判断当前网络是否连接

public class NetworkUtils {
    public static boolean isNetworkAvailable(Context context) {
        ConnectivityManager manager = (ConnectivityManager) context
                .getApplicationContext().getSystemService(
                        Context.CONNECTIVITY_SERVICE);
        if (manager == null) {
            return false;
        }

        NetworkInfo networkinfo = manager.getActiveNetworkInfo();

        if (networkinfo == null || !networkinfo.isAvailable()) {
            return false;
        }

        return true;
    }
}