如何将JNI与AAR库一起使用? [英] How do I use JNI with AAR library?

问题描述

我正在创建一个Android库(.aar文件)，我需要使用JNI. (我很清楚Google尽量不要使用JNI/NDK，但在这种情况下是不可能的).

I am creating an Android library (.aar file) and I need to use JNI. (I am very well aware of Google's discouragement of using JNI/NDK if possible, but in this case, it's not possible).

我从一个独立的hello-jni示例APP开始(首先学习JNI)，其中包含以下文件:

I started with a standalone hello-jni example APP (to first learn JNI), with the following files:

HelloJni.java

public class HelloJni extends Activity
{
    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);

        TextView  tv = new TextView(this);
        tv.setText( stringFromJNI() );
        setContentView(tv);
    }

    public native String  stringFromJNI();

    static {
        System.loadLibrary("hello-jni");
    }
}

Android.mk

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

LOCAL_MODULE    := hello-jni
LOCAL_SRC_FILES := hello-jni.c

include $(BUILD_SHARED_LIBRARY)

Application.mk

APP_ABI := all

hello-jni.c

#include <string.h>
#include <jni.h>

jstring
Java_com_example_hellojni_HelloJni_stringFromJNI( JNIEnv* env,
                                                  jobject thiz )
{
    return (*env)->NewStringUTF(env, "Hello from JNI!");
}

以下内容可作为应用程序(apk)很好地构建，并且可以在我的设备上运行它，并显示"JNI的Hello！".如预期的那样.

The following builds fine as an app (apk) and I am able to run it on my device, which prints "Hello from JNI!" as expected.

现在，我做了同样的事情，但是我创建了一个库项目来生成aar，而不是apk.除了HelloJni.java，我将所有文件都保持不变，将其更改为以下内容:

Now, I did the same thing, but instead of an apk, I built a library project to produce an aar. I kept all the files the same except HelloJni.java, which I changed to the following:

HelloJni.java

public class HelloJni {
    public native String stringFromJNI();

    static {
        System.loadLibrary("hello-jni");
    }
}

aar构建良好，但是当我将aar导入一个单独的应用程序项目中并尝试在我的设备上运行它时，它在应用程序启动时崩溃，并且我收到以下错误logcat消息:

The aar builds fine, but when I import the aar into a separate app project, and try to run it on my device, it crashes on app start and I get the following error logcat message:

com.test.sample.mysampleapplication E/AndroidRuntime:致命异常: 主要的 流程:com.test.sample.mysampleapplication，PID:20047 java.lang.UnsatisfiedLinkError:dalvik.system.PathClassLoader [DexPathList [[zip文件 "/data/app/com.test.sample.mysampleapplication-1/base.apk"]，nativeLibraryDirectories=[/data/app/com.test.sample.mysampleapplication-1/lib/arm， /vendor/lib，/system/lib]]]找不到"libhello-jni.so" 在java.lang.Runtime.loadLibrary(Runtime.java:366) 在java.lang.System.loadLibrary(System.java:988)...

com.test.sample.mysampleapplication E/AndroidRuntime﹕ FATAL EXCEPTION: main Process: com.test.sample.mysampleapplication, PID: 20047 java.lang.UnsatisfiedLinkError: dalvik.system.PathClassLoader[DexPathList[[zip file "/data/app/com.test.sample.mysampleapplication-1/base.apk"],nativeLibraryDirectories=[/data/app/com.test.sample.mysampleapplication-1/lib/arm, /vendor/lib, /system/lib]]] couldn't find "libhello-jni.so" at java.lang.Runtime.loadLibrary(Runtime.java:366) at java.lang.System.loadLibrary(System.java:988) ...

这个"libhello-jni.so"文件到底是什么?为什么我需要它?我能够以apk的形式完美运行.但是，谁能解释为什么当我将它放入aar并将其导入到应用程序项目中以使用它时为什么它不起作用?我是否缺少将其放入库(和使用库)所需的一些其他步骤?谢谢！

What in the world is this "libhello-jni.so" file? And why do I need it? I was able to run this perfectly fine as an apk. But can anyone explain why it doesn't work when I make it into an aar, and import it to an app project to use it? Am I missing some additional steps needed to make it into a library (and use it)? Thanks!

这就是我将aar导入到我的应用程序中的方式. 1.单击文件"->新建"->新模块". 2.选择导入.JAR或.AAR包"作为模块类型. 3.将我的aar文件设置为新模块 4.然后打开文件"->项目结构" 5.在依赖项"选项卡中，添加模块依赖项"并选择我的aar文件 如果这不是将aar导入到我的应用程序的好方法，请也告诉我.谢谢！

This is how I imported my aar to my app. 1. Click "File" -> "New" -> "New Module". 2. Select "Import .JAR or .AAR Package" as module type. 3. Set my aar file as new module 4. And then open "File" -> "Project Structure" 5. In the "Dependencies" tab, add "Module dependency" and select my aar file If that's not a good way to import aar to my app, then also please let me know. Thank you!

推荐答案

结果是，我不得不在AAR模块目录中的build.gradle文件中添加一些NDK配置.

Turns out I had to add some NDK config in my build.gradle file inside my AAR module directory.

build.gradle:

android {
    compileSdkVersion 22
    buildToolsVersion "22.0.1"

    defaultConfig {
        minSdkVersion 15
        targetSdkVersion 22
        versionCode 1
        versionName "1.0"

        // This determines the .so filename
        ndk {
            moduleName "hello-jni"
        }
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

在build.gradle中不添加该文件将生成一个.so文件，该文件默认为您的项目名称，在我的情况下为"libsample-aar.so".使用上面的配置，然后生成的.so文件将是"libhello-jni.so".

Not having that added in build.gradle will produce an .so file that's defaulted to your project's name, in my case "libsample-aar.so". With that config above, the generated .so file will then be "libhello-jni.so".

这篇关于如何将JNI与AAR库一起使用?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！