How to detect when internet is available on Android?

You can use this to test:

Log.e("netHabilitada", Boolean.toString(isNetDisponible()));
Log.e("accInternet",   Boolean.toString(isOnlineNet()));

To check if the network is enabled:

private boolean isNetDisponible() {

    ConnectivityManager connectivityManager = (ConnectivityManager)
                                               getSystemService(Context.CONNECTIVITY_SERVICE);

    NetworkInfo actNetInfo = connectivityManager.getActiveNetworkInfo();

    return (actNetInfo != null && actNetInfo.isConnected());
}

To check if there is internet access:

public Boolean isOnlineNet() {

    try {
        Process p = java.lang.Runtime.getRuntime().exec("ping -c 1 www.google.es");

        int val           = p.waitFor();
        boolean reachable = (val == 0);
        return reachable;

    } catch (Exception e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    return false;
}

Add (in Manifest.permission) also what you need in the permissions for example these if you use both:

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

Manifest.permission (english link):

android.permission.ACCESS_NETWORK_STATE

android.permission.INTERNET

January 2020 update:

As of Android 10 the use of the NetWorkInfo class and its methods is obsolete, now the class ConectivityManagerand method getNetworkCapabilities()or Class must be usedNetworkCapabilities

public static boolean isNetworkAvailable(Context context) {

    ConnectivityManager connectivityManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);

    if (connectivityManager != null) {
           NetworkCapabilities capabilities = connectivityManager.getNetworkCapabilities(connectivityManager.getActiveNetwork());
            if (capabilities != null) {
                if (capabilities.hasTransport(NetworkCapabilities.TRANSPORT_CELLULAR)) {
                    Log.i(TAG, "NetworkCapabilities.TRANSPORT_CELLULAR");
                    return true;
                } else if (capabilities.hasTransport(NetworkCapabilities.TRANSPORT_WIFI)) {
                    Log.i(TAG, "NetworkCapabilities.TRANSPORT_WIFI");
                    return true;
                }  else if (capabilities.hasTransport(NetworkCapabilities.TRANSPORT_ETHERNET)){
                    Log.i(TAG, "NetworkCapabilities.TRANSPORT_ETHERNET");
                    return true;
                }
            }
        }

    return false;

}

Executing a process to perform a ping would not do it, for that we have the NetWorkInfo class and its methods!

• If you need to know if there is internet available, you should check if there is connectivity you can use isAvailable()

• If you need to know if there is connectivity and it is possible to establish a connection, use isConnected()

Example:

private static ConnectivityManager manager;

public static boolean isOnline(Context context) {
    ConnectivityManager connectivityManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo networkInfo = connectivityManager.getActiveNetworkInfo();
    return networkInfo != null && networkInfo.isAvailable() && networkInfo.isConnected();
}

Very important to add the permissions, to determine the status of the network:

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

and to have connectivity:

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

On the other hand you can determine the type of network if it is WiFi :

public static boolean isConnectedWifi(Context context) {
    ConnectivityManager connectivityManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo networkInfo = connectivityManager.getActiveNetworkInfo();
    return networkInfo != null && networkInfo.getType() == ConnectivityManager.TYPE_WIFI;
}

or if it is Mobile :

public static boolean isConnectedMobile(Context context) {
    ConnectivityManager connectivityManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo networkInfo = connectivityManager.getActiveNetworkInfo();
    return networkInfo != null && networkInfo.getType() == ConnectivityManager.TYPE_MOBILE;
}

This solution allows you to detect if your Android device is connected to the Internet, validating whether there is a Wi-Fi connection or mobile networks such as 3G or 4G.

     ConnectivityManager cm;
     NetworkInfo ni;
     cm = (ConnectivityManager) this.getSystemService(Context.CONNECTIVITY_SERVICE);
     ni = cm.getActiveNetworkInfo();
     boolean tipoConexion1 = false;
     boolean tipoConexion2 = false;

     if (ni != null) {
          ConnectivityManager connManager1 = (ConnectivityManager) this.getSystemService(Context.CONNECTIVITY_SERVICE);
          NetworkInfo mWifi = connManager1.getNetworkInfo(ConnectivityManager.TYPE_WIFI);

          ConnectivityManager connManager2 = (ConnectivityManager) this.getSystemService(Context.CONNECTIVITY_SERVICE);
          NetworkInfo mMobile = connManager2.getNetworkInfo(ConnectivityManager.TYPE_MOBILE);

          if (mWifi.isConnected()) {
               tipoConexion1 = true;
          }
          if (mMobile.isConnected()) {
               tipoConexion2 = true;
          }

          if (tipoConexion1 == true || tipoConexion2 == true) {
               /* Estas conectado a internet usando wifi o redes moviles, puedes enviar tus datos */
          }
    } 
    else {
       /* No estas conectado a internet */
    }

Remember to add the corresponding permissions to execute this code in your manifest:

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

Hope it helps, cheers.

My own solution, to detect if there is an internet connection: Summarizing the function isOnlinechecks if there is any existing connection if it is connected and then checks if it can query google.es

public static boolean isOnline(Context context) {

     ConnectivityManager connectivityManager = (ConnectivityManager)     
         context.getSystemService(Context.CONNECTIVITY_SERVICE);
     NetworkInfo networkInfo = connectivityManager.getActiveNetworkInfo();

        RunnableFuture<Boolean> futureRun = new FutureTask<Boolean>(new Callable<Boolean>() {
            @Override
            public Boolean call() throws Exception {
                if ((networkInfo .isAvailable()) && (networkInfo .isConnected())) {
                    try {
                        HttpURLConnection urlc = (HttpURLConnection) (new URL("http://www.google.com").openConnection());
                        urlc.setRequestProperty("User-Agent", "Test");
                        urlc.setRequestProperty("Connection", "close");
                        urlc.setConnectTimeout(1500);
                        urlc.connect();
                        return (urlc.getResponseCode() == 200);
                    } catch (IOException e) {
                        Log.e(TAG, "Error checking internet connection", e);
                    }
                } else {
                    Log.d(TAG, "No network available!");
                }
                return false;
            }
        });

        new Thread(futureRun).start();


        try {
            return futureRun.get();
        } catch (InterruptedException | ExecutionException e) {
            e.printStackTrace();
            return false;
        }

    }

I use the following method, I hope it works for you:

public static boolean compruebaConexion(Context context)
{
    boolean connected = false;
    ConnectivityManager connec = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);

    // Recupera todas las redes (tanto móviles como wifi)
    NetworkInfo[] redes = connec.getAllNetworkInfo();

    for (int i = 0; i < redes.length; i++) {
        // Si alguna red tiene conexión, se devuelve true
        if (redes[i].getState() == NetworkInfo.State.CONNECTED) {
            connected = true;
        }
    }
    return connected;
}