Flutter not getting sent response from Flask rest API

Question

I am building a mobile app with flutter and communicating with a rest API i built with Flask. I am new to the two technologies though. Everything works well when I test with postman but when I test from my flutter app, the request actually processes and logs status code 200 in my Flask app but the response somehow doesn't get returned or is not well formatted as Flutter always shows an error rather saying: XMLHttpRequest error instead of the json response.

Dart code:

final String url = 'http://127.0.0.1:5000/endpoint';
http.Response response = await http.post(url, body: json.encode(body)); 
print(json.decode(response.body));

Flask code:

@app.route('/endpoint', methods=['POST'])
def save_point():
    try:
        body = utils.bytes_to_dict(request.get_data())
        assets = body.get('assets', [])
        if len(assets) < 1:
            raise Exception("'assets' is required")
        
        admin.insert(data = {'selected_assets': assets, 'created_at': utils.gettime()}, id = 'selected_assets')


        return jsonify({ # response is returned here
            'status': True,
            'message': 'Selected assets saved',
            'data': assets
        })
    except Exception as e:
        print('error', e)
        return {
            'status': False,
            'message': str(e)
        }

I already tried adding content-type header to the request in flutter via: await http.post(url, body: json.encode(body), headers: {'Content-type': 'application/json'}); but this causes the request not to get processed in Flask for reasons I do not know.

Please what could be wrong ? Is there a way to get flutter to understand the response ?

The response content type is probably XML, ie, not JSON. The Flask code seems to have `jsonify()` to convert the response to JSON — blackraven, Jun 06 '21 at 10:25
I already added jsonify to my code.. still don't get why it's that way — emmaakachukwu, Jun 06 '21 at 11:33
How about flutter to expect `await http.post(url, body: body, headers: {'Content-type': 'application/json'});` or ``await http.post(url, body: body, headers: {'Accept': '*/*'});`` — blackraven, Jun 06 '21 at 12:53

score 0 · Answer 1 · answered Jun 06 '21 at 10:17

0

I had to add headers: {"Content-Type": "application/json"} in my post request.

answered Jun 06 '21 at 10:17

Archit

31
2

I mentioned in my question that this did not work for me – emmaakachukwu Jun 06 '21 at 11:34

score 0 · Answer 2 · answered Jun 06 '21 at 12:57

0

I think the error is in this line:

body: json.encode(body)

The format of 'body' is already JSON, and this line is encoding it again

answered Jun 06 '21 at 12:57

blackraven

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Flutter not getting sent response from Flask rest API

2 Answers2