CODEWITHSUNDEEP
javaandroidarraysjava-native-interface
Panu
Panu

Reputation: 23

Cannot use GetMethodID with byte array parameters in JNI

I'm trying to call a java method via JNI by setting a byte array param according to the code below.

extern "C"
JNIEXPORT void JNICALL
Java_test_example_test_MainActivity_testOnProgress(JNIEnv *env, jobject instance,
                                                   jobject callback) {

    //declare ref java class
    jclass jClassTestCallBack = env->GetObjectClass(callback);

    //declare java method id
    jmethodID jMethodIdOnProgress = env->GetMethodID(jClassTestCallBack,"onProgress","([B)V");

    //check null
    if(jMethodIdOnProgress == 0){
        return;
    }

    jbyteArray result = env->NewByteArray(10);
    env->CallVoidMethod(callback,jMethodIdOnProgress,result);

}

In java.

public class MainActivity extends AppCompatActivity {

    private final String TAG = getClass().getSimpleName();

    // Used to load the 'native-lib' library on application startup.
    static {
        System.loadLibrary("native-lib");
    }

    /**
     * A native method that is implemented by the 'native-lib' native library,
     * which is packaged with this application.
     */
    public native void testOnSuccess(TestCallback callback);
    public native void testOnProgress(TestCallback callback);

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // Example of a call to a native method
        final TextView tv =  findViewById(R.id.sample_text);

        testOnProgress(new TestCallback() {
            @Override
            public void onSuccess(String msg) {
                Log.i(TAG, "onSuccess: " + msg);
                tv.setText(msg);
            }

            @Override
            public void onProgress(Byte[] data) {
                if(data!=null){
                    Log.i(TAG, "onProgress: " + data.length);
                    tv.setText("onProgress: data size " + data.length);
                }

            }
        });
    }

}

I don't understand how to declare the ByteArray parameter in GetMethodID correctly but this is my logcat.

08-28 14:08:49.702 3015-3015/? E/AndroidRuntime: FATAL EXCEPTION: main
        Process: test.example.test, PID: 3015
        java.lang.NoSuchMethodError: no non-static method "Ltest/example/test/MainActivity$1;.onProgress([B)V"
    at test.example.test.MainActivity.testOnProgress(Native Method)
    at test.example.test.MainActivity.onCreate(MainActivity.java:25)
    at android.app.Activity.performCreate(Activity.java:6915)
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1123)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2746)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2864)
    at android.app.ActivityThread.-wrap12(ActivityThread.java)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1567)
    at android.os.Handler.dispatchMessage(Handler.java:105)
    at android.os.Looper.loop(Looper.java:156)
    at android.app.ActivityThread.main(ActivityThread.java:6523)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:942)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:832)
    08-28 14:08:49.726 3015-3015/? I/Process: Sending signal. PID: 3015 SIG: 9

But no problems with the string. It can work normally. This is part of the string.

extern "C"
JNIEXPORT void JNICALL
Java_test_example_test_MainActivity_testOnSuccess(JNIEnv *env, jobject instance, jobject callback) {

    //declare ref java class
    jclass jClassTestCallBack = env->GetObjectClass(callback);

    //declare java method id
    jmethodID jMethodIdOnSuccess = env->GetMethodID(jClassTestCallBack,"onSuccess","(Ljava/lang/String;)V");

    //check null
    if(jMethodIdOnSuccess == 0){
        return;
    }

    env->CallVoidMethod(callback,jMethodIdOnSuccess,env->NewStringUTF("Callback Success!!"));

}

Thank you.

Solution

I decided to takes a byte[] in onProgress instead of Byte[].

Upvotes: 2

Views: 2038

Answers (1)

Michael
Michael

Reputation: 58467

[B means byte[], i.e. an array of the primitive type byte.

Your onProgress method takes an array of the class Byte, which is not the same thing.

You can either:

  • Change the declaration of TestCallback so that onProgress takes a byte[].

or

  • Change your GetMethodID call so that it uses the correct signature ([Ljava/lang/Byte;)V. This may require changes to any code that then tries to call that method.

Upvotes: 5

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