How to wrap row items in a card with flutter

I fixed your code with the following changes:

• Removed Row widget inside Wrap.

• Removed Expanded widget.

• Add the property maxLines to your Text widget.

         Widget _buildCategories() {
            return Card(
                margin: const EdgeInsets.only(top: 20.0),
                child: Padding(
                  padding: const EdgeInsets.all(20.0),
                  child: Column(
                    children: <Widget>[
                      Text(
                        'Categories',
                        style: TextStyle(fontFamily: 'MonteSerrat', fontSize: 16.0),
                      ),
                      Wrap(
                        children: <Widget>[
                          _checkBox('Gaming'),
                          _checkBox('Sports'),
                          _checkBox('Casual'),
                          _checkBox('21 +'),
                          _checkBox('Adult'),
                          _checkBox('Food'),
                          _checkBox('Club'),
                          _checkBox('Activities'),
                          _checkBox('Shopping')
                        ],
                      )
                    ],
                  ),
                ));
          }
  
          Widget _checkBox(String category) {
            return Column(
                  children: <Widget>[
                    Text(
                      '$category',
                      maxLines: 1,
                      textAlign: TextAlign.center,
                      style: TextStyle(fontFamily: 'MonteSerrat'),
                    ),
                    Checkbox(
                      value: false,
                      onChanged: (value) {
                        // We will update the value to the firebase data here
                        print('updated value to: $value');
                      },
                    )
                  ],
                );
          }
        } 
  

Also you can add the properties runSpacing and spacing to your Wrap widget to give more space between your items in horizontal and vertical.

     Wrap(
            runSpacing: 5.0,
            spacing: 5.0,

More info here: https://api.flutter.dev/flutter/widgets/Wrap-class.html