title: Multiple select options in flutter
body: <p>I want to create a choice chip list of options and select multiple choices in that. I also want to change the colour when the options are selected. the options are dynamic.
  I tried using the below function but the onselectionchanged displays null error and the color doesn't change when tapped. Any suggestions please??</p>
  <pre><code>_buildChoiceList() {
      List&lt;Widget&gt; choices = [];
      options.forEach((item) {
        choices.add(Container(
          padding: const EdgeInsets.all(2.0),
          child: ChoiceChip(
            label: Text(item),
            selected: selectedOptions.contains(item),
            backgroundColor: Color(0xffff08222),
            onSelected: (selected) {
              setState(() {
                selectedOptions.contains(item)
                    ? selectedOptions.remove(item)
                    : selectedOptions.add(item);
                widget.onSelectionChanged(selectedOptions);
              });
            },
          ),
        ));
      });
      return choices;
    }
  </code></pre>