The View Binding library makes it easy to reduce the need to use findViewById() lookups. Once this option is enabled in your project, special binding classes will be generated from any of your layout XML files. If you have a layout called activity_simple.xml, for instance, a special class called ActivitySimpleBinding will be generated that will have references automatically created for you. Some major advantages are:
NOTE: the View Binding library is separate from the Data Binding Library, which provides two-way and layout variables support.
Add the following to app/build.gradle file:
android {
buildFeatures {
viewBinding true
}
}Once you have enabled this option, make sure to click Rebuild Project. You will need to rebuild your entire project in order to make sure the view binding class are created.
Once you have enabled and recompiled your project, the binding classes should be available to you. In this example, a ActivitySimpleBinding class should have been generated for a activity_simple.xml file. Instead of using setContentView(activity_simple.xml), we replace that line with a call with ActivitySimpleBinding.inflate():
class ExampleActivity extends AppCompatActivity {
private TextView title;
private ActivitySimpleBinding binding;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// activity_simple.xml -> ActivitySimpleBinding
binding = ActivitySimpleBinding.inflate(getLayoutInflater());
// layout of activity is stored in a special property called root
View view = binding.getRoot();
setContentView(view);
// set bindings more efficiently through bindings
title = binding.title; // was title = findViewById(R.id.title);
title.setText("My title");
// alternately, access views through binding when needed, instead of variables
binding.title.setText("My title");
}
}class ExampleActivity : AppCompatActivity() {
private lateinit var title: TextView
private lateinit var binding: ActivitySimpleBinding
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
// activity_simple.xml -> ActivitySimpleBinding
binding = ActivitySimpleBinding.inflate(layoutInflater)
// layout of activity is stored in a special property called root
val view = binding.root
setContentView(view)
// set bindings more efficiently through bindings
title = binding.title // was title = findViewById(R.id.title)
title.text = "My title"
// alternately, access views through binding when needed, instead of variables
binding.title.text = "My title"
}
}This can be done within Activity, Fragment, or Adapter classes. For example, fragment usage would look like:
public class FancyFragment extends Fragment {
Button button1;
Button button2;
FancyFragmentBinding binding;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
// fancy_fragment.xml -> FancyFragmentBinding
binding = FancyFragmentBinding.inflate(getLayoutInflater(), container, false);
// layout of fragment is stored in a special property called root
View view = binding.getRoot();
// TODO Use fields...
// binding.
return view;
}
@Override
public void onDestroyView() {
super.onDestroyView();
binding = null;
}
}class FancyFragment : Fragment() {
private lateinit var button1: Button
private lateinit var button2: Button
// Used to inflate and destroy the view
private var _binding: FancyFragmentBinding? = null
// Used throughout the class
private val binding get() = _binding!!
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View {
// fancy_fragment.xml -> FancyFragmentBinding
_binding = FancyFragmentBinding.inflate(getLayoutInflater(), container, false)
// layout of fragment is stored in a special property called root
View view = binding.getRoot()
// TODO Use fields...
// binding.
return view
}
override fun onDestroyView() {
super.onDestroyView()
_binding = null
}
}Build -> Rebuild Project.