Question

I’m new to android and i would like to create an application that reads data from mysql server. I’ve taken from web an example about this, but i cannot make it work

I’m using eclipse for this and for the other part, php and mysql.
First of all, here is my php script that is running ok (city.php):

<?php
//connecting to database
$sql=mysql_query("select * from city");
$output = array();
while(list($id,$name)=mysql_fetch_array($sql)){
    $output[$id]=$name;

}
print(json_encode($output));
mysql_free_result($sql);

?>

This is returning:

{"1":"Brasov","2":"Bucuresti"}

On my android project from eclipse, I have in the MainActivity.java:

package com.example.mycity;


import android.os.Bundle;
import android.app.Activity;


import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.HttpClient;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import android.net.ParseException;
import android.util.Log;
import android.widget.Toast;

public class MainActivity extends Activity {

JSONArray jArray;
String result = null;
InputStream is = null;
StringBuilder sb=null;

@Override
public void onCreate(Bundle savedInstanceState) {


super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

 ArrayList<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();
//http post
try{
     HttpClient httpclient = new DefaultHttpClient();
     HttpPost httppost = new HttpPost("http://www.steagu.ro/android/city.php");
     httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
     HttpResponse response = httpclient.execute(httppost);
     if (response.getStatusLine().getStatusCode() != 200) {
            Log.d("MyApp", "Server encountered an error.");

     }
     HttpEntity entity = response.getEntity();
     is = entity.getContent();
     }catch(Exception e){
         //e.printStackTrace();
         Log.e("log_tag", "Error in http connection: "+e.toString());
    }

  }


}

But when I’m running this, I receive an error on logcat:it’s not connecting to the file:Error in http connection: android.os.NetworkOnMainThreadException

10-24 13:04:34.429: I/dalvikvm(982): threadid=3: reacting to signal 3
10-24 13:04:34.649: I/dalvikvm(982): Wrote stack traces to '/data/anr/traces.txt'
10-24 13:04:34.859: E/log_tag(982): Error in http connection: android.os.NetworkOnMainThreadException
10-24 13:04:34.919: I/dalvikvm(982): threadid=3: reacting to signal 3
10-24 13:04:34.949: I/dalvikvm(982): Wrote stack traces to '/data/anr/traces.txt'
10-24 13:04:35.151: D/gralloc_goldfish(982): Emulator without GPU emulation detected.
10-24 13:04:35.479: I/dalvikvm(982): threadid=3: reacting to signal 3
10-24 13:04:35.499: I/dalvikvm(982): Wrote stack traces to '/data/anr/traces.txt'

I have permission for internet in the AndroidManifest.xml:

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.mycity"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="15" />
<uses-permission android:name="android.permission.INTERNET"></uses-permission>
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE"></uses-permission>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"></uses-permission>

    <application
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name=".MainActivity"
            android:label="@string/title_activity_main" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

I don’t know where is the problem. Can anybody help me with this? Thank you!

Answer 1

You may use an AsyncTask class to carry out your network operations as strictmode does not allow it to be done on the main UI example as follows

          public class MainActivity extends Activity {

         JSONArray jArray;
         String result = null;
         InputStream is = null;
          StringBuilder sb=null;

         @Override
        public void onCreate(Bundle savedInstanceState) {


        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

       new httpRequest().execute();

        }


         private class httprRequest extends AsyncTask<String, Integer, String>{

                @override
                public String doInBackground(String.... params){
                   ArrayList<NameValuePair> nameValuePairs = new             ArrayList<NameValuePair>();
        //http post
          try{
           HttpClient httpclient = new DefaultHttpClient();
           HttpPost httppost = new HttpPost("http://www.steagu.ro/android/city.php");
           httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
           HttpResponse response = httpclient.execute(httppost);
           if (response.getStatusLine().getStatusCode() != 200) {
               Log.d("MyApp", "Server encountered an error.");

              }
          HttpEntity entity = response.getEntity();
          is = entity.getContent();
          }catch(Exception e){
          //e.printStackTrace();
          Log.e("log_tag", "Error in http connection: "+e.toString());
           }

                }
              }

           }
       }