Fetch Data from the Internet

Key Points

• Fetching data from the internet is usually executed asynchronously using specific libraries the allow for making HTTP requests.
• Data fetched from APIs are usually encoded in the JSON format and need to mapped internally to a custom data structure. This process is called deserialization.
• In order to make HTTP requests set the corresponding permissions (Android) and/or entitlements (macOS).
• Use the dart:html package to make HTTP requests.
• The response is usually stored in a Future.
• A Future is a core Dart class for working with asynchronous operations. A Future object represents a potential value or error that will be available at some time in the future.
• The http.Response class contains the data received from a successful http call.
• To display the data on screen, use the FutureBuilder widget. The FutureBuilder widget comes with Flutter and makes it easy to work with asynchronous data sources.
• Bad practice: Do not place or execute API calls in build() methods.
• Before you request data from an API, test it using common API/endpoint test tools or IDE extensions.

Recommended Learning Resources

• Read in this cookbook how to fetch data from the internet: https://docs.flutter.dev/cookbook/networking/fetch-data
• Learn the handling and usage of Futures in Flutter/Dart: https://api.flutter.dev/flutter/dart-async/Future-class.html
• Learn how to use the FutureBuilder class to display asynchronous data: https://api.flutter.dev/flutter/widgets/FutureBuilder-class.html
• Learn more about different network topics; the following page provides a good overview of the different related topics: https://docs.flutter.dev/cookbook/networking