Question

I am a relatively new Android programmer and I was wondering how you could get read text off the internet in 4.0.3. I keep finding code that gives me a Network on Main exception: http://developer.android.com/reference/android/os/NetworkOnMainThreadException.html and was wondering if anyone could provide me some sample code to get around this, for reference I got the code I tried to use here: http://android-er.blogspot.com/2011/04/read-text-file-from-internet-using-java.html. Thanks a lot.

Answer 1

In Honeycomb and Ice Cream Sandwich (i.e. Android 3.0+) , you cannot connect to the internet in the main thread (onCreate(), onPause(), onResume() etc.), and you have to instead start a new thread. The reason why this has changed is because network operations can make the app wait for a long time, and if you’re running them in the main thread, the whole application becomes unresponsive. If you try to connect from the main thread, Android will throw a NetworkOnMainThreadException.

To bypass this, you can run networking code from a new thread, and use runOnUiThread() to do things in the main thread, such as update the user interface. Generally, you can do something like:

class MyActivity extends Activity {
  public onCreate(Bundle savedInstanceState) {
    super.onCreate();

    // Create thread
    Thread networkThread = new Thread() {
      @Override
      public void run() {
        try {
          // this is where your networking code goes
          // I'm declaring the variable final to be accessible from runOnUiThread
          final String result = someFunctionThatUsesNetwork();

          runOnUiThread(new Runnable() {
            @Override
            public void run() {
              // this is where you can update your interface with your results
              TextView myLabel = (TextView) findViewById(R.id.myLabel);
              myLabel.setText(result);
            }
          }
        } catch (IOException e) {
          Log.e("App", "IOException thrown", e);
        }
      }
    }
  }
}