Flutter - Streambuilder Error due to no return

Question

I am getting an error with my Streambuilder. I do not understand how to fix it. Please, can you help me to solve this? Many thanks.

══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════ The following assertion was thrown building StreamBuilder(dirty, state: _StreamBuilderBaseState<QuerySnapshot, AsyncSnapshot>#47274): A build function returned null. The offending widget is: StreamBuilder Build functions must never return null.

StreamBuilder<QuerySnapshot>(
                  stream: FirebaseFirestore.instance
                      .collection('Users')
                      .doc(FirebaseAuth.instance.currentUser.uid)
                      .collection('projects')
                      .snapshots(),
                  builder: (context, snapshot) {
                    if (!snapshot.hasData)
                      const Text("Loading.....");
                    else {
                      List<DropdownMenuItem> projectItems = [];
                      for (int i = 0; i < snapshot.data.docs.length; i++) {
                        DocumentSnapshot snap = snapshot.data.docs[i];
                        projectItems.add(
                          DropdownMenuItem(
                            child: Text(
                              (snap.data()['project_Name']),
                              style: TextStyle(color: Colors.black),
                            ),
                            // snap.id,
                            //  style: TextStyle(color: Color(0xff11b719)),
                            // ),
                            value: (snap.data()['project_Name']),
                          ),
                        );
                        return Row(
                          mainAxisAlignment: MainAxisAlignment.start,
                          children: <Widget>[
                            DropdownButton(
                              items: projectItems,
                              onChanged: (projectSelected) {

                                final snackBar = SnackBar(
                                  content: Text(
                                    'Selected project is $projectSelected',
                                    style: TextStyle(color: Color(0xff11b719)),
                                  ),
                                );
                                Scaffold.of(context).showSnackBar(snackBar);
                                setState(() {
                                  selectedProject = projectSelected;
                                });
                              },
                              value: selectedProject,
                              isExpanded: false,
                              hint: new Text(
                                projectName,
                                style: TextStyle(color: Color(0xff11b719)),
                              ),
                            ),
                          ],
                        );
                      }
                    }
                  }),

I think, you should close your for loop `}' before that `return Row(...` statement. — Midhun MP, Dec 19 '20 at 17:25
Thank you. I have tried. I do not get the error message any more. But, the dropdown is not active any more. I can not select the data in the dropdown — Laurent Thomas, Dec 19 '20 at 17:33
I think `snapshot.data.docs.length` is zero. Just print the value and check. — Midhun MP, Dec 19 '20 at 17:34
Is your dropdown shows the values? What's the issue you are facing now ? — Midhun MP, Dec 19 '20 at 18:11
The dropdown is showing the value in Firebase, I mean the record in FireBase. When I click on it, I should get the list of all the project names available — Laurent Thomas, Dec 19 '20 at 18:21
Let us [continue this discussion in chat](https://chat.stackoverflow.com/rooms/226178/discussion-between-midhun-mp-and-laurent-thomas). — Midhun MP, Dec 19 '20 at 18:37

score 0 · Answer 1 · answered Dec 20 '20 at 22:35

The problem is obvious and compiler said you about it. builder always need to return a Widget. But your code does not do this when condition if (!snapshot.hasData) is executed. You must change it to:

if (!snapshot.hasData) {
  return Text('Loading...');
}

Flutter - Streambuilder Error due to no return

1 Answers1