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author | E.Z. Hart <hartez@users.noreply.github.com> | 2016-08-02 14:54:57 -0600 |
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committer | Jason Smith <jason.smith@xamarin.com> | 2016-08-02 13:54:57 -0700 |
commit | 34048b7bb4e8bf55c712ffd92303cf260c491c0e (patch) | |
tree | 19236fb4e72b8833c87e19fd15d0958b947764fc /Xamarin.Forms.Core/WeakEventManager.cs | |
parent | 08e282350cb3f1c2345125682f14934111af2f9c (diff) | |
download | xamarin-forms-34048b7bb4e8bf55c712ffd92303cf260c491c0e.tar.gz xamarin-forms-34048b7bb4e8bf55c712ffd92303cf260c491c0e.tar.bz2 xamarin-forms-34048b7bb4e8bf55c712ffd92303cf260c491c0e.zip |
Change SourceChanged event on ImageSource to weak event to allow Images (#268)
referencing application-wide StaticResource ImageSources to be GCed
Diffstat (limited to 'Xamarin.Forms.Core/WeakEventManager.cs')
-rw-r--r-- | Xamarin.Forms.Core/WeakEventManager.cs | 159 |
1 files changed, 159 insertions, 0 deletions
diff --git a/Xamarin.Forms.Core/WeakEventManager.cs b/Xamarin.Forms.Core/WeakEventManager.cs new file mode 100644 index 00000000..226f329a --- /dev/null +++ b/Xamarin.Forms.Core/WeakEventManager.cs @@ -0,0 +1,159 @@ +using System; +using System.Collections.Generic; +using System.Reflection; + +namespace Xamarin.Forms +{ + internal class WeakEventManager + { + readonly Dictionary<string, List<Subscription>> _eventHandlers = + new Dictionary<string, List<Subscription>>(); + + public void AddEventHandler<TEventArgs>(string eventName, EventHandler<TEventArgs> handler) + where TEventArgs : EventArgs + { + if (eventName == null) + { + throw new ArgumentNullException(nameof(eventName)); + } + + if (handler == null) + { + throw new ArgumentNullException(nameof(handler)); + } + + AddEventHandler(eventName, handler.Target, handler.GetMethodInfo()); + } + + public void AddEventHandler(string eventName, EventHandler handler) + { + if (eventName == null) + { + throw new ArgumentNullException(nameof(eventName)); + } + + if (handler == null) + { + throw new ArgumentNullException(nameof(handler)); + } + + AddEventHandler(eventName, handler.Target, handler.GetMethodInfo()); + } + + public void HandleEvent(object sender, object args, string eventName) + { + var toRaise = new List<Tuple<object, MethodInfo>>(); + + List<Subscription> target; + if (_eventHandlers.TryGetValue(eventName, out target)) + { + foreach (Subscription subscription in target) + { + object subscriber = subscription.Subscriber.Target; + + if (subscriber == null) + { + // The subscriber was collected, so there's no need to keep this subscription around + target.Remove(subscription); + } + else + { + toRaise.Add(Tuple.Create(subscriber, subscription.Handler)); + } + } + } + + foreach (Tuple<object, MethodInfo> tuple in toRaise) + { + tuple.Item2.Invoke(tuple.Item1, new[] { sender, args }); + } + } + + public void RemoveEventHandler<TEventArgs>(string eventName, EventHandler<TEventArgs> handler) + where TEventArgs : EventArgs + { + if (eventName == null) + { + throw new ArgumentNullException(nameof(eventName)); + } + + if (handler == null) + { + throw new ArgumentNullException(nameof(handler)); + } + + RemoveEventHandler(eventName, handler.Target, handler.GetMethodInfo()); + } + + public void RemoveEventHandler(string eventName, EventHandler handler) + { + if (eventName == null) + { + throw new ArgumentNullException(nameof(eventName)); + } + + if (handler == null) + { + throw new ArgumentNullException(nameof(handler)); + } + + RemoveEventHandler(eventName, handler.Target, handler.GetMethodInfo()); + } + + void AddEventHandler(string eventName, object handlerTarget, MethodInfo methodInfo) + { + List<Subscription> target; + if (!_eventHandlers.TryGetValue(eventName, out target)) + { + target = new List<Subscription>(); + _eventHandlers.Add(eventName, target); + } + + target.Add(new Subscription(new WeakReference(handlerTarget), methodInfo)); + } + + void RemoveEventHandler(string eventName, object handlerTarget, MemberInfo methodInfo) + { + List<Subscription> subscriptions; + if (!_eventHandlers.TryGetValue(eventName, out subscriptions)) + { + return; + } + + for (int n = subscriptions.Count; n > 0; n--) + { + Subscription current = subscriptions[n - 1]; + + if (current.Subscriber != handlerTarget + || current.Handler.Name != methodInfo.Name) + { + continue; + } + + subscriptions.Remove(current); + } + } + + struct Subscription + { + public Subscription(WeakReference subscriber, MethodInfo handler) + { + if (subscriber == null) + { + throw new ArgumentNullException(nameof(subscriber)); + } + + if (handler == null) + { + throw new ArgumentNullException(nameof(handler)); + } + + Subscriber = subscriber; + Handler = handler; + } + + public readonly WeakReference Subscriber; + public readonly MethodInfo Handler; + } + } +}
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