“Flutter (software)”的意思、由来-开放百科全书

The first version of Flutter was known as "Sky" and ran on the Android operating system. It was unveiled at the 2015 Dart developer summit, with the stated intent of being able to render consistently at 120 frames per second.^[7] During the keynote of Google Developer Days in Shanghai, Google announced Flutter Release Preview 2 which is the last big release before Flutter 1.0.^[8] On December 4th, 2018, Flutter 1.0 was released at the Flutter Live event, denoting the first "stable" version of the Framework.

Framework architecture

Dart platform

Flutter apps are written in the Dart language and make use of many of the language's more advanced features.^[9]

On Android, and on Windows, macOS and Linux via the semi-official Flutter Desktop Embedding project, Flutter runs in the Dart virtual machine which features a just-in-time execution engine. Due to App Store restrictions on dynamic code execution, Flutter apps use ahead-of-time (AOT) compilation on iOS.^[9]

A notable feature of the Dart platform is its support for "hot reload" where modifications to source files can be injected into a running application. Flutter extends this with support for stateful hot reload, where in most cases changes to source code can be reflected immediately in the running app without requiring a restart or any loss of state.^[10] This feature as implemented in Flutter has received widespread praise{{citation needed|date=January 2019}}.

Flutter engine

Flutter's engine, written primarily in C++, provides low-level rendering support using Google's Skia graphics library. Additionally, it interfaces with platform-specific SDKs such as those provided by Android and iOS.^[11] The Flutter Engine is a portable runtime for hosting Flutter applications. It implements Flutter's core libraries, including animation and graphics, file and network I/O, accessibility support, plugin architecture, and a Dart runtime and compile toolchain. Most developers will interact with Flutter via the Flutter Framework, which provides a modern, reactive framework, and a rich set of platform, layout and foundation widgets.

Foundation library

The Foundation library, written in Dart, provides basic classes and functions which are used to construct applications using Flutter, such as APIs to communicate with the engine.^[11]^[12]

Widgets

UI design in Flutter typically involves assembling and/or creating various widgets. A widget in Flutter represents an immutable description of part of the user interface; all graphics, including text, shapes, and animations are created using widgets. More complex widgets can be created by combining many simpler ones.

However, the use of widgets is not strictly required to build Flutter apps. An alternative option is to use the Foundation library's methods directly, interfacing with "canvas" commands to draw shapes, text, and imagery directly to the screen. This property of Flutter has been utilized in a few frameworks, such as the open-source [https://github.com/luanpotter/flame Flame] game engine.

Design-specific widgets

The Flutter framework contains two sets of widgets which conform to specific design languages. Material Design widgets implement Google's design language of the same name, and Cupertino widgets imitate Apple's iOS design.^[11]^[13]^[14]

References

1. ^{{cite web |url=https://github.com/flutter/flutter/releases/tag/v0.0.6 |title=Release v0.0.6: Rev alpha branch version to 0.0.6, flutter 0.0.26 (#10010) · flutter/flutter |author=Chris Bracken |date= |website=GitHub |publisher= |access-date=2018-08-08 |quote=}}
2. ^https://github.com/flutter/flutter/releases
3. ^https://developers.googleblog.com/2018/09/flutter-release-preview-2-pixel-perfect.html
4. ^https://github.com/flutter/flutter/wiki/Changelog
5. ^{{cite web |url=https://flutter.io/faq/ |title=FAQ - Flutter |author= |date= |website= |publisher= |access-date=2018-08-08 |quote=}}
6. ^{{cite web|url=https://arstechnica.com/gadgets/2017/05/googles-fuchsia-smartphone-os-dumps-linux-has-a-wild-new-ui/|title=Google's "Fuchsia" smartphone OS dumps Linux, has a wild new UI|publisher=Ars Technica}}
7. ^{{cite web|url=https://arstechnica.com/gadgets/2015/05/googles-dart-language-on-android-aims-for-java-free-120-fps-apps/|title=Google's Dart language on Android aims for Java-free, 120 FPS apps|first=Ron|last=Amadeo|date=1 May 2015|publisher=Ars Technica}}
8. ^{{cite web|url=https://www.apptunix.com/whats-new-in-googles-flutter-for-mobile-app-developers|publisher=Apptunix|title=Google Announced Flutter Release Preview 2}}
9. ^{{Cite web|url=https://proandroiddev.com/flutters-compilation-patterns-24e139d14177|title=Flutter’s Compilation Patterns|last=stephenwzl|date=2018-08-01|website=ProAndroidDev|access-date=2018-12-06}}
10. ^{{Cite web|url=https://hackernoon.com/why-flutter-uses-dart-dd635a054ebf|title=Why Flutter Uses Dart|last=Lelel|first=Wm|date=26 February 2018|website=HackerNoon|archive-url=|archive-date=|dead-url=|access-date=5 December 2018}}
11. ^¹²³{{Cite web|url=https://flutter.io/technical-overview/|title=Technical Overview - Flutter|website=flutter.io|language=en|access-date=2017-12-13}}
12. ^{{Cite web|url=https://docs.flutter.io/flutter/foundation/foundation-library.html|title=foundation library - Dart API|website=docs.flutter.io|language=en|access-date=2017-12-13}}
13. ^{{Cite web|url=https://flutter.io/widgets/material/|title=Material Design Widgets - Flutter|website=flutter.io|language=en|access-date=2017-12-13}}
14. ^{{Cite web|url=https://flutter.io/widgets/cupertino/|title=Cupertino (iOS-style) Widgets - Flutter|website=flutter.io|language=en|access-date=2017-12-13}}

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