counter_app

MaterialApp (provided by material library)

• This widget sets up a basic layout in android to show some output.
• The background is black in color and text styling by default doesn't look neat.
• home is a required argument for MaterialApp.
• Text widget can be passed to home to show some basic text.

Scaffold (provided by material library)

• This creates a basic white background for the app.
• appbar will create a appbar at the top.
• Pass widget to body to show the content to the main screen.

Column

• To pass multiple widgets use column which takes a list of widgets.

RaisedButton

• To create a button.
• onPressed is a required argument(will get a warning if not used).
• A function can be passed to onPressed to do some action.

State in Flutter

• We have created a list of questions and button increases a count so that we can show the questions in the list.
• But the count increases but doesn't gets updated in the screen.
• It is because the widget is stateless.
• To overcome this problem(recreate UI when state changes) we need to change the widget to a stateful widget.

Stateful Widget

• Two classes create a stateful widget:
  • State class (along with pointer to the Widget class) to persist data
  • StatefulWidget class to recreate widget on state change
• State class is created as private class to prevent using it from other files.
• Connection is created between State class and Widget class.
• Value is updated in setState class method given by State class.
• setState takes a anonymous function.
• setState forces flutter to re-render the widget (only in which the state has changed).
• Now if the data or state changes the widget gets recreated.

Text Widget

• In style argument we can pass TextStyle widget to add styling like size, font, etc.
• textAlign argument takes an enum TextAlign. But since the Text widget takes the size only needed for text, it wont work unless we put it in a container and add some width to the text.

Dart features

• enums
• multiple constructors
• Map or {} (like dictionary in python)
• .toList() - Used to convert a iterable(output of map) to a list.
• ...list - used to spread list of items into individual items.

final vs const

• final is runtime constant - We won't change once instantiated(runtime)
• const is compile time constant - We won't change once assigned(during coding)
• var numbers = const [1,2,3] makes the list(value) immutable.

Module 1 End

• Created a quiz app with score display and quiz reset.
• Basics of Dart
• Basics of flutter