How to Fix 'Android.Os.Networkonmainthread
exception'

How can I fix 'android.os.NetworkOnMainThreadException'?

NOTE : AsyncTask was deprecated in API level 30.

AsyncTask | Android Developers

This exception is thrown when an application attempts to perform a networking operation on its main thread. Run your code in AsyncTask:

class RetrieveFeedTask extends AsyncTask<String, Void, RSSFeed> {

    private Exception exception;

    protected RSSFeed doInBackground(String... urls) {
        try {
            URL url = new URL(urls[0]);
            SAXParserFactory factory = SAXParserFactory.newInstance();
            SAXParser parser = factory.newSAXParser();
            XMLReader xmlreader = parser.getXMLReader();
            RssHandler theRSSHandler = new RssHandler();
            xmlreader.setContentHandler(theRSSHandler);
            InputSource is = new InputSource(url.openStream());
            xmlreader.parse(is);

            return theRSSHandler.getFeed();
        } catch (Exception e) {
            this.exception = e;

            return null;
        } finally {
            is.close();
        }
    }

    protected void onPostExecute(RSSFeed feed) {
        // TODO: check this.exception
        // TODO: do something with the feed
    }
}

How to execute the task:

In MainActivity.java file you can add this line within your oncreate() method

new RetrieveFeedTask().execute(urlToRssFeed);

Don't forget to add this to AndroidManifest.xml file:

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

How to fix NetworkonMainThreadException in Android?

Your Exception actually tells you exactly what you are doing wrong. You are not using another thread to perform NetworkOperations. Instead, you perform the network operation on your UI-Thread, which cannot (does not) work on Android.

Your code that connects to the url should be executed for example inside an AsyncTasks doInBackground() method, off the UI-Thread.

Take a look at this question on how to use the AsyncTask: How to use AsyncTask

Android - android.os.NetworkOnMainThreadException

NetworkOnMainThreadException: The exception that is thrown when an application attempts to perform a networking operation on its main thread.

You should call sendfeedback method on asynctask then only above code will work. As webserver is taking lot of time to response main thread becomes unresponsive. To avoid it you should call it on another thread. Hence asynctask is better.

here is link that illustrates how to use asynctask

how do i fix FATAL EXCEPTION:main android.os.NetworkOnMainThreadException

The issue is that inside the AsyncTask's onPostExecute you call the following:

socket.getOutputStream() 

This happens on the MainThread and therefore the exception is thrown. Move it to the doInBackground inside the try catch block so it looks like this:

public class ConnectPhoneTask extends AsyncTask<String,Void,Boolean> {

    @Override
    protected Boolean doInBackground(String... params) {
        boolean result = true;
        try {
            InetAddress serverAddr = InetAddress.getByName(params[0]);
            socket = new Socket(serverAddr, Constants.SERVER_PORT);//Open socket on server IP and port
            if(isConnected) {
                out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(socket
                        .getOutputStream())), true); //create output stream to send data to server
            }
        } catch (IOException e) {
            Log.e("remotedroid", "Error while connecting", e);
            result = false;
        }
        return result;
    }

    @Override
    protected void onPostExecute(Boolean result)
    {
        isConnected = result;
        Toast.makeText(context,isConnected?"Connected to server!":"Error while connecting",Toast.LENGTH_LONG).show();
    }
}

android.os.NetworkOnMainThreadException on service start on android

This happens because you are doing a network operation on the main thread, and this is not allowed on Android 3.0 and above. Even though it is in a service, services are run on the UI thread unless you specifically launch them in another thread or create a thread inside it.

You can fix this by running the task in a service off the main UI thread, by using a Thread or an AsyncTask.

Try creating a new thread in onStartCommand(), as suggested by @CommonsWare.

How to resolve android.os.NetworkOnMainThreadException?

The Android OS does not allow heavy process to execute in the main thread/UI Thread because the application will slow down, decreasing performance and the application will lag.

However, you can execute it in an AsyncTask as shown here. Do your process/call your function in the doInBackground of this asyncTask.

private class Download extends AsyncTask<String, Void, String> {
    ProgressDialog pDialog;

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        Log.d("Hi", "Download Commencing");

        pDialog = new ProgressDialog(MainActivity.this);
        pDialog.setMessage("Downloading Database...");


        String message= "Executing Process";

        SpannableString ss2 =  new SpannableString(message);
        ss2.setSpan(new RelativeSizeSpan(2f), 0, ss2.length(), 0);  
        ss2.setSpan(new ForegroundColorSpan(Color.BLACK), 0, ss2.length(), 0); 

        pDialog.setMessage(ss2);

        pDialog.setCancelable(false);
        pDialog.show();
    }

    @Override
    protected String doInBackground(String... params) {

        //INSERT YOUR FUNCTION CALL HERE

        return "Executed!";

    }

    @Override
    protected void onPostExecute(String result) {
        super.onPostExecute(result);
        Log.d("Hi", "Done Downloading.");
        pDialog.dismiss();

    }
}

and call it as such: new Download().execute(""); from another function.

You can do away with the Progress Dialog. I personally like it because I know my process will finish (like data loading) before the user can do anything, ensuring that no error occurs when the user interacts with the program.

android.os.NetworkOnMainThreadException with android 4.2

Write below code into your MainActivity file after setContentView(R.layout.activity_main);

if (android.os.Build.VERSION.SDK_INT > 9) {
    StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
    StrictMode.setThreadPolicy(policy);
}

And below import statement into your java file.

import android.os.StrictMode;

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