60.3 Designing the User Interface
Locate the activity_main.xml file in the Project tool window and double-click on it to load it into the Layout Editor tool. With the Layout Editor tool in Design mode, right-click on the default TextView instance, choose the Convert view... menu option and select the Button view from the resulting dialog and click Apply. Change the text property of the button to read “Send Message” and extract the string to a new resource named send_message.
Finally, configure the onClick property to call a method named sendMessage.