Android Help : April 2016

Creating Layout:

The Main layout for our project is “activity_main” which has a ListView to display the array.

activity_main.xml

<RelativeLayout 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:paddingBottom="@dimen/activity_vertical_margin"

    android:paddingLeft="@dimen/activity_horizontal_margin"

    android:paddingRight="@dimen/activity_horizontal_margin"

    android:paddingTop="@dimen/activity_vertical_margin"

    tools:context=".MainActivity" >

    <ListView

        android:id="@+id/list"

        android:layout_width="fill_parent"

        android:layout_height="wrap_content"

        android:layout_above="@+id/getdata" />

    <Button

        android:id="@+id/getdata"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_alignParentBottom="true"

        android:layout_centerHorizontal="true"

        android:layout_marginBottom="23dp"

        android:text="Get Data" />

</RelativeLayout>

Next step is to create a layout for the list item that is to be displayed in ListView. Create the layout as list_v.xml which has three TextView’s to display the Array in each list item. Here I have created the TextView’s in LinearLayout.

list_v.xml

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<?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/vers"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        />

    <TextView

        android:id="@+id/name"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        />

    <TextView

        android:id="@+id/api"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        />

</LinearLayout>

Creating Activity:

Before creating the MainActivity we need to create a JSON Parser class which gets the JSON data from the URL and returns JSON Object.
In your Project create a new folder library in the src folder such that the package is “learn2crack.listview.library”. Create the JSONParser.java in the library folder.

JSONParser.java

package smr.listview.library;

import java.io.BufferedReader;

import java.io.IOException;

import java.io.InputStream;

import java.io.InputStreamReader;

import java.io.UnsupportedEncodingException;

import org.apache.http.HttpEntity;

import org.apache.http.HttpResponse;

import org.apache.http.client.ClientProtocolException;

import org.apache.http.client.methods.HttpPost;

import org.apache.http.impl.client.DefaultHttpClient;

import org.json.JSONException;

import org.json.JSONObject;

import android.util.Log;

public class JSONParser {

    static InputStream is = null;

    static JSONObject jObj = null;

    static String json = "";

    // constructor

    public JSONParser() {

    }

    public JSONObject getJSONFromUrl(String url) {

        // Making HTTP request

        try {

            // defaultHttpClient

            DefaultHttpClient httpClient = new DefaultHttpClient();

            HttpPost httpPost = new HttpPost(url);

            HttpResponse httpResponse = httpClient.execute(httpPost);

            HttpEntity httpEntity = httpResponse.getEntity();

            is = httpEntity.getContent();

        } catch (UnsupportedEncodingException e) {

            e.printStackTrace();

        } catch (ClientProtocolException e) {

            e.printStackTrace();

        } catch (IOException e) {

            e.printStackTrace();

        }

        try {

            BufferedReader reader = new BufferedReader(new InputStreamReader(

                    is, "iso-8859-1"), 8);

            StringBuilder sb = new StringBuilder();

            String line = null;

            while ((line = reader.readLine()) != null) {

                sb.append(line + "n");

            }

            is.close();

            json = sb.toString();

        } catch (Exception e) {

            Log.e("Buffer Error", "Error converting result " + e.toString());

        }

        // try parse the string to a JSON object

        try {

            jObj = new JSONObject(json);

        } catch (JSONException e) {

            Log.e("JSON Parser", "Error parsing data " + e.toString());

        }

        // return JSON String

        return jObj;

    }

}

Next step is to create MainActivity.The Button “Get Data” is used to trigger the AsyncTask which process the backgroung Data. Here we are defining the array “oslist” which is displayed as text in ListView. The JSONArray is “android” which we got from the URL. It is then stored in a string. We are using ListAdapter is generate ListView. Finally we are using OnItemClickListener to display the OS in Toast when it is clicked.

MainActivity.java

package learn2crack.listview;

import java.util.ArrayList;

import java.util.HashMap;

import org.json.JSONArray;

import org.json.JSONException;

import org.json.JSONObject;

import android.app.Activity;

import android.app.ProgressDialog;

import android.os.AsyncTask;

import android.os.Bundle;

import android.view.View;

import android.widget.AdapterView;

import android.widget.Button;

import android.widget.ListAdapter;

import android.widget.ListView;

import android.widget.SimpleAdapter;

import android.widget.TextView;

import android.widget.Toast;

import learn2crack.listview.library.JSONParser;

public class MainActivity extends Activity {

    ListView list;

    TextView ver;

    TextView name;

    TextView api;

    Button Btngetdata;

    ArrayList<HashMap<String, String>> oslist = new ArrayList<HashMap<String, String>>();

    //URL to get JSON Array

    private static String url = "http://api.learn2crack.com/android/jsonos/";

    //JSON Node Names

    private static final String TAG_OS = "android";

    private static final String TAG_VER = "ver";

    private static final String TAG_NAME = "name";

    private static final String TAG_API = "api";

    JSONArray android = null;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        oslist = new ArrayList<HashMap<String, String>>();

        Btngetdata = (Button)findViewById(R.id.getdata);

        Btngetdata.setOnClickListener(new View.OnClickListener() {

            @Override

            public void onClick(View view) {

                 new JSONParse().execute();

            }

        });

    }

    private class JSONParse extends AsyncTask<String, String, JSONObject> {

         private ProgressDialog pDialog;

        @Override

        protected void onPreExecute() {

            super.onPreExecute();

             ver = (TextView)findViewById(R.id.vers);

             name = (TextView)findViewById(R.id.name);

             api = (TextView)findViewById(R.id.api);

            pDialog = new ProgressDialog(MainActivity.this);

            pDialog.setMessage("Getting Data ...");

            pDialog.setIndeterminate(false);

            pDialog.setCancelable(true);

            pDialog.show();

        }

        @Override

        protected JSONObject doInBackground(String... args) {

            JSONParser jParser = new JSONParser();

            // Getting JSON from URL

            JSONObject json = jParser.getJSONFromUrl(url);

            return json;

        }

         @Override

         protected void onPostExecute(JSONObject json) {

             pDialog.dismiss();

             try {

                    // Getting JSON Array from URL

                    android = json.getJSONArray(TAG_OS);

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

                    JSONObject c = android.getJSONObject(i);

                    // Storing  JSON item in a Variable

                    String ver = c.getString(TAG_VER);

                    String name = c.getString(TAG_NAME);

                    String api = c.getString(TAG_API);

                    // Adding value HashMap key => value

                    HashMap<String, String> map = new HashMap<String, String>();

                    map.put(TAG_VER, ver);

                    map.put(TAG_NAME, name);

                    map.put(TAG_API, api);

                    oslist.add(map);

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

                    ListAdapter adapter = new SimpleAdapter(MainActivity.this, oslist,

                            R.layout.list_v,

                            new String[] { TAG_VER,TAG_NAME, TAG_API }, new int[] {

                                    R.id.vers,R.id.name, R.id.api});

                    list.setAdapter(adapter);

                    list.setOnItemClickListener(new AdapterView.OnItemClickListener() {

                        @Override

                        public void onItemClick(AdapterView<?> parent, View view,

                                                int position, long id) {

                            Toast.makeText(MainActivity.this, "You Clicked at "+oslist.get(+position).get("name"), Toast.LENGTH_SHORT).show();

                        }

                    });

                    }

            } catch (JSONException e) {

                e.printStackTrace();

            }

         }

    }

}

Creating Manifest:

Add the permision “android.permission.INTERNET” to the Manifest file as we need to access external Address.No other special Permissions are required for our project.

AndroidManifest.xml

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

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

    package="learn2crack.listview"

    android:versionCode="1"

    android:versionName="1.0" >

    <uses-sdk

        android:minSdkVersion="8"

        android:targetSdkVersion="19" />

    <application

        android:allowBackup="true"

        android:icon="@drawable/ic_launcher"

        android:label="@string/app_name"

        android:theme="@style/AppTheme" >

        <activity

            android:name="learn2crack.listview.MainActivity"

            android:label="@string/app_name" >

            <intent-filter>

                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />

            </intent-filter>

        </activity>

    </application>

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

</manifest>

Finally run the project in the Emulator.

Project Running in Emulator

Android Help

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Wednesday, April 6, 2016

Android Populate ListView from JSON – Example

Creating Layout:

Creating Activity:

Creating Manifest: