How do I create a checkable listview?

(FYI, I'm targeting 2.2 Froyo in my project, so any solution would have to work at that build level.)

What I want to do seems quite simple; show a list of items in a ListView, and allow the user to tap to select multiple items before performing an operation on all of them at once.

To provide a little more detail, I am binding a ListView to an array of objects. The screen consists of other controls, with the ListView in the middle. Each list item has several components; two images, and a text label. NO checkbox. Instead, when the user taps an item, the background should change to indicate that it is checked. If the item is tapped again, the background should change back to indicate it is not checked. The user may tap one or more items. If the user scrolls the list off the screen and scrolls it back, the state of those items should be preserved.

From what I've researched, I gather that I need to:

• use a Drawable as the background for the list items with selectors for checked, pressed and default states
• create a custom class extending LinearLayout or RelativeLayout and implementing Checkable, then use this as the root View for the list item layout

I've found several tutorials online, but none work. Either they have runtime errors, or simple don't do anything... pressing the buttons does not change their appearance to checked.

I found an alternative approach in the O'Reilly "Android Cookbook." Rather than doing all of the above, they add a boolean to the objects the ListView i开发者_C百科s bound to, then manually add code to change that boolean when a list item is clicked and to change the background in the adapter for an item where the boolean is true. In other words, they don't use Checkable at all. This does not seem like an ideal solution to me; abandoning the Android API in favor of custom hacks often seems to cause bugs later on, and I'm uncomfortable with adding GUI information (whether or not an item is selected) to what should be a purely data-carrying POJO conceptually representing a chunk of information.

My question is this: does anyone have a WORKING tutorial to accomplish what I have described, using Android's Checkable functionality? Or is this so problematic that something like the O'Reilly hack always has to be used?

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I have never read Android Cookbook but their strategy is exactly what I would do. I would decline to call this a hack and suggest this is the kind of thing that the Android framework intends to do. A selected state in my opinion is part of the model you wish to protect, I do see how it could be in a gray area as it removes the purity of your POJO's.

There is a second strategy you could use to protect the purity of your POJO's use the state of the background to find if something is selected or not. Additionally you could also use a plain color resource instead of a drawable background.