I have an issue with HttpUrlConnection

Question

please help with this issue I am facing:

I am trying to call a method from a class which will connect to a php service. It has none errors but when I run it, it is closed with the message sorry, the app was stoped.

this is the Main activity:

import android.support.v7.app.AppCompatActivity;

import android.os.Bundle;

import android.view.View;

import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    public String result;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    public void hhtp(View view) throws Exception {
        result="";
        JavaHttpUrlConnectionReader con = new JavaHttpUrlConnectionReader();
        result = con.doHttpUrlConnectionAction("http://example.com/app.php");
        Toast.makeText(getApplicationContext(),"Button is clicked"+result,Toast.LENGTH_LONG).show();
    }
}

this is the class:

import java.io.BufferedReader;

import java.io.IOException;

import java.io.InputStreamReader;

import java.net.HttpURLConnection;

import java.net.URL;

public class JavaHttpUrlConnectionReader {

    public static void main(String[] args)
            throws Exception
    {
        new JavaHttpUrlConnectionReader();
    }
   public String doHttpUrlConnectionAction(String desiredUrl)
            throws Exception
    {
        URL url = null;
        BufferedReader reader = null;
        StringBuilder stringBuilder;

        try
        {
            // create the HttpURLConnection
            url = new URL(desiredUrl);
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();

            // just want to do an HTTP GET here
            connection.setRequestMethod("GET");

            // uncomment this if you want to write output to this url
            //connection.setDoOutput(true);

            // give it 15 seconds to respond
            connection.setReadTimeout(15*1000);
            connection.connect();

            // read the output from the server
            reader = new BufferedReader(new InputStreamReader(connection.getInputStream()));
            stringBuilder = new StringBuilder();

            String line = null;
            while ((line = reader.readLine()) != null)
            {
                stringBuilder.append(line + "\n");
            }
            return stringBuilder.toString();
        }
        catch (Exception e)
        {
            e.printStackTrace();
            throw e;
        }
        finally
        {
            // close the reader; this can throw an exception too, so
            // wrap it in another try/catch block.
            if (reader != null)
            {
                try
                {
                    reader.close();
                }
                catch (IOException ioe)
                {
                    ioe.printStackTrace();
                }
            }
        }
    }
}

this is the main.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/http_url_request_button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="hhtp"
        android:text="Checa si hay nueva Sol" />

</android.support.constraint.ConstraintLayout>

and finally this is the web service in php:

<?php
$data=$_POST['dato'];
$rsp="1";
echo $rsp;
?>

score 1 · Answer 1 · answered Dec 05 '18 at 02:38

1

You are doing a network call on UI thread, which has thrown the exception. Try using an AsyncTask class, and do network connections from there.

answered Dec 05 '18 at 02:38

starrydeveloper

42
6

thank you for replay, now, if I use AsyncTask then how can I get the websevice response back into my variable result? I need this one to trigger new tasks depending of the value of it. – Luis Dec 05 '18 at 19:23

score 1 · Answer 2 · answered Dec 05 '18 at 07:10

You are experiencing the "Networking on the Main Thread" exception! Congratulations, you are now a L2 Android developer :D

This is enforced by the Android OS in order to make sure apps are not being non-responsive and to ensure that developers are handling asynchronous work, well... asynchronously!

See the rationale here --> https://developer.android.com/reference/android/os/NetworkOnMainThreadException

There are several ways of approaching a solution here - AsyncTasks, Runnables, Handlers, Java Futures, Kotlin Coroutines, Rx (in approximate order of complexity).

Here are some similar questions that have been answered in the past around this issue:

Good luck, and post back here if you can't find the way forward!

score 0 · Answer 3 · answered Sep 08 '22 at 17:02

The error is due to executing long running operations in main thread And Ui thread, You can easily rectify the problem by using ExecutorService or Thread. You can checkout the bellow code for better handling.

 ExecutorService executorService = Executors.newSingleThreadExecutor();
            Handler handler = new Handler(Looper.getMainLooper());
            executorService.execute(() -> {
                try {
                           //Do background work here
                } catch (Exception e) {
                    e.printStackTrace();
                }
                handler.post(() -> {
                        //do post execute work here/or ui update
                    });
            });

I have an issue with HttpUrlConnection

3 Answers3