Flutter futurebuilder not updating

Flutter FutureBuilder Not Updating

The Flutter FutureBuilder widget is commonly used to handle asynchronous operations in Flutter applications. It has built-in support for updating the UI based on the state of the Future it’s constructed with. However, there are some common pitfalls that can prevent the FutureBuilder from updating as expected.

1. Verify the Future is Complete

One of the common reasons for FutureBuilder not updating is when the Future isn’t marked as complete. Ensure that the Future you provide to the builder property of FutureBuilder has correctly completed, either with a value or an error. For example:

    
      Future<String> fetchData() async {
        final response = await http.get('https://example.com/data');
        if (response.statusCode == 200) {
          return response.body;
        } else {
          throw Exception('Failed to fetch data');
        }
      }
    
      ...
    
      FutureBuilder(
        future: fetchData(),
        builder: (context, snapshot) {
          if (snapshot.hasData) {
            return Text(snapshot.data);
          } else if (snapshot.hasError) {
            return Text('Error: ${snapshot.error}');
          }
          return CircularProgressIndicator();
        },
      )
    
  

2. Ensure UI Rebuild is Triggered

Sometimes the UI doesn’t rebuild because the state didn’t change visibly. Make sure the state update is done in a way that triggers the UI to rebuild. For example, use setState() or a state management solution like Provider or Riverpod.

3. Check for Equality in Async Snapshots

When using FutureBuilder, it’s essential to consider the equality comparison for snapshot data. If the snapshot data remains the same across different Future completions, the UI won’t update. Ensure that the updated data results in a different object reference. For example:

    
      List<String> data = ['Value'];
    
      Future<void> fetchData() async {
        await Future.delayed(Duration(seconds: 2));
        data[0] = 'Updated Value';
      }
    
      ...
    
      FutureBuilder(
        future: fetchData(),
        builder: (context, snapshot) {
          if (snapshot.connectionState != ConnectionState.done) {
            return CircularProgressIndicator();
          } else if (snapshot.hasError) {
            return Text('Error: ${snapshot.error}');
          }
    
          if (snapshot.data[0] == 'Value') { // No update, as object reference is the same
            return Text('Value is still the same');
          } else {
            return Text('Updated Value is applied: ${snapshot.data[0]}');
          }
        },
      )
    
  

By following these tips, you can ensure that your Flutter FutureBuilder updates as expected. Remember to handle edge cases properly and consider best practices for state management in Flutter applications.