Building the SwiftUI Sample App in Flutter

Kevin Gray (Principal Engineer), Martin Rybak (Engineering Director), and Albert Lardizabal (Principal Engineer) contributed to the writing of this article and the development of the Flutter Landmarks project. Read more of their content on the Very Good Ventures blog.

How Does SwiftUI Compare to Flutter?

When Apple announced SwiftUI at WWDC 2019, the team at Very Good Ventures got really excited as did many other mobile developers. We’ve been building iOS and Android apps for a long time, and for the last two years we’ve been building declarative UIs with Flutter. We wanted to learn more about Apple’s approach to building a declarative and composable layout system.

So, we enthusiastically downloaded the Xcode 11 beta app and started exploring SwiftUI. Apple provided an excellent example project, Landmarks, with a step-by-step tutorial to learn how to get up and running with SwiftUI.

Since the declarative nature of SwiftUI has similarities with Flutter and we have a lot of experience with Flutter, we wanted to know: “How does SwiftUI compare to Flutter?”

We decided it would be a fun challenge and a fruitful educational exercise to recreate the Landmarks app in Flutter. Then, we could compare the resulting codebases and identify similarities and differences between the two.

Landmarks Flutter

Our team dove in and attempted to faithfully reproduce the Landmarks app using Flutter. We’ve made the git repo publicly available so that anyone can download the code and see how it compares.

Check out our version of SwiftUI’s Landmarks project built in Flutter on GitHub!

Prepping Assets

Prepping the Flutter app to use the assets in Apple’s example project was quick to set up. Simply copy the Resources folder over to the assets folder and make the folder known in the pubspec.yaml, and we now have access to all of the data that the iOS project has!

flutter:
  assets:
    - assets/

The User Interface

Stacks

Stacks in SwiftUI are comparable to Flex widgets in that they display their children in one-dimensional arrays. So a VStack is similar to a Column, an HStack is similar to a Row, and a ZStack lays out its children one on top of the other, which (surprise!) is the kind of Stack Flutter developers are familiar with. Composing views with HStack s and VStacks in SwiftUI feels very familiar to a Flutter developer.

The code in SwiftUI feels a bit lighter owing to the lack of return statements and child or children params everywhere. The naming of the SwiftUI Stack widgets will take some time to get used to since Flutter’s Row, Column, and Stack widgets seem to be more intuitively named.

ListViews

Table views in UIKit are now Lists in SwiftUI. Wrap children objects in a List and you’re all set. This is a welcome improvement over implementing a number of delegate methods to set up a table view on iOS.

On the Flutter side, you have your choice of several options. You can use a ListView for displaying multiple children or a SingleChildScrollView if you have only one child to display. For our example in Flutter, we used a CustomScrollView and slivers in order to recreate the same animations with the navigation bar you get in the SwiftUI Landmarks example.

SwiftUI uses a ForEach command to generate List children on demand. We opted to use a SliverList and a SliverChildBuilderDelegate to leverage the builder callback to dynamically generate our LandmarkCell widgets. Slivers are optimized to lazily load their children and are Viewport-aware, so that child views aren’t built until they are displayed.

SwiftUI

ForEach(userData.landmarks) { landmark in
    if !self.userData.showFavoritesOnly || landmark.isFavorite {
        NavigationButton(
        destination: LandmarkDetail(landmark: landmark)) {
            LandmarkRow(landmark: landmark)
        }
    }
}

Flutter

SliverList(
  delegate: SliverChildBuilderDelegate(
    (context, index) {
      final landmark = landmarks[index];
      return LandmarkCell(
        landmark: landmark,
        onTap: () {
          Navigator.push(
            context,
            CupertinoPageRoute(
              builder: (context) => LandmarkDetail(
                landmark: landmark,
              ),
            ),
          );
        },
      );
    },
    childCount: landmarks.length,
  ),
),

Loading and Parsing Data

Loading

Loading our raw data from assets is similar in Dart and Swift. We have some data we know is JSON, and we want to create some models from it.

Swift

let file = Bundle.main.url(forResource: filename, withExtension: nil)
data = try Data(contentsOf: file)

Dart

final fileString = await rootBundle.loadString(‘assets/$filename’);

Parsing

Parsing our data into a list of Landmark objects is where the path diverges a bit. Flutter does not currently support reflection, so we are unable to parse JSON in the same way that Swift does it. Let’s take a look at the definition of the load function in Swift:

func load(_ filename: String, as type: T.Type = T.self) -> T

and with this, Swift is able to generate the data model with this simple call and no manual data parsing:

**let** landmarkData: [Landmark] = load(“landmarkData.json”)

The reason it can do this is because in Swift, Landmark is a Codable and therefore a Decodable. So by some underlying magic the type T can be instantiated and decoded.

As stated, this just isn’t currently possible in Flutter. Try to instantiate an object just by its type and you’ll find it quite impossible yourself! So, we need to manually parse this data. Our load function in the Flutter app is defined:

Future load(String filename, T Function(dynamic) builder) async

What this does is the generic function of loading the data, but leaves the building of the data up to the caller of the function. So we load the landmarkData in the following way:

Future loadData() async {
  _landmarkData = await _load('landmarkData.json', (data) =>   List.unmodifiable((data).map((element) =>         Landmark.fromJSON(element))));
}

The fromJSON function of Landmark is a factory constructor that does exactly what you expect, constructs a Landmark from a Map. We opted to manually parse this small amount of data, but there are options for code generation if you’re interested.

Navigation

For most of our development in Flutter, we use Material widgets. But since we wanted to create a real apples-to-apples comparison, we decided use a Cupertino theme.

Navigation controllers in UIKit have been replaced with a NavigationView. In Flutter, we used a CupertinoPageScaffold with a CustomScrollView child. To get the expanding/collapsing animation of the navigation bar, such as in the SwiftUI example, a CupertinoSliverNavigationBar was perfect. When expanded, the widget passed into the largeTitle property of the CupertinoSliverNavigationBar is displayed. When you scroll down and the navigation bar collapses, a smaller version of the title is displayed in the middle of the collapsed navigation bar.

We’ve become accustomed to using callbacks on the children of a ListView to communicate data back to the parent widget when the user taps a cell. SwiftUI’s approach of wrapping List children in NavigationButtons to control the presentation of the next route is an interesting approach that we’ll have to explore in future posts.

Architecture

iOS

For architecture, we attempted to mimic the same flow of data seen in the iOS app. The iOS app used some nifty Swift features so that the UI of the application updates in response to changes in the data. For example, when you dive into a Landmark detail and favorite it, the app just updates the isFavorite boolean of the Landmark like this:

**self**.userData.landmarks[**self**.landmarkIndex].isFavorite.toggle()

and the star turns yellow in response. There is no explicit changing of this color, it just updates when the model updates. There is a similar flow of data for the favorites toggle on the Landmark list screen.

So how does this work on the iOS side? The answer is in the UserData object which is a BindableObject. A BindableObject is defined by Apple as:

A type of object that notifies the framework when changed.

So, the two bits of data we use to update UI (showFavoritesOnly and landmarkData ) will notify the framework when they change. The views that wish to be notified, LandmarkDetail for example, add…

@EnvironmentObject **var** userData: UserData

…to the declaration the view. The usage of @EnvironmentObject is defined as:

A linked View property that reads a `BindableObject` supplied by an ancestor view that will automatically invalidate its view when the object changes.

So, whenever one of those two pieces of data are updated, the views that listen to them will be invalidated and rebuild.

Flutter

We were able to get a similar flow in the Flutter app. We simply set the Landmark model’s isFavorite value:

landmark.setFavorite(value);

and the UI updates in response. We achieved this by having the Landmarkmodel extend the ChangeNotifier class. We added the following function to the class:

void setFavorite(bool value) {
  isFavorite = value;
  notifyListeners();
}

and now anyone who cares to listen to changes in the model can do so. Here’s an example from our LandmarkDetail widget. Did you know that AnimatedBuilder can listen to a ChangeNotifier?

AnimatedBuilder(
  animation: landmark,
  builder: (context, widget) {
    return StarButton(
      isFavorite: landmark.isFavorite,
      onTap: (value) {
        landmark.setFavorite(value);
      },
    );
  },
),

For toggling the favorites list, we simply have a boolean on the StatefulWidget that builds the list, and when the toggle occurs we call setState.

You may notice a subtle difference in this flow, which is that in the iOS app, the view will be notified whenever the landmarkData list is updated, including any of the data of its children. We only listen to changes in a single Landmarkobject. Due to how Flutter builds, the favorites list will still update when we pop back to the list from a detail which works perfectly for our needs.

It is certainly possible to create an architecture where we listen to changes in any child of the list, and it depends on the size and efficiency of your data. For exampleListenable.merge(landmarkData) with ListenableBuilder would work here, but you can imagine this could get inefficient with a huge list of data.

Future Improvements to the Flutter version

You may notice that a few things are missing from our Flutter implementation.

First, the separator line between empty cells on the main screen’s SliverList is missing. This is the default behavior in a native iOS implementation (and is not often desired).

Second, you’ll see that when toggling the favorites switch, the table cells don’t animate in and out as they do in a standard iOS table view. We are working on implementing this functionality on a separate branch. We are using the AnimatedListwidget and got the animations pretty close but not perfect.

One challenge is that AnimatedList is not a SliverList and can’t be used inside a CustomScrollView. It must be wrapped inside a SliverToBoxAdapter. A SliverList is more efficient because it instantiates only child widgets that are actually visible through the scroll view’s viewport. This is not an issue for small lists as in this example, but could introduce a performance problem for much larger ones. We have reached out to the Flutter team for some guidance on these issues.

Do you have any ideas for improvements on making the code cleaner or simpler? Please file a pull request!

Early Takeaways From Our Comparison

Code Complexity

At first glance, it appears as if the Flutter version has a bit more lines of code and complexity. That’s the elephant in the room, so let’s explore why that is. It’s important to recognize that Apple has fine-tuned SwiftUI for working exclusively within Apple’s design system. That is, elements like the navigation bar and table animations appear trivial to implement because they are magically implemented behind the scenes. But if you want to tweak or modify this behavior, there is not much you can do.

In contrast, nothing in Flutter, including the fancy navigation bar, is implemented in a black box. Everything is explicit, composable, and modifiable. So in this example, special-looking things (such as fancy scrolling effects) have special-looking code (slivers). Flutter has a Cupertino theming library that makes it easier to build iOS-style experiences, but that’s not its mainstay. Flutter excels at empowering custom UI experiences that let your unique brand shine through, on multiple platforms. That said, where there is room for improvement to make iOS-only development easier, let the Flutter team know! We’ve already pointed out a few issues above.

Declarative UI FTW

Ultimately, we’re excited that Apple is moving towards the declarative programming paradigm. We think SwiftUI affirms what React Native and Flutter have already embraced.

Combined with Swift’s concise syntax, SwiftUI feels very modern to work with, compared to the often unwieldy layout constraint code that usually comprised half of the code in a class on iOS.

On the other hand, we were able to rebuild the SwiftUI Landmarks with Flutter in a really short amount of time. That’s an endorsement of Flutter, but also of the overall trend towards declarative UI—which of course now includes SwiftUI!

SwiftUI is just getting started

It’s important to note that SwiftUI is very new — it probably wont be ready for wide-scale production for some time (it is only an early beta after all). Flutter, on the other hand has been in the wild for a couple of years and officially out of beta since December 2018.

There are a few things in SwiftUI that are particularly promising. For instance, the designer is pretty cool, PreviewProviders that let you pin views with data is useful, and built-in support for things like accessibility, dark mode, and RTL are impressive. SwiftUI’s new ability to “hot reload” is something that Flutter developers have been enjoying for a while, and while it’s not quite the same, it’ll certainly make a lot of iOS developers happier.

It’s going to a take some time for SwiftUI to really get into the mainstream, but it’ll be fun to see how it evolves. At the end of the day, we anticipate it’ll lead to more high quality apps as developer productivity increases. It’ll also be fun to observe how Flutter and React Native evolve in parallel.

Design Guidelines (or are they rules?)

It’s an obvious statement to say that SwiftUI is for creating apps for Apple’s platforms. At the moment, SwiftUI really isn’t great if you want to create an app that doesn’t look and feel like an Apple app. There’s nothing really wrong with that, but it may be limiting from a design perspective.

This is in contrast to Flutter’s design goals — Flutter has always been about creating unique branded app experiences, not necessarily something wholly conforming to the design guidelines of a specific platform. So, as of this moment, Flutter is more flexible for creating a unique and custom UI experience compared to SwiftUI.

This is a huge topic with many camps and opinions. For now, it’ll suffice to say that it will be interesting to watch and see what kind of support SwiftUI provides in the long run for fully custom app designs.

Portability

One obvious area where SwiftUI has some early drawbacks is its portability. Currently, Apple’s documentation clearly states that SwiftUI will only work with iOS13.0+ beta, macOS10.15+ beta, tvOS 13.0+ beta, and watchOS 6.0+.

Flutter, on the other hand, will run on multiple platforms (iOS, Android, macOS, Windows, ChromeOS, Raspberry Pi, and Web), and is compatible with the long tail of iOS and Android devices running a variety of older OS versions. In fact, we were able to get the Flutter version running on Android with a trivial amount of extra work.

Again, it’s very early for SwiftUI, so we’ll have to see what kind of backwards compatibility and platform portability they’ll be able to achieve in the future. Who knows…perhaps one day we’ll be able to run SwiftUI on other platforms. (We can dream, can’t we?)

The Future is Composable

In the end, SwiftUI indicates a huge step forward for app developers. We’re excited to see how it develops, and watch as Apple and Google continue to create better tools for developers to create incredible apps.

Our team at Very Good Ventures is going to continue to explore SwiftUI (and Flutter too!). We’d love to hear from you what you think we should dig into next.

• A comparison of app performance?
• Side-by-side “hot reload” comparison?
• A deep dive on the different tools for SwiftUI and Flutter?

Let us know what we should research next in the comments!

Tell us in the comments what we should dig into next in our comparison of SwiftUI and Flutter.

Thanks for reading!

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What is GEEK

Buddha Community

Google's Flutter 1.20 stable announced with new features - Navoki

Flutter Google cross-platform UI framework has released a new version 1.20 stable.

Flutter is Google’s UI framework to make apps for Android, iOS, Web, Windows, Mac, Linux, and Fuchsia OS. Since the last 2 years, the flutter Framework has already achieved popularity among mobile developers to develop Android and iOS apps. In the last few releases, Flutter also added the support of making web applications and desktop applications.

Last month they introduced the support of the Linux desktop app that can be distributed through Canonical Snap Store(Snapcraft), this enables the developers to publish there Linux desktop app for their users and publish on Snap Store.  If you want to learn how to Publish Flutter Desktop app in Snap Store that here is the tutorial.

Flutter 1.20 Framework is built on Google’s made Dart programming language that is a cross-platform language providing native performance, new UI widgets, and other more features for the developer usage.

Here are the few key points of this release:

Performance improvements for Flutter and Dart

In this release, they have got multiple performance improvements in the Dart language itself. A new improvement is to reduce the app size in the release versions of the app. Another performance improvement is to reduce junk in the display of app animation by using the warm-up phase.

If your app is junk information during the first run then the Skia Shading Language shader provides for pre-compilation as part of your app’s build. This can speed it up by more than 2x.

Added a better support of mouse cursors for web and desktop flutter app,. Now many widgets will show cursor on top of them or you can specify the type of supported cursor you want.

Autofill for mobile text fields

Autofill was already supported in native applications now its been added to the Flutter SDK. Now prefilled information stored by your OS can be used for autofill in the application. This feature will be available soon on the flutter web.

A new widget for interaction

InteractiveViewer is a new widget design for common interactions in your app like pan, zoom drag and drop for resizing the widget. Informations on this you can check more on this API documentation where you can try this widget on the DartPad. In this release, drag-drop has more features added like you can know precisely where the drop happened and get the position.

Updated Material Slider, RangeSlider, TimePicker, and DatePicker

In this new release, there are many pre-existing widgets that were updated to match the latest material guidelines, these updates include better interaction with Slider and RangeSlider, DatePicker with support for date range and time picker with the new style.

New pubspec.yaml format

Other than these widget updates there is some update within the project also like in pubspec.yaml file format. If you are a flutter plugin publisher then your old pubspec.yaml  is no longer supported to publish a plugin as the older format does not specify for which platform plugin you are making. All existing plugin will continue to work with flutter apps but you should make a plugin update as soon as possible.

Preview of embedded Dart DevTools in Visual Studio Code

Visual Studio code flutter extension got an update in this release. You get a preview of new features where you can analyze that Dev tools in your coding workspace. Enable this feature in your vs code by _dart.previewEmbeddedDevTools_setting. Dart DevTools menu you can choose your favorite page embed on your code workspace.

Network tracking

The updated the Dev tools comes with the network page that enables network profiling. You can track the timings and other information like status and content type of your** network calls** within your app. You can also monitor gRPC traffic.

Generate type-safe platform channels for platform interop

Pigeon is a command-line tool that will generate types of safe platform channels without adding additional dependencies. With this instead of manually matching method strings on platform channel and serializing arguments, you can invoke native class and pass nonprimitive data objects by directly calling the Dartmethod.

There is still a long list of updates in the new version of Flutter 1.2 that we cannot cover in this blog. You can get more details you can visit the official site to know more. Also, you can subscribe to the Navoki newsletter to get updates on these features and upcoming new updates and lessons. In upcoming new versions, we might see more new features and improvements.

You can get more free Flutter tutorials you can follow these courses:

• Setup Flutter Desktop on Windows, Linux, MacOS using VSCode and Build – Flutter Tutorial
• Flutter Desktop Linux app | Build and Publish on Snapcraft Store
• Firebase Local Emulator Suite in Flutter

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The Ultimate Guide To Tik Tok Clone App With Firebase - Ep 2

The Ultimate Guide To Tik Tok Clone App With Firebase - Ep 2
In this video, I'm going to show you how to make a Cool Tik Tok App a new Instagram using Flutter,firebase and visual studio code.

In this tutorial, you will learn how to Upload a Profile Pic to Firestore Data Storage.

🚀 Nice, clean and modern TikTok Clone #App #UI made in #Flutter⚠️

Starter Project : https://github.com/Punithraaj/Flutter_Tik_Tok_Clone_App/tree/Episode1

► Timestamps 
0:00 Intro 0:20 
Upload Profile Screen 
16:35 Image Picker
20:06 Image Cropper 
24:25 Firestore Data Storage Configuration.

⚠️ IMPORTANT: If you want to learn, I strongly advise you to watch the video at a slow speed and try to follow the code and understand what is done, without having to copy the code, and then download it from GitHub.

► Social Media 
GitHub: https://github.com/Punithraaj/Flutter_Tik_Tok_Clone_App.git
LinkedIn: https://www.linkedin.com/in/roaring-r...
Twitter: https://twitter.com/roaringraaj
Facebook: https://www.facebook.com/flutterdartacademy

► Previous Episode : https://youtu.be/QnL3fr-XpC4
► Playlist: https://youtube.com/playlist?list=PL6vcAuTKAaYe_9KQRsxTsFFSx78g1OluK

I hope you liked it, and don't forget to like,comment, subscribe, share this video with your friends, and star the repository on GitHub!
⭐️ Thanks for watching the video and for more updates don't forget to click on the notification. 
⭐️Please comment your suggestion for my improvement. 
⭐️Remember to like, subscribe, share this video, and star the repo on Github :)

Hope you enjoyed this video!
If you loved it, you can Buy me a coffee : https://www.buymeacoffee.com/roaringraaj

LIKE & SHARE & ACTIVATE THE BELL Thanks For Watching :-)
 
https://youtu.be/F_GgZVD4sDk

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