Question

I’m a newbie in Android development.

I have Eclipse with ADT (sdk version: 17 , Android 4.2).

I don’t understand what is the difference between:

• DEFINING a View (via visual editor provided by ADT or directly in the XML layout file corresponding to the current activity)

and

• INSTANTIATING a View (PASSING THE CONTEXT AS PARAMETER) such as: TextView tv = new TextView(getContext()); (taken from : What is 'Context' on Android? , first asnwer)

and

• INSTANTIATING a View (WITHOUT PASSING THE CONTEXT AS PARAMETER) such as: TextView tv = new TextView();

Thank in advance for any advice.

Kind regards

Answer 1

To use your terminology:

When DEFINING a View in XML (or the ADT editor – which just creates the XML for you), it still needs to be inflated by a layout inflater. A layout inflater will INSTANTIATE the View(s) for you. This can be done behind the scenes – such as when you call Activity.setContentView(), or directly using View.inflate(). The inflater effectively just runs through the XML and instantiates all of the Views it contains.

When INSTANTIATING a View, you’re giving it the Context so it has a reference to resources – so it can load images, strings, dimensions etc – plus other Android related functionality (which you can probably ignore for now).

You can’t INSTANTIATE a View without the context.