Android NDK编程（七）--- JNI中List结构的类数据返回

    public void btnclick(View view) {
        List<CProduct> products=new ArrayList<>();
        for (int i=0; i < 4; i++) {
            CProduct product=new CProduct();
            product.incode="000"+i;
            product.fname="商品"+i;
            product.price=3;
            product.qty=10;

            products.add(product);
        }
    }

extern "C"
JNIEXPORT jobject JNICALL
Java_dem_vac_vaccaendk_VaccaeJNI_getlistproduct(JNIEnv *env, jclass type) {

    //获取ArrayList类引用
    jclass list_jcls = env->FindClass("java/util/ArrayList");
    if (list_jcls == NULL) {
        LOGI("ArrayList没找到相关类!");
        return 0;
    }

    //获取ArrayList构造函数id
    jmethodID list_init = env->GetMethodID(list_jcls, "<init>", "()V");
    //创建一个ArrayList对象
    jobject list_obj = env->NewObject(list_jcls, list_init, "");

    
    //获取ArrayList对象的add()的methodID
    jmethodID list_add = env->GetMethodID(list_jcls, "add", "(Ljava/lang/Object;)Z");


    //然后获取我们的CProduct类的class
    jclass jcls = env->FindClass("dem/vac/vaccaendk/CProduct");
    if (jcls == NULL) {
        return 0;
    }

    //定义类里面的属性
    jfieldID incode = env->GetFieldID(jcls, "incode", "Ljava/lang/String;");
    jfieldID fname = env->GetFieldID(jcls, "fname", "Ljava/lang/String;");
    jfieldID price = env->GetFieldID(jcls, "price", "F");
    jfieldID qty = env->GetFieldID(jcls, "qty", "I");

    for (int i = 0; i < 5; i++) {
        //首先实例化类
        jobject jobj = env->AllocObject(jcls);
        //然后对类中的各属性赋值
        //商品编码
        char *code = new char[5];
        sprintf(code,"0000%d",i);
        env->SetObjectField(jobj, incode, env->NewStringUTF(code));
        //商品名称
        char *tmpname = const_cast<char *>("名称");
        char *name = new char[strlen(tmpname) + strlen(code)];
        strcpy(name, tmpname);
        strcat(name, code);
        env->SetObjectField(jobj, fname, env->NewStringUTF(name));
        //价格
        env->SetFloatField(jobj, price, i);
        //数量
        env->SetIntField(jobj, qty, i + 10);

        env->CallBooleanMethod(list_obj, list_add, jobj);
    }

    return list_obj;
}