如何使用 Android NDK 和 Gradle 构建单个 APK

Question

我正在使用 OpenCV（C++ 而不是 Java）开发一个新的 android 应用程序，而且我对 opencv 和 NDK 都是新手。我使用下面的 Gradle 文件成功构建（并运行）它，在 Android Studio 中我可以选择一个变体并点击构建（例如 x86）。

我有两个问题：

1. 有没有一种方法可以让我构建一个支持所有架构的 APK 的变体？ （我知道文件会更大）

2. 我能否在不为每个变体指定所有相同库的情况下实现构建。有什么办法可以让构建系统每次都拿起库，因为它们都在项目中并按架构名称组织？

   apply plugin: 'com.android.application'
   
   android {
   compileSdkVersion 21
   buildToolsVersion "21.0.0"
   
   defaultConfig {
       applicationId "uk.co.xxx.androidcppimagereader"
       minSdkVersion 17
       targetSdkVersion 21
       versionCode 1
       versionName "1.0"
   }
   
   def libsDir = projectDir.path + "/libs/"
   
   productFlavors {
       x86 {
           versionCode Integer.parseInt("3" + defaultConfig.versionCode)
           ndk {
               abiFilter "x86"
               moduleName "Processing"
               stl "gnustl_static"
               cFlags "-I/opt/local/include/opencv -I/opt/local/include"
               ldLibs libsDir + "x86/libopencv_core.a"
               ldLibs libsDir + "x86/libopencv_ts.a"
               ldLibs libsDir + "x86/libopencv_contrib.a"
               ldLibs libsDir + "x86/libopencv_ml.a"
               ldLibs libsDir + "x86/libopencv_java.so"
               ldLibs "log"
               ldLibs "z", "jnigraphics"
           }
       }
       armv7 {
           versionCode Integer.parseInt("2" + defaultConfig.versionCode)
           ndk {
               abiFilter "armeabi-v7a"
               moduleName "Processing"
               stl "gnustl_static"
               cFlags "-I/opt/local/include/opencv -I/opt/local/include"
               ldLibs libsDir + "armeabi-v7a/libopencv_core.a"
               ldLibs libsDir + "armeabi-v7a/libopencv_ts.a"
               ldLibs libsDir + "armeabi-v7a/libopencv_contrib.a"
               ldLibs libsDir + "armeabi-v7a/libopencv_ml.a"
               ldLibs libsDir + "armeabi-v7a/libopencv_java.so"
               ldLibs "log"
               ldLibs "z", "jnigraphics"
           }
       }
       arm {
           versionCode Integer.parseInt("1" + defaultConfig.versionCode)
           ndk {
               abiFilter "armeabi"
               moduleName "Processing"
               stl "gnustl_static"
               cFlags "-I/opt/local/include/opencv -I/opt/local/include"
               ldLibs libsDir + "armeabi/libopencv_core.a"
               ldLibs libsDir + "armeabi/libopencv_ts.a"
               ldLibs libsDir + "armeabi/libopencv_contrib.a"
               ldLibs libsDir + "armeabi/libopencv_ml.a"
               ldLibs libsDir + "armeabi/libopencv_java.so"
               ldLibs "log"
               ldLibs "z",  "jnigraphics"
           }
       }
   
   }
   
       buildTypes {
            release {
               minifyEnabled false
               proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
           }
       }
   }
   
   dependencies {
       compile fileTree(dir: 'libs', include: ['*.jar'])
       compile 'com.android.support:appcompat-v7:21.0.3'
   }
   

Answer 1

在 build.gradle 文件中定义了计划包含在 apk 中的所有架构后，请使用关键字“fat”，如下面的代码中突出显示的那样。这将构建一个 FAT 二进制文件。观看此视频了解更多详情https://www.youtube.com/watch?v=kFtxo7rr2HQ

arm {
    versionCode Integer.parseInt("1" + defaultConfig.versionCode)
    ndk {
        abiFilter "armeabi"
        moduleName "Processing"
        stl "gnustl_static"
        cFlags "-I/opt/local/include/opencv -I/opt/local/include"
        ldLibs libsDir + "armeabi/libopencv_core.a"
        ldLibs libsDir + "armeabi/libopencv_ts.a"
        ldLibs libsDir + "armeabi/libopencv_contrib.a"
        ldLibs libsDir + "armeabi/libopencv_ml.a"
        ldLibs libsDir + "armeabi/libopencv_java.so"
        ldLibs "log"
        ldLibs "z",  "jnigraphics"
    }
    fat // <- HERE
}

buildTypes {
    release {
        minifyEnabled false
        proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
    }
}

Answer 2

为了正确链接您的库，您必须像当前所做的那样为每个架构声明不同的 ldLib。

不幸的是，如果您要同时为所有架构构建，则无法使用当前插件从 gradle 执行此操作。

在我看来，最好的解决方案是停用内置（当前已弃用）的 ndk 支持并改用常规 Android.mk / Application.mk 文件。你的 build.gradle 看起来像这样：

import org.apache.tools.ant.taskdefs.condition.Os

apply plugin: 'com.android.application'

android {
    compileSdkVersion 21
    buildToolsVersion "21.1"

    defaultConfig {
        applicationId "uk.co.xxx.androidcppimagereader"
        minSdkVersion 17
        targetSdkVersion 21
        versionCode 1
        versionName "1.0"
    }

    sourceSets.main {
        jniLibs.srcDir 'src/main/libs' //set libs as default directory for .so files inclusion, instead of jniLibs
        jni.srcDirs = [] //disable automatic ndk-build call
    }

    // call regular ndk-build(.cmd) script from app directory
    task ndkBuild(type: Exec) {
        if (Os.isFamily(Os.FAMILY_WINDOWS)) {
            commandLine 'ndk-build.cmd', '-C', file('src/main').absolutePath
        } else {
            commandLine 'ndk-build', '-C', file('src/main').absolutePath
        }
    }

    tasks.withType(JavaCompile) {
        compileTask -> compileTask.dependsOn ndkBuild
    }
}