Android NDK: Entrando no Mundo Nativo

Intel Developers Relations Division
androidndk:Entrandonomundonativo
Eduardo Carrara
Developer Evangelist – Intel
@DuCarrara
+EduardoCarraraDeAraujo

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?

Androidndk
O 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

e talvez você já esteja fazendo isso...
... vamos explorar alguns usos interessantes do NDK.

AplicaçõesdoNDK
O 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

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?!

Entendendoondk

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

Na Prática...
Microchip Icon – Icon Finder.
App
0010011100
0011100111
x86
ARM
MIPS
O seu código:
• Mais próximo do HW
• Dependente de Plataforma
Você deve se preocupar
com isso!

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...

Utilizandoondk

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.
JNICode
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?

Androidstudio+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.

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'))
}
}

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

obrigado

Legal Notices and Disclaimers
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parties are not authorized by Intel to use code names in advertising, promotion or marketing of any product or services and any such use of Intel's internal code names is at the sole risk
of the user.
 Software and workloads used in performance tests may have been optimized for performance only on Intel microprocessors. Performance tests, such as SYSmark and MobileMark, are
measured using specific computer systems, components, software, operations and functions. Any change to any of those factors may cause the results to vary. You should consult other
information and performance tests to assist you in fully evaluating your contemplated purchases, including the performance of that product when combined with other products. For
more information go to http://www.intel.com/performance
 Intel, Intel Inside, the Intel logo, Centrino, Centrino Inside, Intel Core, Intel Atom and Pentium are trademarks of Intel Corporation in the United States and other countries.
 Material in this presentation is intended as product positioning and not approved end user messaging.
 This document contains information on products in the design phase of development.
 *Other names and brands may be claimed as the property of others.
Copyright © 2016 Intel Corporation.

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certain capabilities may be limited over a host OS-based VPN or when connecting wirelessly, on battery power, sleeping, hibernating or powered off. Setup requires
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Legal Notices and Disclaimers, cont.

Android NDK: Entrando no Mundo Nativo

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