Question

在我的应用程序中，我希望拥有以下控件组：

<StackPanel Height="110" Orientation="Horizontal" HorizontalAlignment="Right">
    <StackPanel>
        <TextBlock Name="NameTextBox"/>
        <TextBlock Name="NumberTextBox"/>
    </StackPanel>
    <Image Name="ProfileImage"/>
</StackPanel>

我希望在项目的不同页面中共享。但问题出在这里：

TextBlock和Image控件的内容在运行时在PageLoad事件中加载。因此，每次导航发生时都必须加载它们。我不希望这种情况发生。我尝试将控件放在UserControl中，将其加载到UserControl的{{1}}事件中，并将Loaded包含在各个页面中。但是UserControl的{{1}}事件仍会在每个页面上触发。我可以通过一种方式将其加载一次并且每个页面都使用它吗？希望我明白这个问题。

Answer 1

考虑利用带参数的消息传递来在对象之间传递数据。

您可以使用EventAggregator或MessageBus。

我们的想法是让您的用户控件订阅他们想要响应的事件。

注：

我使用viewmodels执行此操作。但是，我认为将此代码添加到用户控件时会出现代码异味，无论使用它们的应用程序如何，这些代码都是通用的。

我使用 发布订阅模式 来处理复杂的类依赖项：

<强>视图模型：

    public class ViewModel : ViewModelBase
    {
        public ViewModel()
        {
            CloseComand = new DelegateCommand((obj) =>
                {
                    MessageBus.Instance.Publish(Messages.REQUEST_DEPLOYMENT_SETTINGS_CLOSED, null);
                });
        }
}

<强>窗口：

public partial class SomeWindow : Window
{
    Subscription _subscription = new Subscription();

    public SomeWindow()
    {
        InitializeComponent();

        _subscription.Subscribe(Messages.REQUEST_DEPLOYMENT_SETTINGS_CLOSED, obj =>
            {
                this.Close();
            });
    }
}

您可以利用Bizmonger.Patterns获取MessageBus。

<强> MessageBus

public class MessageBus
{
    #region Singleton
    static MessageBus _messageBus = null;
    private MessageBus() { }

    public static MessageBus Instance
    {
        get
        {
            if (_messageBus == null)
            {
                _messageBus = new MessageBus();
            }

            return _messageBus;
        }
    }
    #endregion

    #region Members
    List<Observer> _observers = new List<Observer>();
    List<Observer> _oneTimeObservers = new List<Observer>();
    List<Observer> _waitingSubscribers = new List<Observer>();
    List<Observer> _waitingUnsubscribers = new List<Observer>();

    int _publishingCount = 0;
    #endregion

    public void Subscribe(string message, Action<object> response)
    {
        Subscribe(message, response, _observers);
    }

    public void SubscribeFirstPublication(string message, Action<object> response)
    {
        Subscribe(message, response, _oneTimeObservers);
    }

    public int Unsubscribe(string message, Action<object> response)
    {
        var observers = new List<Observer>(_observers.Where(o => o.Respond == response).ToList());
        observers.AddRange(_waitingSubscribers.Where(o => o.Respond == response));
        observers.AddRange(_oneTimeObservers.Where(o => o.Respond == response));

        if (_publishingCount == 0)
        {
            observers.ForEach(o => _observers.Remove(o));
        }

        else
        {
            _waitingUnsubscribers.AddRange(observers);
        }

        return observers.Count;
    }

    public int Unsubscribe(string subscription)
    {
        var observers = new List<Observer>(_observers.Where(o => o.Subscription == subscription).ToList());
        observers.AddRange(_waitingSubscribers.Where(o => o.Subscription == subscription));
        observers.AddRange(_oneTimeObservers.Where(o => o.Subscription == subscription));

        if (_publishingCount == 0)
        {
            observers.ForEach(o => _observers.Remove(o));
        }

        else
        {
            _waitingUnsubscribers.AddRange(observers);
        }

        return observers.Count;
    }

    public void Publish(string message, object payload)
    {
        _publishingCount++;

        Publish(_observers, message, payload);
        Publish(_oneTimeObservers, message, payload);
        Publish(_waitingSubscribers, message, payload);

        _oneTimeObservers.RemoveAll(o => o.Subscription == message);
        _waitingUnsubscribers.Clear();

        _publishingCount--;
    }

    private void Publish(List<Observer> observers, string message, object payload)
    {
        Debug.Assert(_publishingCount >= 0);

        var subscribers = observers.Where(o => o.Subscription.ToLower() == message.ToLower());

        foreach (var subscriber in subscribers)
        {
            subscriber.Respond(payload);
        }
    }

    public IEnumerable<Observer> GetObservers(string subscription)
    {
        var observers = new List<Observer>(_observers.Where(o => o.Subscription == subscription));
        return observers;
    }

    public void Clear()
    {
        _observers.Clear();
        _oneTimeObservers.Clear();
    }

    #region Helpers
    private void Subscribe(string message, Action<object> response, List<Observer> observers)
    {
        Debug.Assert(_publishingCount >= 0);

        var observer = new Observer() { Subscription = message, Respond = response };

        if (_publishingCount == 0)
        {
            observers.Add(observer);
        }
        else
        {
            _waitingSubscribers.Add(observer);
        }
    }
    #endregion
}

}

<强>订阅

public class Subscription
{
    #region Members
    List<Observer> _observerList = new List<Observer>();
    #endregion

    public void Unsubscribe(string subscription)
    {
        var observers = _observerList.Where(o => o.Subscription == subscription);

        foreach (var observer in observers)
        {
            MessageBus.Instance.Unsubscribe(observer.Subscription, observer.Respond);
        }

        _observerList.Where(o => o.Subscription == subscription).ToList().ForEach(o => _observerList.Remove(o));
    }

    public void Subscribe(string subscription, Action<object> response)
    {
        MessageBus.Instance.Subscribe(subscription, response);
        _observerList.Add(new Observer() { Subscription = subscription, Respond = response });
    }

    public void SubscribeFirstPublication(string subscription, Action<object> response)
    {
        MessageBus.Instance.SubscribeFirstPublication(subscription, response);
    }
}

如何在不同的Windows手机页面之间共享xaml代码？

1 个答案: