1. Flutter

How to perform a hot reload (flutter)

To hot reload a Flutter app:

  1. Run the app from a supported flutter editor  or a terminal window. Either a physical or virtual device can be the target. Only Flutter apps in debug mode can be hot reloaded.
  2. Modify one of the Dart files in your project. Most types of code changes can be hot reloaded; for a list of changes that require a hot restart, see special cases .
  3. If you’re working in an IDE/editor that supports Flutter’s IDE tools, select Save All (cmd-s/ctrl-s), or click the hot reload button on the toolbar.If you’re running the app at the command line using flutter run, enter r in the terminal window.

After a successful hot reload operation, you’ll see a message in the console similar to:

Performing hot reload…
Reloaded 1 of 448 libraries in 978ms.

How hot-reload works.
When hot-reload is invoked, the host machine checks the edited code since last compilation and recompile the following libraries:
Any library with changed code.
The application’s main library.
The libraries from the main library leading to affected libraries.
The updated source codes are sent into a running Dart Virtual Machine. The Dart VM then reloads all the libraries with updated code, The hot-reload mechanism updates classes with the new versions of fields and functions, the Flutter framework automatically rebuild, repaint ,re-layout the widget tree, allowing one to quickly view the effects of the changes.