Future returning null also using FutureBuilder in Flutter

[leo nx]

I want to use a FutureBuilder to check if a url is a png image, and then build either one or two images(in a list). But somehow the Future always returns null when i print it...

The result is the app always building the listview with the two CachedNetworkImages, which is not what i want it to do. If the URL is an image, it should just build a CachedNetworkImage with that url, and if not it should alter the url and build a listview with 2 images.

    child: new FutureBuilder(
                    future: _getImages(widget.imgUrl),
                    builder: (BuildContext context, AsyncSnapshot snapshot) {
                      switch (snapshot.connectionState) {
                        case ConnectionState.none:
                          return new Text('Press button to start');
                        case ConnectionState.waiting:
                          return new Text('Awaiting result...');
                        default:
                          if (snapshot.hasError)
                            return new Text('Error: ${snapshot.error}');
                          else {
                            print(snapshot.data);
                            if (snapshot.data == "image/png") {
                              return new SingleChildScrollView(
                                child: new CachedNetworkImage(
                                  imageUrl: widget.imgUrl,
                                  placeholder: new Center(
                                      child: new AdaptiveProgressIndicator()),
                                ),
                              );
                            } else {
                              return new ListView(
                                children: <Widget>[
                                  new CachedNetworkImage(
                                    imageUrl:
                                        widget.imgUrl.split('.png')[0] + '-0.png',
                                    placeholder: new Center(
                                        child: new AdaptiveProgressIndicator()),
                                  ),
                                  new CachedNetworkImage(
                                    imageUrl:
                                        widget.imgUrl.split('.png')[0] + '-1.png',
                                  )
                                ],
                              );
                            }
                          }
                      }
                    }),
              ),
            ));
      }
   
      Future<String> _getImages(String url) async {
        await http.get(url).then((result) {
          return result.headers['content-type'];
        });
      }

[Jonah Williams]

It looks like you aren't returning the Future from _getImages.  The return type is still a future because you are calling await, but if you want to use the value in that future you need to return it explicitly.

Future<String> _getImages(String url) async {

  final result = await http.get(url);
  return result.headers['content-type'];

}

Or

Future<String> _getImages(String url)  {
  return http.get(url).then((result) {
    return result.headers['content-type'];
  });

}

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[Allan Jeremy]

This is a really good answer, the internet needs more people like you, cheers

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