Alfonz - Adapter Module

Generic adapters for RecyclerView or ViewPager with data binding support.

The purpose of this module is to simplify usage of adapters. You can extend one of the predefined generic adapters. It depends if you want to use it for RecyclerView or ViewPager, if you have just one type of data or multiple types, if you prefer to use ArrayList or ArrayMap, if you prefer to use LiveData and DiffUtil. The adapters for RecyclerView use OnRebindCallback for a better performance and correct handling of animations. Implementation of the base recycler adapter was inspired by android-ui-toolkit-demos.

This module also contains a few useful binding adapters for setting up RecyclerView. You can find them in BindingUtility class.

How to use

Choose an adapter which suits your needs:

• SimpleDataBoundPagerAdapter
• SimpleDataBoundRecyclerAdapter
• SimpleMapDataBoundRecyclerAdapter
• MultiDataBoundPagerAdapter
• MultiDataBoundRecyclerAdapter
• MultiMapDataBoundRecyclerAdapter
• DataBoundListAdapter

Simple-type adapters can be used directly - just create a new instance. Multi-type adapters are abstract. Create a class, extend the generic adapter and call super in the constructor. Pass item layout, view (view layer in MVVM) and observable array collection in the super. Adapter will inflate the layout for an item and bind the view and the data into BR.view and BR.data variables.

public class ProductListAdapter extends SimpleDataBoundRecyclerAdapter {
	public ProductListAdapter(ProductListView view, ProductListViewModel viewModel) {
		super(R.layout.fragment_product_list_item, view, viewModel.products);
	}
}

For multi-type adapters, you also have to specify which layout you want to inflate for a specific item or type. See samples for more info.

Create an XML layout, define view and data variables, use view for invoking event callbacks and data for accessing data entity from the observable array collection defined in a view model.

<layout
	xmlns:android="http://schemas.android.com/apk/res/android">

	<data>
		<variable name="view" type="com.example.ui.ProductListView" />
		<variable name="data" type="com.example.entity.ProductEntity" />
	</data>

	<LinearLayout
		android:layout_width="match_parent"
		android:layout_height="wrap_content"
		android:onClick="@{() -> view.onItemClick(data)}">

		<TextView
			android:layout_width="wrap_content"
			android:layout_height="wrap_content"
			android:text="@{data.name}" />

	</LinearLayout>
</layout>

Create a new instance of the adapter and set it in your RecyclerView. Implement event callbacks in the MVVM view layer - it is usually Fragment.

public interface ProductListView extends AlfonzView, AdapterView {
	void onItemClick(ProductEntity product);
}

public class ProductListFragment
		extends BaseFragment<ProductListView, ProductListViewModel, FragmentProductListBinding>
		implements ProductListView {
	private ProductListAdapter mAdapter;

	@Override
	public void onActivityCreated(Bundle savedInstanceState) {
		super.onActivityCreated(savedInstanceState);
		setupAdapter();
	}

	@Override
	public void onItemClick(ProductEntity product) {
		startProductDetailActivity(product.getId());
	}

	private void setupAdapter() {
		if (mAdapter == null) {
			mAdapter = new ProductListAdapter(this, getViewModel());
			getBinding().fragmentProductListRecycler.setAdapter(mAdapter);
		}
	}
}

When you are adding multiple new items in ObservableList, always do it in a transaction with addAll(). Keep in mind, that using add() would invoke OnListChangedCallback callback in the generic adapter and notifyItemRangeInserted() for each item which is pretty inefficient.

If you want to use setHasStableIds() with getItemId() in a recycler adapter or getPageTitle() in a pager adapter, just extend the generic adapter and implement these methods as usual.

DataBoundListAdapter extends ListAdapter and uses DiffUtil for computing diffs between lists. It works nicely with LiveData.

There are also a few useful binding adapters for setting up recycler layout, decoration and animator. You can use following XML attributes in your RecyclerView:

• recyclerLayout
• recyclerLayoutSpanCount
• recyclerLayoutSpanSize
• recyclerDecoration
• recyclerDecorationMargin
• recyclerDecorationBoundaryMargin
• recyclerAnimator

RecyclerLayout supports these layout variants:

• BindingUtility.LAYOUT_LINEAR_VERTICAL
• BindingUtility.LAYOUT_LINEAR_HORIZONTAL
• BindingUtility.LAYOUT_GRID_VERTICAL
• BindingUtility.LAYOUT_GRID_HORIZONTAL
• BindingUtility.LAYOUT_STAGGERED_GRID_VERTICAL
• BindingUtility.LAYOUT_STAGGERED_GRID_HORIZONTAL
• BindingUtility.LAYOUT_LINEAR_VERTICAL_REVERSE
• BindingUtility.LAYOUT_LINEAR_HORIZONTAL_REVERSE
• BindingUtility.LAYOUT_GRID_VERTICAL_REVERSE
• BindingUtility.LAYOUT_GRID_HORIZONTAL_REVERSE
• BindingUtility.LAYOUT_STAGGERED_GRID_VERTICAL_REVERSE
• BindingUtility.LAYOUT_STAGGERED_GRID_HORIZONTAL_REVERSE

RecyclerDecoration provides these decorations:

• BindingUtility.DECORATION_LINEAR_DIVIDER_VERTICAL
• BindingUtility.DECORATION_LINEAR_DIVIDER_HORIZONTAL
• BindingUtility.DECORATION_GRID_DIVIDER
• BindingUtility.DECORATION_GRID_SPACING

RecyclerAnimator has these animators:

• BindingUtility.ANIMATOR_DEFAULT

Dependencies

• AndroidX
• Data Binding Library

Samples and download

See the main README file.