Why can I not check if Flutter list isnotempty?-CodePudding

I have created a flutter list but how do I check if it is empty?
List<int> selectedItems = [];
However, selectedItems.isNotEmpty gives me Conditions must have a static type of 'bool'. error. How do I fix this?

I created a dropdown

SearchChoices.multiple(
                        clearIcon: const Icon(FontAwesomeIcons.times),
                        underline: Container(
                          color: const Color(0xffF0F0F0),
                        ),
                        items:
                            _list.map<DropdownMenuItem<String>>((String value) {
                          return DropdownMenuItem<String>(
                            value: value,
                            child: Text(value),
                          );
                        }).toList(),
                        selectedItems: selectedItems,
                        hint: const Padding(
                          padding: EdgeInsets.all(12.0),
                          child: Text("Select any"),
                        ),
                        searchHint: "Select any",
                        onChanged: (value) {
                          setState(() {
                            value = selectedItems;
                          });
                        },
                        closeButton: (selectedItems) {
                          return selectedItems.isNotEmpty
                              ? "Save ${selectedItems.length == 1 ? '"'   items[selectedItems.first].value.toString()   '"' : '('   selectedItems.length.toString()   ')'}"
                              : "Save without selection";
                        },
                        isExpanded: true,
                      ),

The error is here

closeButton: (selectedItems) {
                          return selectedItems.isNotEmpty
                              ? "Save ${selectedItems.length == 1 ? '"'   items[selectedItems.first].value.toString()   '"' : '('   selectedItems.length.toString()   ')'}"
                              : "Save without selection";
                        },

The dropdown package I used is: Screenshot of variable

CodePudding user response：

Try giving a type to the selectedItems,

According to the searchable_dropdown docs

closeButton: String|Widget|Function with parameter: selectedItems returning String|Widget displayed at the bottom of the search dialog box.

closeButton: (List<int> selectedItems) {
                          return selectedItems.isNotEmpty
                              ? "Save ${selectedItems.length == 1 ? '"'   items[selectedItems.first].value.toString()   '"' : '('   selectedItems.length.toString()   ')'}"
                              : "Save without selection";
                        },