Error: String `` is not a PID

[jingchan]

Verification succesful
Performing Incremental Install
Serving...
Unknown command: install-incremental
Performing Streamed Install
Success
Starting: Intent { act=android.intent.action.MAIN cmp=rust.openxr_test/android.app.NativeActivity }
Status: ok
LaunchState: COLD
Activity: com.oculus.shellenv/.ShellEnvActivity
TotalTime: 23
WaitTime: 24
Complete
Error: String `` is not a PID

Caused by:
    cannot parse integer from empty string

cargo apk run succeeds sometimes, but I run into this error frequently (>50% of the time). Repeatedly running the command will eventually lead to success. Appears to be a race condition where apk.start is called before the system is ready to start the app and return a PID, leading to a failure on this line: https://github.com/rust-windowing/android-ndk-rs/blob/master/cargo-apk/src/apk.rs#L251

[JohnScience]

I often faced this issue too and it's annoying.

[MarijnS95]

Ported the fix in #33.