Gain insights into building a Todo app with Flutter, Firebase, AdMob, and InAppPurchases. Delve into UI design, CRUD functionality, and app monetization. Publish to Google Play Store.

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This course is designed to guide you through the process of building your first app using Flutter, a popular cross-platform framework for mobile application development. The course assumes that you are familiar with the object-oriented programming paradigm, which is a fundamental programming approach used in many modern programming languages, including Dart (the language used in Flutter).

In this course, you will learn how to build a Todo app, which will have CRUD functionality. You will also learn how to design the user interface of the app using Flutter widgets and handle user input and data storage using Firebase, a popular backend-as-a-service platform. Moreover, you understand how to monetize your app by integrating AdMob and InAppPurchases. 

By the end of the course, you will have a working Todo app that you can publish on the Google Play Store. You will also have a solid foundation in using Flutter, Firebase, AdMob, and InAppPurchases to build and monetize your mobile applications.

Build and Publish Your First Mobile App Using Flutter

The `LoggedUser` class will keep an instance of the currently logged-in users and their details like name, email, etc. It also includes the following functions:

* `upgradeMembership()`: It updates the user's membership from standard (default) to premium.
* `fetchMembership()`: It returns the current membership type that the user has.
* `setPurchaseToken(String val)`: It sets the purchase token of the user.
* `setProfileInfo()`: It fetches the user's profile information from the Firestore and stores it in the app.


## Implementation
Create a `.dart` file inside the `models` folder and name it `logged_user.dart`.

The `main` function is the entry point of the app. It calls the `runApp` function with an instance of `MyApp` as the argument. This function takes the given widget and makes it the root of the app, which means it will be displayed on the screen when the app is launched.

The `MyApp` widget is a `StatelessWidget`, which means it doesn't have an internal state that can change. It has a single `build` method that returns a widget tree. This tree describes the user interface of the app and how it should look.

The `MaterialApp` widget is a top-level widget that configures the app's `title`, `theme`, and `home` page. The `home` property specifies the default route for the app, which is the `MyHomePage` widget in this case.

The `MyHomePage` widget is a `StatefulWidget`, which means it has an internal state that can change. It has a single `createState` method that returns an instance of the `_MyHomePageState` class. This class extends the state and holds the mutable state for the `MyHomePage` widget. It has a field (`_counter`) that represents the current count and an `_incrementCounter` method that increments the count by one.

The `build` method of the `_MyHomePageState` class returns a `Scaffold` widget, which is a widget that provides a basic visual structure for the app. It has an `appBar` property that displays a top app bar, and a `body` property that displays the main content of the app. In this case, the main content is a `Column` widget that contains two `Text` widgets and a `FloatingActionButton` widget. The `Text` widgets display the current count, and the `FloatingActionButton` widget is a button that, when pressed, calls the `_incrementCounter` method to increment the count.

The `Theme.of(context).textTheme.headline4` value is the default text style for large headlines as defined by the current theme of the app. It's passed to the `style` property of the second `Text` widget to specify the text style for that widget.


## Explanation
The `LoggedUser` class is written with the `ChangeNotifier` class, which is where we get methods like `notifyListeners()` from. So whichever class or widget is listening to `LoggedUser` will be able to get updated values.

The class `LoggedUser` has fields related to a specific user of the app like name, email, ID, etc.
The default membership is Standard, and once the user purchases our premium subscription, they will be upgraded to Premium. This class also has some functions to update its values in the Firestore.

**Line 19**: We have `upgradePremium`, which will update the `membership` field to Premium.

**Line 55**: We have `setPurchaseToken`, which will set the `purchasedToken` coming from an in-app purchase.

**Line 65**: We have `setProfileInfo`, which first identifies who is currently logged in to the app, gets its details from `users` collections, and searches the document by authentication ID.



The `LoggedUser` class will keep an instance of the currently logged-in users and their details like name, email, etc. It also includes the following functions:

* `upgradeMembership()`: It updates the user's membership from standard (default) to premium.
* `fetchMembership()`: It returns the current membership type that the user has.
* `setPurchaseToken(String val)`: It sets the purchase token of the user.
* `setProfileInfo()`: It fetches the user's profile information from the Firestore and stores it in the app.


# Implementation
Create a `.dart` file inside the `models` folder and name it `logged_user.dart`.

The `main` function is the entry point of the app. It calls the `runApp` function with an instance of `MyApp` as the argument. This function takes the given widget and makes it the root of the app, which means it will be displayed on the screen when the app is launched.

The `MyApp` widget is a `StatelessWidget`, which means it doesn't have an internal state that can change. It has a single `build` method that returns a widget tree. This tree describes the user interface of the app and how it should look.

The `MaterialApp` widget is a top-level widget that configures the app's `title`, `theme`, and `home` page. The `home` property specifies the default route for the app, which is the `MyHomePage` widget in this case.

The `MyHomePage` widget is a `StatefulWidget`, which means it has an internal state that can change. It has a single `createState` method that returns an instance of the `_MyHomePageState` class. This class extends the state and holds the mutable state for the `MyHomePage` widget. It has a field (`_counter`) that represents the current count and an `_incrementCounter` method that increments the count by one.

The `build` method of the `_MyHomePageState` class returns a `Scaffold` widget, which is a widget that provides a basic visual structure for the app. It has an `appBar` property that displays a top app bar, and a `body` property that displays the main content of the app. In this case, the main content is a `Column` widget that contains two `Text` widgets and a `FloatingActionButton` widget. The `Text` widgets display the current count, and the `FloatingActionButton` widget is a button that, when pressed, calls the `_incrementCounter` method to increment the count.

The `Theme.of(context).textTheme.headline4` value is the default text style for large headlines as defined by the current theme of the app. It's passed to the `style` property of the second `Text` widget to specify the text style for that widget.


# Explanation
The `LoggedUser` class is written with the `ChangeNotifier` class, which is where we get methods like `notifyListeners()` from. So whichever class or widget is listening to `LoggedUser` will be able to get updated values.

The class `LoggedUser` has fields related to a specific user of the app like name, email, ID, etc.
The default membership is Standard, and once the user purchases our premium subscription, they will be upgraded to Premium. This class also has some functions to update its values in the Firestore.

**Line 19**: We have `upgradePremium`, which will update the `membership` field to Premium.

**Line 55**: We have `setPurchaseToken`, which will set the `purchasedToken` coming from an in-app purchase.

**Line 65**: We have `setProfileInfo`, which first identifies who is currently logged in to the app, gets its details from `users` collections, and searches the document by authentication ID.



Learn how to build a class for logged-in users.

Introduction to Course

Flutter Basics

Common Widgets

Firebase Setup

State Management

AdMob and InAppPurchase

Todo App Models

Todo UI Screens

Essential Tools to Enhance Your Flutter Workflow

Publishing to the Play Store

Appendix

LoggedUser Model

Implementation