Question

I am trying to run my application, but whenever I make a call to a native function it gives me an error and the program crashes. I’m sure it has to do with how I am naming something either in Java or in C.

Here is my call to the functions in Java :

package my.commander;

public class RelayAPIModel {

    public static class NativeCalls {

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

        public native static byte InitRelayJava();

        public native static void FreeRelayJava();
    }

Here are the functions in the .c file:

void Java_my_commander_RelayAPIModel_FreeRelayJava( JNIEnv * env, jobject this ) {
    RelayAPI_DataValid = 0;
    RelayAPI_SetBaud = 0;
    RelayAPI_get = 0;
    RelayAPI_put = 0;
    RelayAPI_flush = 0;
    RelayAPI_delay = 0;
    RelayAPI_initilized = 0;
}


BYTE Java_my_commander_RelayAPIModel_InitRelayJava( JNIEnv *env, jobject obj  ) {
    ...
    ...
}

Here they are in the .h file :

void Java_my_commander_RelayAPIModel_FreeRelayJava( JNIEnv * env, jobject obj );

BYTE Java_my_commander_RelayAPIModel_InitRelayJava( JNIEnv *env, jobject obj );

Here is my LogCat:

08-01 09:58:21.933: E/AndroidRuntime(17170): FATAL EXCEPTION: main
08-01 09:58:21.933: E/AndroidRuntime(17170): java.lang.UnsatisfiedLinkError: InitRelayJava
08-01 09:58:21.933: E/AndroidRuntime(17170):    at my.eti.commander.RelayAPIModel$NativeCalls.InitRelayJava(Native Method)
08-01 09:58:21.933: E/AndroidRuntime(17170):    at my.eti.commander.MainMenu.initMain(MainMenu.java:241)
08-01 09:58:21.933: E/AndroidRuntime(17170):    at my.eti.commander.MainMenu.onCreate(MainMenu.java:81)
08-01 09:58:21.933: E/AndroidRuntime(17170):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
08-01 09:58:21.933: E/AndroidRuntime(17170):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
08-01 09:58:21.933: E/AndroidRuntime(17170):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
08-01 09:58:21.933: E/AndroidRuntime(17170):    at android.app.ActivityThread.access$1500(ActivityThread.java:117)
08-01 09:58:21.933: E/AndroidRuntime(17170):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
08-01 09:58:21.933: E/AndroidRuntime(17170):    at android.os.Handler.dispatchMessage(Handler.java:99)
08-01 09:58:21.933: E/AndroidRuntime(17170):    at android.os.Looper.loop(Looper.java:130)
08-01 09:58:21.933: E/AndroidRuntime(17170):    at android.app.ActivityThread.main(ActivityThread.java:3683)
08-01 09:58:21.933: E/AndroidRuntime(17170):    at java.lang.reflect.Method.invokeNative(Native Method)
08-01 09:58:21.933: E/AndroidRuntime(17170):    at java.lang.reflect.Method.invoke(Method.java:507)
08-01 09:58:21.933: E/AndroidRuntime(17170):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
08-01 09:58:21.933: E/AndroidRuntime(17170):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
08-01 09:58:21.933: E/AndroidRuntime(17170):    at dalvik.system.NativeStart.main(Native Method)

I would like to clarify now, that I have tried changing the C method names to Java_my_commander_RelayAPIModel_NativeCalls_FreeRelayJava and Java_my_commander_RelayAPIModel_NativeCalls_InitRelayJava. The application still failed to launch and this was the LogCat for that:

08-01 11:22:10.735: E/AndroidRuntime(17441): FATAL EXCEPTION: main
08-01 11:22:10.735: E/AndroidRuntime(17441): java.lang.UnsatisfiedLinkError: InitRelayJava
08-01 11:22:10.735: E/AndroidRuntime(17441):    at my.eti.commander.RelayAPIModel$NativeCalls.InitRelayJava(Native Method)
08-01 11:22:10.735: E/AndroidRuntime(17441):    at my.eti.commander.MainMenu.initMain(MainMenu.java:241)
08-01 11:22:10.735: E/AndroidRuntime(17441):    at my.eti.commander.MainMenu.onCreate(MainMenu.java:81)
08-01 11:22:10.735: E/AndroidRuntime(17441):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
08-01 11:22:10.735: E/AndroidRuntime(17441):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
08-01 11:22:10.735: E/AndroidRuntime(17441):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
08-01 11:22:10.735: E/AndroidRuntime(17441):    at android.app.ActivityThread.access$1500(ActivityThread.java:117)
08-01 11:22:10.735: E/AndroidRuntime(17441):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
08-01 11:22:10.735: E/AndroidRuntime(17441):    at android.os.Handler.dispatchMessage(Handler.java:99)
08-01 11:22:10.735: E/AndroidRuntime(17441):    at android.os.Looper.loop(Looper.java:130)
08-01 11:22:10.735: E/AndroidRuntime(17441):    at android.app.ActivityThread.main(ActivityThread.java:3683)
08-01 11:22:10.735: E/AndroidRuntime(17441):    at java.lang.reflect.Method.invokeNative(Native Method)
08-01 11:22:10.735: E/AndroidRuntime(17441):    at java.lang.reflect.Method.invoke(Method.java:507)
08-01 11:22:10.735: E/AndroidRuntime(17441):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
08-01 11:22:10.735: E/AndroidRuntime(17441):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
08-01 11:22:10.735: E/AndroidRuntime(17441):    at dalvik.system.NativeStart.main(Native Method)

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Now, I think that the error lies in the code above. If you all think there is nothing wrong with it, I’m going to add some more information down here just in case the problem lies elsewhere.

This application that I’m creating, uses the functions above to call a library that has been being used for a while. This library was previously used to call functions in a Palm Pilot program which utilize the Palm’s bluetooth capabilities. Since Android devices have different bluetooth libraries/capabilities, I am adding code to the native library to call BACK to the java code, to access the Android device’s bluetooth capabilities. I do not want to post all of the code pertaining to this here, but if someone feels that it needs to be posted I will.

Answer 1

The error message says it’s at:

my.eti.commander.RelayAPIModel$NativeCalls.InitRelayJava (Native Method)

So make sure that:

• the native method declaration is indeed inside the RelayAPIModel class, not insude the RelayAPIModel.NativeCalls nested class.
• the package name on Java side is my.commander as opposed to my.eti.commander

EDIT: or you can fix that on the C side. If you want to create native methods in the nested class, the proper name for it would be:

Java_my_commander_RelayAPIModel_00024NativeCalls_InitRelayJava()

The 00024 is the code of the $ character, which is the nested class delimiter in Java internals. Also, the meaning of the of second parameter (jobject Obj) will be different – instead of this pointer/class pointer for RelayAPIModel, it will be the one for the RelayAPIModel.NativeCalls. You won’t be able to use it to resolve/call methods in the RelayAPIModel.