Develop Reference

Does Android Wear support C++ (JNI) in Android Studio?

I cannot get an Android Wear project to use C++. I am able to get a "Phone and Tablet" project to use C++. Here is what I have done.
Here is an image of the SDK Tools I have installed. I also have SDK API Levels 24-27 installed.
I create a new project. I check "Include C++ support". I check "Wear" (API 26: Android 8.0 (Oreo)). I select "Next" a bunch.
For C++ Standard I have tried all three (Toolchain Default, C++11, c++14).
I do not check -fexceptions or -frtti.
In the project that is created under the "mobile" Module, I have a "cpp" folder, but I do not have one under the "wear" Module.
If I create a project without "Phone and Tablet" support ("mobile" Module), then I still do not get a "cpp" folder under the "wear" Module.
I tried forcing the project to use C++ under the "wear" Module. Here is what I did.
I modified build.gradle (Module: wear) to look like this
apply plugin: 'com.android.application'
android {
compileSdkVersion 26
defaultConfig {
applicationId "com.example.xorgaming.watchtestcpp"
minSdkVersion 25
targetSdkVersion 26
versionCode 1
versionName "1.0"
testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
externalNativeBuild {
cmake {
cppFlags "-std=c++11"
}
}
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
}
}
externalNativeBuild {
cmake {
path "CMakeLists.txt"
}
}
}
dependencies {
implementation fileTree(dir: 'libs', include: ['*.jar'])
implementation 'com.google.android.support:wearable:2.2.0'
implementation 'com.google.android.gms:play-services-wearable:11.8.0'
implementation 'com.android.support:percent:26.1.0'
implementation 'com.android.support:support-v4:26.1.0'
implementation 'com.android.support:recyclerview-v7:26.1.0'
implementation 'com.android.support:wear:26.1.0'
compileOnly 'com.google.android.wearable:wearable:2.2.0'
}
I restart the project which makes a "cpp" folder under the "wear" module.
I create a native-lib.cpp file in the "cpp" folder. It looks like this:
extern "C"
JNIEXPORT jstring JNICALL Java_com_example_xorgaming_watchtestcpp_MainActivity_stringFromJNIWatch(
JNIEnv *env, jobject /* this */)
{
std::string hello = "Hello from C++ WATCH!";
return env->NewStringUTF(hello.c_str());
}
In my java onCreate() function, I call: stringFromJNIWatch().
Everything builds without error (green hammer)
When I run the project (as a wearable device) I get this error:
No implementation found for java.lang.String com.example.xorgaming.watchtestcpp.MainActivity.stringFromJNIWatch()
Any idea what I'm doing wrong? Does Android Wear support C++?

Things have changed quite a bit since this question was posted. But half of the answer is: Yes, you can use C++ and Java together with Wear OS. You can follow the same instructions for Android applications.
As for why this failed, my suggestion would be double-check the paths. If you follow the instructions here you will note that the cpp directory goes in the same directory with the java directory. Typically something like MyApplication/app/src/main will have a java directory and a cpp directory. That helps everything get wrapped up into the eventual .apk

Debugging C++/native library modules not working with Android Studio (Cmake used)

I'm having trouble debugging C++ files of my library module.
Is this possible in general?
The debugging works fine if the application project contains the c++ code.
But I want to move the C++ Code to a library module.
The Error Message while starting the session:
Now Launching Native Debug Session
Attention! No symbol directories found - please check your native debug configuration
gradle file of my lib:
apply plugin: 'com.android.library'
android {
compileSdkVersion 24
buildToolsVersion "25.0.2"
defaultConfig {
minSdkVersion 16
targetSdkVersion 21
versionCode 1
versionName "1.0"
externalNativeBuild {
cmake {
arguments "-DANDROID_PLATFORM_LEVEL=${11}",
'-DANDROID_TOOLCHAIN=clang', '-DANDROID_STL=gnustl_static'
}
}
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
}
}
externalNativeBuild {
cmake {
path "CMakeLists.txt"
}
}
}
dependencies {
compile fileTree(dir: 'libs', include: ['*.jar'])
compile 'com.android.support:support-annotations:24.2.0'
}
In the run configuration the debugger is set to auto
Additions:
Im using:
Gradle : 2.2.3
Android Studio : 2.2.3
in the LLLB Console, i checked the breakpoint List with:
breakpoint list -v
all my checkpoints are listed there.
Not Working Breakpoint
1: file = 'C:\android-dev\...\test.cpp', line = 19, exact_match = 0
..thats all
Working Breakpoint
1: file = 'C:\android-dev\...\test.cpp', line = 19, exact_match = 0
1.1:
module = C:\android-dev\...\test.so
compile unit = gl_code.cpp
function = testFunc(..)
location = C:\android-dev\...\test.cpp:16
address = 0x0000007f871d068c
resolved = true
hit count = 1

The reason seems to be, that a release version of the lib is created,
which does not support debugging, even if the app is built with debug options.
Solution:
To solve this issue, do the following workaround. It ensures that a debug version is built.
In your apps build.gradle change:
compile project(':nativelib')
to
compile project(path: ':nativelib' , configuration: 'debug')
In the libs build.gradle add:
android {
publishNonDefault true //this line
compileSdkVersion 24
buildToolsVersion "25.0.2"
defaultConfig {
...
}
...
}
Updates:
See the google issue for updates:
https://code.google.com/p/android/issues/detail?id=222276

I had the same error ("Attention! No symbol directories found - please check your native debug configuration."). My solution was (Android Studio 3.2):
Run → Edit Configuration → "Debugger" tab → add your working path to Symbol Directories.

I had the similar issue with my own libraries some months ago because I thought that if I added the -g (gcc) flag it would generate the debug symbols, as the desktop (linux, unix kernel) apps.
But, actually it does not work to generate debug symbols.
I see that you use Cmake as a external build tool and clang compiler.
So in my case I configure my cmake script with gcc but out of gradle scripting, but I think it will be the same, I add -mapcs-frame in the CMAKE_CXX_FLAGS.
externalNativeBuild {
cmake {
arguments "-DANDROID_PLATFORM_LEVEL=${11}",
'-DANDROID_TOOLCHAIN=gcc',
'-DANDROID_STL=gnustl_static',
'DCMAKE_CXX_FLAGS=-mapcs-frame'
}
}
I know that if you use clang compile may be this flag could not work. But my idea was to share my experience with android native debugging.
I Hope this clues could help you.
Cheers.
Unai.

In my case, it was because of co-worker who changed the visibility of symbols.
set(CMAKE_CXX_FLAGS -fvisibility=hidden)
After changing the above code to be applied only in release build, debugger(including breakpoints) works fine.

Is there any way to link my native code against prebuilt shared libraries without using the experimental Android Gradle plugin?

I have a project that uses the non-experimental version of the Android Gradle plugin (com.android.tools.build:gradle:2.1.3). I have some native code that I build into a shared library libnative.so.
The problem is that now I want to link libnative.so against a prebuilt library. Let's call this file libfoo.so. If I set the jniLibs.srcDir to the folder containing libfoo.so for the different ABIs I see that it gets bundled into my APK.
However I don't understand how I am supposed to link against it successfully. If I add "foo" to ldLibs I get a linker error saying that it can't find the library. This is probably because the folder containing libfoo.so is not included as a search path to the linker.
How am I supposed to do this? Is it simply not possible without switching to the experimental gradle plugin?
This is my gradle file. I stripped away the part that probably is irrelevant for this problem:
apply plugin: 'com.android.application'
android {
compileSdkVersion 23
buildToolsVersion "23.0.2"
defaultConfig {
applicationId "com.foo.bar"
minSdkVersion 15
targetSdkVersion 23
versionCode 11
versionName "0.0.11"
def foodir = "${project.buildDir}/../../foo"
ndk {
moduleName "native"
ldLibs "foo"
stl "gnustl_static"
}
sourceSets {
main {
jniLibs.srcDirs = ["${foodir}"]
}
}
}
}

android studio experimental ndk c library

I built some test c and c++ programs using gradle following these examples
I was also able to setup android studio with the experimental features to build a android project calling native functions with the help of this answer
I know that I can build this project using the android.useDeprecatedNdk=true
and provide my android.mk file for android studio to compile and build the app.
Is it possible with the experimental feature to build this same program? This project is built with CMAKE and there are some compilation steps that output files that needs to link. ndk-build creates these files but I can't find a way to do it with with android experimental features.
I am attempting for testing purposes and to build a non trivial example of building a more complex project. I decided to try to build the zlib library.
Here is my build.gradle
apply plugin: 'com.android.model.application'
model {
android {
compileSdkVersion = 23
buildToolsVersion = "23.0.1"
defaultConfig.with {
applicationId = "me.test.testnative_exp"
minSdkVersion.apiLevel = 10
targetSdkVersion.apiLevel = 23
versionCode = 1
versionName = "1.0"
buildConfigFields.with {
create() {
type = "int"
name = "VALUE"
value = "1"
}
}
}
}
compileOptions.with {
sourceCompatibility=JavaVersion.VERSION_1_7
targetCompatibility=JavaVersion.VERSION_1_7
}
android.ndk {
moduleName = "hello-jni"
cppFlags += "-I${file("src/main/jni/zlib")}".toString()
stl = "stlport_static"
}
android.buildTypes {
release {
minifyEnabled = false
proguardFiles += file('proguard-rules.pro')
}
}
android.sources {
main {
java {
source {
srcDir 'src'
}
}
}
}
}
dependencies {
compile fileTree(dir: 'libs', include: ['*.jar'])
compile 'com.android.support:appcompat-v7:23.0.1'
compile 'com.android.support:design:23.0.1'
}
my project structure is
app/
build/
libs/
src/
src/main/testActivity.java
jni/zlib <- the zlib folder is the one that I downloaded from the zlib website.
jni/hello-jni.c
After syncing the build.gradle I get a link error on the header in file:
infbak9.c cannot find #include "zutil.h"
but both files are in the zlib directory under jni.
Is it possible to use the android studio experimental ndk build to compile this project?

there is good project in github that i use its structure in mine, it is nice example for start on "how use experimental(v_0.4.0) plugin in complex project?" :
https://github.com/frogermcs/FlatBuffs
*there are zlib in android NDK, just add appropriate cflag and ldLibs.add("z") in gradle. and in your native code include <zlib.h>
and a good experimental gradle config from google :
https://github.com/googlesamples/android-ndk/blob/229cbe86238d401bb06166b8dfadec8198532589/native-codec/app/build.gradle

you might check this repo for a group of samples:
https://github.com/googlesamples/android-ndk
your issue might be able to fixed by adding something as[from Teapot sample there]:
cppFlags.addAll(['-I' + "${ndkDir}/sources/android/cpufeatures",'-I' + file('src/main/jni/ndk_helper')])
just replace the directory with your own path "zutil.h" etc. you may also use the latest gradle-experimental version to simplify your script -- like removing ".with" for defaultConfig.with, delete java 7 version section( the latest android studio could handle java 8 ), those ".toString()" thing is also wordy so the samples have changed style to use "+" [those is not problem for your build error though]

RenderScript BCC Compiler failed while running BasicRenderScriptSample

I have seen the question already asked in Can't find ScriptC_saturation in BasicRenderScript Sample
but as I am new in RenderScript, I can make it out they have already done much, so I cannot find the question as low level as I am asking:
I am using Eclipse Juno and have imported the BasicRenderScriptSample.
I am using the android.support.v8.renderscript (
(eclipse) project properties:
renderscript.target=18
renderscript.support.mode=true
sdk.buildtools=19.0.3
When I was not sure why the ScriptC_saturation is not auto generated, I was stuck till I followed the answer below, and copied the .rc file in the necessary folder, and everything compiled well.
Update:
Setup the necessary gradle properties as below (using jcenter rather than mavencentral):
apply plugin: 'com.android.application'
android {
compileSdkVersion 'android-L'
buildToolsVersion "20.0.0"
defaultConfig {
applicationId "com.example.android.basicrenderscript"
minSdkVersion 'L'
targetSdkVersion 'L'
versionCode 1
versionName "1.0"
}
buildTypes {
release {
runProguard false
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
}
}
}
dependencies {
compile fileTree(dir: 'libs', include: ['*.jar'])
compile "com.android.support:appcompat-v7:18.0.+"
}
On Compilation I get this error in emulator and device all alike (from eclipse as well):
RenderScript﹕ bcc compiler terminated unexpectedly
RenderScript﹕ bcc: FAILS to prepare executable for 'saturation'
What could be the reason?
update 2: My Eclipse version of this project, somehow ran after series of cleaning, on the device (less than L) properly, but Gradle version project runs with THE error everywhere.

Don't put the .rs file in your res/ folders. It is a source file, not a resource. It dynamically creates .bc files which do end up automatically in your res/raw folder.