Question

I want to read the content of a URL with the following code :

        myUrl=new URL(url);
        stream=myUrl.openStream();

but the second line of code triggers an “android.os.NetworkOnMainThreadException” without any other explanation.

I work under Androïd 4 and I can add this code used to work with Androïd 2.3.3.

Any idea?

Thanks in advance for the time you will spend trying to help me.

Answer 1

So problem is that application attempts to perform a networking operation on main thread and this is not allowed.

For your goal i recommend to you use AsyncTask and do your work in background Thread.

Here is example from my little app:

protected InputStream doInBackground(String... params) {

            int contentLength = 0;
            int buffLength = 0;
            int progress = 0;
            InputStream inputStream = null;
            try {

                URL url = new URL(params[0]);
                HttpURLConnection urlConntection = (HttpURLConnection) url.openConnection();
                urlConntection.setRequestMethod("GET");
                urlConntection.setAllowUserInteraction(false);
                urlConntection.setInstanceFollowRedirects(true);
                urlConntection.connect();
                if (urlConntection.getResponseCode() == HttpURLConnection.HTTP_OK) {
                    contentLength = urlConntection.getContentLength();
                    progressDialog.setMax(contentLength);
                    inputStream = urlConntection.getInputStream();

                    while ((buffLength = inputStream.read(MAX_BUFFER)) != -1) {
                        try {
                            Thread.sleep(1);
                            progress += buffLength;
                            DataTransmitted data = new DataTransmitted(progress, contentLength);
                            publishProgress(data);
                        }
                        catch (InterruptedException ex) {
                            Log.e(this.getClass().getName(), ex.getMessage());
                        }
                    }

                }
                else {
                    throw new IOException("No response.");
                }

            }
            catch (MalformedURLException ex) {
                Log.e(this.getClass().getName(), ex.getMessage());
            }
            catch (IOException ex) {
                errorDialog.show();
            }
            return inputStream;
        }

Or here is similar topic:

• Download a file with Android, and showing the progress in a
ProgressDialog