Android InputMethodService implementation that allows to build IME UI via Jetpack Compose

ComposedInputMethodService.kt

import android.content.Intent
import android.inputmethodservice.InputMethodService
import android.view.View
import androidx.annotation.CallSuper
import androidx.compose.ui.platform.AbstractComposeView
import androidx.compose.ui.platform.ViewCompositionStrategy
import androidx.lifecycle.Lifecycle
import androidx.lifecycle.LifecycleOwner
import androidx.lifecycle.ServiceLifecycleDispatcher
import androidx.lifecycle.ViewModelStore
import androidx.lifecycle.ViewModelStoreOwner
import androidx.lifecycle.setViewTreeLifecycleOwner
import androidx.lifecycle.setViewTreeViewModelStoreOwner
import androidx.savedstate.SavedStateRegistry
import androidx.savedstate.SavedStateRegistryController
import androidx.savedstate.SavedStateRegistryOwner
import androidx.savedstate.setViewTreeSavedStateRegistryOwner

/*
 * Dependencies:
 * `androidx.compose.ui:ui`
 * `androidx.lifecycle:lifecycle-common`
 * `androidx.lifecycle:lifecycle-viewmodel`
 * `androidx.lifecycle:lifecycle-service`
 * `androidx.savedstate:savedstate`
 */

/**
 * Base class for IME UI implemented via AndroidX Jetpack Compose
 *
 * @see InputMethodService
 * @see AbstractComposeView
 */
@Suppress("LeakingThis")
abstract class ComposedInputMethodService : InputMethodService(), LifecycleOwner, ViewModelStoreOwner, SavedStateRegistryOwner {
    abstract fun onCreateInputComposeView(): AbstractComposeView

    private val lifecycleDispatcher = ServiceLifecycleDispatcher(this)
    override val lifecycle: Lifecycle
        get() = lifecycleDispatcher.lifecycle

    override val viewModelStore = ViewModelStore()

    private val savedStateRegistryController = SavedStateRegistryController.create(this)
    override val savedStateRegistry: SavedStateRegistry
        get() = savedStateRegistryController.savedStateRegistry

    @CallSuper
    override fun onCreate() {
        lifecycleDispatcher.onServicePreSuperOnCreate()
        super.onCreate()
        savedStateRegistryController.performRestore(null)
    }

    @CallSuper
    override fun onBindInput() {
        lifecycleDispatcher.onServicePreSuperOnBind()
        super.onBindInput()
    }

    @CallSuper
    override fun onCreateInputView(): View {
        val view = onCreateInputComposeView().apply { // compose runtime exception when trying to create Abstract/ComposeView in abstract class
            setViewCompositionStrategy(ViewCompositionStrategy.DisposeOnLifecycleDestroyed(lifecycle))
        }

        window?.window?.decorView?.let { decorView ->
            decorView.setViewTreeLifecycleOwner(this)
            decorView.setViewTreeViewModelStoreOwner(this)
            decorView.setViewTreeSavedStateRegistryOwner(this)
        }

        return view
    }

    @CallSuper
    override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
        return super.onStartCommand(intent, flags, startId)
    }

    @CallSuper
    override fun onDestroy() {
        lifecycleDispatcher.onServicePreSuperOnDestroy()
        super.onDestroy()
    }
}