Post data using json Android

( 1 ) Create Android Application

  • File >> New >> Android Application
  • App Name: POST JSON
  • Enter Project Name: android-post-json
  • Pakcage: com.hmkcode.android
  • Keep other defualt selections, go Next  till you reach Finish

( 2 ) The App Layout & Views

  • Main layout is LinearLayout
  • One TextView that shows connection status “the one in green”.
  • One child layout RelativeLayout holding data entry part.
  • Three TextViews “Name, Country & Twitter” baseline-aligned with their correspondingEditText
  • One Button to send “post” data to the server.
  • res/layout/activity_main.xml

<?xml version=”1.0″ encoding=”utf-8″?>
<LinearLayout xmlns:android=”http://schemas.android.com/apk/res/android&#8221;
    android:layout_width=”match_parent”
    android:layout_height=”match_parent”
    android:orientation=”vertical” >
 
    <TextView
        android:id=”@+id/tvIsConnected”
        android:layout_width=”wrap_content”
        android:layout_height=”wrap_content”
        android:layout_gravity=”center_horizontal”    
        android:background=”#FF0000″
        android:textColor=”#FFF”
        android:textSize=”18dp”
        android:layout_marginBottom=”5dp”
        android:text=”is connected?” />
 
   <RelativeLayout
        android:layout_width=”wrap_content”
        android:layout_height=”wrap_content”>
 
       <TextView
            android:id=”@+id/tvName”
            android:layout_width=”50dp”
            android:layout_height=”wrap_content”
            android:text=”Name”
            android:layout_alignBaseline=”@+id/etName”/>
       <EditText
            android:id=”@+id/etName”
            android:layout_width=”150dp”
            android:layout_height=”wrap_content”
            android:layout_toRightOf=”@+id/tvName”/>
       <TextView
            android:id=”@+id/tvCountry”
            android:layout_width=”50dp”
            android:layout_height=”wrap_content”
            android:layout_below=”@+id/tvName”
            android:text=”Country”
            android:layout_alignBaseline=”@+id/etCountry”/>
       <EditText
            android:id=”@+id/etCountry”
            android:layout_width=”150dp”
            android:layout_height=”wrap_content”
            android:layout_toRightOf=”@+id/tvCountry”
            android:layout_below=”@+id/etName”/>
       <TextView
            android:id=”@+id/tvTwitter”
            android:layout_width=”50dp”
            android:layout_height=”wrap_content”
            android:layout_below=”@+id/tvCountry”
            android:text=”Twitter”
            android:layout_alignBaseline=”@+id/etTwitter”/>
       <EditText
            android:id=”@+id/etTwitter”
            android:layout_width=”150dp”
            android:layout_height=”wrap_content”
            android:layout_toRightOf=”@+id/tvTwitter”
            android:layout_below=”@+id/etCountry”/>
   </RelativeLayout>
 
   <Button
       android:id=”@+id/btnPost”
       android:layout_width=”200dp”
       android:layout_height=”wrap_content”
       android:layout_gravity=”center_horizontal”
       android:text=”POST”/>
 
</LinearLayout>

( 3 ) The Person Class

 

This is a simple model class to hold person information “name, country & twitter account”.

  • /src/com/hmkcode/android/vo/Person.java

 

package com.hmkcode.android.vo;
 
public class Person {
 
    private String name;
    private String country;
    private String twitter;
 
//getters & setters….
 
}

( 4 ) The Activity Class

  • onCreate()
    1. Get reference to the defined views in layout file
    2. Check for connection status
    3. Add click listener to the Post button
  • POST(url, Person)
      1. Open Http connection.
      2. Create HttpPOST object passing the url.
      3. Create Person object & convert it to JSON string.
      4. Add JSON to HttpPOST, set headers & send the POST request.
      5. Get the response Inputstream, convert it to String and return it.
  • HttpAsyncTask
    1. Helps in creating the connection in a separate thread so the UI will not freeze.
  • onClick
    1. This method is executed when user click on Post button
    2. It create HttpAsyncTask object and execute it.
  • isConnected()
    1. Check if there is network connection or not
  • validate()
    1. Helper method to check that data is not empty before send the request.
  • convertInputStreamToString()
    1. Helper method to convert inputstream to String
  • src/com/hmkcode/android/ActivityMain.java

package com.hmkcode.android;
 
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONObject;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
import android.app.Activity;
import com.hmkcode.android.vo.Person;
 
public class MainActivity extends Activity implements OnClickListener {
 
    TextView tvIsConnected;
    EditText etName,etCountry,etTwitter;
    Button btnPost;
 
    Person person;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
 
        // get reference to the views
        tvIsConnected = (TextView) findViewById(R.id.tvIsConnected);
        etName = (EditText) findViewById(R.id.etName);
        etCountry = (EditText) findViewById(R.id.etCountry);
        etTwitter = (EditText) findViewById(R.id.etTwitter);
        btnPost = (Button) findViewById(R.id.btnPost);
 
        // check if you are connected or not
        if(isConnected()){
            tvIsConnected.setBackgroundColor(0xFF00CC00);
            tvIsConnected.setText(“You are conncted”);
        }
        else{
            tvIsConnected.setText(“You are NOT conncted”);
        }
 
        // add click listener to Button “POST”
        btnPost.setOnClickListener(this);
 
    }
 
    public static String POST(String url, Person person){
        InputStream inputStream = null;
        String result = “”;
        try {
 
            // 1. create HttpClient
            HttpClient httpclient = new DefaultHttpClient();
 
            // 2. make POST request to the given URL
            HttpPost httpPost = new HttpPost(url);
 
            String json = “”;
 
            // 3. build jsonObject
            JSONObject jsonObject = new JSONObject();
            jsonObject.accumulate(“name”, person.getName());
            jsonObject.accumulate(“country”, person.getCountry());
            jsonObject.accumulate(“twitter”, person.getTwitter());
 
            // 4. convert JSONObject to JSON to String
            json = jsonObject.toString();
 
            // ** Alternative way to convert Person object to JSON string usin Jackson Lib
            // ObjectMapper mapper = new ObjectMapper();
            // json = mapper.writeValueAsString(person);
 
            // 5. set json to StringEntity
            StringEntity se = new StringEntity(json);
 
            // 6. set httpPost Entity
            httpPost.setEntity(se);
 
            // 7. Set some headers to inform server about the type of the content   
            httpPost.setHeader(“Accept”, “application/json”);
            httpPost.setHeader(“Content-type”, “application/json”);
 
            // 8. Execute POST request to the given URL
            HttpResponse httpResponse = httpclient.execute(httpPost);
 
            // 9. receive response as inputStream
            inputStream = httpResponse.getEntity().getContent();
 
            // 10. convert inputstream to string
            if(inputStream != null)
                result = convertInputStreamToString(inputStream);
            else
                result = “Did not work!”;
 
        } catch (Exception e) {
            Log.d(“InputStream”, e.getLocalizedMessage());
        }
 
        // 11. return result
        return result;
    }
 
    public boolean isConnected(){
        ConnectivityManager connMgr = (ConnectivityManager) getSystemService(Activity.CONNECTIVITY_SERVICE);
            NetworkInfo networkInfo = connMgr.getActiveNetworkInfo();
            if (networkInfo != null && networkInfo.isConnected())
                return true;
            else
                return false;    
    }
    @Override
    public void onClick(View view) {
 
        switch(view.getId()){
            case R.id.btnPost:
                if(!validate())
                    Toast.makeText(getBaseContext(), “Enter some data!”, Toast.LENGTH_LONG).show();
                // call AsynTask to perform network operation on separate thread
                new HttpAsyncTask().execute(“http://hmkcode.appspot.com/jsonservlet&#8221;);
            break;
        }
 
    }
    private class HttpAsyncTask extends AsyncTask<String, Void, String> {
        @Override
        protected String doInBackground(String… urls) {
 
            person = new Person();
            person.setName(etName.getText().toString());
            person.setCountry(etCountry.getText().toString());
            person.setTwitter(etTwitter.getText().toString());
 
            return POST(urls[0],person);
        }
        // onPostExecute displays the results of the AsyncTask.
        @Override
        protected void onPostExecute(String result) {
            Toast.makeText(getBaseContext(), “Data Sent!”, Toast.LENGTH_LONG).show();
       }
    }
 
    private boolean validate(){
        if(etName.getText().toString().trim().equals(“”))
            return false;
        else if(etCountry.getText().toString().trim().equals(“”))
            return false;
        else if(etTwitter.getText().toString().trim().equals(“”))
            return false;
        else
            return true;    
    }
    private static String convertInputStreamToString(InputStream inputStream) throws IOException{
        BufferedReader bufferedReader = new BufferedReader( new InputStreamReader(inputStream));
        String line = “”;
        String result = “”;
        while((line = bufferedReader.readLine()) != null)
            result += line;
 
        inputStream.close();
        return result;
 
    }   
}

Note: do not forget to add the permissions to AndroidManifest.xml file

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

( 5 ) Run & Check

  • Deploy the app and run it
  • Enter name, country & twitter
  • Click on “POST” button.
  • Wait for the “Data Sent!” message

Reference : http://hmkcode.com/android-send-json-data-to-server/

 

 

 

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