NDK Builds and gradle (basic)

While I believe SJoshi (oracle guy) has the most complete answer, the SWIG project is a special case, interesting and useful one, at that, but not generalized for the majority of projects that have done well with the standard SDK ant based projects + NDK. We all would like to be using Android studio now most likely, or want a more CI friendly build toolchain for mobile, which gradle theoretically offers.

I've posted my approach, borrowed from somewhere (I found this on SO, but posted a gist for the app build.gradle: https://gist.github.com/truedat101/c45ff2b69e91d5c8e9c7962d4b96e841 ). In a nutshell, I recommend the following:

Don't upgrade your project to the latest gradle build
Use com.android.tools.build:gradle:1.5.0 in your Project root
Use com.android.application in your app project
Make sure gradle.properties has: android.useDeprecatedNdk=true (in case it's complaining)
Use the above approach to ensure that your hours and hours of effort creating Android.mk files won't be tossed away. You control which targets arch(s) to build. And these instructions are kind to Windows users, who should theoretically be able to build on windows without special issues.

Gradle for Android has been a mess in my opinion, much as I like the maven concepts borrowed and the opinionated structure of directories for a project. This NDK feature has been "coming soon" for almost 3+ years.

Generally building with the NDK is as simple as correctly specifying an ndkBuild path to Android.mk or cmake path to CMakeLists.txt. I recommend CMake over the older Android.mk because Android Studio's C/C++ support is based upon CLion and it uses CMake as its project format. This in my experience has tended to make the IDE more responsive on larger projects. Everything compiled in your project will be built and copied into the APK automatically.

If your project exported from eclipse,add the codes below in gradle file?

android {
   sourceSets{
        main{
           jniLibs.srcDir['libs']  
      }  
    }
}

2.If you create a project in Android studio:

create a folder named jniLibs in src/main/ ?and put your *.so files in the jniLibs folder.

And copy code as below in your gradle file ?

android {
    sourceSets{  
       main{  
         jniLibs.srcDir['jniLibs']  
      }  
    }
}

apply plugin: 'com.android.library'

android {
    compileSdkVersion 19
    buildToolsVersion "25.0.2"

    defaultConfig {
        minSdkVersion 19
        targetSdkVersion 19

        ndk {
            abiFilters 'armeabi', 'armeabi-v7a', 'x86'
            // 64-bit support requires an Android API level higher than 19; Namely 21 and higher
            //abiFilters 'armeabi', 'armeabi-v7a', 'arm64-v8a', 'x86', 'x86_64'
        }

        externalNativeBuild {
            cmake {
                arguments '-DANDROID_TOOLCHAIN=clang',
                        '-DANDROID_PLATFORM=android-19',
                        '-DANDROID_STL=gnustl_static',
                        '-DANDROID_ARM_NEON=TRUE'

            }
        }
    }

    externalNativeBuild {
        cmake {
            path 'src/main/jni/CMakeLists.txt'
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
}

Adding prebuilt libraries to the project (advanced)

Static libraries (.a) in your NDK build will automatically be included, but prebuilt dynamic libraries (.so) will need to be placed in jniLibs. This can be configured using sourceSets, but you should adopt the standard. You DO NOT NEED any additional commands in build.gradle when including prebuilt libraries.

The layout of `jniLibs`

You can find more information about the structure in the Android Gradle Plugin User Guide.

|--app:
|--|--build.gradle
|--|--src:
|--|--|--main
|--|--|--|--java
|--|--|--|--jni
|--|--|--|--|--CMakeLists.txt
|--|--|--|--jniLibs
|--|--|--|--|--armeabi
|--|--|--|--|--|--.so Files
|--|--|--|--|--armeabi-v7a
|--|--|--|--|--|--.so Files
|--|--|--|--|--x86
|--|--|--|--|--|--.so Files

You can then validate the resulting APK contains your .so files, typically under build/outputs/apk/, using unzip -l myApp.apk to list the contents.

Building shared libraries

If you're building a shared library in the NDK you do not need to do anything further. It will be correctly bundled in the APK.

now.I can load the so success!

1.add the .so file to this path

Project:

|--src |--|--main |--|--|--java |--|--|--jniLibs |--|--|--|--armeabi |--|--|--|--|--.so files

2.add this code to gradle.build

android {
splits {
    abi {
        enable true
        reset()
        include 'x86', 'x86_64', 'arm64-v8a', 'armeabi-v7a', 'armeabi'
        universalApk false
    }
}

}

3.System.loadLibrary("yousoname");

goodluck for you,it is ok with g

Tuesday, April 6, 2021

NDK Builds and gradle (basic)