romainpiel / cwac-sacklist

CommonsWare Android Components: SackOfViewsAdapter

CWAC SackOfViewsAdapter: Just the Views, Only the Views

ListView in Android supports header and footer views -- views that do not belong to the underlying adapter but otherwise show up in the list and scroll along with the contents. However, they only work if you have not yet set your own adapter and are therefore not terribly flexible.

The SackOfViewsAdapter is another way of approaching this. Here, you provide the Views that make up the rows, and the adapter feeds them to Android as if they were newly created.

The SackOfViewsAdapter is designed to be subclassed, mostly to determine how isEnabled() behaves, so you can control which of those views are selectable and which simply scroll with the list.

While standalone, this is not terribly useful, in conjunction with other adapters, perhaps other ones in the CWAC collection, it has greater benefit.

This is packaged as an Android library project, though a simple JAR is also available.

Usage

You can use SackOfViewsAdapter directly or subclass it. The latter is needed to support on-demand row creation or controlling which rows are/are not enabled.

Constructors

SackOfViewsAdapter either takes a count or a List of View objects as parameters. In the first case, the count indicates how many total rows there will be. If you choose to pass in a List, and you want to add to it later on, make sure it is a mutable list (e.g., created by new ArrayList<View>()).

Defining Views at Runtime

If you pass in just a count of rows in the constructor, you need to extend SackOfViewsAdapter and override newView(), to return a row View given a position and the ViewGroup that is the row's parent (e.g., a ListView). SackOfViewsAdapter will then hang onto that row and return it to Android whenever that position is requested.

If you pass in a List of View objects in the constructor, some of those positions in the list can be null. In that case, you again have to extend SackOfViewsAdapter and override newView(), but you will only be called for those rows initially defined as null.

Other Methods to Override

You are welcome to override other methods as well, since this is just an Adapter. In particular, if all rows are not enabled for selection, you will want to override isEnabled() and return true or false as needed to indicate which rows are selectable and which are not (e.g., header rows).

Miscellany

You can call hasView() on a SackOfViewsAdapter to determine if it contains a certain View or not.

Dependencies

None at present.

This project should work on API Level 4 and higher, except for any portions that may be noted otherwise in this document. Please report bugs if you find features that do not work on API Level 4 and are not noted as requiring a higher version.

Version

This is version v0.4.0 of this module, meaning that its growth has slowed.

Demo

In the demo/ sub-project you will find a sample activity that demonstrates the use of SackOfViewsAdapter.

License

The code in this project is licensed under the Apache Software License 2.0, per the terms of the included LICENSE file.

Questions

If you have questions regarding the use of this code, please post a question on StackOverflow tagged with commonsware and android. Be sure to indicate what CWAC module you are having issues with, and be sure to include source code and stack traces if you are encountering crashes.

If you have encountered what is clearly a bug, please post an issue. Be certain to include complete steps for reproducing the issue.

Do not ask for help via Twitter.

Release Notes

• v0.4.0: added hasView()
• v0.3.1: fixed copy-and-paste error in build.xml
• v0.3.0: converted to Android library project

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