Xamarin: Cross-Platform Mobile Application Development

Composing messages

For the final piece of our application, we need to implement some custom functionality that Apple doesn't provide with their APIs. We need to add a text field with a button that appears to be attached to the bottom of the table view. Most of this will require writing code and wiring up a lot of events.

Let's begin by adding some new member variables to our MessagesController class as follows:

UIToolbar toolbar;
UITextField message;
UIBarButtonItem send;
NSObject willShowObserver, willHideObserver;

We will place the text field and bar buttons inside the toolbar, as shown in the following code. The NSObject fields will be an example of iOS's event system called notifications. We'll see how these are used shortly:

public override void ...