Archie  Clayton

Archie Clayton

1560919130

Better Errors Messages for Flutter

Imagine that it’s blinking…

… is probably an article I should have published on April 1st. Still, here it is. The Amiga had an iconic way to display fatal errors: The guru meditation alert. Let’s recreate this for Flutter.

Here is how I want to display the alert:

showAlert(context, 42);

Instead of complicated and talkative text messages, I will display succient hexadecimal error codes which need no translation or localization. I’m utterly convinced that this is the future.

import 'package:flutter/widgets.dart';
void showAlert(BuildContext context, int code) {
  final hex = code.toRadixString(16).toUpperCase().padLeft(8, '0');
  ...
}

Notice, how I not try to include a library for left-padding my string for improved stability and protection against rage-quitting developers.

To display anything above the normal UI, an OverlayEntry which is then added to the current Overlay can be used. The such an Overlay is automatically created as part of a WidgetsApp or MaterialApp widget. The overlay entry must be explicitly removed again. I’m using a GestureDetector so that the user has to tap the overlay to make it go away.

void showAlert(BuildContext context, int code) {
  final hex = code.toRadixString(16).toUpperCase().padLeft(8, '0');
  final black = Color(0xFF000000);
  final red = Color(0xFFFF0000);
  OverlayEntry overlay;
  overlay = OverlayEntry(builder: (context) {
    return Positioned(
      left: 0,
      right: 0,
      child: GestureDetector(
        onTap: () => overlay.remove(),
        child: Container(
          color: black,
          height: 128,
        ),
      ),
    );
  });
  Overlay.of(context).insert(overlay);
}

Because I don’t want to depend on material.dart I create my own Color objects. And because I need to refer to the overlay variable inside of the onTap handler of the builder function I cannot use the usual final variable definition that declares and initializes a variable in one step. Overlays are a bit special.

The Overlay widget is basically a Stack so I can use a Positioned widget to position my alert (currently just a black Container wrapped inside a GestureDetector) at the top edge of the screen.

At this point, I can display a black overlay which is removed if I tap it.


Because an OverlayEntry isn’t automatically wrapped with a DefaultTextStyle, Text widgets without style or with a TextStyle that does not explicitly prohibits inheritance are displayed with a very ugly default text style (large redish text that has yellow double-underlining). Therefore, it is important to add an inherit: false property like so:

          Container(
            alignment: Alignment.center,
            color: black,
            height: 128,
            child: Text(
              'Software Failure.  Tap to continue.\n\n'
              'Guru Meditation #48454C50.$hex',
              textAlign: TextAlign.center,
              style: TextStyle(
                color: red,
                fontFamily: 'Courier',
                fontSize: 16,
                fontWeight: FontWeight.bold,
                inherit: false,
              ),
            ),
          )

It starts to look like the real deal (please ignore the notch for now):


Let’s add the iconic red border next. There’s one problem, though. I don’t want the text to wrap (which would happen on smaller devices). Furthermore, if you compare the Courier font I used with the original Amiga font, it runs too wide. So let’s transform the Text widget by scaling it horizontally to 75%. To keep it at the same width, I have to enlarge the width by 133% at the same time. The text should now always fit the screen.

          Container(
            alignment: Alignment.center,
            decoration: BoxDecoration(
              color: black,
              border: Border.all(color: red, width: 8),
            ),
            padding: EdgeInsets.symmetric(
              horizontal: 8,
              vertical: 16,
            ),
            child: FractionallySizedBox(
              widthFactor: 4 / 3,
              child: Transform(
                alignment: Alignment.center,
                transform: Matrix4.identity().scaled(3 / 4, 1),
                child: Text(
                  ...
                ),
              ),
            ),
          ),

We’re almost there…


As you probably see on my screen shots, if the device has a notch, the alert doesn’t look right. I’d like to move the box below the notch but cover everything above in black. The Amiga also displays a small black border around the red border, so let’s add this, too. A SafeArea widget inside another Container can do both. I need to disable its bottom margin, though.

    return Positioned(
      left: 0,
      right: 0,
      child: Container(
        color: black,
        child: SafeArea(
          minimum: EdgeInsets.all(8),
          bottom: false,
          child: GestureDetector(
            ...
          ),
        ),
      ),
    );

And there, it is, perfectly aligned:


For the final and most important step, I will add blinking.

The following might be a bit hacky, I don’t know, but it works and I don’t have to create a custom StatefulWidget. I’m using a StatefulBuilder instead. Each time, that widget asks its builder function to recreate the UI, I setup a timer to toggle the border color from red to black and back again after 700ms. Then, I’m using an AnimatedContainer to implicitly animate this color change within 300ms. Some things are just too easy in Flutter.

          GestureDetector(
            onTap: () {
              blink = null;
              overlay.remove();
            },
            child: StatefulBuilder(
              builder: (context, setState) {
                Future.delayed(Duration(milliseconds: 700))
                .then((_) {
                  if (blink != null) setState(() => blink = !blink);
                });
                return AnimatedContainer(
                  duration: Duration(milliseconds: 300),
                  curve: Curves.easeInOut,
                  alignment: Alignment.center,
                  decoration: BoxDecoration(
                    color: black,
                    border: Border.all(
                      color: blink ? red : black, width: 8),
                  ),
                  ...
                );
              },
            ),
          ),

Here is the hacky part: Because Flutter throws an exception if I tap the alert and setState is then called on a disposed widget, I need to protect myself against this case by setting blink to null and explicitly checking for it. Perhaps, I should have used a Timer instead of a Future because that timer could be cancelled, I think. The future is inevitable.


Back to the future…

And there you have it, an alert box that looks much better than the usual modal dialog. And at least with old folk like myself, people will have a positive nostalgic feeling instead of cold-blooded anger because your app didn’t work for them as expected.

Here is the source code, by the way.

Thanks for reading ❤

If you liked this post, share it with all of your programming buddies!

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Learn More

Learn Flutter & Dart to Build iOS & Android Apps

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Building DashCast, a podcast app in Flutter

#flutter #mobile-apps #ios #android

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.

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

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

#dart #flutter #uncategorized #flutter framework #flutter jobs #flutter language #flutter meaning #flutter meaning in hindi #google flutter #how does flutter work #what is flutter

Adobe XD plugin for Flutter with CodePen Tutorial

Recently Adobe XD releases a new version of the plugin that you can use to export designs directly into flutter widgets or screens. Yes, you read it right, now you can make and export your favorite design in Adobe XD and export all the design in the widget form or as a full-screen design, this can save you a lot of time required in designing.

What we will do?
I will make a simple design of a dialogue box with a card design with text over it as shown below. After you complete this exercise you can experiment with the UI. You can make your own components or import UI kits available with the Adobe XD.

#developers #flutter #adobe xd design export to flutter #adobe xd flutter code #adobe xd flutter code generator - plugin #adobe xd flutter plugin #adobe xd flutter plugin tutorial #adobe xd plugins #adobe xd to flutter #adobe xd tutorial #codepen for flutter.

Brain  Crist

Brain Crist

1602147600

Flutter App Development Trends 2020

As the new decade dawns upon us, a slew of technologies has been making a lot of noise to grab the developers’ attention. While native app development is going strong, the trade winds are now blowing towards going cross-platform.

Adobe PhoneGap, React Native, Xamarin and Ionic are all leaving no stone unturned to be the undefeated champion of cross-platform development. Still, Google’s Flutter is all set to take them all on at once.

There are a tonne of resources available online to learn about Flutter, and you can start with this step by step flutter guide.

With reduced code development time, increased time-to-market speed, near-native performance, and a bevy of advantages under its hood, Flutter is set to dominate the market this decade.

Before we take a look at trends making the Flutter race ahead in 2020, let us do a quick recap of what Flutter is, for those who have been living under a rock.

#flutter #flutter-for-mobile-app #flutter-app-development #mobile-app-development #flutter-trends #software-development #advantages-of-flutter-mobile #pros-and-cons-of-flutter

Maida  Ratke

Maida Ratke

1590832500

Themes in Flutter: Part 3

In the 1st part, we saw 15 parameters of ThemeData class. Those were brightness, visualDensity, primaryColor, primaryColorBrightness, primaryColorLight, primaryColorDark, canvasColor, ascentColor, ascentColorBrightness, scaffoldNBackgroundColor, bottomAppBarColor, cardColor, dividerColor, focusColor.
In the 2nd part, we saw 27 parameters of ThemeData class. Those were hoverColor, hightlightColor, splashColor, splashFactory, selectedRowColor, unselectedWidgetColor, disabledColor, buttonTheme, toggleButtonsTheme, buttonColor, secondaryHeaderColor, textSelectionColor, cursorColor, textSelectionHandleColor, backgroundColor, dialogBackgroundColor, indicatorColor, hintColor, errorColor, toggleableActiveColor, textTheme, primaryTextTheme, accentTextTheme, inputDecorationTheme, iconTheme, primaryIconTheme, accentIconTheme.
Let’s start with 3rd set fo ThemeData parameters.

#flutter #flutter-color #flutter-widget #flutter-theme #flutter-ui