Generate the list of todos

Display the list of todos using a ListView

So far, so good.
This generates 20 todos and displays them in a ListView.

3. Create a Todo screen to display the list

For this, we create a StatelessWidget. We call it TodosScreen.
Since the contents of this page won’t change during runtime,
we’ll have to require the list
of todos within the scope of this widget.

We pass in our ListView.builder as body of the widget we’re returning to build().
This’ll render the list on to the screen for you to get going!

With Flutter’s default styling, you’re good to go without sweating about 
things that you’d like to do later on!

4. Create a detail screen to display information about a todo

Now, create the second screen. The title of the screen contains the
title of the todo, and the body of the screen shows the description.