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Introduction to Flutter

Iiro Krankka
September 14, 2017

Introduction to Flutter

These are the slides for my internal talk session about Flutter in our company, Codemate. The talk spurred a lot of conversation and interest towards Flutter.

First, we go through some basics about Flutter. After that, a simple sample app is broken down into parts.

The article and link for the source app: https://codemate.com/considering-flutter

Iiro Krankka

September 14, 2017
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  1. Introduction to Flutter Slides for an internal talk we had

    at Codemate Ltd. 14th of September 2017
  2. What is Flutter? • SDK for building cross-platform mobile apps,

    built by Google • Targets Android, iOS and Fuchsia • Consistent UIs across devices and manufacturers • Superb performance
  3. Why Flutter? • Strongly typed, modern language (Dart with Strong

    Mode on) • Same codebase, two platforms: Android & iOS • AOT compilation -> no Javascript or any other runtime / VM • No WebViews, no native Views ◦ Why? We’ll see. • Once your UI works, it just works. And keeps working. ◦ Manufacturers / OS versions / different devices can’t break it • Especially Android APIs require a lot of ceremony for simple things ◦ Flutter was able to start from scratch and avoid previously made pitfalls
  4. Base image from: https://speakerdeck.com/passsy/flutter-60-fps-ui-of-the-future Our cross-platform code Native land •

    Also fast performance here, however: ◦ Expensive to travel to • We can’t afford to go here too often, just like we can’t afford beach vacations every week • Everything in our control • Things we do here have fantastic performance and are cheap • We should stay here as much as possible
  5. Widgets • To build UIs, we have Widgets -> the

    only UI building block in Flutter • The whole app is a Widget. A screen is a Widget that contains Widgets. Widgets are made by composing basic Widgets into more advanced Widgets. ◦ Yo dawg? • There’s a huge amount of different Widgets • Can represent a: ◦ UI element, such as Text, Button, BottomNavigationBar, TextField, etc. ◦ Layout element, such as Padding, Center, Stack, Column, etc. ◦ Completely new screen (Activity/ViewController equivalent), for example:
  6. Stateless Widgets • Have no state (duh) • Immutable ->

    all instance fields are final • For displaying something that doesn’t change once it has been initialized
  7. Stateful Widgets • Have a state (duh) • The state

    has mutable instance fields that can be read synchronously • Call setState() method for updating the state • Framework handles UI Widget updates intelligently and efficiently when necessary • So basically, really similar to React concepts (count = count + 1;)
  8. Widget rendering • No native Views or WebViews • Instead,

    a completely blank Canvas as seen on left • The Material & Cupertino widgets are made by composing more basic Widgets • Widgets are made of low-level rendering layer objects ◦ In the end, Skia, C++ graphics library, renders them directly to these Canvases • We have direct access to Canvas ◦ pretty much any UI, even a wilder one, is doable
  9. Here’s how it looked like weird black lines Supposed to

    be white Dropdown items that are supposed to be, you know, visible?
  10. Dependency management • Ships with Pub, a modern dependency manager

    for Dart • Official package repository hosted at pub.dartlang.org • The whole existing ecosystem of Dart libraries available ◦ Excludes lots of web-related libraries • Also supports packages from Git, if you’re feeling lucky
  11. Native Plugins • Allow access to every native platform API

    ◦ Bluetooth, geolocation, sensors, fingerprint, camera, etc. • Both official and community-driven plugins available • Some plugins missing or in early stages ◦ There’s a community-driven geolocation plugin with really limited API ◦ There’s a community-driven Bluetooth plugin that doesn’t work with iOS just yet • If a plugin for your use case doesn’t exist, you’ll have to make it yourself • This is where other frameworks like React Native & Xamarin currently shine and Flutter takes the loss ◦ Situation expected to be solved with time
  12. Icons • Ships with a whole lot of premade, quality

    vector icons • Just say “new Icon(Icons.add_call);” • You can also import your own icons & icon fonts if you want
  13. • Column is a vertical stack of children. ◦ Opposite

    of Row, which stacks its children horizontally • We give padding to the Text widget by wrapping it inside the Padding widget • Styles come from the app level Theme object, so the whole theme of the app can be easily changed ◦ You have the freedom to define your own styles inline too
  14. Performance overlay (GIF taken on slow debug mode) Debug Paint

    Quickly switch between Android / iOS UI on the same device Debug tools Also debugger, logs and animation debugging.
  15. Drawbacks • UI markup & layout system learning curve ◦

    UI code can look quite ugly • Not a lot of “hold your hand guides” available ◦ Documentation is amazing • Google’s product loyalty • Inline maps & video, etc. can’t be done (at least yet) ◦ Possible on full screen though • Hot reload • AOT compilation & direct canvas rendering for widgets -> amazing performance • UI will work the same on different devices & manufacturers ◦ Native look and feel on Android & iOS ◦ Nobody can break our UIs • You can create as complex and customized UIs as you want However...
  16. Thanks! Questions? • Flutter - A new hope: https://www.youtube.com/watch?v=0ijVuVtu6a4 •

    Flutter - 60 FPS UI of the Future: https://speakerdeck.com/albrecht87/flutter-60-fps-ui-of-the-future-droidcon-2017 • The Official Flutter homepage: https://flutter.io/ Inspiration & references