已發布事件未訂閱或未發布

當我嘗試將事件從 SimpleFreeDrawModifier 類發布到 FieldSettingViewModel 類時，訂閱者類無法訂閱事件，反之亦然。

發布事件代碼：

  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();
                }
            }
        }
    }

訂閱事件代碼

  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();
    }

你能提供任何建議嗎？

uj5u.com熱心網友回復：

如果我錯了，請糾正我，但它看起來像實體化SimpleFreeDrawModifier并且FieldSettingViewModel是通過依賴注入實作的。

您確定FieldSettingViewModel已經創建了一個實體并且它正在接收相同的實體IEventAggregator嗎？

這個沒有 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
{
}

檢查 EventAggregator 的 DI 生命周期 isSingleton和 not Transient，還嘗試在建構式中放置斷點FieldSettingViewModel以確保它運行。

如果它沒有運行并且您正在為 DI 注冊它services.AddSingleton<FieldSettingViewModel>()，請嘗試使用services.AddSingleton<FieldSettingViewModel>(new FieldSettingViewModel())以確保有一個實體化。

uj5u.com熱心網友回復：

SimpleFreeDrawModifier的建構式使用EventAggregator而不是介面IEventAggregator因此正如 hwoodiwiss 所精確的那樣，即使它已注冊為單例，它們也不會使用相同的實體。

它已經發生在我身上，我花了很長時間才看到失蹤的我

標籤：C＃ wpf 虚拟机 棱镜

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