CODEWITHSUNDEEP
javaandroidc++java-native-interface
Martin j
Martin j

Reputation: 521

Error in JNI call back

i am researching on JNI call backs

my sample code in cpp is as follows

JNIEXPORT jstring JNICALL
Java_com_example_arjunh_myapplication_MainActivity_getJniString(JNIEnv *env, jobject instance) {

jstring jstr = env->NewStringUTF("This string comes from JNI");

jclass clazz = env->FindClass("MainActivity");  // Error at this line

jmethodID messageMe = env->GetMethodID(clazz, "messageMe", "(Ljava/lang/String;)V");


jobject result = env->CallObjectMethod(instance, messageMe, jstr);

const char* str = env->GetStringUTFChars((jstring) result, NULL);
printf("%s\n", str);

env->ReleaseStringUTFChars(jstr, str);


return env->NewStringUTF("Hello from JNI!");
}

my java class is as follows ( MainActivity )

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


    btnAdd = (Button) findViewById(R.id.btnAdd);
    tv = (TextView) findViewById(R.id.sample_text);

    btnAdd.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            getJniString();

        }
    });

}


public void messageMe(String text) {

    tv.setText(text);

}

the error is 

 ClassNotFoundException: Didn't find class "MainActivity" on path: DexPathList[[zip file "/data/app/com.example.arjunh.myapplication-1/base.apk"],nativeLibraryDirectories=[/data/app/com.example.arjunh.myapplication-1/lib/arm64, /data/app/com.example.arjunh.myapplication-1/base.apk!/lib/arm64-v8a, /system/lib64, /vendor/lib64]]

How to refer the class

jclass clazz = env->FindClass("MainActivity");

Upvotes: 0

Views: 635

Answers (1)

ApriOri
ApriOri

Reputation: 2688

I think you should specify package name as the documentation suggest:

name: a fully-qualified class name (that is, a package name, delimited by “/”, followed by the class name). If the name begins with “[“ (the array signature character), it returns an array class. The string is encoded in modified UTF-8.

jclass clazz = env->FindClass("your/package/name/MainActivity")

Upvotes: 2

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