oneporter oneporter - 1 year ago 112
Android Question

What is the intent of the methods getItem and getItemId in the Android class BaseAdapter?

I'm curious about the purpose of the methods getItem and getItemId in the class Adapter in the Android SDK.

From the description, it seems that getItem should return the underlying data. So, if I have an array of names ["cat","dog","red"] and I create an adapter a using that, then a.getItem(1) should return "dog", correct? What should a.getItemId(1) return?

If you've made use of these methods in practice, could you provide an example?

Answer Source

I see these methods as a cleaner approach to accessing my list's data. Instead of directly accessing my adapter object via something like myListData.get(position) i can simply call the adapter like adapter.get(position).

The same goes for getItemId. Usually I would use this method when I want to execute some task based on the unique ID of an object in the list. This is especially useful when working with a database. The returned id could be a reference to an object in the database which I then could perform different operations on(update/delete/etc).

So instead of accessing the ID from the raw data object like myListData.get(position).getId() you can use adapter.getItemId(position).

One example of where i've felt like I needed to use these methods was in a project using the SeparatedListViewAdapter. This adapter can contain multiple different kinds of adapters, each representing data of a different type(typically). When calling getItem(position) on the SeparatedListViewAdapter, the object returned may be different depending on which "section" the position is that you send it.

For example, if you had 2 sections in your list(fruit and candy): If you used getItem(position) and position happened to be on an item in the fruit section, you would receive a different object than if you requested getItem(position) with position pointing to an item in the candy section. You might then return some sort of constant ID value in getItemId(position) which represents what kind of data getItem(position) is returning, or use instanceof to determine what object you have.

Other than what I've mentioned, I've never felt like I really needed to use these methods

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