If your application stores data locally and you are planning to transfer data across different platforms (e.g. between mobile apps and websites, it is a good idea to store the data in JSON format. In this Android tip, I am going to show you how to read JSON array from the assets directory to display in a ListView.
Now in the assets directory of your current working project, you create a JSON file called jsondata.json. In the file, you have JSON data as shown below. There is a JSON array. In the JSON array, there are three JSON objects. Each object contains information (id, name, and sex) of a student. So, there are three students in the JSON file that will be displayed in the ListView.

[{"id":"100","sex":"M","name":"Andrew"},{"id":"101","sex":"F","name":"Stephie"}, {"id":"102","sex":"M","name":"Kalvin"}]

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

   xmlns:tools="http://schemas.android.com/tools"

   android:layout_width="match_parent"

   android:layout_height="match_parent"

   android:orientation="vertical"

   android:padding="10dp"

   tools:context=".MainActivity"

  >

<ListView

   android:id="@+id/listv"

   android:layout_width="match_parent"

   android:layout_height="wrap_content">

   </ListView>

</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

   android:orientation="horizontal"

   android:layout_width="match_parent"

   android:layout_height="match_parent"

   android:padding="10dp"

   >

   <TextView

      android:id="@+id/txtid"

      android:layout_width="wrap_content"

      android:layout_height="wrap_content"

      android:layout_weight="1"      

      />

   <TextView

      android:id="@+id/txtname"

      android:layout_width="wrap_content"

      android:layout_height="wrap_content"

      android:layout_weight="1"

      />

   <TextView

      android:id="@+id/txtsex"

      android:layout_width="wrap_content"

      android:layout_height="wrap_content"

      android:layout_weight="1"      

      />

</LinearLayout>

import android.content.Context;

import android.view.LayoutInflater;

import android.view.View;

import android.view.ViewGroup;

import android.widget.ArrayAdapter;

import android.widget.TextView;

import org.json.JSONException;

import org.json.JSONObject;

import java.util.ArrayList;

public class ListAdapter extends ArrayAdapter<JSONObject>{

   int vg;

   ArrayList<JSONObject> list;

   Context context;

   public ListAdapter(Context context, int vg, int id, ArrayList<JSONObject> list){

      super(context,vg, id,list);

      this.context=context;

      this.vg=vg;

      this.list=list;

   }

   public View getView(int position, View convertView, ViewGroup parent) {

      LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);

      View itemView = inflater.inflate(vg, parent, false);

      TextView txtId=(TextView)itemView.findViewById(R.id.txtid);

      TextView txtName=(TextView)itemView.findViewById(R.id.txtname);

      TextView txtSex=(TextView)itemView.findViewById(R.id.txtsex);

      try {

        txtId.setText(list.get(position).getString("id"));

        txtName.setText(list.get(position).getString("name"));

        txtSex.setText(list.get(position).getString("sex"));



      } catch (JSONException e) {

        e.printStackTrace();

      }



      return itemView;

   }

}

import android.support.v7.app.ActionBarActivity;

import android.os.Bundle;

import android.view.Menu;

import android.view.MenuItem;

import android.widget.ListView;

import org.json.JSONArray;

import org.json.JSONException;

import org.json.JSONObject;

import java.io.IOException;

import java.io.InputStream;

import java.util.ArrayList;



public class MainActivity extends ActionBarActivity {

     protected void onCreate(Bundle savedInstanceState) {

      super.onCreate(savedInstanceState);

      setContentView(R.layout.activity_main);

      JSONArray jsonArray=getJSonData("jsondata.json");

      ArrayList<JSONObject> listItems=getArrayListFromJSONArray(jsonArray);

      ListView listV=(ListView)findViewById(R.id.listv);

      ListAdapter adapter=new ListAdapter(this,R.layout.list_layout,R.id.txtid,listItems);

      listV.setAdapter(adapter);

     }

   private JSONArray getJSonData(String fileName){

      JSONArray jsonArray=null;

      try {

        InputStream is = getResources().getAssets().open(fileName);

        int size = is.available();

        byte[] data = new byte[size];

        is.read(data);

        is.close();

        String json = new String(data, "UTF-8");

        jsonArray=new JSONArray(json);

      }catch (IOException e){

        e.printStackTrace();

      }catch (JSONException je){

        je.printStackTrace();

      }

      return jsonArray;

   }

   private ArrayList<JSONObject> getArrayListFromJSONArray(JSONArray jsonArray){

      ArrayList<JSONObject> aList=new ArrayList<JSONObject>();

      try {

        if (jsonArray != null) {

           for (int i = 0; i < jsonArray.length(); i++) {

              aList.add(jsonArray.getJSONObject(i));

           }

        }

      }catch (JSONException je){je.printStackTrace();}

      return  aList;

   }

}

Posted by: Dara | post date: 05-20-2015 | Subject: Android Apps Development