObservableCollection<FeedModel>(list);
                    return true;
                }
            }
            catch
            {
                return false;
            }
        }

        private void Save()
        {
            var fileService = this.GetService<IMvxSimpleFileStoreService>();
            fileService.WriteFile(LocationDataService.StoreFileName, (stream) =>
            {
                var serializer = new XmlSerializer(typeof(List<FeedModel>));
                serializer.Serialize(stream, m_feeds.ToList());
            });
        }

        private ObservableCollection<FeedModel> m_feeds;
        public ObservableCollection<FeedModel> Feeds
        {
            get { return this.m_feeds; }
        }

    }
}

BaseViewModel：

using Cirrious.MvvmCross.Commands;
using Cirrious.MvvmCross.ExtensionMethods;
using Cirrious.MvvmCross.Interfaces.Commands;
using Cirrious.MvvmCross.Interfaces.ServiceProvider;
using Cirrious.MvvmCross.ViewModels;
using Core.Interfaces;

namespace Core.ViewModels
{
    public class BaseViewModel
        : MvxViewModel
        , IMvxServiceConsumer<IDataStore>
    {
        protected IDataStore DataStore
        {
            get { return this.GetService<IDataStore>(); }
        }
    }
}

FeedManagerViewModel：

using Cirrious.MvvmCross.Commands;
using Cirrious.MvvmCross.Interfaces.Commands;
using Core.Controls;
using Core.Models;
using System;
using System.Collections.ObjectModel;

namespace Core.ViewModels
{
    public class FeedsManagerViewModel
        : BaseViewModel
    {

        public ObservableCollection<FeedModel> Feeds { get { return this.DataStore.Feeds; } }

       ...
    }
}

查看xml：

<Mvx.MvxBindableListView
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            local:MvxBind="{'ItemsSource':{'Path':'Feeds'}, 'ItemClick':{'Path':'DisplayItemCommand'}}"
            local:MvxItemTemplate="@layout/feedlist_viewmodel" />

Answer 1

这很可能是XML中的错误...但仅仅从那一行痕迹就很难分辨出来。

您运行的是什么版本的MvvmCross？

Master和vNext的tip版本都将第133行显示为

  MvxBindingTrace.Trace(MvxTraceLevel.Error, "Exception during creation of {0} from type {1} - exception {2}", name, viewType.FullName, exception.ToLongString());

因此，希望如果你使用这个技巧，那么它应该会给你更多关于哪里出了问题的信息。

除此之外，您始终可以尝试在有问题的行上设置断点，以提取更多信息。

如果异常位于第99行，则将错误记录从以下位置更改为：

MvxBindingTrace.Trace(MvxTraceLevel.Error, "Exception thrown during the view binding ", exception.ToLongString());

至：

MvxBindingTrace.Trace(MvxTraceLevel.Error, "Exception thrown during the view binding {0}", exception.ToLongString());

错误会出现在某个地方:)

另一种好的调试技术是逐行注释，直到问题消失-这有助于确定问题所在。

您已经有了一个工作的开发环境和一个非常强大的调试器-使用它是一项很好的学习技能。“'Code”是我最喜欢的书之一:)