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Refactor Entry ClearButton observer lifecycle to prevent NRE on older iOS versions #14828

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Nov 8, 2021
Merged

Refactor Entry ClearButton observer lifecycle to prevent NRE on older iOS versions #14828

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21 changes: 12 additions & 9 deletions Xamarin.Forms.Platform.iOS/Renderers/EntryRenderer.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -40,6 +40,7 @@ public abstract class EntryRendererBase<TControl> : ViewRenderer<Entry, TControl

bool _disposed;
IDisposable _selectedTextRangeObserver;
IDisposable _clearButtonSublayerObserver;
bool _nativeSelectionIsUpdating;

bool _cursorPositionChangePending;
Expand Down Expand Up @@ -92,8 +93,7 @@ protected override void Dispose(bool disposing)
Control.EditingDidEnd -= OnEditingEnded;
Control.ShouldChangeCharacters -= ShouldChangeCharacters;
_selectedTextRangeObserver?.Dispose();

ClearButton?.Layer?.RemoveObserver(this, new NSString("sublayers"));
_clearButtonSublayerObserver?.Dispose();
}
}

Expand Down Expand Up @@ -128,7 +128,7 @@ protected override void OnElementChanged(ElementChangedEventArgs<Entry> e)
textField.ShouldChangeCharacters += ShouldChangeCharacters;
_selectedTextRangeObserver = textField.AddObserver("selectedTextRange", NSKeyValueObservingOptions.New, UpdateCursorFromControl);

ClearButton?.Layer.AddObserver(this, new NSString("sublayers"), NSKeyValueObservingOptions.New, IntPtr.Zero);
_clearButtonSublayerObserver = ClearButton?.Layer.AddObserver(new NSString("sublayers"), NSKeyValueObservingOptions.New, UpdateClearButtonSublayer);
}

// When we set the control text, it triggers the UpdateCursorFromControl event, which updates CursorPosition and SelectionLength;
Expand Down Expand Up @@ -160,12 +160,6 @@ protected override void OnElementChanged(ElementChangedEventArgs<Entry> e)
UpdateClearButtonVisibility();
}

public override void ObserveValue(NSString keyPath, NSObject ofObject, NSDictionary change, IntPtr context)
{
if (keyPath == new NSString("sublayers") && _defaultClearImage == null)
UpdateClearButtonVisibility();
}

protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e)
{
if (e.PropertyName == Entry.PlaceholderProperty.PropertyName || e.PropertyName == Entry.PlaceholderColorProperty.PropertyName)
Expand Down Expand Up @@ -440,6 +434,15 @@ void UpdateCursorFromControl(NSObservedChange obj)
}
}

void UpdateClearButtonSublayer(NSObservedChange obj)
{
if (Control == null || Element == null)
return;

if (_defaultClearImage == null)
UpdateClearButtonVisibility();
}

void UpdateCursorSelection()
{
if (_nativeSelectionIsUpdating || Control == null || Element == null)
Expand Down