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How to Send or Post Data to Web Server in Android?

Photo of Mike Dalisay
Modified Thursday, April 25, 2013
by - @ninjazhai
Hi guys! Today we are going to code an example app that can post a file and text data to a web server with PHP file as a receiver. Having the ability to (do HTTP Post Request) post data from android app to remote server is required for most apps. Here are some example use of this functionality:
  • You want to get statistics on how your app is being used (you have to tell your user and they must agree of course!)
  • Your app has an upload file feature.
  • A user should register on your database before using more features of your app.
The code we used in this post can be downloaded here:

download code - Android HTTP Example

In this example, we are using a small library for posting a file, it is called the HttpComponents from the Apache Software Foundation. Please note that you won't need this library if you're just posting text data. The download can be found here: HttpComponents
  1. As of the moment, I downloaded the binary 4.2.3.zip
  2. When you extracted the zip file, find the lib folder and copy all the jar files there
  3. Copy those jar files to your project's lib folder, here's how to do that:
  4. Go to your workspace directory, find your project folder and inside, find the libs folder, put the jar files we extracted earlier
  5. Go back to eclipse and refresh your project files in the project explorer, now you can see the jar files inside your lib directory. See the screenshot below to visualize the goal of these 5 steps above.
Highlighted is HttpComponents library.

How To Post Text Data?

// url where the data will be posted
String postReceiverUrl = "http://yourdomain.com/post_data_receiver.php";
Log.v(TAG, "postURL: " + postReceiverUrl);

// HttpClient
HttpClient httpClient = new DefaultHttpClient();

// post header
HttpPost httpPost = new HttpPost(postReceiverUrl);

// add your data
List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(2);
nameValuePairs.add(new BasicNameValuePair("firstname", "Mike"));
nameValuePairs.add(new BasicNameValuePair("lastname", "Dalisay"));
nameValuePairs.add(new BasicNameValuePair("email", "mike@testmail.com"));

httpPost.setEntity(new UrlEncodedFormEntity(nameValuePairs));

// execute HTTP post request
HttpResponse response = httpClient.execute(httpPost);
HttpEntity resEntity = response.getEntity();

if (resEntity != null) {
    
    String responseStr = EntityUtils.toString(resEntity).trim();
    Log.v(TAG, "Response: " +  responseStr);
    
    // you can add an if statement here and do other actions based on the response
}

How To Post A File?

You can use this code to post other file types such as an image.

// the file to be posted
String textFile = Environment.getExternalStorageDirectory() + "/sample.txt";
Log.v(TAG, "textFile: " + textFile);

// the URL where the file will be posted
String postReceiverUrl = "http://yourdomain.com/post_data_receiver.php";
Log.v(TAG, "postURL: " + postReceiverUrl);

// new HttpClient
HttpClient httpClient = new DefaultHttpClient();

// post header
HttpPost httpPost = new HttpPost(postReceiverUrl);

File file = new File(textFile);
FileBody fileBody = new FileBody(file);

MultipartEntity reqEntity = new MultipartEntity(HttpMultipartMode.BROWSER_COMPATIBLE);
reqEntity.addPart("file", fileBody);
httpPost.setEntity(reqEntity);

// execute HTTP post request
HttpResponse response = httpClient.execute(httpPost);
HttpEntity resEntity = response.getEntity();

if (resEntity != null) {
    
    String responseStr = EntityUtils.toString(resEntity).trim();
    Log.v(TAG, "Response: " +  responseStr);
    
    // you can add an if statement here and do other actions based on the response
}

Compelete MainActivity Code:

This is our MainActivity.java code. In this code, we are:
  • Using AsyncTask to prevent the network on main thread error. 
  • To test posting the text data, you must change the actionChoice variable value to 1.
  • Else if you are to test posting a sample file, you must change the actionChoice to 2. Also, don't forget to put a sample.txt file in your SD card root directory.
package com.example.androidpostdatatophpserver;

import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.mime.HttpMultipartMode;
import org.apache.http.entity.mime.MultipartEntity;
import org.apache.http.entity.mime.content.FileBody;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.util.EntityUtils;

import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.app.Activity;

public class MainActivity extends Activity {

    private static final String TAG = "MainActivity.java";
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        // we are going to use asynctask to prevent network on main thread exception
        new PostDataAsyncTask().execute();
        
    }

    public class PostDataAsyncTask extends AsyncTask<String, String, String> {

        protected void onPreExecute() {
            super.onPreExecute();
            // do stuff before posting data
        }

        @Override
        protected String doInBackground(String... strings) {
            try {

                // 1 = post text data, 2 = post file
                int actionChoice = 2;
                
                // post a text data
                if(actionChoice==1){
                    postText();
                }
                
                // post a file
                else{
                    postFile();
                }
                
            } catch (NullPointerException e) {
                e.printStackTrace();
            } catch (Exception e) {
                e.printStackTrace();
            }
            return null;
        }

        @Override
        protected void onPostExecute(String lenghtOfFile) {
            // do stuff after posting data
        }
    }
    
    // this will post our text data
    private void postText(){
        try{
            // url where the data will be posted
            String postReceiverUrl = "http://yourdomain.com/post_data_receiver.php";
            Log.v(TAG, "postURL: " + postReceiverUrl);
            
            // HttpClient
            HttpClient httpClient = new DefaultHttpClient();
            
            // post header
            HttpPost httpPost = new HttpPost(postReceiverUrl);
    
            // add your data
            List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(2);
            nameValuePairs.add(new BasicNameValuePair("firstname", "Mike"));
            nameValuePairs.add(new BasicNameValuePair("lastname", "Dalisay"));
            nameValuePairs.add(new BasicNameValuePair("email", "mike@testmail.com"));
            
            httpPost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
    
            // execute HTTP post request
            HttpResponse response = httpClient.execute(httpPost);
            HttpEntity resEntity = response.getEntity();
            
            if (resEntity != null) {
                
                String responseStr = EntityUtils.toString(resEntity).trim();
                Log.v(TAG, "Response: " +  responseStr);
                
                // you can add an if statement here and do other actions based on the response
            }
            
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    
    // will post our text file
    private void postFile(){
        try{
            
            // the file to be posted
            String textFile = Environment.getExternalStorageDirectory() + "/sample.txt";
            Log.v(TAG, "textFile: " + textFile);
            
            // the URL where the file will be posted
            String postReceiverUrl = "http://yourdomain.com/post_data_receiver.php";
            Log.v(TAG, "postURL: " + postReceiverUrl);
            
            // new HttpClient
            HttpClient httpClient = new DefaultHttpClient();
            
            // post header
            HttpPost httpPost = new HttpPost(postReceiverUrl);
            
            File file = new File(textFile);
            FileBody fileBody = new FileBody(file);
    
            MultipartEntity reqEntity = new MultipartEntity(HttpMultipartMode.BROWSER_COMPATIBLE);
            reqEntity.addPart("file", fileBody);
            httpPost.setEntity(reqEntity);
            
            // execute HTTP post request
            HttpResponse response = httpClient.execute(httpPost);
            HttpEntity resEntity = response.getEntity();
    
            if (resEntity != null) {
                
                String responseStr = EntityUtils.toString(resEntity).trim();
                Log.v(TAG, "Response: " +  responseStr);
                
                // you can add an if statement here and do other actions based on the response
            }
            
        } catch (NullPointerException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

PHP file that will receive the posted data:

This is the post_date_receiver.php code. You must upload it in your server and specify the URL to our MainActivity.java
<?php
// if text data was posted
if($_POST){
    print_r($_POST);
}

// if a file was posted
else if($_FILES){
    $file = $_FILES['file'];
    $fileContents = file_get_contents($file["tmp_name"]);
    print_r($fileContents);
}
?>

AndroidManifest.xml Code:

Well, we are just having an INTERNET permission here.

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.androidpostdatatophpserver"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-permission android:name="android.permission.INTERNET" />
    
    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="17" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.example.androidpostdatatophpserver.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>

</manifest>

Output Screenshots:

Response is what post_date_receiver.php outputs when it receives the posted data.

Posting Text Data. The response array have our key-value pairs.

Posting Text File. The response is the content of my sample.txt file.
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