改造错误：java.lang.IllegalStateException：预期 BEGIN_OBJECT 但在第 1 行第 2 列路径 $ [重复] 处为 BEGIN_ARRAY

Question

学习如何在我的 Android 应用中使用 Retrofit，出现以下错误： 如果可以的话请帮忙。谢谢，

java.lang.IllegalStateException: Expected BEGIN_OBJECT but was BEGIN_ARRAY at line 1 column 2 path $

这是我的代码：如果您也可以，请提供帮助：

public void clickButton(View view){
    button = (Button) findViewById(R.id.button);
    drawDate = (TextView)findViewById(R.id.drawDate);

    LotteryAPI.Factory.getIstance().getLottery().enqueue(new Callback<Lottery>() {
        @Override
        public void onResponse(Call<Lottery> call, Response<Lottery> response) {
            Log.d(TAG, "getting Draw Date");
            Log.d(TAG, "Draw Date is: " + response.body().getDrawDate());
            String DRAW_DATE = response.body().getDrawDate();
            drawDate.setText("DRAW_DATE");
            Log.d(TAG, "done setting Draw Date");
        }

        @Override
        public void onFailure(Call<Lottery> call, Throwable t) {
            Log.e("Failed",  t.getMessage());
            Log.d(TAG, "At onFailure - Something Failed!!");
            Log.d(TAG, "error is: " + t.getCause());

        }
    });
}

这是我的界面：

String BASE_URL = "https://data.ny.gov/resource/h6w8-42p9.json/";

@GET("?$$app_token=xxxxxxGtxKw3s6gurSxxxxxx")
Call<Lottery> getLottery();


class Factory {
    public static LotteryAPI service;

    public static LotteryAPI getIstance() {
        if (service == null) {
            Retrofit retrofit = new Retrofit.Builder().addConverterFactory(GsonConverterFactory.create()).baseUrl(BASE_URL).build();
            service = retrofit.create(LotteryAPI.class);
            return service;
        } else {
            return service;
        }
    }
}

这是我的 POJO：

@Generated("org.jsonschema2pojo")
public class Lottery {

    @SerializedName("draw_date")
    @Expose
    private String drawDate;
    @SerializedName("mega_ball")
    @Expose
    private String megaBall;
    @SerializedName("multiplier")
    @Expose
    private String multiplier;
    @SerializedName("winning_numbers")
    @Expose
    private String winningNumbers;

    /**
     * 
     * @return
     *     The drawDate
     */
    public String getDrawDate() {
        return drawDate;
    }

    /**
     * 
     * @param drawDate
     *     The draw_date
     */
    public void setDrawDate(String drawDate) {
        this.drawDate = drawDate;
    }

    /**
     * 
     * @return
     *     The megaBall
     */
    public String getMegaBall() {
        return megaBall;
    }

    /**
     * 
     * @param megaBall
     *     The mega_ball
     */
    public void setMegaBall(String megaBall) {
        this.megaBall = megaBall;
    }

    /**
     * 
     * @return
     *     The multiplier
     */
    public String getMultiplier() {
        return multiplier;
    }

    /**
     * 
     * @param multiplier
     *     The multiplier
     */
    public void setMultiplier(String multiplier) {
        this.multiplier = multiplier;
    }

    /**
     * 
     * @return
     *     The winningNumbers
     */
    public String getWinningNumbers() {
        return winningNumbers;
    }

    /**
     * 
     * @param winningNumbers
     *     The winning_numbers
     */
    public void setWinningNumbers(String winningNumbers) {
        this.winningNumbers = winningNumbers;
    }

}

Answer 1

问题是端点正在返回您的 Lottery 类项目的列表，而您要求 Retrofit 将响应映射到单个 Lottery 项目。

尝试将Call<Lottery> getLottery(); 更改为Call<List<Lottery>> getLottery();。您还需要在 Retrofit 调用定义中对其进行更改。

Answer 2

你应该改变 POJO 类结构的结构，因为我可以看到你的 json 字符串是一个包含对象的数组。你必须做 POJO 类：

class Lottery {
  private String draw_date, mega_ball, multiplier, winning_numbers;

public Lottery() {}

public String getDraw_date() {
    return draw_date;
}

public void setDraw_date(String draw_date) {
    this.draw_date = draw_date;
}

public String getWinning_numbers() {
    return winning_numbers;
}

public void setWinning_numbers(String winning_numbers) {
    this.winning_numbers = winning_numbers;
}

public String getMega_ball() {
    return mega_ball;
}

public void setMega_ball(String mega_ball) {
    this.mega_ball = mega_ball;
}

public String getMultiplier() {
    return multiplier;
}

public void setMultiplier(String multiplier) {
    this.multiplier = multiplier;
}

}

您还必须将以下行从

更改为 LotteryAPI 接口

Call<Lottery> getLottery();

到

Call<List<Lottery>> getLottery();

然后在 onResponse() 回调中你应该遍历 LotteryObj 列表

 public void clickButton(View view){
    button = (Button) findViewById(R.id.button);
    drawDate = (TextView)findViewById(R.id.drawDate);

    LotteryAPI.Factory.getIstance().getLottery().enqueue(new Callback<List<Lottery>>() {
        @Override
        public void onResponse(Response<List<Lottery>> response, Retrofit retrofit) {
            Log.e(TAG, response.body()+"");
            for (Lottery lt : response.body()) {
                Log.e(TAG, lt.getDraw_date());
                Log.e(TAG, lt.getMega_ball());
                if (lt.getMultiplier() != null) Log.e(TAG, lt.getMultiplier());
                Log.e(TAG, lt.getWinning_numbers());
            }
                Log.d(TAG, "getting Draw Date");

// Log.d(TAG, "绘制日期为：" + response.body().getDrawDate()); // String DRAW_DATE = response.body().getDrawDate(); drawDate.setText("DRAW_DATE"); Log.d(TAG, "完成设置绘制日期"); }

        @Override
        public void onFailure(Throwable t) {
            Log.e("Failed",  t.getMessage());
            Log.d(TAG, "At onFailure - Something Failed!!");
            Log.d(TAG, "error is: " + t.getCause());
        }
    });
}