Flutter is Google’s open-source and accessible framework to create native mobile applications. Flutter was released in 2017, and it enables developers to develop mobile applications for iOS and Android with a single programming language and codebase. This Flutter tutorial discusses its widgets, approach to developing mobile applications, and Animation.
Generally, building a mobile application is a challenging and difficult task. We have various frameworks to develop mobile applications. Android offers a native framework according to the Java language, and iOS offers a native framework according to Swift-language/ Objective C. But, for developing the application that supports both OSs, we have to code in two different languages through two different frameworks. To overcome this difficulty, we have frameworks that support both OS. But, these frameworks also have certain disadvantages; one of the main disadvantages is their slow performance.
At this stage, Flutter is a high-performance and simple framework on the basis of Dart language, offering high performance by interpreting UI in the canvas of the operating system instead of using the native framework. It offers various ready-for-use widgets for creating modern applications. According to a report from Statista, the popularity of Flutter among developers has risen from 30% in 2019 to 42% in 2021. In May 2021, Google announced that there were more than 2,00,000 flutter apps in the App store. So, Join our Flutter training to have a promising career in mobile app development.
In this Flutter tutorial, you will learn what Flutter is and how to develop mobile applications using the Flutter framework. Before we start, let us have a look at what we will be discussing in this article:
Flutter is the freeware framework for creating high-performance and high-quality mobile applications throughout the mobile operating systems-iOS and Android. It provides a robust, easy-to-understand SDK for writing a mobile application in Google’s programming language, Dart. It’s unique because it utilizes neither OEM nor WebView objects sent with the device. Instead, it utilizes its high-performance rendering engine for drawing the widgets.
It also deploys almost all systems like gestures, widgets, and animation in the Dart programming language that enables readers to change, replace, remove or read things easily. Flutter has the following unique features in comparison to other SDKs and Java:
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Step 1: Configuring the Flutter SDK
https://docs.flutter.dev/development/tools/sdk/releases
Step 2: Insert Flutter in the path: However, not necessary. It is suggested to set the “PATH VARIABLE” for making the Flutter simply accessible from anywhere in the system.
3. Restart the Windows after configuring the PATH variables to work.
Step 3: Configuring the Android Studio: Android Studio mechanically downloads the development tools necessary for the Flutter to work with the Android.
Step 4: Configuring the Visual Studio Code: Visual Studio Code is a light code editor that we can use in the Flutter development.
3. Install Git Bash: It is optional, but it is a suggested command prompt. Git Bash offers several general Unix commands that are helpful for some rapid tasks.
4. Run Flutter Doctor: Flutter doctor is the built-in tool provided by flutter that we use for checking the status of Flutter installation. After configuring the PATH variable, we can open the Command Prompt and run:
Create the empty template project:
Step 1: Go to the place where you have to create your project. Open the command prompt and type the command for creating the new project:
Step 2: Open the project folder in VS Code. We can right-click and utilize the context menu for opening into VS Code or starting VS Code and later open this folder as the project.
Step 3: The large panel on the left-side that shows all the folders and files is called Explorer Panel. Go to the ‘lib’ folder and choose the “main. dart” file. This file is a point of entry from where the application begins its execution.
Dart is the general-purpose, object-oriented, open-source programming language with the C-language style syntax designed by Google in 2011. Dart programming intends to create frontend user interfaces for web and mobile applications. It is in active development, compiled to native machine code to build mobile apps, influenced by the programming languages like Javascript, Java, C#.
As Dart is the compiled language, we cannot execute our code directly; rather, the compiler parses and transfers it into the machine code. It supports almost all common concepts of the programming languages like Interfaces, Classes, Functions; a contrast to other programming languages, the Dart programming language will not support arrays directly.
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In Dart, every value we use in the program will have a data type either number or string should be known when we compile the code. Following are some common data types:
1. String: String variables store text values.
2. Num: Num Data type refers to number. Dart has two kinds of numerical values:
3. Boolean: It utilizes the “bool” keyword for representing the Boolean values true and false.
4. Object: In Dart, everything is an object, but a thing can be more difficult.
Variables are defined as the namespaces that store values. The names of the variables are known as identifiers. Variables are the data containers that can store the value of any data type. For example:
Var myAge = 10;
In the above example, “myAge” is the variable that holds the integer value 10.
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Dart programming language supports all the operators available in the other programming languages like Java, C, C#. Following are the operators of Dart:
Decision-Making statements are the features that enable us to determine the condition before the instructions are implemented. Dart programming language supports the below decision-making statements:
We use Loops for executing a code block repeatedly until a particular condition becomes true. Dart programming language supports the following loop statements:
Functions are another essential feature of any programmiThisg language. They are statements that carry out a particular task. They are arranged into the building blocks of the code that are maintainable, reusable, and readable. The function declaration includes the return type, parameters, and function name.
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Comments are defined as non-executable code lines. They are one of the primary aspects of all programming languages. Dart programming supports the following kinds of comments:
The continue statement enables us to jump the rest of the code in the loop and instantly go to the later loop iteration.
void main() {
for (int i=1;i<=10; i++) {
if(i==5){
print("Hello");
continue; //it will skip the rest statement
}
print(i);
}
}
The break statement allows us to stop the existing flow of the program and consistent execution after the loop body.
void main() {
for (int i=1;i<=10;i++){
if(i==5){
print("Hello"); break;//it will terminate the rest statement
}
print(i);
}
}
We use the Final statement for restricting the user. We can use it in various perspectives like classes, methods, and variables.
We use the “Const” keyword for declaring the constants. After announcing a constant, we cannot modify the value.
void main() {
final a 100;
const pi 3.14;
print (a;
print (pi);
}
In Dart, everything and value is an object, so Dart is object-oriented. In Dart, a number is also an object.
Object: Object is defined as the entity which has behavior and state. It can be logical or physical. Dart enables us to develop our custom objects for expressing complex relations between the data.
Class: Class is a group of objects. It indicates that we create objects through classes because all the objects require a blueprint according to which we can create a separate entity. The class definition contains the below things:
-class Mobile {
// Property Declaration
String color, brandName, modelName;
// Method Creation
String calling() {
return "Mobile can do call to everyone.";
}
String musicPlay() {
return "Mobile can play all types of Music.";
}
String clickPicture() { return "Mobile can take pictures.";
}
}
void main() {
// Object Creation
var myMob = new Mobile();
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In Flutter, whenever we code to build anything, it will be available in a widget. The primary purpose is to create the apps from the devices. It explains how our app view must appear with their present state and configuration. When we make any modification in the code, the widget redevelops its descriptions by computing the difference of current and previous widgets for determining the minimum changes to render in the User Interface(UI) of the application.
Kinds of Widgets
In Dart, we can divide the Flutter Widgets into two kinds:
1. Visible Widget
Visible Widgets are associated with the user output and input data. Following are the essential types of this Widget are:
2. Invisible Widget
The Invisible Widgets are associated with the control and layout of widgets. It offers controlling how widgets truly behave and how they look into the screen. Some of the essential kinds of these widgets are:
Flutter IDE is defined as the software program that enables us to create and edit text files. In the development field, editors generally relate to utilizing the editor plugins for a better experience. These plugins contain Code completion, Syntax highlighting, debug support, widget editing assists, etc. Following are the famous IDEs that support the Flutter application development:
It is a freeware and rapid tool that we utilize for building the application on every kind of android device. It offers an entire experience to develop the flutter applications like code completion, syntax highlighting, refactoring, navigation, support, etc. The primary objective of android studio is to accelerate the application building process and develop high-quality applications for all android devices.
VS Code IDE or Visual Studio Code is a popular editor to develop flutter applications. It is simple and easy for using. Almost all developers use the IDE for building flutter applications, yet Microsoft’s trusted company supports it. It is comparatively high support and growth. It offers Code completion, Syntax highlighting, Type Hierarchy, Pub Get Packages Command, etc.
It is the most famous and robust IDE among developers that is maintained and developed by the JetBrains company. It supports various languages for developing applications. Apache 2.0 licensed it. If we want to build applications using the Dart language, it serves as the front runner in comparison with other IDEs.
The primary concept of the layout process is widgets. Thus, the icon, image, text, and layout of our application are all widgets. Flutter enables us to create the layout by forming multiple widgets for building more difficult widgets.
The container is the widget class that customizes the child widget. It is primarily used for adding borders, margins, padding, background color, etc. The text widget gets into the container to add the margins. The complete row is stored in the container to add margin and pad around the rows. The remaining UI is governed by the properties like text style, color, etc.
Layout the Widget
Step1: First, we have to choose the widget layout.
Step2: Later, create the visible widget.
Step3: After that, insert the widget into the layout widget.
Step4: Lastly, insert the widget layout to the page where we have to display it.
1. Single Child Widgets
Single Child Widget is a kind of widget that can store only one widget in the parent layout widget. These widgets can also include particular layout functionality. Flutter offers several child widgets for making application UI attractive. If we utilize the widgets properly, it can reduce our time and causes the app code to be readable.
2. Multiple Child Widgets
Multiple Child Widgets are a kind of widget that includes multiple child widgets, and the layout of these widgets is distinct. For instance, the Row widget laying out of the child widget in the vertical direction.
Rows and Columns are not one widget; they are two distinct widgets, namely column, and row. We can integrate those two widgets because they have the same properties that allow us to understand rapidly and efficiently. Row and Column are two important widgets that enable us to coordinate children vertically and horizontally as per our requirements.
The Widget organizes the children in the horizontal direction on the screen. Put it differently, and it will anticipate child widgets in the horizontal array. If the child requires to fill the accessible horizontal space, we should enfold children’s widgets in the expanded widget.
The row widget does not display scrollable, yet the widgets appear in the visible view. Therefore, it is regarded wrong if we have more children in the row, which will not suit in available space. If we have to make the scrollable list of widgets. We can control the child widget of the row through the below properties:
The Column Widget organizes its children in the vertical direction on screen. Put it differently, and it will anticipate the vertical array of the child widgets. If child widgets have to occupy existing vertical space, we need to enfold the children’s widgets in the expanded widget. The Column Widget does not arise scrollable because it exhibits the widget's invisible view. Therefore, it is wrong if we have more children in the column that will not suit in the accessible space. If we have to make the scrollable list of the column widgets, we have to use the “ListView” widget.
Buttons are defined as the graphical control elements that offer the user to invoke the event like making choices, taking actions, searching for things, etc. We can locate the buttons anywhere in the UI, like forms, cards, toolbars, dialogs, etc. Buttons are Flutter widgets which is a portion of the material design library. Flutter offers various kinds of buttons that contain different styles, features, and shapes. Following are the features of the buttons:
Kinds of Flutter Buttons
Following are the different kinds of Flutter buttons:
Animation is a very famous and essential concept in the Flutter. We cannot think of any mobile app without animations. When we move the cursor on the button or shift from one page to another are all the animations. Animations improve the user experience and make the applications more communicative. It offers excellent support for the animation and divides the animation into two primary categories:
It is a kind of animation that enables us to make the application feel interactive and realistic. It imitates real-time movement or animation like we have to animate the widget like falling, swinging, spring with gravity. So, the animation animates in response to the user input or movement. An easy example is the flight time and distance covered will be computed as per the physics laws.
It is the concise form of “in-betweening.” In the tween animation, we have to define the “start” and “endpoint” of the animation. It indicates that the animation starts with the starting value, later goes through the group of intermediate values, and lastly reaches the end value. It also offers the curve and timeline, which specifies the speed and time of the transition. The widget framework provides the computation of how to transition from the start and endpoint.
Step 1: Open the Android Studio.
Step 2: Create the Flutter Project; for that, press “File/New/New Flutter Project.”
Step 3: Choose the Flutter Application. For that, choose “Flutter Application” and press “Next.”
Step 4: Set up the application as follows and press Next
Step 5: Configuring the project
Configure the company domain as the “flutterapp.MindMajix.com” and press “Finish.”
Step 6: Provide the company domain.
Android Studio creates an entirely working Flutter application with minimum functionality. The structure of a flutter application:
Following are the components of the structure of the Flutter application:
Step 7: Substitute the dart code in lib/main.dart file with the following code:
Step 8: Execute the application through “Run/Run main.dart.”
Step 9: Output of the application is:
Lists are the most famous elements of all mobile or web applications. Lists are composed of multiple rows of items that contain buttons, text, icons, toggles, thumbnails, etc. We can utilize it to display information like tabs, menus or break the tedium of pure text files. In Flutter, we have different kinds of Flutter:
Basic Lists: Flutter contains a “ListView” widget to work with Lists. The ListView is a good standard to display lists that include only a few items. ListView also contains the ListTitle widget, which provides more properties to the visual structure for the lust of the data.
Flutter as an essential routing mechanism, “Navigator” widget, and idiomatic declarative routing mechanism, the router widget. We can use those systems together. In Flutter, Pages and Screens are called Routes. For Navigating to another screen, we should use the “Navigator. push” together with “MaterialPageRoute”:
To Navigate Back, we will use:
Manual JSON decoding relates to utilizing the in-built JSON decoder in “dart: convert.” It includes passing the raw JSON to the “JsonDecode()” function and later looking for the values we require in the resulting Map<String, Dynamic>. It has no explicit or specific setup process. Manual decoding does not carry out well when the project becomes bigger. Developing and Decoding logic can be hard to error-prone and handle.
The JSON Serialization with the code generation indicates having an explicit create the enciphering boilerplate for us. After the initial setup, we execute the file watcher that creates the code from our model classes. For instance, “built_value” and “json_serializable” are these types of libraries. This approach is suitable for large projects.
Whenever we have to store the data on local and later, we have to utilize SQLite for persisting the user data.
SQLite is a famous selection as the integrated database software for a client or local storage in application software like web browsers.
SQLite is not available in Flutter SDK, but we have the plugin “SQLite” that does all the operations on the database just as iOS and Android.
Step1: Adding Dependencies
For working with the SQLite databases, import “path” and “sqflite” packages.
Step2: Create the Model Class
SQLite generates the table for the model class, fields in the class corresponding to the columns in the table. Thus, the classes are likely to be small model classes that don’t have any logic. Our class represents the model for data in a database. If we have to insert it into the database, we have to convert the class into the database. If we want to fetch data from the database, then we have to convert the database into a class.
Step3: Create the database
We will make an individual class as the “database. dart” for making the code modular and insert all the requirements myths to manage the database that we can access anywhere in the application.
Step4: Open the database
Before we read and write the data to the database, we have to open the connection to the database. This includes two steps:
We classify the widgets into two categories, one is the Stateless Widget, and another one is Stateful Widget. Stateless Widget does not have any implicit state. It indicated once it is developed, we cannot modify or alter it unless they are initialized again. At the same time, a Stateful Widget has a state, and it is dynamic. It indicates we can alter or change it simply across the lifecycle without reinitiating it again.
The state is the information that we can read when the widget is developed and may be altered or changed over the application’s lifetime. If we want to modify our widget,
We have to update the state object, which we can do using the setState() function useful for the Stateful widgets. setState() function enables us to configure the properties of the state objects that invoke the redraw of the UI.
Unit testing is the simplest method to test software or an application. It tests one class, method, or function. The objective of the unit testing is to assure the exactness of the code in various conditions. Usually, unit testing does not communicate with the user input, render on screen, write or read from disk.
Widget testing is used for testing a single widget. The intent of this testing is to assure that the Widget’s User Interface(UI) looks and interacts with other widgets as anticipated. The process of the widget testing is the same as the unit testing. Flutter offers the following tools to test the widget:
The integration testing includes both widget testing and unit testing, along with the explicit elements of the application. It verifies the entire application or the large part of the application. The intent of the integration testing is to assure that all the services and widgets work together as anticipated. It also utilizes the performance of the application.
BDD is a functional approach for the software teams that shuts up the gap between those working on the business side of the project and those on the technical side. This can be achieved by:
Flutter is the UI toolkit used for developing rapid, amazing, and compiled applications for web, desktop, and mobile with a single programming language and codebase. The Flutter applications use Dart programming language to create the applications. I hope this Flutter tutorial provides you with the required information about Flutter widgets, Dart programming, and app development in a flutter.
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Viswanath is a passionate content writer of Mindmajix. He has expertise in Trending Domains like Data Science, Artificial Intelligence, Machine Learning, Blockchain, etc. His articles help the learners to get insights about the Domain. You can reach him on Linkedin