我的 Java 对象构造函数返回“null”

Question

我创建了一个 class，其中包含各种 Activity 的构造函数。但是，当我尝试订阅该对象以显示产品的一些图像、价格和名称时，我收到 "null" 作为输出。但是当我尝试在 else 语句中传递相同的函数时它起作用但仍然返回 null。请帮助我理解为什么会出现此错误。并告诉我如何解决在此先感谢。

mCompositeDisposable.add(mIMyRestaurantAPI.getFoodOfMenu(Common.API_KEY,
                event.getCategory().getId())
                .subscribeOn(Schedulers.io())
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(foodModel -> {

                    if (foodModel.isSuccess()) {
                        adapter = new MyFoodAdapter(this, foodModel.getResult());
                        recycler_food_list.setAdapter(adapter);
                        recycler_food_list.setLayoutAnimation(mLayoutAnimationController);
                    } else {
                        Toast.makeText(this, "[GET FOOD RESULT]" + foodModel.getMessage(), Toast.LENGTH_LONG).show();
                    }

                    mDialog.dismiss();

                }, throwable -> {
                    mDialog.dismiss();
                    Toast.makeText(this, "[GET FOOD]" + throwable.getMessage(), Toast.LENGTH_SHORT).show();
                }));

我不断收到 GET FOOD RESULT=null..这就是我的 FOODMODEL 构造器的样子

public class FoodModel {
private boolean success;
private String message;
private List<Food> result;

public boolean isSuccess() {
    return success;
}

public void setSuccess(boolean success) {
    this.success = success;
}

public String getMessage() {
    return message;
}

public void setMessage(String message) {
    this.message = message;
}

public List<Food> getResult() {
    return result;
}

public void setResult(List<Food> result) {
    this.result = result;
}

这是 FOOD 构造函数的样子

public class Food {

private int id;
private String name;
private String description;
private String image;
private Double price;
private boolean isSize;
private boolean isAddon;
private int discount;

public int getId() {
    return id;
}

public void setId(int id) {
    this.id = id;
}

public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}

public String getDescription() {
    return description;
}

public void setDescription(String description) {
    this.description = description;
}

public String getImage() {
    return image;
}

public void setImage(String image) {
    this.image = image;
}

public Double getPrice() {
    return price;
}

public void setPrice(Double price) {
    this.price = price;
}

public boolean isSize() {
    return isSize;
}

public void setSize(boolean size) {
    isSize = size;
}

public boolean isAddon() {
    return isAddon;
}

public void setAddon(boolean addon) {
    isAddon = addon;
}

public int getDiscount() {
    return discount;
}

public void setDiscount(int discount) {
    this.discount = discount;
}

这是我使用改造从后端传递连接的地方。

 @GET("food")

Observable<FoodModel> getFoodOfMenu(@Query("key") String apiKey,
                                    @Query("menuId") int menuId);

这是我使用 nodejs 的 api 后端..

router.get('/food', function (req, res, next) {
if (req.query.key == API_KEY) {
    req.getConnection(function (error, conn) {
        var menu_id = req.query.menuId
        if (menu_id != null) {
            conn.query('SELECT id,name,description,image,price, CASE WHEN isSize=1 THEN \'TRUE\' ELSE \'FALSE\' END as isSize,'
                +'CASE WHEN isAddon=1 THEN \'TRUE\' ELSE \'FALSE\' END as isAddon,'
                + 'discount FROM Food WHERE Id in (SELECT foodId FROM Menu_Food WHERE MenuId=?)', [menu_id], function (err, rows, fields) {

                if (err) {
                    res.status(500)
                    res.send(JSON.stringify({ sucess: false, message: err.message }))
                }
                else {
                    if (rows.length > 0) {
                        res.send(JSON.stringify({ sucess: true, result: rows }))
                    }
                    else {
                        res.send(JSON.stringify({ sucess: false, message: "Empty" }))
                    }
                }
            })
        } else {
            res.send(JSON.stringify({ sucess: false, message: "Missing menu_id" }))
        }
    })
}
else {
    res.send(JSON.stringify({ success: false, message: "Wrong api key marfe" }))
}

})

这里是 json 回复

{"sucess":true,"result":[{"id":1,"name":"ROASTED QUARTER CHICKEN","description":"Served with mushroom gravy, cranberry & mint sauces","image":"http://10.0.2.2:3000/4_roasted_quarter_chicken_with_special_sauces.jpg","price":25,"isSize":"FALSE","isAddon":"FALSE","discount":0},{"id":2,"name":"CURRY CHICKEN","description":"Chicken served in curry that is made from more than 10 spices to bring out the authentic traditional taste. Served with rice and 3 side dishes\r\n","image":"http://10.0.2.2:3000/2_curry_chic.jpg","price":25,"isSize":"FALSE","isAddon":"FALSE","discount":0},{"id":3,"name":"\r\nRENDANG CHICKEN","description":"Simmered chicken in spices. Served with rice and 3 side dishes","image":"http://10.0.2.2:3000/1_classic_rendang.jpg","price":25,"isSize":"FALSE","isAddon":"FALSE","discount":0},{"id":4,"name":"HERBAL STEAMED CHICKEN","description":"Steamed chicken with red dates and mushroom. Served with rice and 3 side dishes","image":"http://10.0.2.2:3000/3_herbal_steamed_chic.jpg","price":25,"isSize":"FALSE","isAddon":"FALSE","discount":0}]}

Answer 1

您必须从 api 响应中得到 null。或者您的 Java 对象及其字段应与您的 json 响应中的属性相匹配。

例如你有这个json{ "countries": [ { "name": "Israel", "phoneCode": "972", "code": "IL" }, { "name": "Afghanistan", "phoneCode": "93", "code": "AF" }, { "name": "Albania", "phoneCode": "355", "code": "AL" }]}

那么你的模型就是这样

public class CountryModel {

private List<Country> countries = new ArrayList<>();

public List<Country> getCountries() {
    return countries;
}

public void setCountries(List<Country> countries) {
    this.countries = countries;
}

public static class Country {
    private String name;
    private String code;
    private String phoneCode;

    public Country(String name, String code, String phoneCode) {
        this.name = name;
        this.code = code;
        this.phoneCode = phoneCode;
    }


    public String getCode() {
        return code;
    }

    public void setCode(String code) {
        this.code = code;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPhoneCode() {
        return phoneCode;
    }

    public void setPhoneCode(String phoneCode) {
        this.phoneCode = phoneCode;
    }

}

}

你的 json 你的 Java 模型应该是这样的

public class Example {

private Boolean sucess;
private List<Result> result = null;

public Boolean getSucess() {
return sucess;
}

public void setSucess(Boolean sucess) {
this.sucess = sucess;
}

public List<Result> getResult() {
return result;
}

public void setResult(List<Result> result) {
this.result = result;
}

}

我的 Java 对象构造函数返回“null”

My Java object constructor returning “null”

null

android

object

rx-java