Skip to content

Reducing View Boilerplate with ViewBinding

Jump to bottom
Christopher Clement edited this page Oct 9, 2021 · 10 revisions

Overview

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:

  • improved null safety
  • better type safety
  • greater efficiency with complex views

NOTE: the View Binding library is separate from the Data Binding Library, which provides two-way and layout variables support.

Setup

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.

Activity View Lookups

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" } }

Fragment View Lookups

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 } }

Troubleshooting

  • If you are missing a view binding class even though it is imported, try to Build -> Rebuild Project.

References

Created by CodePath with much help from the community. Contributed content licensed under cc-wiki with attribution required. You are free to remix and reuse, as long as you attribute and use a similar license.

Finding these guides helpful?

We need help from the broader community to improve these guides, add new topics and keep the topics up-to-date. See our contribution guidelines here and our topic issues list for great ways to help out.

Check these same guides through our standalone viewer for a better browsing experience and an improved search. Follow us on twitter @codepath for access to more useful Android development resources.

Clone this wiki locally