Why i can not save the json object into the json array?

Question

I'm beginner in android,write simple application to send json array to server,write this code:

JSONArray jsonArray = new JSONArray();
            JSONObject obj = new JSONObject();
            String DATABASE_NAME = "TEMPFOOD";
            String TABLE_NAME = "tempData";
            try{
                SQLiteDatabase mydb = openOrCreateDatabase(DATABASE_NAME, TempActivity.MODE_PRIVATE,null);
                Cursor allrows  = mydb.rawQuery("SELECT * FROM "+  TABLE_NAME, null);
                if(allrows.moveToFirst()){
                    do{
                        String Food_Name = allrows.getString(0);
                        String Value = allrows.getString(1);
                        String NOBAT = allrows.getString(2);
                        String TIME = allrows.getString(3);
                        String DATE = allrows.getString(4);
                        try {
                            obj.put("Food_Name", Food_Name)
                                    .put("Value", Value)
                                    .put("NOBAT", NOBAT)
                                    .put("TIME", TIME)
                                    .put("DATE", DATE);
                        } catch (JSONException e) {
                            e.printStackTrace();
                        }
                        jsonArray.put(obj);
                    }
                    while(allrows.moveToNext());
                }
                mydb.close();
            }catch(Exception e){
                //Toast.makeText(getApplicationContext(), "Error", Toast.LENGTH_LONG).show();
            }
            String jsonText = jsonArray.toString();

for example i read 4 record from sqlite,save into the jsonArray latest record,why?how can i solve that?thanks.

try putting JSONObject obj = new JSONObject(); inside do-while loop. I think it's happening because you are using same JSONObject. just like List. — Dhaval Patel, Nov 17 '15 at 17:25

score 2 · Accepted Answer · answered Nov 17 '15 at 17:27

It is only storing the last record because you are not creating a new JSONObject in your do...while loop. See my edited code.

JSONArray jsonArray = new JSONArray();
        JSONObject obj = new JSONObject();
        String DATABASE_NAME = "TEMPFOOD";
        String TABLE_NAME = "tempData";
        try{
            SQLiteDatabase mydb = openOrCreateDatabase(DATABASE_NAME, TempActivity.MODE_PRIVATE,null);
            Cursor allrows  = mydb.rawQuery("SELECT * FROM "+  TABLE_NAME, null);
            if(allrows.moveToFirst()){
                do{
                    obj = new JSONObject();
                    String Food_Name = allrows.getString(0);
                    String Value = allrows.getString(1);
                    String NOBAT = allrows.getString(2);
                    String TIME = allrows.getString(3);
                    String DATE = allrows.getString(4);
                    try {
                        obj.put("Food_Name", Food_Name)
                                .put("Value", Value)
                                .put("NOBAT", NOBAT)
                                .put("TIME", TIME)
                                .put("DATE", DATE);
                    } catch (JSONException e) {
                        e.printStackTrace();
                    }
                    jsonArray.put(obj);
                }
                while(allrows.moveToNext());
            }
            mydb.close();
        }catch(Exception e){
            //Toast.makeText(getApplicationContext(), "Error", Toast.LENGTH_LONG).show();
        }
        String jsonText = jsonArray.toString();

Pankaj Nimgade · Answer 2 · 2015-11-17T17:41:33.857

Another example to show use of Gson library

make a Record.java class

import com.google.gson.annotations.SerializedName;

public class Record {

    @SerializedName("Name")
    private String name;

    @SerializedName("password")
    private String password;

    @SerializedName("item1")
    private String item1;

    public String getName() {
        return name;
    }

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

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String getItem1() {
        return item1;
    }

    public void setItem1(String item1) {
        this.item1 = item1;
    }
}

make a test for this RecordTestDrive.java

import java.util.ArrayList;

import com.google.gson.Gson;

public class RecordTestDrive {

    public static void main(String[] args) {

        ArrayList<Record> records = new ArrayList<>();

        for (int i = 0; i < 4; i++) {
            Record record = new Record();
            record.setName("Name_"+i);
            record.setPassword("password_"+i);
            record.setItem1("item_"+i);
            records.add(record);
        }

        String jsonResult = (new Gson()).toJson(records);
        System.out.println(""+jsonResult);

    }
}

output==>

[
  {
    "Name": "Name_0",
    "password": "password_0",
    "item1": "item_0"
  },
  {
    "Name": "Name_1",
    "password": "password_1",
    "item1": "item_1"
  },
  {
    "Name": "Name_2",
    "password": "password_2",
    "item1": "item_2"
  },
  {
    "Name": "Name_3",
    "password": "password_3",
    "item1": "item_3"
  }
]

In this manner once you have data read from the SQLite database into your objects, after which you can easily make array of JSON String from the data you have gathered from the database to send it to server

Why i can not save the json object into the json array?

2 Answers2

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