Setup android manifest for VR

[agrande]

As documented here:
https://developer.oculus.com/documentation/native/android/mobile-native-manifest/

Using the syntax of cargo-apk 0.7
https://crates.io/crates/cargo-apk

This fixes a few lifecyle issues. In particular, the app can be launched again through the oculus menu.

[blaind]

Thank you for the pull request! This is great work, and hopefully fixes #3.

One question though, did you get the Quest 2 example running with cargo-apk 0.7 cargo version, or did you patch it based on the version referred in this repo, or other way? Needed for the Oculus loader .so to be added into the .apk. I see that rust-mobile/ndk#138 is still open.

[agrande]

I got it running with the version from the PR linked above (rust-mobile/ndk#138), which is based on 0.7.

I believe it's a different version from the cargo-apk version you used. I have additional local changes to make it work (i.e. libs/aarch64-linux-android => runtime_libs/arm64-v8a and modified build.rs accordingly).

[agrande]

I think it partially fixes #3. Seems to work in most cases, but I ran into some situations where it still wouldn't seem to load properly after navigation.
Also, it seems to keep rendering frames even if the app is in the background.

[blaind]

Allright, I'll have a look into android-ndk-rs and create a patched version based on 0.7.

Regarding frame loop, in current version the bevy systems actually run even if the app is in the background, but wgpu render should not occur:

How it works currently:

• xr detects openxr events at https://github.com/blaind/bevy_openxr/blob/main/crates/bevy_openxr_core/src/lib.rs#L116
• the state is pushed into WgpuRenderState
• app runner is triggered per frame https://github.com/blaind/bevy_openxr/blob/main/crates/bevy_openxr_core/src/runner.rs#L11
• wgpu render pass is done based on the state (https://github.com/blaind/bevy/blob/bevy_openxr/crates/bevy_wgpu/src/wgpu_renderer.rs#L145)

I guess eventually the runner should detect the state, and if not in running state, the runner should poll XR for state changes.

[agrande]

Allright, I'll have a look into android-ndk-rs and create a patched version based on 0.7.

Regarding this, I could also clean up my local changes and push them in this PR if you want.

[blaind]

No worries, I got it working by merging https://github.com/blaind/android-ndk-rs with the latest upstream master. Also had to a small fix to get hand tracking working again: e1dc316

Tested also with Quest2, lifecycle is remarkably better now. However, there's still the process::exit() which Oculus seem to complain about the app crashing. Also, it doesn't really do proper cleanup of openxr resources in that way.

https://github.com/blaind/bevy_openxr/blob/main/crates/bevy_openxr_core/src/lib.rs#L135

Tried removing the exit, but it seems that for some reason Oculus still tries to launch the main activity multiple times. Commenting out https://github.com/blaind/xrbevy/blob/main/examples/xr_apk_scene.rs#L7 did not help, though.