I get `android.os.NetworkOnMainThreadException` while using a seperate thread

Question

In my Activity I use a handler

Handler handler = new Handler() {
    @Override
    public void handleMessage(Message msg)  {   
               //do GUI stuff, edit views, etc..
    }
};

I also have a Runnable, which posts to php and waits for a json response

Runnable runnable3 = new Runnable() {
        public void run() { 
            JSONParserArray jsonParserRun = new JSONParserArray();
            List<NameValuePair> params = new ArrayList<NameValuePair>();
            params.add(new BasicNameValuePair("p1", "myParam1"));
            try {
                String link = "http://mylink.com/someFileOnServer.php";
                JSONArray jArray = jsonParserRun.makeHttpRequest(link , "POST",
                        params);
                if (jArray != null && jArray.length() != 0) {
                } else {
                    //either null (because of throwing exception) or empty
                }
            } catch (Exception e) {
            }
        }
        handler.sendEmptyMessage(0);
        handler.postDelayed(runnable, 30000);
  }

I repeat the task every 30 seconds, finally inside my onCreate() I creat a thread and passing it the Runnable

@Override
public void onCreate(Bundle savedInstanceState) {
            //other stuff
    Thread t = new Thread(runnable3);
    t.start();
}

This code throws android.os.NetworkOnMainThreadException even thought I am starting a new thread and passing the Runnable to it. The class JSONParserArray works fine in other cases (so no worries there)

However, when I run this method inside the Runnable, it is working fine.

private boolean hasActiveInternetConnection() {
        try {
            new Socket().connect(new InetSocketAddress("google.com", 80), 3000);    
            return true;
        } catch (Exception e) {
            Log.i("tag", e.toString());
            return false;
        }
    }

Answer 1

Handler.postDelayed() executes the Runnable in the Thread in which the Handler was created. In your case you create it in your Activity on the UI Thread. So the first time, the Runnable gets executed in a separate Thread, but the second time in the UI Thread.

Answer 2

There is another way to overcome the exception.

StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy); 

In your manifest

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