Setting up JNA in Android Studio

Question

I try to import jna.jar into my project since JNA is a very useful tool to call Native library which is base on JNI.

OS: Windows 10

IDE: Android Studio 1.5.1

JDK: 1.8.0_73

NDK: r10e

What I have done (AS = Android Studio)

Create a new project by AS with API18.
Download jna.jar from their GitHub.

https://github.com/java-native-access/jna
copy jna.jar into project folder.

JNATest\app\libs\jna.jar
In AS, right-click on the icon of jna.jar, choose Add as Library
Wait for few seconds, check the File->Project Structure->app->Dependencies. We do have the jna.jar. (Same as app\build.gradle) build gradle
Implement JAVA code about JNA in MainActivity.java
Run app on real device Sony Z3 (arm)
Crash by CLibrary.Instance.printf("Hello, JNA");

Error Message on Android Monitor

E/AndroidRuntime: FATAL EXCEPTION: main
                   Process: i3d.jnatest, PID: 1068
                   java.lang.UnsatisfiedLinkError: Native library (com/sun/jna/android-arm/libjnidispatch.so) not found in resource path (.)
                     at com.sun.jna.Native.loadNativeDispatchLibraryFromClasspath(Native.java:866)
                     at com.sun.jna.Native.loadNativeDispatchLibrary(Native.java:826)
                     at com.sun.jna.Native.<clinit>(Native.java:140)
..
... so on

Java code

package i3d.jnatest;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

import com.sun.jna.Library;
import com.sun.jna.Native;

    public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        CLibrary.Instance.printf("Hello, JNA");
    }

    public interface  CLibrary extends Library
    {
        CLibrary Instance = (CLibrary) Native.loadLibrary("msvcrt", CLibrary.class);
        void printf(String format, Object... args);
    }
}

Question

According to error message, I miss /android-arm/libjnidispatch.so in runtime.

Did I put the wrong place for jna.jar?
How should I get and use /android-arm/libjnidispatch.so?

I am a newbie about Android Studio, so maybe misunderstanding something key-point.

which JNA.jar file did you use? I tried 4.1.0 and 4.2.2 but still got errors building for android — Mr. Supasheva, Oct 24 '16 at 10:18

score 13 · Answer 1 · answered Feb 26 '19 at 15:19

13

For Android, reference the JNA library adding @aar at the end of the string instead of downloading the JNA jar:

https://github.com/java-native-access/jna/blob/master/www/FrequentlyAskedQuestions.md#jna-on-android

answered Feb 26 '19 at 15:19

Marcelo

131
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score 11 · Answer 2 · edited Mar 01 '21 at 18:38

11

Put the .so file in the following directory (when using android studio): yourproject\app\src\main\jniLibs\armeabi-v7a\libjnidispatch.so

Update I: (up to version <= 4.3.0) Since some of you asked where to find the *.so file:

On the official JNA site you will find all the supported architectures (30+) for download:

https://github.com/java-native-access/jna/tree/master/lib/native

Download the jar of the architecture you'd like and open it with some zip tool. In there you'll find the libjnidispatch.so file (of course only for unix architectures. For windows its a dll)

Update II: (starting from version >= 4.4.0)

Use the jna-X.X.0.aar file, supplied by the JNA project

As mentioned in a comment - starting from version 4.4.0 JNA publishes an AAR to maven central with all the libjnidispatch.so's in it. Users have had better luck using gradle than straight maven here, which doesn't always select or properly handle aars.

edited Mar 01 '21 at 18:38

fuzzyTew

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answered Apr 18 '16 at 14:56

Lonzak

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not working for me! same error is coming! can you please help!! – Parth Apr 04 '17 at 12:20
Unfortunatly not because you did not supply any information on your problem. Please open another question here on SO and also others may help you... – Lonzak Apr 05 '17 at 19:09
2

Where can i find the .so file? – Steve Luck Mar 21 '18 at 02:43
JNA publishes an AAR to maven central with all the libjnidispatch.so's in it. There shouldn't be a need to manually copy. – fuzzyTew Feb 27 '21 at 10:43

score 2 · Answer 3 · answered Mar 30 '16 at 10:23

2

I found this comment in a file in the library github repo - "If you're using Google's Eclipse plugin then you must manually remove libjnidispatch.so from jna.jar/lib/armeabi and add it into your project's libs/armeabi directory."

Since this file was created in 2012 and Android Studio was still in very early phase and not super popular by that time, I assume it might be a valid note for Eclipse and also for Android Studio. I suggest you try it.

answered Mar 30 '16 at 10:23

Lachezar

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Thank you for this information. But I hit the wall when building the JNA source code. http://imgur.com/VQbH1F9 I will keep trying. – Pow Lee Mar 30 '16 at 10:42
I build successfully by deleting some characters which are UTF-8 escape char. Trying to do rest of steps.. – Pow Lee Mar 31 '16 at 02:26
You don't need to rebuild JNA; just extract the file from jna.jar and place it into your project's native libs directory. – technomage Mar 31 '16 at 14:42

Setting up JNA in Android Studio

3 Answers3

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