By default, the logging package does not do anything useful with the log messages. You must configure the logging level and add a handler for the log messages.
Here is a simple logging configuration that logs all messages via print
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Logger.root.level = Level.ALL; Logger.root.onRecord.listen((LogRecord rec) { print('${rec.level.name}: ${rec.time}: ${rec.message}'); });
First, set the root [Level]. All messages at or above the level are sent to the [onRecord] stream.
Then, listen on the [onRecord] stream for [LogRecord] events. The [LogRecord] class has various properties for the message, error, logger name, and more.
Create a [Logger] with a unique name to easily identify the source of the log messages.
final Logger log = new Logger('MyClassName');
Here is an example of logging a debug message and an error:
var future = doSomethingAsync().then((result) { log.fine('Got the result: $result'); processResult(result); }).catchError((e, stackTrace) => log.severe('Oh noes!', e, stackTrace));
When logging more complex messages, you can pass a closure instead that will be evaluated only if the message is actually logged:
log.fine(() => [1, 2, 3, 4, 5].map((e) => e * 4).join("-"));
See the [Logger] class for the different logging methods.