Question

I have an activity which shows some List entries. When I click on a list item my app checks which connection type is available (“WIF” or “MOBILE”), through NetworkInfo.getTypeName(). As soon as I call this method I get a NullpointerException. Why?

I tested this on the emulator, cause my phone is currently not available (it’s broken…). I assume this is the problem? This is the only explanation that I have, if that’s not the case I have no idea why this would be null.

Here’s some code snippet:

public class VideoList extends ListActivity{
 ...
 public void onCreate(Bundle bundle){
  final ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
  ...
  listview.setOnItemClickListener(new OnItemClickListener(){
   public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
    ...
    NetworkInfo ni = cm.getActiveNetworkInfo();
    String connex = ni.getTypeName(); //Nullpointer exception here
    if(connex.equals("WIFI")doSomething();
   }
  });
 }
}

Answer 1

The call getActiveNetworkInfo() can return null if there is no active network and you need to check for that. Here’s the source code from here.

/**
 * Return NetworkInfo for the active (i.e., connected) network interface.
 * It is assumed that at most one network is active at a time. If more
 * than one is active, it is indeterminate which will be returned.
 * @return the info for the active network, or {@code null} if none is active
 */
public NetworkInfo getActiveNetworkInfo() {
    enforceAccessPermission();
    for (NetworkStateTracker t : mNetTrackers) {
        NetworkInfo info = t.getNetworkInfo();
        if (info.isConnected()) {
            return info;
        }
    }
    return null;
}

Note in particular the javadoc: “return the info for the active network, or null if none is active”.