获得支持NDK的OpenCV可在Android Studio中使用

Question

I'm very new to openCV and android programming and I want to use openCV in my project. For now I'm trying to run openCV's 2nd tutorial in my android studio but I always get the following NDK error:

Error:Execution failed for task ':openCVTutorial2MixedProcessing:compileDebugNdk'.

NDK not configured. Download the NDK from http://developer.android.com/tools/sdk/ndk/.Then add ndk.dir=path/to/ndk in local.properties. (On Windows, make sure you escape backslashes, eg C:\\ndk rather than C:\\ndk)

Then I looked at internet and some guys suggested that I should add these to my gradle.build file:

    jniLibs.srcDirs = ['native-libs']
    jni.srcDirs = [] //disable automatic ndk-build

after adding these it works but I get the following error:

java.lang.UnsatisfiedLinkError: dalvik.system.PathClassLoader[DexPathList[[zip file "/data/app/org.opencv.samples.tutorial2-2/base.apk"],nativeLibraryDirectories=[/data/app/org.opencv.samples.tutorial2-2/lib/arm64, /vendor/lib64, /system/lib64]]] couldn't find "libopencv_java3.so"

This is my gradle file:

    apply plugin: 'com.android.application'

android {
    compileSdkVersion 23
    buildToolsVersion "23.0.1"

    defaultConfig {
        applicationId "org.opencv.samples.tutorial2"
        minSdkVersion 21
        targetSdkVersion 23

        ndk {
            moduleName "mixed_sample"
        }
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.txt'
        }
    }
    sourceSets{main {jni.srcDirs = ['src/main/jni','src/main/jniLibs']
        jniLibs.srcDirs = ['native-libs']
        jni.srcDirs = [] //disable automatic ndk-build
    }}
}

dependencies {
    compile project(':openCVLibrary310')
}

Answer 1

Well, that code you pasted in does exactly what the comment says:

jni.srcDirs = [] //disable automatic ndk-build

You don't see that first error is because the entire compileDebugNdk step is skipped. This means the NDK side of your application isn't built, which means none of the OpenCV libraries are in the APK, which means Java isn't able to load them, hence couldn't find "libopencv_java3.so" .

You need to write a bit of logic to build the C++ side of your project. Currently there are a couple of ways to do this, the easiest of which is to reference the NDK samples which document how to build and use native code with only a build.gradle. The build.gradle file from hello-libs is a good place to start for a project with 3rd-party dependencies.