List Adapter and getView function explanation

I'm thoroughly confused about the life cycle of list view. More specifically, what does the list adapter do exactly? Does it just provide data to t开发者_JAVA百科he given view? And when/where does the getView() function gets called? And what purpose does this getView() function provide? From just looking at the code, it looks like getView() is "assigning" data to the view to be displayed. I'd like to be able to use list views without having to memorize, do this and then this in order for it to work. I'd much rather understand it so I can use it properly. Someone please help me understand all of this.

Also, if someone can explain to me.. what's the difference between BaseAdapter and ArrayAdapter? and any other kind of adapters that comes with Android.

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What I have understood is your adapter constructor instantiated by activity and then on activity launch the getView() method is called. the {@param position, view, viewGroup}

1. position: it refers to the position of the view as given by adapter. Please Note it is different from the position in {OnItemClick(AdapterView adapter, View v, int position,long id)} here position is the list item position. The {position} in {getView()} changes after particular object in the list are displayed again for eg. when you scroll.

2. view: the view here is the view you want to be presented through getView(). It can be a particular XML layout for each row. So this states clearly that getView is called to plot every row. this view needs to be valid one or another layout (LinearLayout by default) will be selected to maintain uniqueness.

3. viewgroup: as you might know and as name says will be the container of your @param:view

any other point is appreciated.

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getView() fills in the data into the item's view with the given index. The view which is given as a parameter may be a pre-inflated view. If it is not, you have to infalte it yourself. An ArrayAdapter simply calls setText on the given view with the result of toString() of the object with the respective index from the array. If you override it, you can do more complex stuff, like assigning a picture or filling in more TextViews.

I recommend the following tutorial: http://www.softwarepassion.com/android-series-custom-listview-items-and-adapters/

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Hi list adaper provides view for listview.

when user scrolls listview at that time getview is called.

getview is used to populate your view with data hence the name adapter.

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The Adapter does all the "rember to do this" for you. If you change a list view's backing data structure through the adapter's methods (e.g. "add()") it will fire all the datachanged and update events you'll need for the list view to show the new state of the data.