Android Native JSON - ListView Multiple Fields - Download,Parse then Show

October 7, 2017 Oclemy Android JSON, Android ListView, Android HttpURLConnection 8 minutes, 20 seconds

Introduction

  • Stands for JavaScript Object Notation.
  • Is a data exchange format that is both light and easy for humans to read and write.
  • Based on a subset of JavaScript Programming language
  • Is text format that’s completely language independent and uses conventions familiar with C-family programming languages.

Structure

  • Can exist as a Collection of name/value pairs.

Each pair translates to Object, struct, dictionary, record, hashtable or associative array. Obviously this depends on the programming language at use.

  • Can also exist as an ordered list of values.

Then this corresponds to an array, vector, list, or sequence.

JSONObject and JSONArray

  • JSONObject – Is an unordered set of name/value pairs.

Typically surrounded with braces i.e.” { }”. Each name is then followed by a colon i.e. “:”. Then value of course. However, name/value pairs are separated by comma.

  • JSONArray – Is an ordered collection of values.

Typically begins with “[“and ends with “]” just as a normal array. Values are separated by comma. A value can be String, number, Boolean, null, Object, or an array.  

Section 1 : Our Connector Class

--

  • Establish connection for us.
  • Set connection properties.
package com.tutorials.hp.jsonlistviewmulti_items.m_JSON;

import java.io.IOException;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;

/**
 * -------------------ROLES-----------------------
 * 1.SET CONNECTION PROPRTIES
 * 2.ESTABLISH AND RETURN CONNECTION OBJ
 */
public class Connector {

    public static Object connect(String jsonURL)
    {
        try
        {
            URL url=new URL(jsonURL);
            HttpURLConnection con= (HttpURLConnection) url.openConnection();

            //CON PROPS
            con.setRequestMethod("GET");
            con.setConnectTimeout(15000);
            con.setReadTimeout(15000);
            con.setDoInput(true);

            return con;

        } catch (MalformedURLException e) {
            e.printStackTrace();
            return "Error "+e.getMessage();

        } catch (IOException e) {
            e.printStackTrace();
            return "Error "+e.getMessage();

        }
    }

}

Section 2 : Our JSON Downloader Class

  • Where we download our json data from network.
  • We do this in background thread using AsyncTask.
  • Meanwhile we show a progress dialog.
  • After this, we pass our json data to JSONParser class to be parsed.
package com.tutorials.hp.jsonlistviewmulti_items.m_JSON;

import android.app.ProgressDialog;
import android.content.Context;
import android.os.AsyncTask;
import android.widget.ListView;

import java.io.BufferedInputStream;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;

/**
 * -----------------------ROLES-------------------------
 * 1.CONNECT TO NETWORK
 * 2.DOWNLOAD DATA IN BACKGROUND THREAD
 * 3.SEND THE DATA TO PARSER TO BE PARSED
 */
public class JSONDownloader extends AsyncTask<Void,Void,String> {

    Context c;
    String jsonURL;
    ListView lv;

    ProgressDialog pd;

    public JSONDownloader(Context c, String jsonURL, ListView lv) {
        this.c = c;
        this.jsonURL = jsonURL;
        this.lv = lv;
    }

    @Override
    protected void onPreExecute() {
        super.onPreExecute();

        pd=new ProgressDialog(c);
        pd.setTitle("Download JSON");
        pd.setMessage("Downloading...Please wait");
        pd.show();

    }

    @Override
    protected String doInBackground(Void... voids) {
        return downlaod();
    }

    @Override
    protected void onPostExecute(String jsonData) {
        super.onPostExecute(jsonData);

        pd.dismiss();
        if(jsonData.startsWith("Error"))
        {
            String error=jsonData;
        }else
        {
            //PARSE
            new JSONParser(c,jsonData,lv).execute();
        }

    }

    private String downlaod()
    {
        Object connection=Connector.connect(jsonURL);
        if(connection.toString().startsWith("Error"))
        {
            return connection.toString();
        }

        //DOWNLOAD
        try
        {
            HttpURLConnection con= (HttpURLConnection) connection;
            if(con.getResponseCode()==con.HTTP_OK)
            {
                //GET INPUT FROM STREAM
                InputStream is=new BufferedInputStream(con.getInputStream());
                BufferedReader br=new BufferedReader(new InputStreamReader(is));

                String line;
                StringBuffer jsonData=new StringBuffer();

                //READ
                while ((line=br.readLine()) != null)
                {
                    jsonData.append(line+"n");
                }

                //CLOSE RESOURCES
                br.close();
                is.close();

                //RETURN JSON
                return jsonData.toString();

            }else
            {
                return "Error "+con.getResponseMessage();
            }
        } catch (IOException e) {
            e.printStackTrace();
            return "Error "+e.getMessage();
        }
    }

}

Section 3 : Our JSON Parser Class

  • Receives the JSON string we downloaded.
  • So we parse this particular json,filling an arraylist.
  • Then we bind our arraylist of data our view component via an adapter.
package com.tutorials.hp.jsonlistviewmulti_items.m_JSON;

import android.app.ProgressDialog;
import android.content.Context;
import android.os.AsyncTask;
import android.widget.ListView;
import android.widget.Toast;

import com.tutorials.hp.jsonlistviewmulti_items.m_Model.User;
import com.tutorials.hp.jsonlistviewmulti_items.m_UI.CustomAdapter;

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

import java.util.ArrayList;

/**
 * -----------------    ROLES -----------------------
 * 1.RECEIVE DOWNLOADED DATA
 * 2.PARSE IT
 * 3.CALL ADAPTER CLASS TO BIND IT TO CUSTOM GRIDVIEW
 */
public class JSONParser extends AsyncTask<Void,Void,Boolean>{

    Context c;
    String jsonData;
    ListView lv;

    ProgressDialog pd;
    ArrayList<User> users=new ArrayList<>();

    public JSONParser(Context c, String jsonData, ListView lv) {
        this.c = c;
        this.jsonData = jsonData;
        this.lv = lv;
    }

    @Override
    protected void onPreExecute() {
        super.onPreExecute();

        pd=new ProgressDialog(c);
        pd.setTitle("Parse JSON");
        pd.setMessage("Parsing...Please wait");
        pd.show();
    }

    @Override
    protected Boolean doInBackground(Void... voids) {
        return parse();
    }

    @Override
    protected void onPostExecute(Boolean isParsed) {
        super.onPostExecute(isParsed);

        pd.dismiss();
        if(isParsed)
        {
            //BIND
            lv.setAdapter(new CustomAdapter(c,users));
        }else
        {
            Toast.makeText(c, "Unable To Parse,Check Your Log output", Toast.LENGTH_SHORT).show();
        }

   }

    private Boolean parse()
    {
        try
        {
            JSONArray ja=new JSONArray(jsonData);
            JSONObject jo;

            users.clear();
            User user;

            for (int i=0;i<ja.length();i++)
            {
                jo=ja.getJSONObject(i);

                String name=jo.getString("name");
                String username=jo.getString("username");
                String email=jo.getString("email");

                user=new User();

                user.setName(name);
                user.setUsername(username);
                user.setEmail(email);

                users.add(user);
            }

            return true;

        } catch (JSONException e) {
            e.printStackTrace();
            return false;
        }
    }

}

Section 4 : Our CustomAdapter Class

  • Inflate our Custom Model into a View Item for our ListView.
  • Bind data to our AdapterView.
package com.tutorials.hp.jsonlistviewmulti_items.m_UI;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.TextView;

import com.tutorials.hp.jsonlistviewmulti_items.R;
import com.tutorials.hp.jsonlistviewmulti_items.m_Model.User;

import java.util.ArrayList;

/**
 * ---------------------------ROLES-------------------------------
 * | 1.INFLATE MODEL LAYOUT
 * | 2.BIND DATA TO GRIDVIEW
 * ----------------------------------------------------------------
 */
public class CustomAdapter extends BaseAdapter{

    Context c;
    ArrayList<User> users;

    public CustomAdapter(Context c, ArrayList<User> users) {
        this.c = c;
        this.users = users;
    }

    @Override
    public int getCount() {
        return users.size();
    }

    @Override
    public Object getItem(int i) {
        return users.get(i);
    }

    @Override
    public long getItemId(int i) {
        return i;
    }

    @Override
    public View getView(int i, View view, ViewGroup viewGroup) {
        if(view==null)
        {
            view=LayoutInflater.from(c).inflate(R.layout.model,viewGroup,false);
        }

        TextView nameTxt= (TextView) view.findViewById(R.id.nameTxt);
        TextView usernameTxt= (TextView) view.findViewById(R.id.usernameTxt);
        TextView emailTxt= (TextView) view.findViewById(R.id.emailTxt);

        User user= (User) this.getItem(i);

        nameTxt.setText(user.getName());
        emailTxt.setText(user.getEmail());
        usernameTxt.setText(user.getUsername());

        return view;
    }
}

Section 4 : Our MainActivity Class

  • Our launcher activity.
  • We start our downloader, passing in URL as well as other parameters.
package com.tutorials.hp.jsonlistviewmulti_items;

import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.widget.ListView;

import com.tutorials.hp.jsonlistviewmulti_items.m_JSON.JSONDownloader;

public class MainActivity extends AppCompatActivity {

    String jsonURL="http://jsonplaceholder.typicode.com/users";
    ListView lv;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        lv = (ListView) findViewById(R.id.lv);

        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                new JSONDownloader(MainActivity.this,jsonURL, lv).execute();
            }
        });
    }

}

Section 5 : Our Layout

ContentMain.xml

  • Displays our adapter view
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:context="com.tutorials.hp.jsonlistviewmulti_items.MainActivity"
    tools:showIn="@layout/activity_main">

    <ListView
        android:id="@+id/lv"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
         />
</RelativeLayout>

Model.xml

  • Inflated into a single viewitem for our ListView.
<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="horizontal" android:layout_width="match_parent"
    xmlns:card_view="http://schemas.android.com/apk/res-auto"
    android:layout_margin="10dp"
    card_view:cardCornerRadius="5dp"
    card_view:cardElevation="5dp"
    android:layout_height="200dp">

        <LinearLayout
            android:orientation="vertical"
            android:layout_width="match_parent"
            android:layout_height="match_parent">

            <TextView
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:textAppearance="?android:attr/textAppearanceLarge"
                android:text="Name"
                android:id="@+id/nameTxt"
                android:padding="10dp"
                android:textColor="@color/colorAccent"
                android:textStyle="bold"
                android:layout_alignParentLeft="true"
                />

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:textAppearance="?android:attr/textAppearanceLarge"
                android:text="Email....................."
                android:lines="3"
                android:id="@+id/emailTxt"
                android:padding="10dp"
                android:layout_alignParentLeft="true"
                />

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:textAppearance="?android:attr/textAppearanceMedium"
                android:text="Username"
                android:textStyle="italic"
                android:id="@+id/usernameTxt" />

    </LinearLayout>

</android.support.v7.widget.CardView>

Section 6 : Our Manifest

  • Make sure you add permission for accessing internet.
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.tutorials.hp.jsonlistviewmulti_items">

    <uses-permission android:name="android.permission.INTERNET"/>

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity
            android:name=".MainActivity"
            android:label="@string/app_name"
            android:theme="@style/AppTheme.NoActionBar">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

How To Run

  1. Download the project.
  2. You'll get a zipped file,extract it.
  3. Open the Android Studio.
  4. Now close, already open project.
  5. From the Menu bar click on File >New> Import Project.
  6. Now Choose a Destination Folder, from where you want to import project.
  7. Choose an Android Project.
  8. Now Click on “OK“.
  9. Done, your done importing the project,now edit it.

More Resources

Resource Link
GitHub Browse Browse
GitHub Download Link Download

Good day.

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