c# – 在ViewModelViewHost控件中托管的View和ViewModel中使用时

我的应用程序使用视图,这些视图实现了IViewFor< T>接口.视图已在AppBootstrapper中的依赖项解析程序中注册.应用程序通过为控件的ViewModel属性指定相应的视图模型,使用ViewModelViewHost控件显示视图.所有视图模型都实现了ISupportsActivation接口.

我注意到WhenActivated被调用了两次.首先,当视图和视图模型被激活时调用它.然后在停用时,丢弃所有一次性用品,然后立即再次调用WhenActivated,然后处理一次性用品.

我在视图和视图模型中使用以下代码进行测试：

this.WhenActivated(disposables =>
{
    Debug.WriteLine("ViewModel activated.");

    Disposable
        .Create(() =>
        {
            Debug.WriteLine("ViewModel deactivated.");
        })
        .AddTo(disposables);
});

结果输出如下：

// App displays the view:

ViewModel activated.
View activated.

// App hides the view:

ViewModel deactivated.
View deactivated.
ViewModel activated.
View activated.
ViewModel deactivated.
View deactivated.

通过将ViewModelViewHost控件的ViewModel属性设置为null来隐藏视图.

难道我做错了什么？

编辑：这是完整的源代码：https://gist.github.com/dmakaroff/e7d84e06e0a48d7f5298eb6b7d6187d0

按第一个Show然后按Hide按钮将产生以下输出：

SubViewModel activated.
SubView activated.
SubViewModel deactivated.
SubView deactivated.
SubViewModel activated.
SubView activated.
SubViewModel deactivated.
SubView deactivated.

this.WhenActivated(d =>
{
    Debug.WriteLine("SubView activated.");
    d(Disposable.Create(() => { Debug.WriteLine("SubView deactivated."); }));

    d(this // ViewModel -> DataContext
        .WhenAnyValue(v => v.ViewModel)
        .BindTo(this,v => v.DataContext));
});

System.IDisposable whenActivatedSubscription = null;
whenActivatedSubscription = this.WhenActivated(d =>
{
    Debug.WriteLine("SubView activated.");
    d(Disposable.Create(() => { Debug.WriteLine("SubView deactivated."); }));

    d(this // ViewModel -> DataContext
        .WhenAnyValue(v => v.ViewModel)
        .BindTo(this,v => v.DataContext));
    d(whenActivatedSubscription); // <- Dispose of the activation subscription here
});