NetWork On主线程异常

Question

Hi, I try to check network connectivity and Internet present by using following method

check = new ConnectionDetector(getApplicationContext());

conn = check.isConnectingToInternet();

public class ConnectionDetector {

private Context _context;

public ConnectionDetector(Context context){
    this._context = context;
}

/**
 * Checking for all possible internet providers
 * **/
/*public boolean isConnectingToInternet(){
    ConnectivityManager connectivity = (ConnectivityManager) _context.getSystemService(Context.CONNECTIVITY_SERVICE);
      if (connectivity != null)
      {
          NetworkInfo[] info = connectivity.getAllNetworkInfo();
          if (info != null)
              for (int i = 0; i < info.length; i++)
                  if (info[i].getState() == NetworkInfo.State.CONNECTED)
                  {
                      return true;
                  }

      }
      return false;
}*/

public boolean isConnectingToInternet(){
    try{
        ConnectivityManager cm = (ConnectivityManager)_context.getSystemService
                                                    (Context.CONNECTIVITY_SERVICE);
        NetworkInfo netInfo = cm.getActiveNetworkInfo();
        Log.d("NetInfo", String.valueOf(netInfo));
        if (netInfo != null && netInfo.isConnected())
        {
            //Network is available but check if we can get access from the network.
            URL url = new URL("http://www.Google.com/");
            HttpURLConnection urlc = (HttpURLConnection) url.openConnection();
            urlc.setRequestProperty("Connection", "close");
            urlc.setConnectTimeout(2000); // Timeout 2 seconds.
            urlc.connect();
            Log.d("NetInfo Response Code", String.valueOf(urlc.getResponseCode()));
           // Toast.makeText(getApplicationContext(), String.valueOf(urlc.getResponseCode()), Toast.LENGTH_LONG).show();
            if (urlc.getResponseCode() == 200)  //Successful response.
            {
                return true;
            } 
            else 
            {
                 Log.d("NO INTERNET", "NO INTERNET");
                return false;
            }
        }
    }
    catch(Exception e)
    {
        e.printStackTrace();
    }
    return false;
}

}

Note :

But this will return NetworkOnMainThread Exception like follows.kindly any one suggest me what mistakes i made.......

03-27 12:53:35.617: W/System.err(1095): android.os.NetworkOnMainThreadException
03-27 12:53:35.627: W/System.err(1095):     at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1084)
03-27 12:53:35.637: W/System.err(1095):     at java.net.InetAddress.lookupHostByName(InetAddress.java:391)
03-27 12:53:35.637: W/System.err(1095):     at java.net.InetAddress.getAllByNameImpl(InetAddress.java:242)
03-27 12:53:35.647: W/System.err(1095):     at java.net.InetAddress.getAllByName(InetAddress.java:220)
03-27 12:53:35.647: W/System.err(1095):     at libcore.net.http.HttpConnection.<init>(HttpConnection.java:71)
03-27 12:53:35.657: W/System.err(1095):     at libcore.net.http.HttpConnection.<init>(HttpConnection.java:50)
03-27 12:53:35.668: W/System.err(1095):     at libcore.net.http.HttpConnection$Address.connect(HttpConnection.java:351)
03-27 12:53:35.668: W/System.err(1095):     at libcore.net.http.HttpConnectionPool.get(HttpConnectionPool.java:86)
03-27 12:53:35.677: W/System.err(1095):     at libcore.net.http.HttpConnection.connect(HttpConnection.java:128)
03-27 12:53:35.687: W/System.err(1095):     at libcore.net.http.HttpEngine.openSocketConnection(HttpEngine.java:308)
03-27 12:53:35.699: W/System.err(1095):     at libcore.net.http.HttpEngine.connect(HttpEngine.java:303)
03-27 12:53:35.699: W/System.err(1095):     at libcore.net.http.HttpEngine.sendSocketRequest(HttpEngine.java:282)
03-27 12:53:35.707: W/System.err(1095):     at libcore.net.http.HttpEngine.sendRequest(HttpEngine.java:232)
03-27 12:53:35.718: W/System.err(1095):     at libcore.net.http.HttpURLConnectionImpl.connect(HttpURLConnectionImpl.java:80)
03-27 12:53:35.727: W/System.err(1095):     at com.slet.routemytrips.beta.ConnectionDetector.isConnectingToInternet(ConnectionDetector.java:50)
03-27 12:53:35.727: W/System.err(1095):     at com.slet.routemytrips.beta.Disclaimer$1.onClick(Disclaimer.java:178)
03-27 12:53:35.738: W/System.err(1095):     at android.view.View.performClick(View.java:3480)
03-27 12:53:35.738: W/System.err(1095):     at android.view.View$PerformClick.run(View.java:13983)
03-27 12:53:35.748: W/System.err(1095):     at android.os.Handler.handleCallback(Handler.java:605)
03-27 12:53:35.757: W/System.err(1095):     at android.os.Handler.dispatchMessage(Handler.java:92)
03-27 12:53:35.757: W/System.err(1095):     at android.os.Looper.loop(Looper.java:137)
03-27 12:53:35.767: W/System.err(1095):     at android.app.ActivityThread.main(ActivityThread.java:4340)
03-27 12:53:35.777: W/System.err(1095):     at java.lang.reflect.Method.invokeNative(Native Method)
03-27 12:53:35.777: W/System.err(1095):     at java.lang.reflect.Method.invoke(Method.java:511)
03-27 12:53:35.787: W/System.err(1095):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
03-27 12:53:35.797: W/System.err(1095):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
03-27 12:53:35.807: W/System.err(1095):     at dalvik.system.NativeStart.main(Native Method)
03-27 12:57:05.237: D/dalvikvm(90): GC_CONCURRENT freed 666K, 10% free 12624K/14023K, paused 6ms+10ms

Answer 1

You can't make HTTP requests on the main thread, it would cause the UI to freeze up. So it throws that exception. You need to do it in an AsyncTask or another Thread.

Answer 2

http://developer.android.com/reference/android/os/NetworkOnMainThreadException.html

NetworkOnMainThreadException is thrown if you attempt to make a network request in the main UI Thread. So all network related operation should be done on the background thread.

AsyncTask is designed to be a helper class around Thread and Handler and does not constitute a generic threading framework. AsyncTasks should ideally be used for short operations (a few seconds at the most.) If you need to keep threads running for long periods of time, it is highly recommended you use the various APIs provided by the java.util.concurrent pacakge such as Executor, ThreadPoolExecutor and FutureTask.

http://developer.android.com/reference/android/os/AsyncTask.html

class TheTask extends AsyncTask<Void,Void,Void>
{
          protected void onPreExecute()
          {           super.onPreExecute();
                    //display progressdialog.
          } 

           protected void doInBackground(Void ...params)
          {  
                //http request. do not update ui here

                return null;
          } 

           protected void onPostExecute(Void result)
          {     
                    super.onPostExecute(result);
                    //dismiss progressdialog.
                    //update ui
          } 

}

An alternative to asynctask is Robospice. Can make multiple spice request. Notifies on the ui thread. https://github.com/octo-online/robospice

To check Netowrk Connectivity.

In your activity

public class MainActivity extends Activity {

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
   if(CheckNetwork.isInternetAvailable(MainActivity.this))
   {
       //call asyntask and make http request.
   }
 }

CheckNetwork class

public class CheckNetwork {

private static final String TAG = CheckNetwork.class.getSimpleName();

public static boolean isInternetAvailable(Context context)
{
    NetworkInfo info = (NetworkInfo) ((ConnectivityManager)
    context.getSystemService(Context.CONNECTIVITY_SERVICE)).getActiveNetworkInfo();

    if (info == null)
    {
         Log.d(TAG,"no internet connection");
         return false;
    }
    else
    {
        if(info.isConnected())
        {
            Log.d(TAG," internet connection available...");
            return true;
        }
        else
        {
            Log.d(TAG," internet connection");
            return true;
        }

    }
}
}