The tutorial is about how to connect Android apps and online database using the JSON formatted data interchange. The server facilities and JSON encoded data has been explained in the previous tutorials;
( Android and JSON Insert, Android and JSON Search ).
The overview concept of JSON data inter change.
JSON formatted data sample
First we look at our database structure for this project.
Part A: The online database
The table is training, and this is the structure.
There is a PHP script that generate a JSON encoded data from the above table.
The PHP script to generate JSON formatted data;
<?php //search.php /* * Following code will search training based on keywords */ // array for JSON response $response = array(); // include connect class require_once __DIR__ . '/connect.php'; // connecting to db $db = new DB_CONNECT(); $keyword=$_GET["keyword"]; // get idioms based on keyword //using LIKE $result = mysql_query("SELECT * FROM a_training WHERE trainingname LIKE '%$keyword%' LIMIT 0, 20") or die(mysql_error()); // check for empty result if (mysql_num_rows($result) > 0) { // looping through all results $response["traininglist"] = array(); while ($row = mysql_fetch_array($result)) { // temp user array $traininglist= array(); $traininglist["id"] = $row["id"]; $traininglist["trainingname"] = $row["trainingname"]; $traininglist["website"] = $row["website"]; $traininglist["contact"] = $row["contact"]; $traininglist["trainingdesc"] = $row["trainingdesc"]; // push single idiom array into final response array array_push($response["traininglist"], $traininglist); } // success $response["success"] = 1; // echoing JSON response echo json_encode($response); } else { // no products found $response["success"] = 0; $response["message"] = "No training found"; // echo no users JSON echo json_encode($response); } ?>
The expected output as viewed in the Android device.
Part B: The mobile app interfaces
This part is to create a mobile apps interface, by creating a new project in Android Studio. There will be two activities. The first is the search box. And the second screen activity is to display the result.
As you could notice there is a login UI below, that is for the next exercise to create a LOGIN facility.
activity_main.xml – the search box.
<?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: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"
tools:context="net.kerul.jsonlisting.MainActivity"
android:background="@drawable/bgsplit">
<EditText
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:inputType="textNoSuggestions|textPersonName"
android:ems="10"
android:layout_alignParentTop="true"
android:id="@+id/txtsearch"
android:hint="Search training..."
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_toLeftOf="@+id/btnsearch"
android:layout_toStartOf="@+id/btnsearch"
android:layout_alignBottom="@+id/btnsearch" />
<ImageButton
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:srcCompat="@drawable/ic_search48"
android:layout_alignParentRight="true"
android:layout_alignParentEnd="true"
android:id="@+id/btnsearch"
android:layout_alignParentTop="true" />
<LinearLayout
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_below="@+id/txtsearch"
android:layout_marginTop="120dp"
android:layout_alignParentRight="true"
android:layout_alignParentEnd="true"
android:background="#50ff0000">
<TextView
android:text="Authorised login only"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/textView"
android:textColor="#000000"
android:textAlignment="center"
android:textSize="24sp"
android:background="#ff0000" />
<EditText
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:inputType="textPersonName"
android:ems="10"
android:id="@+id/txtuname"
android:hint="Username" />
<EditText
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:inputType="textPassword"
android:ems="10"
android:id="@+id/txtpwd"
android:drawableRight="@android:drawable/ic_secure"
android:hint="Password" />
<Button
android:text="Login"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/btnlogin" />
</LinearLayout>
</RelativeLayout>
activity_listing.xml – the result display. The main UI component here is ListView with the id list.
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/activity_listing"
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="net.kerul.jsonlisting.Listing"
android:background="#FFA233" >
<ListView
android:id="@+id/list"
android:layout_width="fill_parent"
android:layout_height="wrap_content" />
</RelativeLayout>
list_item.xml – this is to display one record. This list_item will be re-used by ListView for each record.
<?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/id"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:paddingBottom="2dip"
android:paddingTop="6dip"
android:textColor="@color/colorPrimaryDark"
android:textSize="16sp"
android:textStyle="bold" />
<TextView
android:id="@+id/trainingname"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:paddingBottom="2dip"
android:textColor="@color/colorAccent" />
<TextView
android:id="@+id/website"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textColor="#5d5d5d"
android:textStyle="bold" />
</LinearLayout>
Part C: The Java files contain;
1. MainActivity.java – main interface where the search box is.
2. Listing.java – will search to the online database do the result listing.
3. HttpHandle.java – to handle the connection to the JSON service online page.
MainActivity.java – the activity screen is activity_main.xml
package net.kerul.jsonlisting;
import android.app.Dialog;
import android.app.ProgressDialog;
import android.content.Intent;
import android.os.AsyncTask;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.ImageButton;
import java.io.InputStream;
public class MainActivity extends AppCompatActivity implements View.OnClickListener{
ImageButton btnsearch;
EditText txtsearch;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//UI
txtsearch=(EditText)findViewById(R.id.txtsearch);
btnsearch=(ImageButton)findViewById(R.id.btnsearch);
btnsearch.setOnClickListener(this);
}//end onCreate
public void onClick(View v){
if(v.getId()==R.id.btnsearch){
Intent listing= new Intent(this,Listing.class);
listing.putExtra("searchkey",txtsearch.getText().toString());
startActivity(listing);
}
}//end onCLick
}
Listing.java – the activity screen is activity_listing.xml
package net.kerul.jsonlisting;
import android.app.ProgressDialog;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.Toast;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.util.ArrayList;
import java.util.HashMap;
public class Listing extends AppCompatActivity {
private String TAG = Listing.class.getSimpleName();
private ProgressDialog pDialog;
private ListView lv;
// URL to get contacts JSON
ArrayList<HashMap<String, String>> traininglist;
String searchkey;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_listing);
Bundle extras = getIntent().getExtras();
searchkey=extras.getString("searchkey").toString();
//rename actionbar title to search keyword
setTitle(searchkey+" Trainings");
//URL with searchkey
traininglist = new ArrayList<>();
lv = (ListView)findViewById(R.id.list);
new GetTraining().execute();
}
/**
* Async task class to get json by making HTTP call
*/
private class GetTraining extends AsyncTask<Void, Void, Void> {
//Log.e(url2);
@Override
protected void onPreExecute() {
super.onPreExecute();
// Showing progress dialog
pDialog = new ProgressDialog(Listing.this);
pDialog.setMessage("Please wait...");
pDialog.setCancelable(false);
pDialog.show();
}
@Override
protected Void doInBackground(Void... arg0) {
HttpHandler sh = new HttpHandler();
//set the URL address of the JSON service page here
String url2 = "http://khirulnizam.com/training/search.php?keyword="+searchkey;
Log.e(TAG,url2);
// Making a request to url and getting response
String jsonStr = sh.makeServiceCall(url2);
Log.e(TAG, "Response from url: " + jsonStr);
//if respon null
if (jsonStr != null) {
try {
JSONObject jsonObj = new JSONObject(jsonStr);
// Getting JSON Array node name
JSONArray contacts = jsonObj.getJSONArray("training");
// looping through All Contacts
for (int i = 0; i < contacts.length(); i++) {
JSONObject c = contacts.getJSONObject(i);
String id = c.getString("id");
String trainingname = c.getString("trainingname");
String website = c.getString("website");
// tmp hash map for single contact
HashMap<String, String> contact = new HashMap<>();
// adding each child node to HashMap key => value
contact.put("id", id);
contact.put("trainingname", trainingname);
contact.put("website", website);
// adding contact to contact list
traininglist.add(contact);
}
//if JSON format error
} catch (final JSONException e) {
Log.e(TAG, "Json parsing error: " + e.getMessage());
runOnUiThread(new Runnable() {
@Override
public void run() {
Toast.makeText(getApplicationContext(),
"Json parsing error: " + e.getMessage(),
Toast.LENGTH_LONG)
.show();
}
});
}
} else {
// if JSON service server not responding
Log.e(TAG, "Couldn't get json from server.");
runOnUiThread(new Runnable() {
@Override
public void run() {
Toast.makeText(getApplicationContext(),
"Couldn't get json from server. Check LogCat for possible errors!",
Toast.LENGTH_LONG)
.show();
}
});
}
return null;
}
@Override
protected void onPostExecute(Void result) {
super.onPostExecute(result);
// Dismiss the progress dialog
if (pDialog.isShowing())
pDialog.dismiss();
/**
* Updating parsed JSON data into ListView
* */
ListAdapter adapter = new SimpleAdapter(
Listing.this, traininglist,
R.layout.list_item, //list_item.xml
new String[]{"id", "trainingname", "website"},//array list
new int[]{R.id.id, R.id.trainingname, R.id.website}//the UIs in list_item.xml
);
lv.setAdapter(adapter);
}
}
}
The Helper class for connection to JSON service server.
HttpHandler.java (no screen for Helper class)
package net.kerul.jsonlisting;
//HttpHandler.java
import android.util.Log;
import java.io.BufferedInputStream;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.ProtocolException;
import java.net.URL;
public class HttpHandler {
private static final String TAG = HttpHandler.class.getSimpleName();
public HttpHandler() {
}
public String makeServiceCall(String reqUrl) {
String response = null;
try {
URL url = new URL(reqUrl);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setRequestMethod("GET");//method type
// read the response
InputStream in = new BufferedInputStream(conn.getInputStream());
response = convertStreamToString(in);
} catch (MalformedURLException e) {
Log.e(TAG, "MalformedURLException: " + e.getMessage());
} catch (ProtocolException e) {
Log.e(TAG, "ProtocolException: " + e.getMessage());
} catch (IOException e) {
Log.e(TAG, "IOException: " + e.getMessage());
} catch (Exception e) {
Log.e(TAG, "Exception: " + e.getMessage());
}
return response;
}
private String convertStreamToString(InputStream is) {
BufferedReader reader = new BufferedReader(new InputStreamReader(is));
StringBuilder sb = new StringBuilder();
String line;
try {
while ((line = reader.readLine()) != null) {
sb.append(line).append('\n');
}
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
is.close();
} catch (IOException e) {
e.printStackTrace();
}
}
return sb.toString();
}
}
Part D: The Internet permission in AndroidManifest.xml
<uses-permission android:name="android.permission.INTERNET" />
Compile and RUN – all the best…
Need face-to-face lesson?, we also provide Android Studio training, 0129034614
http://bit.ly/androidjsk
Disclaimer: Intermediate level. This tutorial works on Android Studio 2.2. Should you have any difficulties, leave your comment in the comment section.
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