Caliburn笔记-Dependent Action(wpf框架)

   http://caliburn.codeplex.com/wikipage?title=Dependent%20Actions&referringTitle=Documentation

   这一部分功能也属于过滤器.再来看两个接口

FilterManager会在构造函数中,对实现该接口的Filter进行初始化

public interface IInitializable : IFilter
{
    /// <summary>
    /// Initializes the filter.
    /// </summary>
    /// <param name="targetType">Type of the target.</param>
    /// <param name="metadataContainer">The metadata container.</param>
    /// <param name="serviceLocator">The serviceLocator.</param>
    void Initialize(Type targetType, IMetadataContainer metadataContainer, IServiceLocator serviceLocator);
}

 

public FilterManager(Type targetType, IMetadataContainer metadataContainer, IServiceLocator serviceLocator)
{
…
    filters.OfType<IInitializable>()
        .Apply(x => x.Initialize(targetType, metadataContainer, serviceLocator));

…
}

IHandlerAware用来实现对事件的监听

public interface IHandlerAware : IFilter
{
    /// <summary>
    /// Makes the filter aware of the <see cref="IRoutedMessageHandler"/>.
    /// </summary>
    /// <param name="messageHandler">The message handler.</param>
    void MakeAwareOf(IRoutedMessageHandler messageHandler);

    /// <summary>
    /// Makes the filter aware of the <see cref="IMessageTrigger"/>.
    /// </summary>
    /// <param name="messageHandler">The message handler.</param>
    /// <param name="trigger">The trigger.</param>
    void MakeAwareOf(IRoutedMessageHandler messageHandler, IMessageTrigger trigger);
}

如DependenciesAttribute的实现,DependencyObserver对实现INotifyPropertyChanged的对象进行了监听.

public void MakeAwareOf(IRoutedMessageHandler messageHandler)
{
    var notifier = messageHandler.Unwrap() as INotifyPropertyChanged;
    if (notifier == null) return;

    var helper = messageHandler.GetMetadata<DependencyObserver>();
    if (helper != null) return;

    helper = new DependencyObserver(messageHandler, notifier);
    messageHandler.AddMetadata(helper);
}

然后在wpf元素初始化后,再次调用,添加事件

public void MakeAwareOf(IRoutedMessageHandler messageHandler, IMessageTrigger trigger)
{
    var helper = messageHandler.GetMetadata<DependencyObserver>();
    if (helper == null) return;

    if(trigger.Message.RelatesTo(_target))
        helper.MakeAwareOf(trigger, _dependencies);
}

DependencyObserver的MakeAwareOf.本质上海还是添加了MessageTrigger

public void MakeAwareOf(IMessageTrigger trigger, IEnumerable<string> dependencies)
{
    foreach (var dependency in dependencies)
    {
        IList<IMessageTrigger> triggers;
       
        if(!_triggersToNotify.TryGetValue(dependency, out triggers))
        {
            triggers = new List<IMessageTrigger>();
            _triggersToNotify[dependency] = triggers;
        }       
        if(!triggers.Contains(trigger))
            triggers.Add(trigger);
    }
}