Add a way to exit/minimize the app on Android when back is pressed #5044
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This changes the default behaviour to exit/minimize the app when pressing back.
osu.Framework/Platform/GameHost.cs
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| /// If <c>true</c>, pressing back will return to the home screen (putting the app in background and suspending it). | ||
| /// If <c>false</c>, the back button will be treated as <see cref="InputKey.Escape"/>. | ||
| /// </remarks> | ||
| public readonly AggregateBindable<bool> AllowExitingAndroid = new AggregateBindable<bool>((a, b) => a & b, new Bindable<bool>(true)); |
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Might be better to rename to AllowSuspendingAndroid (AllowSuspendToBackground without the android suffix maybe?) as it isn't really an exit operation. Not 100% on having android specific variables in here, but I guess it'll have to do for now.
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Just checked and the Android docs seem to call it "stopping the activity" and "moving to background". So AllowSuspendToBackground could work. Maybe there's a better name that would encompass the "when back is pressed" part of this.
How about AllowNativeBackNavigation?
osu.Framework/Platform/GameHost.cs
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| if (!CanSuspendToBackground) | ||
| throw new InvalidOperationException($"Tried to call {nameof(SuspendToBackground)}() on a host that doesn't support it (see {nameof(CanSuspendToBackground)})."); |
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This throw is a bit strange because you can bypass it entirely by overriding SuspendToBackground() and just not calling base. Note that Exit() does not have the same issue because that one's not virtual.
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Agree that this shouldn't throw. If anything having a success return value would be best.
| /// <remarks> | ||
| /// This and <see cref="SuspendToBackground"/> are an alternative way to exit on hosts that have <see cref="CanExit"/> <c>false</c>. | ||
| /// </remarks> | ||
| public virtual bool CanSuspendToBackground => false; |
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Dunno how to feel about this - is there any chance that android could just use the exit flow rather than invent a new one? I'm not sure much value is added upon having them both upon seeing the implementation.
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In the context of the osu!-side changes, having it be merged into Exit() seems wrong, as it's not really exiting. It also has different UX implications, and you can't treat Android's "exit" as a desktop exit. Eg. osu! exits all game screens, and only then exits the host, which absolutely does not work with Android.
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One thing to note is that we may be able to use this behaviour on desktop for the "hide to tray" functionality (aka "boss key") when we get to adding that back. Although minimise may be a closer mapping for the suspend action on desktop.
osu.Framework/Platform/GameHost.cs
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| if (!CanSuspendToBackground) | ||
| throw new InvalidOperationException($"Tried to call {nameof(SuspendToBackground)}() on a host that doesn't support it (see {nameof(CanSuspendToBackground)})."); |
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Agree that this shouldn't throw. If anything having a success return value would be best.
Relevant: ppy/osu#16899.
This should live at framework, as it's useful for any app that wants to follow Android best practices for the back button.
MoveTaskToBack()available since API 1. Calling this will put the activity in the background and return to the last app (eg. the home screen if the game was opened from there, or the file manager if osu! was opened from beatmap import).Tested on:
Breaking changes
Pressing the back key on Android will now exit/minimize the app and return to home screen.
To restore the old behaviour of treating the back key as
InputKey.Escape, add your own bindable toGameHost.AllowExitingAndroidand set it tofalse.To be in line with mobile UX, your app should allow exiting when it's on the initial screen (eg. when backing out is no longer possible / when backing out would close the app on desktop platforms).