It is highly recommended that you use lib.logging package when you want to add logging statements to your Dart package.

Include the lib.logging package in your BUILD.gn target as a dependency:

deps = [

In the main function of your Dart / Flutter app, call the setupLogger() function to make sure logs appear in the Fuchsia console in the desired format.

import 'package:lib.logging/logging.dart';

main() {

After setting this up, you can call one of the following log methods to add log statements to your code:

import 'package:lib.logging/logging.dart';

// add logging statements somewhere in your code as follows:
log.info('hello world!');

The log object is a Logger instance as documented here.

Log Levels

The log methods are named after the supported log levels. To list the log methods in descending order of severity:

log.shout()    // maps to LOG_FATAL in FXL.
log.severe()   // maps to LOG_ERROR in FXL.
log.warning()  // maps to LOG_WARNING in FXL.
log.info()     // maps to LOG_INFO in FXL.
log.fine()     // maps to VLOG(1) in FXL.
log.finer()    // maps to VLOG(2) in FXL.
log.finest()   // maps to VLOG(3) in FXL.

By default, all the logs of which level is INFO or higher will be shown in the console. Because of this, Dart / Flutter app developers are highly encouraged to use log.fine() for their typical logging statements for development purposes.

Currently, the log level should be adjusted in individual Dart apps by providing the level parameter in the setupLogger() call. For example:

setupLogger(level: Level.ALL);

will make all log statements appear in the console.