All 7 Flutter DevTools & Debugging questions
More in Flutter DevTools & Debugging
What is Flutter DevTools, and what are some of the core debugging and performance analysis features it actually provides to help you build and troubleshoot a Flutter app? How does the Flutter DevTools performance timeline help you actually identify specific frames that are taking longer than the ideal sixteen milliseconds needed to maintain a genuinely smooth sixty frames per second animation? How can you use the debugger and breakpoints within an IDE like Visual Studio Code or Android Studio to actually step through your Flutter app's code line by line and inspect the exact current values of your variables? How does the DevTools memory view help you actually detect a genuine memory leak, such as one caused by forgetting to properly dispose of a controller or cancel an active stream subscription? How can you use Flutter DevTools' dedicated network view together with proper logging to effectively debug a genuinely complex issue involving several separate related API calls happening across your application? How can you use the DevTools widget rebuild profiler and the Flutter Inspector's own select widget mode together to actually diagnose a specific widget that is genuinely rebuilding far more frequently than it actually genuinely needs to?
Advertisement
Back to results for “Testing & Debugging”
Flutter › Flutter DevTools & Debugging

What is hot reload in Flutter, and how does it let you see the direct visual result of a code change almost instantly, without needing to fully restart your entire app from scratch every single time?

Beginner

Answer

Hot reload injects your updated source code directly into an already actively running Dart virtual machine while genuinely preserving your app's existing current state, such as which specific screen you are currently on or the exact current values held within your active text fields, letting you see the resulting direct visual effect of a small code change, such as adjusting a specific widget's color or padding, appear almost instantly on screen, which dramatically speeds up the entire iterative development process compared to needing to fully restart your entire app completely from scratch after every single small individual change.
// Save a file while the app is running,
// and Flutter automatically applies a hot reload within roughly one second
Real-world example A developer fine tuning the exact padding and spacing values throughout a complex checkout screen relies heavily on hot reload to instantly see each small individual adjustment reflected immediately on screen, without ever needing to tediously navigate back through several screens after each individual code change.

Common follow-ups: What specific kinds of code changes actually require a full hot restart rather than simply a hot reload?;Why does hot reload not actually work at all for a genuine release build?

Flutter Widgets Fundamentals (Stateless & Stateful);Unit Testing in Flutter
All 7 Flutter DevTools & Debugging questions