Troubleshooting Flutter SearchAnchor Suggestion Builder Not Showing Results

Are you struggling to get the SuggestionBuilder of your SearchAnchor widget in Flutter to display the expected search results? This article provides a step-by-step guide to help you diagnose and resolve common issues that prevent the suggestion list from appearing.

Common Problems and Solutions

1. Data Source Issues

The first step is to ensure your data source is correctly providing the data to the SuggestionBuilder. Here’s how to verify this:

• Check your Data Access Object (DAO): Verify that your DAO is correctly querying the database and returning the expected list of results. Use print() statements to confirm the data being fetched from the database.
• Inspect your Bloc: Ensure the Bloc is receiving the data from the DAO and emitting the correct state with the updated list of suggestions. Again, use print() statements within your Bloc to monitor the data flow.
• Validate Data in the Widget: Before passing data to the SuggestionBuilder, print the list within your widget’s build() method. This ensures the widget is receiving the expected data from the Bloc.

Example of debugging data within your Widget:

 @override
 Widget build(BuildContext context) {
   final studentList = context.select((MyBloc bloc) => bloc.state.students);
   print('Student List in Widget: $studentList'); // Debugging Line
   return SearchAnchor.bar(
     suggestionsBuilder: (BuildContext context, SearchController controller) {
       return studentList.map((student) => ListTile(
         title: Text(student.name),
         onTap: () {
           controller.closeView(student.name);
         },
       )).toList();
     },
   );
 }
 

2. onChanged Not Firing

If the onChanged callback of your SearchAnchor isn’t triggering, the suggestion list won’t update. Here’s how to fix it:

• Using SearchAnchor.bar(): Ensure you are using SearchAnchor.bar() if you expect the onChanged callback to fire as the user types. The standard SearchAnchor requires different handling.
• SearchController issues Confirm that the SearchController is properly linked to your SearchAnchor and that changes to the search field are updating the SearchController‘s value, thus triggering the onChanged callback.

3. Incorrect Use of BlocBuilder

Wrapping your SearchAnchor with a BlocBuilder is often necessary to rebuild the widget when the Bloc’s state changes. However, incorrect usage can lead to unexpected behavior.

• Proper State Management: Ensure your Bloc emits a new state whenever the search query changes. This will trigger the BlocBuilder to rebuild the SearchAnchor with the updated suggestion list.
• Avoid Over-Rebuilding: Make sure the BlocBuilder is only wrapping the necessary part of the widget tree to prevent unnecessary rebuilds.

Example of wrapping SearchAnchor with BlocBuilder:

 BlocBuilder(
   builder: (context, state) {
     return SearchAnchor.bar(
       suggestionsBuilder: (BuildContext context, SearchController controller) {
         return state.filteredStudents.map((student) => ListTile(
           title: Text(student.name),
           onTap: () {
             controller.closeView(student.name);
           },
         )).toList();
       },
     );
   },
 )
 

4. Null or Empty List Issues

The SuggestionBuilder might receive a null or empty list, preventing any suggestions from showing.

• Check for Null Values: Before passing the list to the SuggestionBuilder, ensure it’s not null. Add a null check and handle the case where the list is null (e.g., display a “No results” message).
• Empty State Handling: Implement logic to handle the case where the list is empty. Display a message like “No suggestions found” to provide feedback to the user.

Example of Null Check

 BlocBuilder(
   builder: (context, state) {
     final studentList = state.filteredStudents;
     if (studentList == null || studentList.isEmpty) {
       return Text("No suggestions found.");
     }
     return SearchAnchor.bar(
       suggestionsBuilder: (BuildContext context, SearchController controller) {
         return studentList.map((student) => ListTile(
           title: Text(student.name),
           onTap: () {
             controller.closeView(student.name);
           },
         )).toList();
       },
     );
   },
 )
 

5. Rendering Issues

• Ensure ListTiles have proper Height: If ListTiles do not have proper Height the may not render properly, and hence user might not see the result.

Example: Complete Troubleshooting Checklist

Follow this checklist to systematically identify the cause of the problem:

1. Verify Data Source: Use print statements to trace the data from the DAO to the Bloc and finally to the widget.
2. Check onChanged: Confirm that the onChanged callback is firing as the user types in the search bar.
3. Inspect BlocBuilder: Ensure the BlocBuilder is correctly rebuilding the SearchAnchor when the Bloc’s state changes.
4. Handle Null/Empty Lists: Implement null checks and empty state handling to provide feedback to the user.
5. Check SearchController value: Confirm that the SearchController is properly linked to your SearchAnchor and that changes to the search field are updating the SearchController‘s value.

By following these steps, you should be able to effectively troubleshoot and resolve the issue of your SearchAnchor suggestion builder not displaying results in your Flutter application.