Problem Statement
What are best practices for using FutureBuilder? What are common mistakes to avoid?
Explanation
Never create the Future inside the build method as this creates a new Future every rebuild, causing infinite rebuild loops or unnecessary network requests. Instead, create the Future in initState(), store it in a State variable, and pass that variable to FutureBuilder. This ensures FutureBuilder works with the same Future instance across rebuilds, completing only once.
Always handle all possible states in the builder function - check connectionState for waiting (show loading), check hasError for errors (show error message), and check hasData for success (show data). Failing to handle states leads to crashes or blank screens. Use snapshot.error to get error details and snapshot.data to access the result safely only when hasData is true.
For refresh functionality, use a setState() wrapper around assigning a new Future to the State variable, which causes FutureBuilder to rebuild with the new Future. Don't abuse FutureBuilder for repeatedly fetching data - use streams with StreamBuilder instead for continuous updates. FutureBuilder is for one-time loads that might refresh occasionally, not for polling or real-time data.
Consider using a loading state variable with setState when you need more control than FutureBuilder provides, especially if you need to show loading in specific parts of UI or handle complex loading states. FutureBuilder is convenient for simple cases but manual state management might be clearer for complex scenarios. Understanding when FutureBuilder adds value versus when manual state management is better helps create maintainable async UIs.
