Invoking JNI functions in Android package name containing underscore

Question

I am trying to implement MP3 encoding in Android using the LAME library following these guides: Lame MP3 Encoder compile for Android http://developer.samsung.com/android/technical-docs/Porting-and-using-LAME-MP3-on-Android-with-JNI

However I am getting a java.lang.UnsatisfiedLinkError which I believe might be due to the fact that my package name contains an underscore which it interprets as a full stop .

Looking at my code below is this likely this issue and how do I get around that. Or is there something else causing this. Thanks in advance for any help.

Record.java:

package co.uk.ing_simmons.aberdeensoundsites;

public class Record extends Activity implements OnClickListener {

static {
    System.loadLibrary("mp3lame");
}

private native void initEncoder(int numChannels, int sampleRate, int bitRate, int mode, int quality);

private native void destroyEncoder();

private native int encodeFile(String sourcePath, String targetPath);

[.....]
}

wrapper.c:

void Java_co_uk_ing_simmons_aberdeensoundsites_Record_initEncoder(JNIEnv *env,
        jobject jobj, jint in_num_channels, jint in_samplerate, jint in_brate,
        jint in_mode, jint in_quality) {
[....]

Full log cat error:

04-17 20:58:36.009: E/AndroidRuntime(26768): FATAL EXCEPTION: main
04-17 20:58:36.009: E/AndroidRuntime(26768): java.lang.UnsatisfiedLinkError: initEncoder
04-17 20:58:36.009: E/AndroidRuntime(26768):    at co.uk.ing_simmons.aberdeensoundsites.Record.initEncoder(Native Method)
04-17 20:58:36.009: E/AndroidRuntime(26768):    at co.uk.ing_simmons.aberdeensoundsites.Record.onCreate(Record.java:79)
04-17 20:58:36.009: E/AndroidRuntime(26768):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
04-17 20:58:36.009: E/AndroidRuntime(26768):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1615)
04-17 20:58:36.009: E/AndroidRuntime(26768):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1667)
04-17 20:58:36.009: E/AndroidRuntime(26768):    at android.app.ActivityThread.access$1500(ActivityThread.java:117)
04-17 20:58:36.009: E/AndroidRuntime(26768):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:935)
04-17 20:58:36.009: E/AndroidRuntime(26768):    at android.os.Handler.dispatchMessage(Handler.java:99)
04-17 20:58:36.009: E/AndroidRuntime(26768):    at android.os.Looper.loop(Looper.java:123)
04-17 20:58:36.009: E/AndroidRuntime(26768):    at android.app.ActivityThread.main(ActivityThread.java:3687)
04-17 20:58:36.009: E/AndroidRuntime(26768):    at java.lang.reflect.Method.invokeNative(Native Method)
04-17 20:58:36.009: E/AndroidRuntime(26768):    at java.lang.reflect.Method.invoke(Method.java:507)
04-17 20:58:36.009: E/AndroidRuntime(26768):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:867)
04-17 20:58:36.009: E/AndroidRuntime(26768):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:625)
04-17 20:58:36.009: E/AndroidRuntime(26768):    at dalvik.system.NativeStart.main(Native Method)

Answer 1

You should follow the underscore with the number 1. So if your package name contains ing_simmons then your JNI would be formed like so.

void Java_co_uk_ing_1simmons_aberdeensoundsites_Record_initEncoder

This is true also if you have underscores in any other part of the call, such as class name or method name in the Java file.

Answer 2

JNI spec quote on the _1 rule

The _1 rule scriptocalypse mentions is part of the JNI spec 8 Chapter 2: Design Overview - Resolving Native Method Names:

Escape Sequence     Denotes
_1                  the character “_”