context vs views

can anyone explain the difference between context and vi开发者_高级运维ews and when do we go for context or view ? In most of the program I find either context or view being passed to certain methods , what is actual need of passing context or view to methods?

This is a strange question. View describes one element of your ui. It can have onClickListeners, properties and so on. But every view is created in some context, usually Activity's context.

Context as itself is something like environment your code is executed in. It has access to ui(if it is an activity), it can contain some global data(application context), and has access to the resources(all of the contexts). Also, context allows you to perform common android operations like broadcasting intents, start activities and services.

So, views should be passed when you want to do something with a particular view. Context is passed when you need access to resources, global data or ui context, or launch other android components.

We need to understand how View is constructed and what is Context.

View has three constructors, all of which use Context as an argument.

In Activity, if view is inflated programmatically as against in XML, view is inflated a View is by using LayoutInflater.

LayoutInflater takes Context as an argument and internally saves it in a class level field.

LayoutInfater layoutinflater = LayoutInflater.from(this);

where "this" is the Activity instance.

When inflater inflates view i.e. :

inflater.inflate(R.id.some_view, parent, null),

it is internally passing the saved context field to the constructor of View.

View always takes a Context as an argument and this is obvious because views live in some Context which is the Activity.

To answer your question, when context is needed to be passed to a method which itself is in Activity, you can write "this". If method is not in Activity, and you need to pass Context, then remember that View which has taken Context as a parameter, saves the object reference in a class level field. We can get this object reference by writing view.getContext().