Migrate from Kotlin synthetics to Jetpack view binding

Kotlin Android Extensions is deprecated, which means that using Kotlin synthetics for view binding is no longer supported. If your app uses Kotlin synthetics for view binding, use this guide to migrate to Jetpack view binding.

If your app doesn't already use Kotlin synthetics for view binding, see View binding for basic usage information.

Update the Gradle file

Like Android Extensions, Jetpack view binding is enabled on a module-by-module basis. For each module that uses view binding, set the viewBinding build option to true in the module-level build.gradle file:

android {
    ...
    buildFeatures {
        viewBinding true
    }
}

android {
    ...
    buildFeatures {
        viewBinding = true
    }
}

If your app doesn't use Parcelable features, remove the line that enables Kotlin Android Extensions:

plugins {
  id 'kotlin-android-extensions'
}

plugins {
    kotlin("android.extensions")
}

To learn more about enabling view binding in a module, see Setup instructions.

Update activity and fragment classes

With Jetpack view binding, a binding class is generated for each XML layout file that the module contains. The name of this binding class is the name of the XML file in Pascal case with the word Binding added at the end. For example, if the name of the layout file is result_profile.xml, the name of the generated binding class is ResultProfileBinding.

To use the generated binding classes instead of synthetic properties to reference views, change your activity and fragment classes by doing the following:

1. Remove all imports from kotlinx.android.synthetic.

2. Inflate an instance of the generated binding class for the activity or fragment to use.

   • For activities, follow the instructions in Use view binding in activities to inflate an instance in your activity's onCreate() method.
   • For fragments, follow the instructions in Use view binding in fragments to inflate an instance in your fragment's onCreateView() method.

3. Change all view references to use the binding class instance instead of synthetic properties:

// Reference to "name" TextView using synthetic properties.
name.text = viewModel.nameString

// Reference to "name" TextView using the binding class instance.
binding.name.text = viewModel.nameString

To learn more, see the Usage section in the view binding guide.