Android NDK: Entrando no Mundo Nativo

Intel Developers Relations Division

android ndk: Entrando no mundo nativoEduardo CarraraDeveloper Evangelist – Intel

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Intel Developers Relations Division 2

Agenda

O Android NDK

Será que você o usa e não sabe?

Cuidados com a Interface Binária

Começando com o Android Studio + gradle-experimental

Perguntas?


Android ndkO Native Development Kit


"O Android NDK é um conjunto de ferramentas que

permitem implementar partes de sua aplicação utilizando

linguagens de código nativas como C e C++."

- NDK Android Developers Portal

http://developer.android.com/intl/pt-br/ndk/index.html


e talvez você já esteja fazendo isso...

... vamos explorar alguns usos interessantes do NDK.


Aplicações do NDKO que podemos fazer com ele!?


Game Engines

Outras+…

*Other names and brands may be claimed as the property of others.


Visão Computacional

• Filtros lineares e não lineares de imagens.

• Tranformações Geométricas de imagens.

• Estimativa de Movimentos em videos.

• Subtração de Fundo em videos.

• Rastreamento de objetos.

• ...

Outras: Cardboard-SDK, Vuforia, Layar, LibCCV, Wikitude ...

OpenCV.org


http://opencv.org/


Desenvolvimento Cross Platform



Outros usos e Bibliotecas

Realm

Swift

Libpng

Intel TBB

Intel IPP

Libcairo and libpixman

Libsonic

Busybox

Speex

FFMpeg

OpenSSL

Lua

...



Tantas aplicações bacanas!

Então podemos utilizar o

NDK para TUDO?!


Entendendo o ndk


Fonte: Using the NDK Performantly (Big Android BBQ 2015)

15

Visão Geral da Arquitetura

App Code

Classes do Framework

Runtime

Bibliotecas do Sistema

Kernel Linux

JNI

Suas Bibliotecas

ABI Estável

https://www.youtube.com/watch?v=Wb5HAI73QRE


Na Prática...

Microchip Icon – Icon Finder.

App00100111000011100111

x86

ARM

MIPS

O seu código:

• Mais próximo do HW

• Dependente de Plataforma

Você deve se preocupar com isso!

https://www.iconfinder.com/icons/17978/memory_microchip_processor_ram_icon


Raio-X do seu APK com NDK


3 Regras de Ouro para adoção do NDK

1

2

3 Código legado que deve ser reaproveitado e muito caro para portar.

Problemas Específicos de performance.

Funcionalidades e Experiências que exigem performance.


3 (Principais) Barreiras para adoção do NDK

1

2

3 Ganhos de Performance não são garantidos.

Complexidade de Implementação e Manutenção.

Dependência de Plataforma e Compatibilidade.


Podemos, mas não devemos usar o NDK para tudo.

Logo ...

Ainda interessado?

Tome a “pílula vermelha” e vamos te mostrar o quão

longe isso vai...


Utilizando o ndk


Conceitos Fundamentais: Java Native Interface (JNI)

Define como o Java e o código nativo irão conversar.

Java C / C++

• Carregar a lib com:

• System.loadLibrary()

• Definição de Métodos Nativos:

• Palavra reservada native

• Incluir o header do JNI:• #include <jni.h>

• Utilizar tipos específicos do JNI:• jstring, jint, jboolean, etc.

• Variáveis Especiais:• JNIEnv*, JavaVM*


JNI: Mapeamento de Métodos Java -> C / C++

A Função no C / C++ deve:

Usar e retornar primitivas e objetos Java JNI:

Seguir o padrão de nomenclatura:

Ou ser regitrada manualmente:

jint xxx(JNIEnv* env, jobject instance, ...) { ... }

Java_com_example_hellojni_HelloWorldJni_method

JNIEnv->RegisterNatives();


JNI: Exemplo

Java

C / C++

public class HelloWorldJNI {

static {

System.loadLibrary("hello-jni");

}

public native String getHelloWorldStringFromJNI();

}

#include <jni.h>

jstring

Java_com_example_hellojni_HelloWorldJNI_getHelloWorldStringFromJNI(JNIEnv *env, jobject instance) {

return (*env)->NewStringUTF(env, "Hello World!");

}


Old but Gold

Compilando Apps NDK no estilo clássico.J

NI

Co

de

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

LOCAL_MODULE := hello-jni

LOCAL_SRC_FILES := hello-jni.c

include $(BUILD_SHARED_LIBRARY)

APP_ABI := all

jni/Android.mk jni/Application.mk


Old but Gold

ndk_build script

Compilando Apps NDK no estilo clássico.


Old but Gold

Empacotando Apps NDK no estilo“quase” clássico.

• Adicione as libs no diretório jniLibs.

• Crie as interfaces java – jni.

• Para pre-builts é só isso.

• Para compilar a partir do source é um pouco mais complicado mas possível.


Limitações

• Debug não é possível no AS. Necessário o uso do ndk-gdb e/ou Eclipse.

• Suporte do plugin do gradle atual foi marcado como deprecated (ouch).


... então para onde vamos?


Android studio + ndk + gradle-experimental


Avisos Importantes

• Utilizaremos a versão experimental do android gradle plugin.

• Integração com Android Studio melhorou mas ainda é instável e possui bugs.

• No Windows há problemas com o editor e/ou build que dificultam/impedem o uso. (Issues 195483 e 204552).

• A documentação é praticamente inexistente ou incompleta.

https://code.google.com/p/android/issues/detail?id=195483

https://code.google.com/p/android/issues/detail?id=204552


Integração com AS

Instalação e

configuração do

NDK integrados ao

android studio.


Integração com AS


gradle-experimental

Configuração

distributionUrl=https\://services

.gradle.org/distributions/gradle-

2.10-all.zip

./build.gradle ./gradle/gradle-wrapper/gradle-wrapper.properties

dependencies {

classpath

'com.android.tools.build:gradle-

experimental:0.7.0'

}


gradle-experimental

Configuração: Combinação de Versões

Android Studio 1.5 2.0 2.1

gradle 2.8 2.10 2.10

gradle plugin 1.5.0 2.0.0 2.1.0

gradle-experimental plugin 0.4.0 0.6.0 0.7.0


gradle-experimental

Configuração: build.gradle

mudanças na DSL.

Sempre verifique:

- NDK Samples

- gradle-experimental docs

apply plugin: 'com.android.model.application'

model {

}

android {

compileSdkVersion = 23

buildToolsVersion = "23.0.3"

defaultConfig.with {

applicationId = "com.example.hellojni"

minSdkVersion.apiLevel = 4

targetSdkVersion.apiLevel = 23

}

}

android.ndk {

moduleName = "hello-jni"

}

android.buildTypes {

release {

minifyEnabled = false

proguardFiles.add(file('proguard-rules.txt'))

}

}

https://github.com/googlesamples/android-ndk

http://tools.android.com/tech-docs/new-build-system/gradle-experimental


gradle-experimental

Configuração: múltiplos apks.


model {

}

android.productFlavors {

}

// … standard gradle stuff

// … other gradle stuff

create ("armv7") {

}

create (“x86") {

}

ndk.abiFilters.add("armeabi-v7a")

ndk.abiFilters.add(“x86")

versionCode = calculateVersionCodeFor(

"armeabi-v7a")

versionCode = calculateVersionCodeFor(

“x86")

create (“fat")


gradle-experimental

Configuração: múltiplos apks.


model {

}

def actualVersionCode = 13;

// … gradle stuff

// … other gradle stuff

def baseVersionCode = 1000000;

def versionCodeABIPrefixes = [

'armeabi':1, 'armeabi-v7a':2, 'arm64-v8a':3,

'mips': 5,'mips64': 6,

'x86': 8, 'x86_64': 9];

def calculateVersionCodeFor = { String abi ->

return versionCodeABIPrefixes.get(abi, 0) *

baseVersionCode + actualVersionCode

}


gradle-experimental

• Ainda é possível:

• Configurar bibliotecas pré-compiladas;

• Adicionar flags de compilação (gerais e por flavor);

• A documentação atual geralmente não acompanha os releases, portanto:

• Fique de olho nos NDK Samples para referências!



Pensamentos Finais

Ao usar NDK, direta ou indiretamente, adicione suporte a maior quantidade possível de plataformas.

Use o NDK sabiamente: teste, faça benchmarks e garanta que ele é a solução adequada ao seu problema.

Acompanhe e teste o plugin experimental do gradle para NDK!


Perguntas?


referências


Referências

• NDK Development on Intel

• Intel Tools

• Android* NDK Official Documentation

• Android* NDK Gradle Experimental Documentation

• Android* NDK Google* Samples

• Gradle Stable NDK Support - Xavier Hallade

• New Android Studio NDK Support - Xavier Hallade

https://software.intel.com/en-us/android/articles/ndk-android-application-porting-methodologies

https://software.intel.com/en-us/android/tools

http://developer.android.com/tools/sdk/ndk/index.html

http://tools.android.com/tech-docs/new-build-system/gradle-experimental


http://ph0b.com/android-studio-gradle-and-ndk-integration/

http://ph0b.com/new-android-studio-ndk-support/


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Android NDK: Entrando no Mundo Nativo

Technology

Transcript of Android NDK: Entrando no Mundo Nativo