Question

While working my way through the Android tutorials, I came across something I don’t understand. It’s probably extremely simple, but I just need an idea why it’s this way.

In the tutorial: http://developer.android.com/resources/tutorials/views/hello-autocomplete.html

The tutorial seems to construct a new AutoCompleteTextView using:

AutoCompleteTextView textView = (AutoCompleteTextView) findViewById(R.id.autocomplete_country);

I assume their using the constructor:

AutoCompleteTextView(Context context, AttributeSet attrs)

I think their AttributeSet is the “findViewById(R.id.autocomplete_country)“; while their context is the (AutoCompleteTextView). Is this right?

Also… where’s the new keyword, the comma, and why is there a pair of parenthesis?

I always thought it’d have to be:

AutoCompleteTextView textview = new AutoCompleteTextView(context here, attrs here);

Where am I going wrong?!

Answer 1

findViewById returns the View corresponding to the argument passed in, and you cast the View to be the object of whatever the type you are working with.

Button myButton = (Button) findViewById(R.id.button);
                     ^ casting   ^ returns the View of your button.