Download - Develop Android/iOS app using golang

HelloMobile.goSeongJae Park <[email protected]>

This work by SeongJae Park is licensed under the Creative Commons Attribution-ShareAlike 3.0 Unported License. To

view a copy of this license, visit http://creativecommons.org/licenses/by-sa/3.0/.

http://creativecommons.org/licenses/by-sa/3.0/



This slides were presented duringGopherCon Korea 2015

(https://plus.google.com/u/0/events/c4b79ocq4k9ac11bpb5b2govkes)

https://plus.google.com/u/0/events/c4b79ocq4k9ac11bpb5b2govkes

Nice To Meet You

SeongJae Park

[email protected]

golang newbie programmer

Warning

● This speech could be useless for you○ The speaker is doing this just for fun

https://github.com/golang/mobile/raw/master/doc/caution.png

Warning

● This speech could be useless for you○ The speaker is doing this just for fun

● Don’t try this at office carelessly○ It’s an experiment yet

https://github.com/golang/mobile/raw/master/doc/caution.png

Java is Dangerous, Now

● Oracle may take Java away from Android● Swift is open source now, but...● We need alternatives

http://img.talkandroid.com/uploads/2011/10/OracleGoogle.jpg

golang: Programming Language

● For simple, reliable, and efficient software.

http://blog.golang.org/5years/gophers5th.jpg

golang: Programming Language

● For simple, reliable, and efficient software.● Could it be used for simple, reliable, efficient,

and free mobile application?

http://blog.golang.org/5years/gophers5th.jpg

Golang on Mobile

● Golang supports Android from v1.4● Golang supports iOS from v1.5

○ Though it’s still in experimental stage, there were many improvements especially in tools

● https://github.com/golang/mobile○ Repo of packages and tools for Go on Mobile

https://github.com/golang/mobile

https://github.com/golang/mobile

Goal of This Speak

● Showing how we can use golang on Mobile○ Focus on Android, rather than iOS

(Speaker has no iPhone…)○ By exploring example code

Goal of This Speak

● Showing how we can use golang on Mobile○ Focus on Android, rather than iOS

(Speaker has no iPhone…)○ By exploring example code

● We will explore code based on go1.4, go1.5○ Code based on go1.4 shows naked face of build

process■ based on go1.4: https://github.com/golang/mobile/tree/40f92f7d9f9092072ea68570fd6f5725a5cbcd6b

■ based on go1.5: https://github.com/golang/mobile/tree/25faf494e186f45f8d9704fb53a6c6c555366d20

https://github.com/golang/mobile/tree/40f92f7d9f9092072ea68570fd6f5725a5cbcd6b

https://github.com/golang/mobile/tree/25faf494e186f45f8d9704fb53a6c6c555366d20

Pre-requisites

● Basic development environment(vim, git, gcc, java, gradle, …)

http://www.theprospect.net/wp-content/uploads/2014/02/one-does-not-simply-skip-a-step.jpg



Pre-requisites


● Android SDK & NDK




Pre-requisites


● Android SDK & NDK● Golang 1.4 cross-compiled for GOOS=android

or higher versions




Pure Golang Mobile AppNO JAVA!

Main Idea: NDK

● c / c++ only apk is availableusing NativeActivity○ Golang is a compiled language, too. Why not?

http://www.android.pk/images/android-ndk.jpg



Main Idea: NDK

● c / c++ only apk is availableusing NativeActivity○ Golang is a compiled language, too. Why not?

Plan is as below:● Build golang program as .so file

○ ELF shared object● Process events(draw, touch, …) via OpenGL● Build NativeActivity apk using NDK / SDK




Example Code

https://github.com/golang/mobile/tree/40f92f7d9f9092072ea68570fd6f5725a5cbcd6b/example/basic for 1.4 based

https://github.com/golang/mobile/tree/25faf494e186f45f8d9704fb53a6c6c555366d20/example/basic for 1.5 based

https://github.com/golang/mobile/tree/40f92f7d9f9092072ea68570fd6f5725a5cbcd6b/example/basic




https://github.com/golang/mobile/tree/25faf494e186f45f8d9704fb53a6c6c555366d20/example/basic




Example Code (1.4 based)


$ tree.├── all.bash├── all.bat├── AndroidManifest.xml├── build.xml├── jni│ └── Android.mk├── main.go├── make.bash└── make.bat

1 directory, 8 files





main.go: Register Callbacks

Register callbacks from golang entrypoint(After 1.5, programming model changed a little)

func main() {

app.Run(app.Callbacks{

Start: start,

Stop: stop,

Draw: draw,

Touch: touch,

})

}

(mobile/example/basic/main.go)

main.go: Use OpenGL

func draw() {gl.ClearColor(1, 0, 0, 1)...green += 0.01if green > 1 {

green = 0}gl.Uniform4f(color, 0, green, 0, 1)...debug.DrawFPS()

}

(mobile/example/basic/main.go)

NativeActivity

NativeActivity only application doesn’t need JAVA

<application android:label="Basic" android:hasCode="false"><activity android:name="android.app.NativeActivity"

android:label="Basic"android:configChanges="orientation|keyboardHidden"><meta-data android:name="android.app.lib_name" android:value="basic" /><intent-filter>

<action android:name="android.intent.action.MAIN" /><category android:name="android.intent.category.LAUNCHER" />

</intent-filter></activity></application>

(mobile/example/basic/AndroidManifest.xml)

Build Process

Build golang code into ELF shared object for ARM

mkdir -p jni/armeabiCGO_ENABLED=1 GOOS=android GOARCH=arm GOARM=7 \

go build -ldflags="-shared" -o jni/armeabi/libbasic.so .ndk-build NDK_DEBUG=1ant debug

(mobile/example/basic/make.bash)

Build Process

Build golang code into ELF shared object for ARMNDK to add the so file




Build Process

Build golang code into ELF shared object for ARMNDK to add the so fileSDK to build apk file






gomobile command do build

$ tree.└── main.go

0 directories, 1 file







gomobile command do build$ go get golang.org/x/mobile/cmd/gomobile










$ gomobile init # install ndk if needed










$ gomobile init # install ndk if needed

$ gomobile build -target=android golang.org/x/mobile/example/basic







Pure Golang Android App

Pros: No more JAVA! Yay!!!

Cons: Should I learn OpenGL to show a cat?

Golang as a LibraryCooperate Java and Golang

Main Idea: Gives binding

Java and C language connected via JNI

Java

CJNI


Java and C language connected via JNIC language and Golang connected via cgo

Java

C GOJNI

CGO


Java and C language connected via JNIC language and Golang connected via cgoObjC(Objective C) is a super-set of C language

Java

C GOJNI

CGOObjC


Java and C language connected via JNIC language and Golang connected via cgoObjC(Objective C) is a super-set of C language

Golang supports Java/ObjC-Golang bind(Uses Cgo internally)

Java

C GOJNI

CGO

bind

ObjC

bind


https://github.com/golang/mobile/tree/40f92f7d9f9092072ea68570fd6f5725a5cbcd6b/example/libhello








$ tree.├── all.bash├── all.bat├── AndroidManifest.xml├── build.xml├── hi│ ├── go_hi│ │ └── go_hi.go│ └── hi.go├── main.go├── make.bash├── make.bat├── README└── src ├── com │ └── example │ └── hello │ └── MainActivity.java └── go └── hi └── Hi.java

8 directories, 12 files






Callee in Go

Golang code is implementing Hello() function

func Hello(name string) {fmt.Printf("Hello, %s!\n", name)

}

(mobile/example/libhello/hi/hi.go)

Caller in JAVA

Java code is calling Golang function, Hello()

protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); Go.init(getApplicationContext()); Hi.Hello("world"); }

(mobile/example/libhello/src/com/example/hello/MainActivity.java)

gobind

generate language bindings that make it possible to call Go code and pass objects from Java

$ go install golang.org/x/mobile/cmd/gobind$ gobind -lang=go github.com/libhello/hi > hi/go_hi/go_hi.go # stub$ gobind -lang=java github.com/libhello/hi > src/go/hi/Hi.java # proxy

gobind: Generated Proxy java Code

Provides wrapper function for golang calling code

public static void Hello(String name) { go.Seq _in = new go.Seq(); go.Seq _out = new go.Seq(); _in.writeUTF16(name); Seq.send(DESCRIPTOR, CALL_Hello, _in, _out); }

private static final int CALL_Hello = 1; private static final String DESCRIPTOR = "hi";

(mobile/example/libhello/src/go/hi/Hi.java)

gobind: Generated Stub go Code

Provides proxy and registering for the exported function

func proxy_Hello(out, in *seq.Buffer) {param_name := in.ReadUTF16()hi.Hello(param_name)

}

func init() {seq.Register("hi", 1, proxy_Hello)

}

(mobile/example/libhello/hi/go_hi/go_hi.go)


https://github.com/golang/mobile/tree/25faf494e186f45f8d9704fb53a6c6c555366d20/example/bind

gomobile do binding automatically

$ gomobile bind \

-target=android \golang.org/x/mobile/example/bind/hello

$ tree.├── android│ ├── README ├── ...│ └── settings.gradle├── hello│ └── hello.go└── ios ├── bind │ ├── AppDelegate.h │ ├── AppDelegate.m │ ├── Base.lproj │ │ ├── LaunchScreen.xib │ │ └── Main.storyboard │ ├── Info.plist │ ├── main.m │ ├── ViewController.h │ └── ViewController.m ├── bind.xcodeproj │ └── project.pbxproj └── README






Golang as a Library

Pros: JAVA for UI, Golang for background (Looks efficient enough)

Golang as a Library

Pros: JAVA for UI, Golang for background (Looks efficient enough)

Cons: Binding supports only subset of Go types

Inter-Process Communication

Philosophy of Unix

Main Idea: Android is a Linux

http://www.kitguru.net/wp-content/uploads/2012/03/linux-android.png

Android is a variant of Linux system with ARMx86 Androids exist, though...




Go supports ARM & Linux Officiallywith static-linking




Go supports ARM & Linux Officiallywith static-linking

Remember the philosophy of Unix

Not tested for iOS

Example Code

https://github.com/sjp38/goOnAndroidhttps://github.com/sjp38/goOnAndroidFA

https://github.com/sjp38/goOnAndroid


https://github.com/sjp38/goOnAndroidFA


Example Code

https://github.com/sjp38/goOnAndroidhttps://github.com/sjp38/goOnAndroidFA

Were demonstrated as live-coding from GDG Korea DevFair 2014 (http://devfair2014.gdg.kr/) and GDG Golang Seoul Meetup 2015 (https://developers.google.com/events/5381849181323264/)





http://devfair2014.gdg.kr/



https://developers.google.com/events/5381849181323264/




Golang Process on Android: Plan

1. Cross compile Go program as ARM / Linux


1. Cross compile Go program as ARM / Linux2. Include the binary in assets/ of Android app


1. Cross compile Go program as ARM / Linux2. Include the binary in assets/ of Android app3. Copy the binary in private space of the app


1. Cross compile Go program as ARM / Linux2. Include the binary in assets/ of Android app3. Copy the binary in private space of the app4. Give execute permission to the binary

/data/data/com.example.goRunner/files # ls -al-rwxrwxrwx u0_a55 u0_a55 4512840 2014-11-28 17:45 gobin


1. Cross compile Go program as ARM / Linux2. Include the binary in assets/ of Android app3. Copy the binary in private space of the app4. Give execute permission to the binary5. Execute it

/data/data/com.example.goRunner/files # ls -al-rwxrwxrwx u0_a55 u0_a55 4512840 2014-11-28 17:45 gobin

Go bin Loading

Load golang program from assets to private dir

private void copyGoBinary() { String dstFile = getBaseContext().getFilesDir().getAbsolutePath() + "/verChecker.bin"; try { InputStream is = getAssets().open("go.bin"); FileOutputStream fos = getBaseContext().openFileOutput( "verChecker.bin", MODE_PRIVATE); byte[] buf = new byte[8192]; int offset; while ((offset = is.read(buf)) > 0) { fos.write(buf, 0, offset); } Runtime.getRuntime().exec("chmod 0777 " + dstFile); } catch (IOException e) { } }

Execute Go process

Spawn new process for the program and communicates using stdio

ProcessBuilder pb = new ProcessBuilder(); pb.command(goBinPath()); pb.redirectErrorStream(false); goProcess = pb.start(); new CopyToAndroidLogThread("stderr",

goProcess.getErrorStream()) .start();

Inter Process Communication

Pros: Just normal unix way


Pros: Just normal unix way Golang team is using this for Camlistore (https://github.com/camlistore/camlistore)

https://github.com/camlistore/camlistore


Pros: Just normal unix way Golang team is using this for Camlistore (https://github.com/camlistore/camlistore)

Cons: Hacky, a little x/mobile is comfortable enough, now Not sure whether it works on iOS

https://github.com/camlistore/camlistore

Summary

● Go can run on Mobile○ As a native application,○ as a library,○ or, as a process

● Though it’s an experiment yet, it’s fairly comfortable