From flexblog.faratasystems.com - December 19, 2011 3:42 AM

While Flex framework supports working with focus, you need to help it a little bit in some scenarios. For example, if your application starts with a Login view it would be nice if the cursor would be automatically placed in the user ID field so the user can immediately start typing. Calling the function setFocus() on the TextInput will show a blinking cursor, but the this field doesn’t respond to the keyboard until the user clicks inside the TextInput.