Easy way to bind collections to listviews and recyclerviews with the new Android Data Binding framework.
compile 'me.tatarka.bindingcollectionadapter:bindingcollectionadapter:1.3.0'
compile 'me.tatarka.bindingcollectionadapter:bindingcollectionadapter-recyclerview:1.3.0'requires at least android gradle plugin 1.5.0.
You need to provide your items and an ItemView to bind to the layout. You should use an
ObservableList to automatically update your view based on list changes. However, you can
use any List if you don't need that functionality.
public class ViewModel {
public final ObservableList<String> items = new ObservableArrayList<>();
public final ItemView itemView = ItemView.of(BR.item, R.layout.item);
}Then bind it to the collection view with app:items and app:itemView. There are also some
convience factories to attach a LayoutManager to a RecyclerView with app:layoutManager.
<!-- layout.xml -->
<layout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto">
<data>
<variable name="viewModel" type="com.example.ViewModel"/>
<import type="me.tatarka.bindingcollectionadapter.LayoutManagers" />
</data>
<ListView
android:layout_width="match_parent"
android:layout_height="match_parent"
app:items="@{viewModel.items}"
app:itemView="@{viewModel.itemView}"/>
<android.support.v7.widget.RecyclerView
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layoutManager="@{LayoutManagers.linear()}"
app:items="@{viewModel.items}"
app:itemView="@{viewModel.itemView}"/>
<android.support.v4.view.ViewPager
android:layout_width="match_parent"
android:layout_height="match_parent"
app:items="@{viewModel.items}"
app:itemView="@{viewModel.itemView}"/>
<Spinner
android:layout_width="match_parent"
android:layout_height="match_parent"
app:items="@{viewModel.items}"
app:itemView="@{viewModel.itemView}"
app:dropDownItemView="@{viewModel.dropDownItemView}"/>
</layout>In your item layout, the collection item will be bound to the variable with the
name you passed into the ItemView.
<!-- item.xml -->
<layout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto">
<data>
<variable name="item" type="String"/>
</data>
<TextView
android:id="@+id/text"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="@{item}"/>
</layout>You can use multiple view types by using a ItemViewSelector instead. You can still bind
it to the view with app:itemView.
public final ItemViewSelector<String> itemView = new BaseItemViewSelector<String>() {
@Override
public void select(ItemView itemView, int position, String item) {
itemView.set(BR.item, position == 0 ? R.layout.item_header : R.layout.item);
}
// You need to override this method when using a ListView as it requires to know how
// many view types there are immedeatly. RecyclerView and ViewPager don't need this.
@Override
public int viewTypeCount() {
return 2;
}
};Note that select is called many times so you should not do any complex processing in there. If you
don't need to bind an item at a specific position (a static footer for example) you can use
ItemView.BINDING_VARIABLE_NONE as the binding varibale.
You can set a callback to give an id for each item in the list with
adapter.setItemIds(new BindingListViewAdapter.ItemIds<T>() {
@Override
public long getItemId(int position, T item) {
return // Calculate item id.
}
});or by defining app:itemIds="@{itemIds}" in the ListView in your layout file.
Setting this will make hasStableIds return true which can increase performance of data changes.
You can set a callback for isEnabled() as well with
adapter.setItemEnabled(new BindingListViewAdapter.ItemEnabled<T>() {
@Override
public boolean isEnabled(int position, T item) {
return // Calculate if item is enabled.
}
});or by defining app:itemEnabled="@{itemEnabled}"in the ListView in you layout file.
You can set a callback to give a page title for each item in the list with
adapter.setPageTitles(new PageTitles<T>() {
@Override
public CharSequence getPageTitle(int position, T item) {
return "Page Title";
}
});or by defining app:pageTitles="@{pageTitles}" in the ViewPager in your layout file.
You can construct custom view holders with
adapter.setViewHolderFactory(new ViewHolderFactory() {
@Override
public RecyclerView.ViewHolder createViewHolder(ViewDataBinding binding) {
return new MyCustomViewHolder(binding.getRoot());
}
});or by defining app:viewHolder="@{viewHolderFactory}" in the RecyclerView in your layout file.
Data binding is awesome and all, but you may run into a case where you simply need to manipulate the
views directly. You can do this without throwing away the whole of databinding by subclassing an
existing BindingCollectionAdapter. You can then bind adapter in your layout to your subclass's
class name to have it use that instead. Instead of overriding the normal adapter methods, you should
override onCreateBinding() or onBindBinding() and call super allowing you to run code before
and after those events and get access to the item view's binding.
public class MyRecyclerViewAdapter<T> extends BindingRecyclerViewAdapter<T> {
public LoggingRecyclerViewAdapter(@NonNull ItemViewArg<T> arg) {
super(arg);
}
@Override
public ViewDataBinding onCreateBinding(LayoutInflater inflater, @LayoutRes int layoutId, ViewGroup viewGroup) {
ViewDataBinding binding = super.onCreateBinding(inflater, layoutId, viewGroup);
Log.d(TAG, "created binding: " + binding);
return binding;
}
@Override
public void onBindBinding(ViewDataBinding binding, int bindingVariable, @LayoutRes int layoutId, int position, T item) {
super.onBindBinding(binding, bindingVariable, layoutId, position, item);
Log.d(TAG, "bound binding: " + binding + " at position: " + position);
}
}<android.support.v7.widget.RecyclerView
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layoutManager="@{LayoutManagers.linear()}"
app:items="@{viewModel.items}"
app:itemView="@{viewModel.itemView}"
app:adapter='@{"com.example.MyRecyclerViewAdapter"}'/>You can also use a factory instead of the class name. This allows you to not have reflection and gives you more control over it's construction.
public static final BindingRecyclerViewAdapterFactory MY_FACTORY = new BindingRecyclerViewAdapterFactory() {
@Override
public <T> BindingRecyclerViewAdapter<T> create(RecyclerView recyclerView, ItemViewArg<T> arg) {
return new MyRecyclerViewAdapter<>(arg);
}
}<android.support.v7.widget.RecyclerView
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layoutManager="@{LayoutManagers.linear()}"
app:items="@{viewModel.items}"
app:itemView="@{viewModel.itemView}"
app:adapter="@{MY_FACTORY}"/>There are a few classes to help with common implementations of ItemViewSelector.
ItemViewClassSelector selects an item view based on the class of the item in the list.
selector = ItemViewClassSelector.builder()
.put(String.class, BR.name, R.layout.item_name)
.put(Footer.class, ItemView.BINDING_VARIABLE_NONE, R.layout.item_footer)
.build();ItemViewModelSelector delegates to the items in the list themselves to determine the item view.
selector = new ItemViewModelSelector<Model>();
public class Model implements ItemViewModel {
@Override
public void itemView(ItemView itemView) {
itemView.set(BR.name, R.layout.item_name);
}
}There are many times you want to merge multiple data sources together. This can be as simple as adding headers and footers or as complex as concatenating multiple data sources. It is hard to manage these lists yourself since you have to take into account all items when updating a subset.
MergeObservableList solves this by giving you a "merged" view of your data sources.
ObservableList<String> data = new ObservableArrayList<>();
MergeObservableList<String> list = new MergeObservableList<>()
.insertItem("Header")
.insertList(data)
.insertItem("Footer");
data.addAll(Arrays.asList("One", "Two"));
// list => ["Header", "One", "Two", "Footer"]
data.remove("One");
// list => ["Header", "Two", "Footer"]This is likely because you are using the android-apt
plugin which broke
this in previous versions. Update to 1.6+ to fix it.
If you attempt to retrieve an adapter from a view right after binding it you may find it is null.
This is because databinding waits for the next draw pass to run to batch up changes. You can force
it to run immediately by calling binding.executePendingBindings().
Copyright 2015 Evan Tatarka
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.