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author | Shane Neuville <shane94@hotmail.com> | 2017-03-24 12:58:28 -0600 |
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committer | Jason Smith <jason.smith@xamarin.com> | 2017-03-24 11:58:28 -0700 |
commit | 377d24fd05e7fb597c4f9237c1596ed4fbf86f19 (patch) | |
tree | 9e7ddf6daf4a954d24d4087a0fde32baef30d776 | |
parent | 63af84080454e7b108208b6e8e67bbf503e41209 (diff) | |
download | xamarin-forms-377d24fd05e7fb597c4f9237c1596ed4fbf86f19.tar.gz xamarin-forms-377d24fd05e7fb597c4f9237c1596ed4fbf86f19.tar.bz2 xamarin-forms-377d24fd05e7fb597c4f9237c1596ed4fbf86f19.zip |
Setup a ConditionalWeakTable in ListProxy to hold weak references so that a ListView will work when connected to a Weak Source (#802)
-rw-r--r-- | Xamarin.Forms.Core.UnitTests/ListProxyTests.cs | 92 | ||||
-rw-r--r-- | Xamarin.Forms.Core/ListProxy.cs | 12 |
2 files changed, 102 insertions, 2 deletions
diff --git a/Xamarin.Forms.Core.UnitTests/ListProxyTests.cs b/Xamarin.Forms.Core.UnitTests/ListProxyTests.cs index 6fa85d2c..bf7f6eef 100644 --- a/Xamarin.Forms.Core.UnitTests/ListProxyTests.cs +++ b/Xamarin.Forms.Core.UnitTests/ListProxyTests.cs @@ -422,5 +422,97 @@ namespace Xamarin.Forms.Core.UnitTests return Items.GetEnumerator (); } } + + [Test] + public void WeakToWeak() + { + WeakCollectionChangedList list = new WeakCollectionChangedList(); + var proxy = new ListProxy(list); + + Assert.True(list.AddObject()); + + GC.Collect(); + GC.WaitForPendingFinalizers(); + GC.Collect(); + + Assert.IsTrue(list.AddObject()); + + proxy = null; + + GC.Collect(); + GC.WaitForPendingFinalizers(); + GC.Collect(); + + Assert.IsFalse(list.AddObject()); + } + + public class WeakCollectionChangedList : List<object>, INotifyCollectionChanged + { + List<WeakHandler> handlers = new List<WeakHandler>(); + + public WeakCollectionChangedList() + { + + } + public event NotifyCollectionChangedEventHandler CollectionChanged + { + add { handlers.Add(new WeakHandler(this, value)); } + remove { throw new NotImplementedException(); } + } + + + public bool AddObject() + { + bool invoked = false; + var me = new object(); + + foreach (var handler in handlers.ToList()) + { + if (handler.IsActive) + { + invoked = true; + handler.Handler.DynamicInvoke(this, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, me)); + } + else + { + handlers.Remove(handler); + } + } + + return invoked; + } + + class WeakHandler + { + WeakReference source; + WeakReference originalHandler; + + public bool IsActive + { + get { return this.source != null && this.source.IsAlive && this.originalHandler != null && this.originalHandler.IsAlive; } + } + + public NotifyCollectionChangedEventHandler Handler + { + get + { + if (this.originalHandler == null) + { + return default(NotifyCollectionChangedEventHandler); + } + else + { + return (NotifyCollectionChangedEventHandler)this.originalHandler.Target; + } + } + } + + public WeakHandler(object source, NotifyCollectionChangedEventHandler originalHandler) + { + this.source = new WeakReference(source); + this.originalHandler = new WeakReference(originalHandler); + } + } + } } } diff --git a/Xamarin.Forms.Core/ListProxy.cs b/Xamarin.Forms.Core/ListProxy.cs index c2f5c9d8..b25da163 100644 --- a/Xamarin.Forms.Core/ListProxy.cs +++ b/Xamarin.Forms.Core/ListProxy.cs @@ -3,6 +3,7 @@ using System.Collections; using System.Collections.Generic; using System.Collections.Specialized; using System.Linq; +using System.Runtime.CompilerServices; using Xamarin.Forms.Internals; namespace Xamarin.Forms @@ -12,6 +13,7 @@ namespace Xamarin.Forms readonly ICollection _collection; readonly IList _list; readonly int _windowSize; + readonly ConditionalWeakTable<ListProxy, WeakNotifyProxy> _sourceToWeakHandlers; IEnumerator _enumerator; int _enumeratorIndex; @@ -30,6 +32,7 @@ namespace Xamarin.Forms ProxiedEnumerable = enumerable; _collection = enumerable as ICollection; + _sourceToWeakHandlers = new ConditionalWeakTable<ListProxy, WeakNotifyProxy>(); if (_collection == null && enumerable is IReadOnlyCollection<object>) _collection = new ReadOnlyListAdapter((IReadOnlyCollection<object>)enumerable); @@ -40,7 +43,7 @@ namespace Xamarin.Forms var changed = enumerable as INotifyCollectionChanged; if (changed != null) - new WeakNotifyProxy(this, changed); + _sourceToWeakHandlers.Add(this, new WeakNotifyProxy(this, changed)); } public IEnumerable ProxiedEnumerable { get; } @@ -362,10 +365,15 @@ namespace Xamarin.Forms { readonly WeakReference<INotifyCollectionChanged> _weakCollection; readonly WeakReference<ListProxy> _weakProxy; + readonly ConditionalWeakTable<ListProxy, NotifyCollectionChangedEventHandler> _sourceToWeakHandlers; public WeakNotifyProxy(ListProxy proxy, INotifyCollectionChanged incc) { - incc.CollectionChanged += OnCollectionChanged; + _sourceToWeakHandlers = new ConditionalWeakTable<ListProxy, NotifyCollectionChangedEventHandler>(); + NotifyCollectionChangedEventHandler handler = new NotifyCollectionChangedEventHandler(OnCollectionChanged); + + _sourceToWeakHandlers.Add(proxy, handler); + incc.CollectionChanged += handler; _weakProxy = new WeakReference<ListProxy>(proxy); _weakCollection = new WeakReference<INotifyCollectionChanged>(incc); |