Question

when run my code on the same class is app run good. but when i run this code on two class different, my app was error android.os.networkonmainthreadexception.
when debug i detect error at responseHttp = httpConnection.getResponseCode();
app run to line responseHttp = httpConnection.getResponseCode(); and it go to catch{},it cancel “If..else”.And log error android.os.networkonmainthreadexception.
Can you help me!!

My code class Asynctask

package com.example.finishdemo;

import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLConnection;
import android.os.AsyncTask;

public class TestConnectionNew extends AsyncTask<String, Void, String> {
private int responseHttp = 0;
private String flag="false";

@Override
protected String doInBackground(String... urltest) {
    // TODO Auto-generated method stub
    try {
        URL url = new URL(urltest[0]);
        URLConnection connection = url.openConnection();
        connection.setConnectTimeout(2000);
        HttpURLConnection httpConnection = (HttpURLConnection) connection;
        **responseHttp = httpConnection.getResponseCode();**
        if (responseHttp == HttpURLConnection.HTTP_OK) {
            flag = "true";
        } else {
            flag = "false";
        }
    } catch (Exception e) {
        e.printStackTrace();
        System.out.println("Thong bao loi: "+e.toString());
    }
    return flag;
}
}

Code class main:

package com.example.finishdemo;
public class Hoadon extends Activity {
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.hoadon);
    TestConnectionNew t=new TestConnectionNew();
    String recieve=t.doInBackground("http://longvansolution.tk/monthlytarget.php");
    if(recieve.equalsIgnoreCase("true"))
    {
        doTimerTask();
    }else
        if(recieve.equalsIgnoreCase("false"))
    {
        showAlert("Không kết nối được đến server hoặc thiết bị chưa có kết nối internet!");
    }

Answer 1

use asynctask.execute for executing AsyncTask instead of calling doInBackground manually as:

 TestConnectionNew t = new TestConnectionNew();
 t.execute("http://longvansolution.tk/monthlytarget.php");

Change your TestConnectionNew as

public class TestConnectionNew extends AsyncTask<String, Void, String> {
private int responseHttp = 0;
private String flag="false";

@Override
protected String doInBackground(String... urltest) {
    // TODO Auto-generated method stub
    try {
        URL url = new URL(urltest[0]);
        URLConnection connection = url.openConnection();
        connection.setConnectTimeout(2000);
        HttpURLConnection httpConnection = (HttpURLConnection) connection;
        **responseHttp = httpConnection.getResponseCode();**
        if (responseHttp == HttpURLConnection.HTTP_OK) {
            flag = "true";
        } else {
            flag = "false";
        }
    } catch (Exception e) {
        e.printStackTrace();
        System.out.println("Thong bao loi: "+e.toString());
    }
    return flag;
}

@Override
     protected void onPostExecute(String recieve) {
           if(recieve.equalsIgnoreCase("true"))
            {
               doTimerTask();
           }else
           if(recieve.equalsIgnoreCase("false"))
             {
              showAlert("Không kết nối được đến server hoặc thiết bị chưa có kết nối internet!");
             }
      }
}

and for more help about how we use AsyncTask see:

http://developer.android.com/reference/android/os/AsyncTask.html