MaterialApp class in Flutter
MaterialApp Class: MaterialApp is a predefined class in a flutter. It is likely the main or core component of flutter. We can access all the other components and widgets provided by Flutter SDK. Text widget, Dropdownbutton widget, AppBar widget, Scaffold widget, ListView widget, StatelessWidget, StatefulWidget, IconButton widget, TextField widget, Padding widget, ThemeData widget, etc. are the widgets that can be accessed using MaterialApp class. There are many more widgets that are accessed using MaterialApp class. Using this widget, we can make an attractive app.
State
The state of an app can very simply be defined as anything that exists in the memory of the app while the app is running. This includes all the widgets that maintain the UI of the app including the buttons, text fonts, icons, animations, etc. So now as we know what are these states let’s dive directly into our main topic i.e what are these stateful and stateless widgets and how do they differ from one another.
Stateless Widget
The widgets whose state can not be altered once they are built are called stateless widgets. These widgets are immutable once they are built i.e any amount of change in the variables, icons, buttons, or retrieving data can not change the state of the app. Below is the basic structure of a stateless widget. Stateless widget overrides the build() method and returns a widget. For example, we use Text or the Icon is our flutter application where the state of the widget does not change in the runtime. It is used when the UI depends on the information within the object itself. Other examples can be Text, RaisedButton, IconButtons.
Stateful Widgets
The widgets whose state can be altered once they are built are called stateful Widgets. These states are mutable and can be changed multiple times in their lifetime. This simply means the state of an app can change multiple times with different sets of variables, inputs, data. Below is the basic structure of a stateful widget. Stateful widget overrides the createState() and returns a State. It is used when the UI can change dynamically. Some examples can be CheckBox, RadioButton, Form, TextField.
Scaffold class in Flutter
Scaffold is a class in flutter which provides many widgets or we can say APIs like Drawer, SnackBar, BottomNavigationBar, FloatingActionButton, AppBar etc. Scaffold will expand or occupy the whole device screen. It will occupy the available space. Scaffold will provide a framework to implement the basic material design layout of the application.