Flutter中仅使用StatefulWidget或用不更新的StatefulWidget是否有性能问题？

Let’s break down your questions clearly—this is a super common point of confusion for Flutter developers as they get comfortable with widget types!

1. What happens when using only some StatefulWidgets in an app? #

First, let’s clarify what "using only some" means in practice:

• If you’re mixing StatefulWidgets with StatelessWidgets appropriately (e.g., Stateful for interactive elements like text fields or toggles, Stateless for static UI like headers or icons), this is the standard, recommended approach in Flutter. There’s no issue here—Flutter is designed to let you pick the right widget type for each part of your UI based on whether it needs to manage mutable state.
• If you mean using StatefulWidgets in places where you never actually update their state (no calls to setState()), functionally the UI will work just fine. The only downside is you’re carrying unnecessary overhead from the State object tied to each StatefulWidget—more on that next.
• If you’re referring to incomplete usage (e.g., forgetting to implement createState(), or mishandling the State lifecycle), that will cause runtime errors—Flutter requires StatefulWidgets to have a corresponding State class to function.

2. Will replacing all StatelessWidgets with non-updating StatefulWidgets cause performance issues? #

Short answer: In small apps you might not notice, but yes, it can lead to measurable performance and maintainability problems at scale.

Let’s break down the concrete impacts:

• Memory overhead: Every StatefulWidget creates a persistent State instance that lives alongside the widget. Even if you never call setState(), these State objects take up memory. Multiply this by hundreds or thousands of widgets (like in a long scrollable list), and you’ll see a noticeable increase in memory usage compared to using StatelessWidgets.
• Rebuild inefficiencies: When a parent widget rebuilds, StatefulWidgets go through a slightly longer lifecycle than StatelessWidgets. Flutter checks if the existing State can be reused, calls didUpdateWidget() (even if you don’t override it), then rebuilds the widget. While each instance’s overhead is tiny, it adds up in complex UIs—this can lead to dropped frames in animations or slow scroll performance.
• Code maintainability: This is a non-performance but critical issue. Other developers (or future you) will look at a StatefulWidget and expect it to manage state. Using it for static UI creates confusion, makes the codebase harder to navigate, and increases the chance of bugs if someone later tries to add state management without realizing it’s unnecessary.

Bottom line #

It’s totally fine to use a StatefulWidget occasionally where you don’t need state (maybe you’re prototyping quickly), but replacing all StatelessWidgets with them is a bad habit. Stick to StatelessWidgets for static UI—they’re lighter, cleaner, and aligned with Flutter’s design principles.

内容的提问来源于stack exchange，提问作者Rémy Menard