Flutter - Space Evenly in Column does not work as expected

try this :

 new Container(
            margin: EdgeInsets.only(bottom: 8.0),
            child: Row(
              crossAxisAlignment: CrossAxisAlignment.start,
              children: <Widget>[
                CachedNetworkImage(
                    imageUrl:
                        "https://image.tmdb.org/t/p/w500/${movieDetails
                        .posterPath}",
                    height: 120.0,
                    fit: BoxFit.fill),
                Expanded(
                    child: Container(
                        margin: EdgeInsets.only(left: 8.0),
                        child: Column(
                          mainAxisAlignment: MainAxisAlignment.spaceEvenly, //NOT WORKING!
                          children: <Widget>[
                              new Row(
                                mainAxisAlignment: MainAxisAlignment.spaceEvenly,
                                mainAxisSize: MainAxisSize.max,
                                children: <Widget>[
                                  new Text("Released : "),
                                  new Text("25-07-2018 "), 
                                ],
                              ),
                               new Row(
                                mainAxisAlignment: MainAxisAlignment.spaceEvenly,
                                mainAxisSize: MainAxisSize.max,
                                children: <Widget>[
                                  new Text("Released : "),
                                  new Text("25-07-2018 "), 
                                ],
                              ),
                               new Row(
                                mainAxisAlignment: MainAxisAlignment.spaceEvenly,
                                mainAxisSize: MainAxisSize.max,
                                children: <Widget>[
                                  new Text("Released : "),
                                  new Text("25-07-2018 "), 
                                ],
                              ),
                          ],
                        )))
              ],
            )),

As you have given the height to the image is 120.0, can you do the same for the other Container child. By giving this, I was able to achieve what you want.

Code snippet:

Container(
        margin: EdgeInsets.only(bottom: 8.0),
        child: Row(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: <Widget>[
            CachedNetworkImage(
                imageUrl:
                    "https://image.tmdb.org/t/p/w500/${movieDetails
                    .posterPath}",
                height: 120.0,
                fit: BoxFit.fill),
            Expanded(
                child: Container(
                    height: 120.0 //added to fix
                    margin: EdgeInsets.only(left: 8.0),
                    child: Column(
                      mainAxisAlignment: MainAxisAlignment.spaceEvenly, //NOT WORKING!
                      children: <Widget>[
                        generateRow(
                            Strings.released, movieDetails.releaseDate),
                        generateRow(Strings.runtime,
                            movieDetails.runtime.toString()),
                        generateRow(Strings.budget,
                            movieDetails.budget.toString())
                      ],
                    )))
          ],
        )),

Tips to debug:

• I used Flutter Inspector to find the problem. Refer
• Refer the image below. Even though we gave Expanded, it occupied just half the size of image. Here the size of Expanded is determined by child's size (which is almost half the image size).