JSON Parsing in Android for Beginners

 JSON Parsing in Android for Beginners

What is JSON?

• JSON stands for JavaScript Object Notation.
• In JSON information is stored in an organised and easy to access manner so it  is easily readable and understandable by humans.

Example:

• Above code shows the format of JSON.
• All the variables are stored in key and value pair for ex, from the above data “age” is key and “27” is a value.
• By enclosing the variable’s value in curly braces, we’re indicating that the value is an object i.e data inside {} is object.
• In the above data [ ] indicates an array.All the objects are stored with in an array.
• we can access JSON data using an URL.In below example I am going to use this link “http://www.i2ce.in/reviews/1/1”.

How this program works:

•  Initially we call AsyncTask from mainactivity.java with in that(asynctask) we establish a connection to communicate with the server.
• Server will send the JSON data back to the Asynctask in mainactivity that data is stored temporarily in ratings.java by creating new objects for each rating.
• JSON  data will be received by adapter by get method in Ratings.java and pass this data to the listview.
• And our final listview will be like as shown in above image’s UI layout.

we have to add internet access permission in our manifest file.

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

step-2:

(use this step only if you get any errors while importing http libraries )

Add below line to gradle file after default configuration.

1 2 3

android {         useLibrary 'org.apache.http.legacy'     }

Add below dependencies into dependencies at the end of the gradle file.

1 2	compile 'org.apache.httpcomponents:httpcore:4.4.1'     compile 'org.apache.httpcomponents:httpclient:4.5'

finally your gradle file should look like this.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34

apply plugin: 'com.android.application' android {     compileSdkVersion 24     buildToolsVersion "24.0.0"     defaultConfig {         applicationId "com.some.yrate"         minSdkVersion 15         targetSdkVersion 24         versionCode 1         versionName "1.0"         testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"     }     android {         useLibrary 'org.apache.http.legacy'     }     buildTypes {         release {             minifyEnabled false             proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'         }     } } dependencies {     compile fileTree(dir: 'libs', include: ['*.jar'])     androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {         exclude group: 'com.android.support', module: 'support-annotations'     })     compile 'com.android.support:appcompat-v7:24.2.1'     testCompile 'junit:junit:4.12'     compile 'org.apache.httpcomponents:httpcore:4.4.1'     compile 'org.apache.httpcomponents:httpclient:4.5' }

step-3:

we have to add a listview  in activity_main.xml.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"     xmlns:tools="http://schemas.android.com/tools"     android:id="@+id/activity_main"     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"    > <ListView     android:layout_width="match_parent"     android:layout_height="wrap_content"     android:id="@+id/list_item"    /> </LinearLayout>

step-4:

we have to create a layout contains some list of items which are display in activity-main’s listview.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46

<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"     android:layout_width="match_parent"     android:layout_height="match_parent"     android:orientation="vertical">         <TextView             android:id="@+id/title"             android:layout_width="wrap_content"             android:layout_height="wrap_content"             android:textColor="#166CED"             android:textAppearance="?android:attr/textAppearanceLarge" />         <TextView             android:id="@+id/comment"             android:layout_width="wrap_content"             android:layout_height="wrap_content"             android:textColor="#D64530"             />         <TextView             android:id="@+id/usefulness"             android:layout_width="wrap_content"             android:layout_height="wrap_content"             android:textColor="#D64530"             android:textAppearance="?android:attr/textAppearanceSmall" />         <LinearLayout             android:layout_width="match_parent"             android:layout_height="wrap_content"             android:orientation="vertical">             <TextView                 android:layout_width="match_parent"                 android:layout_height="20dp"                 android:text="overall rating"                 android:textColor="#D64530"/>             <RatingBar                 android:layout_width="wrap_content"                 android:layout_height="40dp"                 android:numStars="5"                 android:stepSize="1"                 android:id="@+id/ratingbar"/>         </LinearLayout> </LinearLayout>

step-5:

create a java class called reviews, declare required variables . create getters and setters for those variables as shown below.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

public class reviews {     String title,comment,usefulness,stars;     public String getTitle() {         return title;     }     public void setTitle(String title) {         this.title = title;     }     public String getComment() {         return comment;     }     public void setComment(String comment) {         this.comment = comment;     }     public String getUsefulness() {         return usefulness;     }     public void setUsefulness(String usefulness) {         this.usefulness = usefulness;     }     public String getStars() {         return stars;     }     public void setStars(String stars) {         this.stars = stars;     } }

step-6:

create reviewsadapter.java class and add below code into that

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67

public class reviewsadapter  extends ArrayAdapter<reviews> {     private ArrayList<reviews> reviewList;     private LayoutInflater vi;     private int Resource;     private ViewHolder holder;     // Button soww;     View view;     //ArrayList<Reviews> cp=0;     int gen=0;     reviewsadapter(Context context, int resource, ArrayList<reviews> objects) {         super(context, resource, objects);         vi = (LayoutInflater) context                 .getSystemService(Context.LAYOUT_INFLATER_SERVICE);         Resource = resource;         this.reviewList = objects;     }     @Override     public View getView(int position, View convertView, @NonNull ViewGroup parent) {         View v = convertView;         // if view is null then set below views         if (v == null) {             holder = new ViewHolder();             v = vi.inflate(Resource, null);             //binding holder variables to xml views             holder.tvtitle = (TextView) v.findViewById(R.id.title);             holder.tvcomment = (TextView) v.findViewById(R.id.comment);             holder.tvusefullness = (TextView) v.findViewById(R.id.usefulness);             holder.rbrating = (RatingBar) v.findViewById(R.id.ratingbar);             v.setTag(holder);         } else {             holder = (ViewHolder) v.getTag();         }         //setting data to the holder vars from "Reviews" getters         holder.tvtitle.setText(reviewList.get(position).getTitle());         holder.tvcomment.setText(reviewList.get(position).getComment());         holder.tvusefullness.setText("usefullness:"+reviewList.get(position).getUsefulness());         holder.rbrating.setRating(Integer.parseInt(reviewList.get(position).getStars()));         return v;     }     private static class ViewHolder {         TextView tvtitle;         TextView tvcomment;         TextView tvusefullness;         RatingBar rbrating;     } }

step-7:

open MainActivity.java and add below code.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105

public class MainActivity extends AppCompatActivity {     ArrayList<reviews> reviewList;     reviewsadapter adapter;     @Override     public void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.activity_main);         reviewList = new ArrayList<reviews>();         new JSONAsyncTask().execute("http://www.i2ce.in/reviews/1/1");         final ListView listview = (ListView) findViewById(R.id.list_item);         adapter = new reviewsadapter(getApplicationContext(), R.layout.row, reviewList);         listview.setAdapter(adapter);     }     class JSONAsyncTask extends AsyncTask<String, Void, Boolean> {         private ProgressDialog dialog;         @Override         protected void onPreExecute() {             super.onPreExecute(); //for displaying progress bar             dialog = new ProgressDialog(MainActivity.this);             dialog.setMessage("Loading, please wait");             dialog.setTitle("Connecting server");             dialog.show();             dialog.setCancelable(false);         }         @Override         protected Boolean doInBackground(String... urls) {             try { //establishing http connection                 //------------------>>                 HttpGet httppost = new HttpGet(urls[0]);                 HttpClient httpclient = new DefaultHttpClient();                 HttpResponse response = httpclient.execute(httppost);                 // StatusLine stat = response.getStatusLine();                 int status = response.getStatusLine().getStatusCode();                 // if connected then access data                 if (status == 200) {                     HttpEntity entity = response.getEntity();                     String data = EntityUtils.toString(entity);                     JSONObject jsono = new JSONObject(data);                     JSONArray jarray = jsono.getJSONArray("reviews");                     for (int i = 0; i < jarray.length(); i++) {                         JSONObject object = jarray.getJSONObject(i);                         reviews rev = new reviews();                         //getting json object values from json array                         rev.setTitle(object.getString("title"));                         rev.setComment(object.getString("comment"));                         rev.setUsefulness(object.getString("usefulness"));                         //getting value within json object                         JSONObject numstar = object.optJSONObject("ratings");                         String sta = numstar.getString("Overall");                         rev.setStars(sta);                         //adding data to the arraylist                         reviewList.add(rev);                     }                     return true;                 }                 //------------------>>             } catch (ParseException e1) {                 e1.printStackTrace();             } catch (IOException e) {                 e.printStackTrace();             } catch (JSONException e) {                 e.printStackTrace();             }             return false;         }         protected void onPostExecute(Boolean result) {             // if data dint fetch from the url             dialog.cancel();             adapter.notifyDataSetChanged();             if (result == false)                 Toast.makeText(getApplicationContext(), "Unable to fetch data from server", Toast.LENGTH_LONG).show();         }     } }

Finally output should look like this: