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HelloMobile.goSeongJae Park <sj38.park@gmail.com>
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/.
This slides were presented duringGopherCon Korea 2015
(https://plus.google.com/u/0/events/c4b79ocq4k9ac11bpb5b2govkes)
Nice To Meet You
SeongJae Park
sj38.park@gmail.com
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
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
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
● Basic development environment(vim, git, gcc, java, gradle, …)
● Android SDK & NDK
http://www.theprospect.net/wp-content/uploads/2014/02/one-does-not-simply-skip-a-step.jpg
Pre-requisites
● Basic development environment(vim, git, gcc, java, gradle, …)
● Android SDK & NDK● Golang 1.4 cross-compiled for GOOS=android
or higher versions
http://www.theprospect.net/wp-content/uploads/2014/02/one-does-not-simply-skip-a-step.jpg
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
http://www.android.pk/images/android-ndk.jpg
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
Example Code (1.4 based)
https://github.com/golang/mobile/tree/40f92f7d9f9092072ea68570fd6f5725a5cbcd6b/example/basic
$ 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)
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)
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
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 fileSDK to build apk file
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)
Example Code (1.5 based)
https://github.com/golang/mobile/tree/25faf494e186f45f8d9704fb53a6c6c555366d20/example/basic
gomobile command do build
$ tree.└── main.go
0 directories, 1 file
Example Code (1.5 based)
https://github.com/golang/mobile/tree/25faf494e186f45f8d9704fb53a6c6c555366d20/example/basic
gomobile command do build$ go get golang.org/x/mobile/cmd/gomobile
$ tree.└── main.go
0 directories, 1 file
Example Code (1.5 based)
https://github.com/golang/mobile/tree/25faf494e186f45f8d9704fb53a6c6c555366d20/example/basic
gomobile command do build$ go get golang.org/x/mobile/cmd/gomobile
$ gomobile init # install ndk if needed
$ tree.└── main.go
0 directories, 1 file
Example Code (1.5 based)
https://github.com/golang/mobile/tree/25faf494e186f45f8d9704fb53a6c6c555366d20/example/basic
gomobile command do build$ go get golang.org/x/mobile/cmd/gomobile
$ gomobile init # install ndk if needed
$ gomobile build -target=android golang.org/x/mobile/example/basic
$ tree.└── main.go
0 directories, 1 file
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
Main Idea: Gives binding
Java and C language connected via JNIC language and Golang connected via cgo
Java
C GOJNI
CGO
Main Idea: Gives binding
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
Main Idea: Gives binding
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
Example Code (1.4 based)
https://github.com/golang/mobile/tree/40f92f7d9f9092072ea68570fd6f5725a5cbcd6b/example/libhello
Example Code (1.4 based)
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)
Example Code (1.5 based)
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...
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
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
Remember the philosophy of Unix
Not tested for iOS
Example Code
https://github.com/sjp38/goOnAndroidhttps://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/)
Golang Process on Android: Plan
1. Cross compile Go program as ARM / Linux
Golang Process on Android: Plan
1. Cross compile Go program as ARM / Linux2. Include the binary in assets/ of Android app
Golang Process on Android: Plan
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
Golang Process on Android: Plan
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
Golang Process on Android: Plan
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
Inter Process Communication
Pros: Just normal unix way Golang team is using this for Camlistore (https://github.com/camlistore/camlistore)
Inter Process Communication
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
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
Recommended