发布的事件未被订阅或发布

Question

当我尝试将事件从 SimpleFreeDrawModifier class 发布到 FieldSettingViewModel class 时，订阅者 class 无法订阅事件，反之亦然。

发布活动代码:

  public SimpleFreeDrawModifier(RegionManager regionManager, EventAggregator eventAggragator)  // Constructor 
    {
        _regionManager = regionManager;
        _eventAggragator = eventAggragator;

        CorodinatesMapDictionary =new Dictionary<object, object>();
    }
     private void AppendPoint(Point mousePoint)
    {
        // On Mouse-down, append another point
        if (_dataSeries != null)
        {
             CorodinatesMapDictionary.Clear();
            _dataSeries.Append((double)XAxis.GetDataValue(mousePoint.X), (double)YAxis.GetDataValue(mousePoint.Y));
           
            GlobalVar.XCoordinate=(double)_dataSeries.XValues[0];
            GlobalVar.YCoordinate=(double)_dataSeries.YValues[0];

            CorodinatesMapDictionary.Add("X",  GlobalVar.XCoordinate);
            CorodinatesMapDictionary.Add("Y", GlobalVar.YCoordinate);

            var calc = Math.Abs(GlobalVar.XCoordinate) * 1.0913;
            if (GlobalVar.YCoordinate < 0)
            {
                if (GlobalVar.YCoordinate >= -(calc))
                {
                    _eventAggragator.GetEvent<MapCoOrdinateChangedEvents>().Publish();
                }
            }
            else
            {
                if(Math.Abs(GlobalVar.XCoordinate) <=25 && GlobalVar.YCoordinate <=25)
                {
                    _eventAggragator.GetEvent<MapCoOrdinateChangedEvents>().Publish();
                }
            }
        }
    }

订阅活动代码

  public FieldSettingViewModel(RegionManager regionManager,IEventAggregator eventAggragator)
    {
        _regionManager = regionManager;
        _eventAggragator = eventAggragator;

        ClearCommand = new DelegateCommand(Clear);
        ApplyFieldSettingCommand = new DelegateCommand(ApplyFieldSetting, canApplyFieldSetting);

        ScanAreaDataSeries = new XyDataSeries<double, double>();
      
        GetScanSeriesData();

        _eventAggragator.GetEvent<MapCoOrdinateChangedEvents>().Subscribe(MapValue);
    }
     private void MapValue()
    {
        //throw new NotImplementedException();
    }

请问有什么建议吗？

Answer 1

如果我错了请纠正我，但看起来 SimpleFreeDrawModifier 和 FieldSettingViewModel 的实例化是通过依赖注入实现的。

您确定 FieldSettingViewModel 的实例已经创建并且它正在接收相同的 IEventAggregator 实例吗？

这个没有 DI 的最小示例有效

using System.Drawing;
using Prism.Events;

var eventAggregator = new EventAggregator();

var pub = new Publisher(eventAggregator);
var sub = new Subscriber(eventAggregator);

pub.AppendPoint(new Point());


public class Publisher
{
    private IEventAggregator _eventAggregator;

    public Publisher(IEventAggregator eventAggregator)  // Constructor 
    {
        _eventAggregator = eventAggregator;

    }
    public void AppendPoint(Point mousePoint)
    {

        _eventAggregator.GetEvent<MapCoOrdinateChangedEvents>().Publish();
    }
}

public class Subscriber
{
    private IEventAggregator _eventAggregator;

    public Subscriber(IEventAggregator eventAggregator)
    {
        _eventAggregator = eventAggregator;

        _eventAggregator.GetEvent<MapCoOrdinateChangedEvents>().Subscribe(MapValue);
    }

    private void MapValue()
    {
        Console.WriteLine("Map value called");
    }
}


internal class MapCoOrdinateChangedEvents : PubSubEvent
{
}

检查您的 EventAggregator 的 DI 生命周期是 Singleton 而不是 Transient，也尝试在 FieldSettingViewModel 的构造函数中放置一个断点以确保它是运行。

如果它不是运行并且您要像 services.AddSingleton<FieldSettingViewModel>() 一样为 DI 注册它，请尝试使用 services.AddSingleton<FieldSettingViewModel>(new FieldSettingViewModel()) 来确保实例化。

Answer 2

SimpleFreeDrawModifier 的构造函数使用 EventAggregator 而不是接口 IEventAggregator 因此由hwoodiwiss 他们没有使用相同的实例，即使它已被注册为单例。

它已经发生在我身上，我花了很长时间才看到失踪的我

发布的事件未被订阅或发布

Published Event not being subscribed or Published

c#

wpf

prism

mvvm