how to use dart devtools
#1. Install DevTools
dart pub global activate devtools
#2. Launch the DevTools server
dart pub global run devtools
#Serving DevTools at http://127.0.0.1:9100
#3. Start the target app
cd path/to/dart/app
dart run --observe main.dart
#Observatory listening on http://127.0.0.1:8181/wYDP3x9mvbw=/
#4. Open DevTools and connect to the target app
#1. Open Chrome browser window and navigate to http://localhost:9100.
#2. Paste the “listening” URL into the text field under Connect to a running app, and click the Connect button.