Android 開發筆記 - 從 Java 端傳遞 HashMap 物件 Android NDK/ JNI C/C++ 操作變更內容

C/C++ Code:

#include <jni.h>

extern "C" {

jobject Java_YourPackageName_updateHashMap(JNIEnv *env, jobject thiz, jobject hashmap) {
    if (!hashmap)
        return hashmap;

    jclass mapClass = env->GetObjectClass(hashmap);
    jmethodID obj_put = env->GetMethodID(mapClass, "put", "(Ljava/lang/Object;Ljava/lang/Object;)Ljava/lang/Object;");

    if (mapClass && obj_put) {
        jstring key = env->NewStringUTF("Haha");
        jstring value = env->NewStringUTF("Hehe");
        env->CallObjectMethod(hashmap, obj_put, key, value);
        env->DeleteLocalRef(key);
        env->DeleteLocalRef(value);
    }

    return hashmap;
}
}

Android Java code:

public native HashMap updateHashMap(HashMap<String, String>map);
static {
        System.loadLibrary("native");
}

void usage() {
HashMap<String, String> mHashMap = new HashMap<String, String>();

        Log.d(tag, "HashMap size: "+mHashMap.size());
updateHashMap(mHashMap);
        Log.d(tag, "HashMap size: "+mHashMap.size());

        Iterator it = mHashMap.entrySet().iterator();
        while (it.hasNext()) {
            Map.Entry pair = (Map.Entry)it.next();
            Log.d(tag, "HashMap key: ["+pair.getKey()+"], value: ["+pair.getValue().toString()+"]");
        }
}