 Attempt to invoke virtual method 'int android.net.NetworkInfo.getType()' on a null object reference

 NetUtlis.class类，出现错误，建议还是做一下是否为null的判断
   public static boolean isWiFi(Context cxt) {
        ConnectivityManager cm = (ConnectivityManager) cxt.getSystemService(Context.CONNECTIVITY_SERVICE);
        // wifi的状态：ConnectivityManager.TYPE_WIFI
        // 3G的状态：ConnectivityManager.TYPE_MOBILE
        return cm.getActiveNetworkInfo().getType() == ConnectivityManager.TYPE_WIFI;
    }