对于ListView适配器，getView（）如何调用？

Question

I've looked around quite a bit but haven't found a real answer to this question. I'm just starting to learn about android adapters and had a few questions. Firstly, do I need to call getView() manually or does it get called automatically? If so, when is it actually called? Lastly, I noticed there's a parameter for "position" with in the list. Is that something I have to increment through iteration or does it get incremented internally somehow?

thanks!

Answer 1

Firstly, do I need to call getView() manually or does it get called automatically?

No, it get called automatically.

If so, when is it actually called?

It will be called when user do something to your ListView , like when the ListView displaying a new item when you scrolling it.

Lastly, I noticed there's a parameter for "position" with in the list. Is that something I have to increment through iteration or does it get incremented internally somehow?

No, it will be your list item's position automatically. Its the same for other params like (the default) View convertView , it will be the View of current item (row of ListView ).

Answer 2

It's part of how the adapter works. You don't need to call any of those methods, since it's called implicitly through your Listview.

Have a look at this,

http://www.vogella.com/tutorials/AndroidListView/article.html

It's a good article on how to use a Listview.

Answer 3

Adapter is a kind of connection between AdapterView (ListView, GridView etc.) and arrays of data. Adapter generates vies that would be displayed in the AdapterView. So when ListView needs to display elements it first calls getCount() method of adapter, after some measurements it makes a few getView() calls to fill visible part of the listView with items. And then during the scrolling ListView will call getView() from the adapter for the next positions. It is important not to make any assumptions on the order of the getView() calls - it's not obligatory that listview will call getView() in the same order as your data ordered. So you don't have to worry about incrementing of position index - this argument is used for situation, for example, when you need to display two different backgrounds for even and for odd rows - and you can use position to make a decision which colour you need to use. There is a good presentation about anatomy of the ListView