Merge pull request #1193 from Microsoft/masterdetailsviewfix

MasterDetailsView: fixed loaded bug
CommunityToolkit · May 31, 2017 · f55a4c5 · f55a4c5
2 parents 9374554 + 00245b7
commit f55a4c5
Showing 1 changed file with 25 additions and 4 deletions.
diff --git a/Microsoft.Toolkit.Uwp.UI.Controls/MasterDetailsView/MasterDetailsView.cs b/Microsoft.Toolkit.Uwp.UI.Controls/MasterDetailsView/MasterDetailsView.cs
@@ -50,6 +50,7 @@ public partial class MasterDetailsView : ItemsControl
         private VisualStateGroup _stateGroup;
         private VisualState _narrowState;
         private Frame _frame;
+        private bool _loaded = false;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="MasterDetailsView"/> class.
@@ -77,6 +78,17 @@ protected override void OnApplyTemplate()
             SetMasterHeaderVisibility();
             OnDetailsCommandBarChanged();
             OnMasterCommandBarChanged();
+
+            if (_loaded && _stateGroup == null)
+            {
+                _stateGroup = (VisualStateGroup)GetTemplateChild(WidthStates);
+                if (_stateGroup != null)
+                {
+                    _stateGroup.CurrentStateChanged += OnVisualStateChanged;
+                    _narrowState = GetTemplateChild(NarrowState) as VisualState;
+                    UpdateView(true);
+                }
+            }
         }
 
         /// <summary>
@@ -156,11 +168,14 @@ private void OnLoaded(object sender, RoutedEventArgs e)
             }
 
             _stateGroup = (VisualStateGroup)GetTemplateChild(WidthStates);
-            _stateGroup.CurrentStateChanged += OnVisualStateChanged;
-
-            _narrowState = GetTemplateChild(NarrowState) as VisualState;
+            if (_stateGroup != null)
+            {
+                _stateGroup.CurrentStateChanged += OnVisualStateChanged;
+                _narrowState = GetTemplateChild(NarrowState) as VisualState;
+                UpdateView(true);
+            }
 
-            UpdateView(true);
+            _loaded = true;
         }
 
         private void OnUnloaded(object sender, RoutedEventArgs e)
@@ -174,6 +189,12 @@ private void OnUnloaded(object sender, RoutedEventArgs e)
                     frame.Navigating -= OnFrameNavigating;
                 }
             }
+
+            if (_stateGroup != null)
+            {
+                _stateGroup.CurrentStateChanged -= OnVisualStateChanged;
+                _stateGroup = null;
+            }
         }
 
         /// <summary>