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Fix NRE if user immediately completes Deferral #13202
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Made the deferral flow more linear and easy to follow Moved the navigation parts of Shell out to a separate class
PureWeen
added
a/shell 🐚
blocker
PureWeen
commented
Dec 19, 2020
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| public ShellNavigatingEventArgs(ShellNavigationState current, ShellNavigationState target, ShellNavigationSource source, bool canCancel) | ||
| { | ||
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| #if NETSTANDARD2_0 | ||
| _deferralFinishedTask = () => Task.CompletedTask; |
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This is the main fix. Just initializing the deferral finished task to a completed task so if no delayed task gets registered the code doesn't crash with an NRE
PureWeen
commented
Dec 19, 2020
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| namespace Xamarin.Forms | ||
| { | ||
| internal class ShellNavigationManager |
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This class is mainly a copy paste of the code that was already inside Shell
PureWeen
commented
Dec 19, 2020
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| bool accept = !navigatingArgs.NavigationDelayedOrCancelled; | ||
| if (navigatingArgs.DeferredTask != null) | ||
| accept = await navigatingArgs.DeferredTask; |
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Before this PR a deferred GotoAsync would always call GotoAsync again once the operation was completed but with these changes the same GotoAsync just continues on after the user has completed the deferral
PureWeen
commented
Dec 19, 2020
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| Func<Task> navigationTask = () => GoToAsync(navArgs.Target, navArgs.Animate, false, navArgs); | ||
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| if (Device.IsInvokeRequired) |
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If the user completes the deferral off the UI Thread
pictos
approved these changes
Dec 20, 2020
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Test failures unrelated |
rmarinho
approved these changes
Dec 23, 2020
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Description of Change
The deferral code was naively assuming there would be a delay between
GetDeferralandCompleteso the DeferralTask was never getting created.Issues Resolved
Platforms Affected
Testing Procedure
PR Checklist