title: Flutter Format Exception : Unexpected Character (at character 1)
body: <p>I am getting a Exception in Flutter project. The error looks like below:</p>
  
  <pre><code>Exception has occurred.
  FormatException (FormatException: Unexpected character (at character 1)
  &lt;!DOCTYPE html&gt;
  ^
  )
  </code></pre>
  
  <p>This is showing in the "throw error" line. The code is below:</p>
  
  <pre><code>Future&lt;void&gt; _authenticate(
        String email, String password, String urlSegment) async {
      final url =
          "https://identitytoolkit.googleapis.com/v1/accounts:$urlSegment?key=AIzaSyC9Rz9CDv-_hc68I_wdvogF2ZnDHCpr2Y8";
      try {
        final response = await http.post(
          url,
          body: json.encode(
            {
              "email": email,
              "password": password,
              "returnSecureToken": true,
            },
          ),
        );
        print(response.body);
        final responseData = json.decode(response.body);
        if (responseData["error"] != null) {
          throw HttpException(responseData["error"]["message"]);
        }
        _token = responseData["idToken"];
        _userId = responseData["localId"];
        _expiryDate = DateTime.now().add(
          Duration(
            seconds: int.parse(
              responseData["expiresIn"],
            ),
          ),
        );
        _autoLogout();
        notifyListeners();
        final prefs = await SharedPreferences.getInstance();
        final userData = json.encode(
          {
            "token": _token,
            "userId": _userId,
            "expiryDate": _expiryDate.toIso8601String(),
          },
        );
        prefs.setString("userData", userData);
      } catch (error) {
        throw error;           //Exception is showing here
      }
    }
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/aTUb3.png" rel="nofollow noreferrer">Error message looks like this as shown in the image (Click)</a></p>
  
  <p>Debug Console is showing the following message:</p>
  
  <pre><code>I/flutter (18432): &lt;!DOCTYPE html&gt;
  I/flutter (18432): &lt;html lang=en&gt;
  I/flutter (18432):   &lt;meta charset=utf-8&gt;
  I/flutter (18432):   &lt;meta name=viewport content="initial-scale=1, minimum-scale=1, width=device-width"&gt;
  I/flutter (18432):   &lt;title&gt;Error 404 (Not Found)!!1&lt;/title&gt;
  I/flutter (18432):   &lt;style&gt;
  I/flutter (18432):     *{margin:0;padding:0}html,code{font:15px/22px arial,sans-serif}html{background:#fff;color:#222;padding:15px}body{margin:7% auto 0;max-width:390px;min-height:180px;padding:30px 0 15px}* &gt; body{background:url(//www.google.com/images/errors/robot.png) 100% 5px no-repeat;padding-right:205px}p{margin:11px 0 22px;overflow:hidden}ins{color:#777;text-decoration:none}a img{border:0}@media screen and (max-width:772px){body{background:none;margin-top:0;max-width:none;padding-right:0}}#logo{background:url(//www.google.com/images/branding/googlelogo/1x/googlelogo_color_150x54dp.png) no-repeat;margin-left:-5px}@media only screen and (min-resolution:192dpi){#logo{background:url(//www.google.com/images/branding/googlelogo/2x/googlelogo_color_150x54dp.png) no-repeat 0% 0%/100% 100%;-moz-border-image:url(//www.google.com/images/brand
  I/flutter (18432): FormatException: Unexpected character (at character 1)
  I/flutter (18432): &lt;!DOCTYPE html&gt;
  I/flutter (18432): ^
  </code></pre>
  
  <p>Please help</p>