title: How to Making Popup error message from API Server on flutter?
body: <p>Sorry for my bad english,
  I just learned flutter dart programming, I want to display a popup when there is an error message from the API server, the debugging status response has come out, but I'm still confused about how to display the popup of the error in my code.</p>
  <p>this is my code:</p>
  <pre class="lang-dart prettyprint-override"><code>    Future&lt;QueueModel&gt; getQueue(
      String norm, String dateBirth, String name, String examDate) async {final String apiUrl = &quot;http://192.168.137.99:81/server_api/api/queueme&quot;;   final response = await http.post(apiUrl,
        body: {&quot;norm&quot;: norm, &quot;dateBirth&quot;: dateBirth, &quot;name&quot;: name, &quot;examDate&quot;: examDate});    if (response.statusCode == 200) {
      final String responseString = response.body;
      return queueModelFromJson(responseString);    } else{ 
      print(response.body);    }    }
  
  </code></pre>