// State is global application-specific state.
// ...
// State is not valid until Run has been called.
var State interface{}

2015-02-27 14:38 GMT-05:00 Burcu Dogan notifications@github.com:

My Android application panics with the following error message, if I try
to access app.State from a package's init.

E/Go (18104): panic: interface conversion: interface is nil, not interface { AndroidContext() unsafe.Pointer; JavaVM() unsafe.Pointer }
E/Go (18104): goroutine 1 [running]:
E/Go (18104): golang.org/x/mobile/audio/al.init·1()
E/Go http://golang.org/x/mobile/audio/al.init%C2%B71()%0AE/Go (18104): /Users/jbd/src/golang.org/x/mobile/audio/al/al_android.go:245 +0x50
E/Go (18104): golang.org/x/mobile/audio/al.init()
E/Go http://golang.org/x/mobile/audio/al.init()E/Go (18104): golang.org/x/mobile/audio/al/_obj/_cgo_import.go:1 +0x3ac
E/Go (18104): main.init()
E/Go (18104): /Users/jbd/src/golang.org/x/mobile/example/basic/main.go:119 +0x70
E/Go (18104): goroutine 17 [syscall, locked to thread]:
E/Go (18104): runtime.goexit()
E/Go (18104): /Users/jbd/pkg/gomobile/android-ndk-r10d/gomobile-init-619773321/go/src/runtime/asm_arm.s:1347 +0x4
E/Go (18104): goroutine 4 [runnable]:
E/Go (18104): golang.org/x/mobile/app.lineLog(0x93c081d0, 0x6)
E/Go (18104): /Users/jbd/src/golang.org/x/mobile/app/stdio_android.go:41
E/Go http://golang.org/x/mobile/app/stdio_android.go:41E/Go (18104): created by golang.org/x/mobile/app.init·1
E/Go http://golang.org/x/mobile/app.init%C2%B71%0AE/Go (18104): /Users/jbd/src/golang.org/x/mobile/app/stdio_android.go:69 +0x108
E/Go (18104): goroutine 5 [runnable]:
E/Go (18104): golang.org/x/mobile/app.lineLog(0x93c081e0, 0x4)
E/Go (18104): /Users/jbd/src/golang.org/x/mobile/app/stdio_android.go:41
E/Go http://golang.org/x/mobile/app/stdio_android.go:41E/Go (18104): created by golang.org/x/mobile/app.init·1
E/Go http://golang.org/x/mobile/app.init%C2%B71%0AE/Go (18104): /Users/jbd/src/golang.org/x/mobile/app/stdio_android.go:76 +0x194

The package causes the panic does the following:

func init() {
state := app.State.(interface {
JavaVM() unsafe.Pointer
AndroidContext() unsafe.Pointer
})
// ...
}

—
Reply to this email directly or view it on GitHub
#10031.

__

But we know about the current VM and the application context on JNI_Onload. We don't have to wait for app.Run to set the State.

We do in Java. I intended State to eventually provide access to some equivalent context on the iOS side, where the initialization order is reversed: Go is the entry point, init runs, then main starts and it is not until app.Run that we initialize UIKit.

The other less important but relevant thought I had on this is packages should work hard to minimize the init work they do in apps. Apps should start fast. I suspect initialization of almost all packages (including audio) should go into an internal sync.Once on first use.

We can keep documenting that the State will be available after app.Run but can set the State resolver earlier and use these values internally if the init is fast enough and not affecting the startup performance. It is an internal implementation detail. If you fear that it will be abused by the users, I'm fine with doing to a sync.Once for the initialization of the audio package.

In favor of accessing app.State after Run is invoked, I am closing the issue.