Navigation in Xamarin.Forms - and any mobile app really - is composed of 2 things:
- Pushing a new page onto the navigation stack.
- Popping that page off the stack to reveal the previous one.
The push and pop could be broken down further to include modal push and pop - modals do not have a back button in the toolbar. But the concept overall is the same.
The code for this episode changed a tiny bit from the last episode.
A new page called DetailPage.xaml. It's already built for you, but it has a single Label on it that's bound to a NoteText property on its view model. It also has a Button whose Command is set to ExitCommand.
Of course there's that view model then. The NoteText is already there. You'll learn about the ExitCommand in the video.
Then in the MainPage.xaml there were some changes to the CollectionView. Namely a new bound property. With this, a property in the view model gets set every time a cell in the CollectionView is selected. And there's a Command that fires whenever a selection on the CollectionView is made.
So now you can checkout the video for more info.
You'll also notice one more thing within the DetailPage ... and that's an additional way to setup the BindingContext of a XAML page to its view model.
The code is located in the code-behind. Instead of doing everything in the XAML - it's done with BindingContext in C#. In the case of DetailPage the view model is passed into the constructor, but there are many times when you'd create the view model in the page itself, and this is a perfectly valid way of setting it up instead of using <ContentPage.BindingContext> in XAML.
So the big takeaway here is the concept of pushing and popping.
The other one - and one that should not be forgotten - is that to do any sort of navigation within Xamarin.Forms, make sure you wrap your main page (no matter what you call it) inside a NavigationPage.
It's that NavigationPage which provides the Navigation property for all the navigation goodness.
I hope you enjoyed and learned a lot from this series. If you have any questions - feel free to reach out to me on Twitter, my DMs are open at @codemillmatt.