Android：jni中的共享首选项

Question

in my android application in need to access the shared memory between the two application ,i knew android kernel is not like Linux kernel to implement the shared memory concept ,so i have choosen the shared preference in android but i need to implement this via JNI not in java part i have tried to create a shared preference in jni but i cant get it properly this my code

JNIEXPORT jlong JNICALL Java_com_sharedpref1_test_savevalue
  (JNIEnv *env, jobject ctx, jstring store, jstring key, jlong value);



        jobject shared_preferences = (*env)->CallObjectMethod(env, ctx, (*env)->GetMethodID(env (*env)->FindClass(env, "android/content/Context"), "getSharedPreferences", "(L/java/lang/String;I)Landroid/content/SharedPreferences;"),
                    jstore,
                    1);
        jobject preferences_editor = (*env)->CallObjectMethod(env, shared_preferences, (*env)->GetMethodID(env,
                (*env)->FindClass(env, "android/content/SharedPreferences"), "editor", "()Landroid/content/SharedPreferences$Editor;"));

        (*env)->CallObjectMethod(env, preferences_editor, (*env)->GetMethodID(env, 
                (*env)->FindClass(env, "android/content/SharedPreferences/Editor"), "putLong", "(Ljava/lang/String;J)Landroid/content/SharedPreferences$Editor;"),
               jkey,
                    value);


    }

can any know how to done shared preference in jni on android.

Answer 1

There's possibly an error in your code. "ctx" is not the Android context. Instead, it is the Java "this" of your calling Java class. Unless your calling class inherits Context, you should pass the Context instance it as an additional parameter.

Besides this, you should split and possibly error check your function calls to make it more readable and errors easier determinable. Eg
Find the class.
If its valid, find the method. And so on.