在我的 android 应用程序开发项目中需要 JSON 解析方面的帮助答案

【问题标题】：need help in JSON parsing for my android application development project在我的 android 应用程序开发项目中需要 JSON 解析方面的帮助
【发布时间】：2017-11-29 22:11:53
【问题描述】：

获取后我可以在 LOGCAT 中看到 JSON，但它没有显示在我的活动中。它一直在加载...

我的网络服务的链接是：“http://dcafe-menu.getsandbox.com/dcafe-menu-friday”

**<-- My FridayMenu.java is:  ->>**
package com.example.nishant.messmenu;

import android.app.ProgressDialog;
import android.os.AsyncTask;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import java.util.HashMap;

public class FridayMenu extends AppCompatActivity {

    private ProgressDialog pDialog;

    // JSON Node names
    private static final String TAG_FRIDAY = "fridaymenu";
    private static final String TAG_DRY_CEREAL = "DRY_CEREAL";
    private static final String TAG_DRINK_ONE = "DRINK_ONE";
    private static final String TAG_DRINK_TWO = "DRINK_TWO";
    private static final String TAG_MAIN = "MAIN";
    private static final String TAG_ACCOMPANIMENT = "ACCOMPANIMENT";
    private static final String TAG_B_BREAD = "B_BREAD";
    private static final String TAG_L_SALAD = "L_SALAD";
    private static final String TAG_L_RICE = "L_RICE";
    private static final String TAG_L_DAL = "L_DAL";
    private static final String TAG_L_PANEER = "L_PANEER DISH";
    private static final String TAG_L_SEMI = "L_SEMI DRY VEG";
    private static final String TAG_L_GRAVY = "L_GRAVY VEGETABLE";
    private static final String TAG_L_DESSERT = "L_DESSERT";
    private static final String TAG_L_BREAD = "L_BREAD";
    private static final String TAG_L_CURD = "L_CURD";
    private static final String TAG_SNACKS = "SNACKS";
    private static final String TAG_DRINK = "DRINK";
    private static final String TAG_D_SALAD = "D_SALAD";
    private static final String TAG_D_RICE = "D_RICE";
    private static final String TAG_D_DAL = "D_DAL";
    private static final String TAG_D_PANEER = "D_PANEER DISH";
    private static final String TAG_D_SEMI = "D_SEMI DRY VEG";
    private static final String TAG_D_GRAVY = "D_GRAVY VEGETABLE";
    private static final String TAG_D_DESSERT = "D_DESSERT";
    private static final String TAG_D_BREAD = "D_BREAD";
    private static final String TAG_D_CURD = "D_CURD";



    // contacts JSONArray
    JSONArray fridaymenu = null;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_friday_menu);


        // Calling async task to get json
        new GetContacts().execute();
    }


    /**
     * Async task class to get json by making HTTP call
     * */
    private class GetContacts extends AsyncTask<Void, Void, Void> {

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            // Showing progress dialog
            pDialog = new ProgressDialog(FridayMenu.this);
            pDialog.setMessage("Please wait...");
            pDialog.setCancelable(false);
            pDialog.show();

        }

        @Override
        protected Void doInBackground(Void... arg0) {
            // Creating service handler class instance
            ServiceHandler sh = new ServiceHandler();

            // Making a request to url and getting response
            String url = "http://dcafe-menu.getsandbox.com/dcafe-menu-friday";
            String jsonStr = sh.makeServiceCall(url, ServiceHandler.GET);

            Log.d("Response: ", "> " + jsonStr);

            if (jsonStr != null) {
                try {
                    JSONObject jsonObj = new JSONObject(jsonStr);
                    // Getting JSON Array node
                    fridaymenu = jsonObj.getJSONArray(TAG_FRIDAY);


                    // looping through All Contacts
                    for (int i = 0; i < fridaymenu.length(); i++) {
                        JSONObject c = fridaymenu.getJSONObject(i);

                        String DRY_CEREAL = c.getString(TAG_DRY_CEREAL);
                        String DRINK_ONE = c.getString(TAG_DRINK_ONE);
                        String DRINK_TWO = c.getString(TAG_DRINK_TWO);
                        String MAIN = c.getString(TAG_MAIN);
                        String ACCOMPANIMENT = c.getString(TAG_ACCOMPANIMENT);
                        String B_BREAD = c.getString(TAG_B_BREAD);
                        String L_SALAD = c.getString(TAG_L_SALAD);
                        String L_RICE = c.getString(TAG_L_RICE);
                        String L_DAL = c.getString(TAG_L_DAL);
                        String L_PANEER = c.getString(TAG_L_PANEER);
                        String L_SEMI = c.getString(TAG_L_SEMI);
                        String L_GRAVY = c.getString(TAG_L_GRAVY);
                        String L_DESSERT = c.getString(TAG_L_DESSERT);
                        String L_BREAD = c.getString(TAG_L_BREAD);
                        String L_CURD = c.getString(TAG_L_CURD);
                        String SNACKS = c.getString(TAG_SNACKS);
                        String DRINK = c.getString(TAG_DRINK);
                        String D_SALAD = c.getString(TAG_D_SALAD);
                        String D_RICE = c.getString(TAG_D_RICE);
                        String D_DAL = c.getString(TAG_D_DAL);
                        String D_PANEER = c.getString(TAG_D_PANEER);
                        String D_SEMI = c.getString(TAG_D_SEMI);
                        String D_GRAVY = c.getString(TAG_D_GRAVY);
                        String D_DESSERT = c.getString(TAG_D_DESSERT);
                        String D_BREAD = c.getString(TAG_D_BREAD);
                        String D_CURD = c.getString(TAG_D_CURD);


                        // tmp hashmap for single contact
                        HashMap<String, String> fridaymenu = new HashMap<String, String>();


                        // adding each child node to HashMap key => value
                        fridaymenu.put(TAG_DRY_CEREAL, DRY_CEREAL);
                        fridaymenu.put(TAG_DRINK_ONE, DRINK_ONE);
                        fridaymenu.put(TAG_DRINK_TWO, DRINK_TWO);
                        fridaymenu.put(TAG_MAIN, MAIN);
                        fridaymenu.put(TAG_ACCOMPANIMENT, ACCOMPANIMENT);
                        fridaymenu.put(TAG_B_BREAD, B_BREAD);
                        fridaymenu.put(TAG_L_SALAD, L_SALAD);
                        fridaymenu.put(TAG_L_RICE, L_RICE);
                        fridaymenu.put(TAG_L_DAL, L_DAL);
                        fridaymenu.put(TAG_L_PANEER, L_PANEER);
                        fridaymenu.put(TAG_L_SEMI, L_SEMI);
                        fridaymenu.put(TAG_L_GRAVY, L_GRAVY);
                        fridaymenu.put(TAG_L_DESSERT, L_DESSERT);
                        fridaymenu.put(TAG_L_BREAD, L_BREAD);
                        fridaymenu.put(TAG_L_CURD, L_CURD);
                        fridaymenu.put(TAG_SNACKS, SNACKS);
                        fridaymenu.put(TAG_DRINK, DRINK);
                        fridaymenu.put(TAG_D_SALAD, D_SALAD);
                        fridaymenu.put(TAG_D_RICE, D_RICE);
                        fridaymenu.put(TAG_D_DAL, D_DAL);
                        fridaymenu.put(TAG_D_PANEER, D_PANEER);
                        fridaymenu.put(TAG_D_SEMI, D_SEMI);
                        fridaymenu.put(TAG_D_GRAVY, D_GRAVY);
                        fridaymenu.put(TAG_D_DESSERT, D_DESSERT);
                        fridaymenu.put(TAG_D_BREAD, D_BREAD);
                        fridaymenu.put(TAG_D_CURD, D_CURD);

                    }

                }
                catch (JSONException e) {
                    e.printStackTrace();
                }
            } else {
                Log.e("ServiceHandler", "Couldn't get any data from the url");
            }

            return null;
        }
    }
}

** 我在 LOGCAT 中得到以下信息 **

我可以在 logcat 中看到 json，但它没有加载到我的应用程序中。在logcat中可以看到以下内容。当我的活动开始时，它会继续加载。我等了15分钟。我仍然无法在我的应用程序中看到所需的结果：

11-30 03:10:32.041 9973-10198/com.example.nishant.messmenu W/System.err: org.json.JSONException: No value for L_SALAD
11-30 03:10:32.070 9973-10198/com.example.nishant.messmenu W/System.err:     at org.json.JSONObject.get(JSONObject.java:389)
11-30 03:10:32.071 9973-10198/com.example.nishant.messmenu W/System.err:     at org.json.JSONObject.getString(JSONObject.java:550)
11-30 03:10:32.072 9973-10198/com.example.nishant.messmenu W/System.err:     at com.example.nishant.messmenu.FridayMenu$GetContacts.doInBackground(FridayMenu.java:109)
11-30 03:10:32.072 9973-10198/com.example.nishant.messmenu W/System.err:     at com.example.nishant.messmenu.FridayMenu$GetContacts.doInBackground(FridayMenu.java:68)
11-30 03:10:32.072 9973-10198/com.example.nishant.messmenu W/System.err:     at android.os.AsyncTask$2.call(AsyncTask.java:304)
11-30 03:10:32.072 9973-10198/com.example.nishant.messmenu W/System.err:     at java.util.concurrent.FutureTask.run(FutureTask.java:237)
11-30 03:10:32.072 9973-10198/com.example.nishant.messmenu W/System.err:     at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:243)
11-30 03:10:32.072 9973-10198/com.example.nishant.messmenu W/System.err:     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1133)
11-30 03:10:32.072 9973-10198/com.example.nishant.messmenu W/System.err:     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:607)
11-30 03:10:32.072 9973-10198/com.example.nishant.messmenu W/System.err:     at java.lang.Thread.run(Thread.java:761)

【问题讨论】：

标签： java android json android-studio get

【解决方案1】：

为此只需做两件事：

在所有 Json 获取对象而不是使用“get”中使用“opt”：

  String DRY_CEREAL = c.optString(TAG_DRY_CEREAL);

其次，在你放入 hashmap 的地方使用这个：

 If(DRY_CEREAL==null||DRY_CEREAL.isEmpty())
 {
        fridaymenu.put(TAG_DRY_CEREAL, " ");
 }
 else
 {
        fridaymenu.put(TAG_DRY_CEREAL, DRY_CEREAL);
 }

对每个 hashmap 条目执行此操作。它会解决你的问题。

【讨论】：

它还在继续加载，我隐藏了对话框，但它仍然没有放入数据。就像你说的那样，我将它用于每个哈希图条目。你能看看我的项目并帮我解决问题吗？[链接](drive.google.com/drive/folders/…)
兄弟，你的java文件不存在。请发邮件给我 ankitpatidar030@gmail.com
我刚刚给你发了邮件，请检查你的收件箱
嘿，你想在屏幕上这样输出.... 干麦片：玉米片，饮料 1：热牛奶
在邮件中查找项目

【解决方案2】：

你必须使用 "opt" 代替 "get" 和默认的回退值

看看它们之间的区别：

getString(String name)

Returns the value mapped by name if it exists, coercing it if necessary, or throws if no such mapping exists. 

 optString(String name, String fallback)

 Returns the value mapped by name if it exists, coercing it if necessary, or fallback if no such mapping exists.

例如你的情况：

当前

  String L_SALAD = c.getString(TAG_L_SALAD);

替换为：

  String L_SALAD = c.optString(TAG_L_SALAD,"");

对每个都做同样的事情。我希望你的问题会得到解决。

【讨论】：

它删除了我提到的错误。但我仍然没有在我的应用程序中得到任何输出。你能看看我的项目并帮助我纠正问题吗？ [链接](drive.google.com/drive/folders/…)

【解决方案3】：

它继续加载的原因是，您没有隐藏进度条。

@Override
    protected void onPostExecute(Void aVoid) {
        super.onPostExecute(aVoid);
        pDialog.hide();
    }

【讨论】：

我把它藏起来了，但我认为它唯一的区别是现在对话框没有出现。但我仍然无法得到输出。