MergeAdapter accepts a mix of Adapters and Views and
presents them as one contiguous whole to whatever ListView
it is poured into. This is good for cases where you have
multiple data sources, or if you have a handful of ordinary
Views to mix in with lists of data, or the like.
Simply create a MergeAdapter and call addAdapter(),
addView(), or addViews() (latter accepting a List<View>),
then attach your adapter to the ListView. You can also
extend MergeAdapter to override isEnabled(), so you can
control which positions are and are not enabled.
There is also MergeSpinnerAdapter for use with Spinner
widgets.
This is packaged as an Android library project, though a simple JAR is also available from the Downloads section of this GitHub repository.
You can use MergeAdapter directly or subclass it. The
latter is needed to support controlling which rows are/are
not enabled.
There is only one, no-argument constructor at this time. Just
call new MergeAdapter() or new MergeSpinnerAdapter() and
you are on your way!
You have three methods for defining what goes into the
MergeAdapter. You can call addAdapter() to have all of that
adapter's rows appear in the combined roster. You can call
addView() to add a single View as a row. You can also call
addViews() to add a List of View objects to use as rows.
NOTE: MergeSpinnerAdapter only supports addAdapter().
Each of these will appear in combined roster in the order they were added.
The addView() and addViews() methods have a variant that
accepts a boolean 2nd parameter. Set this boolean to true if you
want the rows represented by these views to be enabled (i.e.,
selectable). The default is that they are disabled, for use
as if they were header rows. For adapters added via addAdapter(),
the determination of whether or not rows are enabled is determined
by the underlying adapter.
You are welcome to override other methods as well, since this
is just an Adapter.
You must pour the contents into the MergeAdapter before
calling setListAdapter() to associate the MergeAdapter
with a ListView. This limitation is required because Android
only calls getViewTypeCount() once, and adding more views or
adapters adds more view types.
Note, though, that you can modify the underlying adapters. So,
for example, if you add a CursorAdapter to the MergeAdapter,
and you requery() the Cursor, the changes should be reflected
via the MergeAdapter to whatever AdapterView the MergeAdapter
is connected to.
A ListActivity supports a widget in its layout, with an android:id
of @android:id/empty, which will be displayed if the list is
empty. More specifically, it will be displayed if the MergeAdapter
returns true for isEmpty(). The default implementation of
isEmpty() in BaseAdapter checks getCount() and compares it to 0.
In many cases, this default will be fine. However, if you are
adding regular Views to the adapter (e.g., section headings),
then getCount() will include these additional rows, and so isEmpty()
will never return true. In this case, you may need to override
isEmpty() to implement your own business logic to determine
when the list is, indeed, "empty".
You should add properly-configured SpinnerAdapter implementations
(e.g., ArrayAdapter, CursorAdapter) to a MergeSpinnerAdapter
to have it work properly.
This project requires the CWAC SackOfViewsAdapter.
A copy of a compatible JAR can be found in the libs/ directory of
the project, though you are welcome to try newer ones, or
ones that you have patched yourself.
This is version v0.3 of this module, meaning it is not completely scary now.
In the demo/ sub-project you will find
a sample activity that demonstrates the use of MergeAdapter.
Note that when you build the JAR via ant jar, the sample
activity is not included, nor any resources -- only the
compiled classes for the actual library are put into the JAR.
The code in this project is licensed under the Apache Software License 2.0, per the terms of the included LICENSE file.
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.
v0.3.0: added MergeSpinnerAdapter support
v0.2.1: added getAdapter() method to return the ListAdapter associated with a given position
v0.2.0: converted to Android library project, added enabled versions of addView() and addViews(), correctly cascades data set changes from underlying adapters
