Michio JP

Michio JP

1570592821

Tips to use Timer in Dart and Flutter for Developers

Timer is essential part of any application, and is useful in many use-cases. Let me show you some tips to use Timer in Dart and Flutter.

Use Timer in Dart and Flutter

First of all, let take a look at the Timer API documentation.

Basically, Timer is a class that represents a count-down timer that is configured to trigger an action once end of time is reached, and it can fire once or repeatedly.

Make sure to import dart:async package to start of program to use Timer.

1. Trigger actions after countdown

See this example:

Timer(Duration(seconds: 3), () {
  print("Yeah, this line is printed after 3 seconds");
});

If you try to run it on Dart VM or Flutter app main() function, it will print the line after 3 seconds.

Should it run asynchronously? Let’s make a test for it.

Timer(Duration(seconds: 3), () {
  print("Yeah, this line is printed after 3 second");
});

print('This line is printed first');

What’s your expectation?

Well, in reality, the text This line is printed first is indeed printed first before the text print in the callback function. So the callback function of Timer is being executed asynchronously, it doesn’t block the main thread.

2. Repeat actions

In previous section, the timer will trigger the action only once then stops. What if you want do something repeatedly? Here it is.

Timer.periodic(Duration(seconds: 5), (timer) {
  print(DateTime.now());
});

Timer.periodic() is the function designed for this. However, the callback needs to pass an instance of Timer. For what purpose?

Well, you need to stop the timer at some points, cannot let it go free forever.

If you execute the above code, you might get output similar to this

2019-01-22 10:26:36.479593
2019-01-22 10:26:41.473463
2019-01-22 10:26:46.475937
2019-01-22 10:26:51.476327
2019-01-22 10:26:56.473401
2019-01-22 10:27:01.477890
2019-01-22 10:27:06.475911
2019-01-22 10:27:11.473604
2019-01-22 10:27:16.477881

So, the callback is triggered every 5 seconds as configured.

To stop timer when it reaches some certain expectations, call timer.cancel().

3. Trigger timer immediately

What if you want to to trigger action immediately in asynchronous mode?

You might think about configuring the duration to 0. Let’s try it.

Timer(Duration(seconds: 0), () {
  print("Yeah, this line is printed after 3 second");
});

print('This line is printed first');

However, don’t expect that the text in callback will be printed first. It, most of the time, will be output like following result:

This line is printed first
Yeah, this line is printed after 3 second

It is because all async functions are put into a pool to schedule, so it takes a little time for the callback to execute. Therefore, the second line in the code above is always printed first.

There is a shorthand for this, you can use Timer.run() to trigger callback as soon as possible.

Timer.run(() {
  print("Yeah, this must be printed immediately.");
});

Summary

Timer is a powerful utility for us to trigger actions in the background asynchronously. You can use it in both Dart and Flutter applications. Take advantages of Timer and use it properly!

Learn More

#flutter #dart

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Tips to use Timer in Dart and Flutter for Developers

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.

sksl_warm-up

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.

flutter_autofill

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 RangeSliderDatePicker with support for date range and time picker with the new style.

flutter_DatePicker

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:

#dart #developers #flutter #app developed #dart devtools in visual studio code #firebase local emulator suite in flutter #flutter autofill #flutter date picker #flutter desktop linux app build and publish on snapcraft store #flutter pigeon #flutter range slider #flutter slider #flutter time picker #flutter tutorial #flutter widget #google flutter #linux #navoki #pubspec format #setup flutter desktop on windows

Juned Ghanchi

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Hire the flutter app developers in India and get natively compiled top-notch app for mobile, web, and desktop.

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Consult with experts: https://bit.ly/2CWJgHyFlutter app developer

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Terry  Tremblay

Terry Tremblay

1598396940

What is Flutter and why you should learn it?

Flutter is an open-source UI toolkit for mobile developers, so they can use it to build native-looking** Android and iOS** applications from the same code base for both platforms. Flutter is also working to make Flutter apps for Web, PWA (progressive Web-App) and Desktop platform (Windows,macOS,Linux).

flutter-mobile-desktop-web-embedded_min

Flutter was officially released in December 2018. Since then, it has gone a much stronger flutter community.

There has been much increase in flutter developers, flutter packages, youtube tutorials, blogs, flutter examples apps, official and private events, and more. Flutter is now on top software repos based and trending on GitHub.

Flutter meaning?

What is Flutter? this question comes to many new developer’s mind.

humming_bird_dart_flutter

Flutter means flying wings quickly, and lightly but obviously, this doesn’t apply in our SDK.

So Flutter was one of the companies that were acquired by **Google **for around $40 million. That company was based on providing gesture detection and recognition from a standard webcam. But later when the Flutter was going to release in alpha version for developer it’s name was Sky, but since Google already owned Flutter name, so they rename it to Flutter.

Where Flutter is used?

Flutter is used in many startup companies nowadays, and even some MNCs are also adopting Flutter as a mobile development framework. Many top famous companies are using their apps in Flutter. Some of them here are

Dream11

Dream11

NuBank

NuBank

Reflectly app

Reflectly app

Abbey Road Studios

Abbey Road Studios

and many more other apps. Mobile development companies also adopted Flutter as a service for their clients. Even I was one of them who developed flutter apps as a freelancer and later as an IT company for mobile apps.

Flutter as a service

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