java android - iterate JSON objects in array

Question

How can i iterate over all of the "listPages" in this JSON object?

  {
        "listPages": [
            {
                "title": "Accounts",
                "recordType": "Company",
            },
            {
                "title": "Contacts",
                "recordType": "Person",
            }
        ]
    }

I'm trying to add list items to a list from each item in the listPages array via this code:

    JSONObject JSONConfig = envConfig.getEnvConfig(this);

    try{
        JSONArray listPages = JSONConfig.getJSONArray("listPages");         
        for(int i = 0 ; i < listPages.length() ; i++){
            listItems.add(listPages.getJSONObject(i).getString("title"));
        }
        adapter.notifyDataSetChanged();
    }catch(Exception e){
        e.printStackTrace();
    }

I can see in logcat that i'm getting a system error: "java.lang.NullPointerException" on the following line.

JSONArray listPages = JSONConfig.getJSONArray("listPages");

I've tried reading and tweaking things from other questions but i can't figure it out. Help would be much appreciated.

here is my envConfig.java class

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;

import org.json.JSONObject;

import android.content.Context;
import android.util.Log;

public class EnvConfig {

    private String rawJSONString;
    private JSONObject jsonObjRecv;

    public JSONObject getEnvConfig(Context context){
        InputStream inputStream = context.getResources().openRawResource(
                R.raw.envconfigg);
        BufferedReader reader = new BufferedReader(new InputStreamReader(
                inputStream));
        StringBuilder sb = new StringBuilder();

        String line = null;
        try {
            while ((line = reader.readLine()) != null) {
                sb.append(line + "\n");
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                inputStream.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        rawJSONString = sb.toString();
        try {
            JSONObject jsonObjRecv = new JSONObject(rawJSONString);
            Log.i("Test", "<JSONObject>\n" + jsonObjRecv.toString()
                    + "\n</JSONObject>");
        } catch (Exception e) {
            e.printStackTrace();
        }

        return jsonObjRecv;
    }
}

Answer 1

This is a classic problem of instance shadowing. You declare a new variable in your method, in the try block, with the same name as a class variable. So, the class variable is shadowed and thus, never initialized. When you later return it from the method, its null.

public class EnvConfig {

    private String rawJSONString;
    private JSONObject jsonObjRecv; // <-- you declare a class variable here

    // ...

    try {
        JSONObject jsonObjRecv = new JSONObject(rawJSONString); // <-- shadowed here!

Unless you are trying to avoid re-parsing the JSON repeatedly, I would advise getting rid of the class variables altogether. Otherwise, get rid of the local variable.

Answer 2

Here is the code that I use for Parsing my JSON Data, I am not familiar with the JSONConfig that you are using, however this works prefectly for me.

JSONObject jsonObject = (JSONObject) new JSONTokener(/*Json String Data*/).nextValue();
JSONArray jsonArray = jsonObject.getJSONArray(/*Name of JSON Array*/);