Add extension function to retrieve a Flow of NavBackStackEntries #89
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| .withIndex() | ||
| .onEach { (index, backStackEntry) -> | ||
| val expectedDestination = index + 1 | ||
| assertEquals(expectedDestination, backStackEntry.destination.id) |
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Please use Truth asserts (note, we already have an androidTest dependency on Truth) over Junit asserts here:
assertThat(backStackEntry.destination.idt).isEqualTo(expectedDestination)
Or preferably use the assertWithMessage() version that includes a more detailed message that is printed when the assert fails.
| @Suppress("EXPERIMENTAL_API_USAGE") | ||
| public fun NavController.getBackStackEntryFlow(): Flow<NavBackStackEntry> = callbackFlow { | ||
| val listener = NavController.OnDestinationChangedListener { controller, _, _ -> | ||
| controller.currentBackStackEntry?.let(::sendBlocking) |
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would it be better to use second argument instead? given that it is non null it will make things as easy as sendBlocking(destination)
another corner case question: sendBlocking can theoretically block on the main thread, when there is slow consumer and a lot of actions here. Though it seems like fairly theoretical concern
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Would be possible, but then it would be a Flow<NavDestination> instead of a Flow<NavBackStackEntry>, which is not what we want I guess (as NavBackStackEntry is the class that gives access to things like ViewModelStore and the SavedStateRegistry). But maybe it would make sense to have both, a backStackEntryFlow and a destinationFlow?
Valid point, I also wasn't sure what's best to use here. The other option would be to use offer, which could lead to lost items it the consumer is slow.
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We are specifically looking for the NavBackStackEntry here, not NavDestination.
| * it changes. If there is no active [NavBackStackEntry], no item will be emitted. | ||
| */ | ||
| @Suppress("EXPERIMENTAL_API_USAGE") | ||
| public fun NavController.getBackStackEntryFlow(): Flow<NavBackStackEntry> = callbackFlow { |
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I'd probably suggest to shape it as extension property:
public val NavController.backStackEntryFlow : ....
| * Creates and returns a [Flow] that will emit the currently active [NavBackStackEntry] whenever | ||
| * it changes. If there is no active [NavBackStackEntry], no item will be emitted. | ||
| */ | ||
| @Suppress("EXPERIMENTAL_API_USAGE") |
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I think it should be marked as experimental api. We won't be able to release it as stable until callbackFlow will be stable (androidx gives binary compatibility guarantees that could be broken by callbackFlow)
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Just to make sure I understand correctly - since it is part of the public API @ExperimentalCoroutinesApi is required. If it were an internal function, @Suppress would be fine (as it does not cause binary incompatible changes), correct?
| @Suppress("EXPERIMENTAL_API_USAGE") | ||
| public fun NavController.getBackStackEntryFlow(): Flow<NavBackStackEntry> = callbackFlow { | ||
| @ExperimentalCoroutinesApi | ||
| public val NavController.backStackEntryFlow: Flow<NavBackStackEntry> get() = callbackFlow { |
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Could we change this to NavController.currentBackStackEntryFlow to be consistent with NavController.currentBackStackEntry API?
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Good point, done 👍
| @Suppress("EXPERIMENTAL_API_USAGE") | ||
| public fun NavController.getBackStackEntryFlow(): Flow<NavBackStackEntry> = callbackFlow { | ||
| val listener = NavController.OnDestinationChangedListener { controller, _, _ -> | ||
| controller.currentBackStackEntry?.let(::sendBlocking) |
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We are specifically looking for the NavBackStackEntry here, not NavDestination.
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CI is red, but looks unrelated - was this a build flake? Can I retrigger somehow? |
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Hey the build was just fixed! Sorry it took a few days to get it landed - could you try rebasing your change on top of androidx-master-dev and see if the tests pass now? |
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Rebasing fixed the issue 👍 |
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Thanks again for implementing this! It'll become available in Navigation 2.4.0-alpha01. |
Proposed Changes
NavBackStackEntryas aFlow.Testing
Test: Added a test for the new function
Issues Fixed
Fixes: 163947280