flutter: basics

ephemeral v app state

- ephemeral: specific to widget, often part of StatefulWidget and set via setState() - app state: shared across widgets, sessions (e.g. user prefs, login info), often put into redux

check for outdated packages, update

- flutter pub outdated - flutter pub upgrade

flutter

- free, open source mobile UI framework - released in May 2017 by Google - target iOS and Android - Dart language (OO)

flutter pub get

- get packages

widget's main job

- implement build() - describe the widget in terms of other lower-level widgets

flutter widgets

- inspired by React; a component framework - blueprints - describe how to render - when state changes, rebuilds itself - framework diffs for minimal changes to underlying render tree

manual JSON serialization

- jsonDecode() in dart:convert - or, can be built into each model class - Foo.fromJson(), Foo.toJson() - see types.dart in x2flutter w/GraphQL - best for small projects

serialization / deserialization

- encoding/decoding data to/from string - often to JSON

flutter engine

- a primary component - written primarily in c++ - low-level rendering using Google's Skia graphics lib - interfaces to native platform - reactive framework and set of platform, layout and foundation widgets

flutter: imperative or declarative?

- declarative - components that build themselves based on state - simpler coding

flutter doctor

- diagnose setup issues

pubspec.yaml dependencies: auth0:

- don't specify version for latest

automated JSON serialization

- 3rd party json_serializable or built_value - uses annotations on classes: @JsonSerializable() with fromJson() and toJson() - best for medium/large projects

flutter equivalent of RN View container

- Container, Column, Row, Center

remote assets

- Image.network() to access

flutter equivalent of RN FlatList, SectionList

- ListView

dart v react native re compilation

- RN transpiles to native widgets, has JS bridge - dart compiles all the way to native code - dart can transcompile to JS - main() in dart, no specific entry point in JS

RN v flutter re routing

- RN: 3rd party libs - flutter: Route, Navigator

RN v flutter re canvas drawing/painting

- RN: 3rd party libs like react-native-canvas - flutter: CustomPaint and CustomPainter

RN v flutter re icons

- RN: 3rd party libs/frameworks for icons - flutter: Material built in, Cupertino for iOS style

RN v flutter re local storage

- RN: AsyncStorage - flutter: shared_preferences

RN v flutter re styles

- RN: CSS like style props; e.g. style prop on View - flutter: widgets and attrs; e.g. Container, Center, Padding, Align, Stack

RN v flutter re HTTP network requests

- RN: JS fetch - flutter: 3rd party http package both: .then() or async/await

RN v flutter re form input, text fields

- RN: TextInput - flutter: TextField w/TextEditingController

RN v flutter re layering components

- RN: absolute positioning - flutter: Stack()

RN v flutter re platform specific code

- RN: if (Platform.OS === 'ios') - flutter: if (Theme.of(context).platform == TargetPlatform.iOS)

RN v flutter re props

- RN: passed into component as this.props - flutter: passed into widget component constructor

RN v flutter re gesture detection

- RN: wrap in TouchableOpacity, PanResponder - flutter: wrap in GestureDetector

flutter alternatives

- React Native - NativeScript

routing widgets

- Route for app screen/page/view - Navigator for stack of routes

shared_preferences: ^0.4.3 SharedPreferences prefs = await SharedPreferences.getInstance(); _counter = prefs.getInt('counter'); prefs.setInt('counter', ++_counter);

- local storage - same as RN AsyncStorage (wraps NSUserDefaults on iOS, and SharedPreferences on Android) - key/value pairs

where to put packages

- pubspec.yaml - not package.json - will be automatically downloaded

provider package

- pubspec.yaml package for simple pub/sub - not needed if using Redux - class that extends ChangeNotifier and calls notifyListeners() when things change (publish) - ChangeNotifierProvider() above (at top) with app() as child, does the notifying - Consumer() which has builder to handle changes (subscribe) - Provider.of(context) to get data as needed

local assets

- put in assets/ - images, icons, JSON - AssetImage() to access - define in pubspec.yaml

Hot reload vs. hot restart

- reload loads changed code - restart for the entire app

flutter stated intent

- render consistently at 120 fps

stful

- snippet to create stateful class

stanim

- snippet to create stateful class with animation

stless

- snippet to create stateless class

pubspec.yaml dependencies: url_launcher: '>=5.4.0 <6.0.0'

- specify version range

design-specific widgets

- two sets - Material Design for Android - Cupertino for iOS

pubspec.yaml plugin1: git: url: git://github.com/flutter/plugin1.git

- use a github package (private if needed)

pubspec.yaml dependencies: plugin1: path: ../plugin1/

- use a local package

pubspec.yaml dependencies: some_package: another_package: dependency_overrides: url_launcher: '5.4.0'

- uses a specific package version used by dependencies

primary flutter components

1. Dart platform 2. Flutter engine 3. Foundation library 4. Design-specific widgets

a widget can define (3)

1. a structure element like a button or menu 2. a stylistic element like a font or color scheme 3. an aspect of layout like padding or alignment