Question

For example,

Button b = (Button) findViewById (R.id...) 
TextView t = (TextView) findViewById (R.id..)

Why do we do this? When do we have to do this?

Answer 1

We need to do explicit casting whenever we cast object of some class to its subclass.

findViewById returns object of View class, and to get an object of Button, EditText, etc, from this object we need to do explicit cast.

We need to do explicit casting when we need to access methods and fields defined into subclasses, like setText().

We dont need to explicit cast View, when we need to access only View class’s methods, like:

setOnClickListener().