Class to access resources inside ViewModels without worrying about Context.

ResourceHelper.kt

import android.graphics.drawable.Drawable
import android.os.Build
import androidx.annotation.ArrayRes
import androidx.annotation.BoolRes
import androidx.annotation.ColorRes
import androidx.annotation.DimenRes
import androidx.annotation.DrawableRes
import androidx.annotation.IntegerRes
import androidx.annotation.PluralsRes
import androidx.annotation.RequiresApi
import androidx.annotation.StringRes
import kotlinx.coroutines.flow.StateFlow

/**
 * This interface is used to provide resources to the application.
 *
 * It can safely be used in classes like ViewModels.
 */
interface ResourceHelper {
	fun getInt(@IntegerRes id: Int): Int
	fun getBoolean(@BoolRes id: Int): Boolean
	fun getColor(@ColorRes id: Int): Int
	fun getDimension(@DimenRes id: Int): Float
	fun getDimensionPixelOffset(@DimenRes id: Int): Int
	fun getDimensionPixelSize(@DimenRes id: Int): Int

	@RequiresApi(Build.VERSION_CODES.Q)
	fun getFloat(@DimenRes id: Int): Float
	fun getString(@StringRes id: Int): String
	fun getQuantityString(@PluralsRes id: Int, quantity: Int): String
	fun getText(@StringRes id: Int): CharSequence
	fun getQuantityText(@PluralsRes id: Int, quantity: Int): CharSequence
	fun getIntArray(@ArrayRes id: Int): IntArray
	fun getStringArray(@ArrayRes id: Int): Array<String>
	fun getTextArray(@ArrayRes id: Int): Array<CharSequence>
	fun getDrawable(@DrawableRes id: Int): Drawable?

	fun getIntStateFlow(@IntegerRes id: Int): StateFlow<Int>
	fun getBooleanStateFlow(@BoolRes id: Int): StateFlow<Boolean>
	fun getColorStateFlow(@ColorRes id: Int): StateFlow<Int>
	fun getDimensionStateFlow(@DimenRes id: Int): StateFlow<Float>
	fun getDimensionPixelOffsetStateFlow(@DimenRes id: Int): StateFlow<Int>
	fun getDimensionPixelSizeStateFlow(@DimenRes id: Int): StateFlow<Int>

	@RequiresApi(Build.VERSION_CODES.Q)
	fun getFloatStateFlow(@DimenRes id: Int): StateFlow<Float>
	fun getStringStateFlow(@StringRes id: Int): StateFlow<String>
	fun getQuantityStringStateFlow(@PluralsRes id: Int, quantity: Int): StateFlow<String>
	fun getTextStateFlow(@StringRes id: Int): StateFlow<CharSequence>
	fun getQuantityTextStateFlow(@PluralsRes id: Int, quantity: Int): StateFlow<CharSequence>
	fun getIntArrayStateFlow(@ArrayRes id: Int): StateFlow<IntArray>
	fun getStringArrayStateFlow(@ArrayRes id: Int): StateFlow<Array<String>>
	fun getTextArrayStateFlow(@ArrayRes id: Int): StateFlow<Array<CharSequence>>
	fun getDrawableStateFlow(@DrawableRes id: Int): StateFlow<Drawable?>
}

ResourceManagerImpl.kt

import android.content.ComponentCallbacks
import android.content.Context
import android.content.res.Configuration
import android.graphics.drawable.Drawable
import android.os.Build
import androidx.annotation.ArrayRes
import androidx.annotation.BoolRes
import androidx.annotation.ColorRes
import androidx.annotation.DimenRes
import androidx.annotation.DrawableRes
import androidx.annotation.IntegerRes
import androidx.annotation.PluralsRes
import androidx.annotation.RequiresApi
import androidx.annotation.StringRes
import androidx.core.content.ContextCompat
import kotlinx.coroutines.flow.MutableStateFlow
import kotlinx.coroutines.flow.StateFlow

class ResourceHelperImpl(
	private val context: Context,
) : ResourceHelper {

	private val _stateFlowByResource = mutableMapOf<TypedResource, MutableStateFlow<in Any?>>()


	init {
		context.registerComponentCallbacks(object : ComponentCallbacks {
			override fun onConfigurationChanged(newConfig: Configuration) {
				update()
			}

			override fun onLowMemory() {}
		})
	}


	override fun getInt(@IntegerRes id: Int): Int {
		return context.resources.getInteger(id)
	}

	override fun getBoolean(@BoolRes id: Int): Boolean {
		return context.resources.getBoolean(id)
	}

	override fun getColor(@ColorRes id: Int): Int {
		return ContextCompat.getColor(context, id)
	}

	override fun getDimension(@DimenRes id: Int): Float {
		return context.resources.getDimension(id)
	}

	override fun getDimensionPixelOffset(@DimenRes id: Int): Int {
		return context.resources.getDimensionPixelOffset(id)
	}

	override fun getDimensionPixelSize(@DimenRes id: Int): Int {
		return context.resources.getDimensionPixelSize(id)
	}

	@RequiresApi(Build.VERSION_CODES.Q)
	override fun getFloat(@DimenRes id: Int): Float {
		return context.resources.getFloat(id)
	}

	override fun getString(@StringRes id: Int): String {
		return context.resources.getString(id)
	}

	override fun getQuantityString(
		@PluralsRes
		id: Int,
		quantity: Int,
	): String {
		return context.resources.getQuantityString(id, quantity)
	}

	override fun getText(@StringRes id: Int): CharSequence {
		return context.resources.getText(id)
	}

	override fun getQuantityText(
		@PluralsRes
		id: Int,
		quantity: Int,
	): CharSequence {
		return context.resources.getQuantityText(id, quantity)
	}

	override fun getIntArray(@ArrayRes id: Int): IntArray {
		return context.resources.getIntArray(id)
	}

	override fun getStringArray(@ArrayRes id: Int): Array<String> {
		return context.resources.getStringArray(id)
	}

	override fun getTextArray(@ArrayRes id: Int): Array<CharSequence> {
		return context.resources.getTextArray(id)
	}

	override fun getDrawable(@DrawableRes id: Int): Drawable? {
		return ContextCompat.getDrawable(context, id)
	}

	override fun getIntStateFlow(@IntegerRes id: Int) = getOrCreateResourceStateFlow(
		typedResource = TypedResource.Integer(id),
		getResource = ::getInt,
	)

	override fun getBooleanStateFlow(@BoolRes id: Int) = getOrCreateResourceStateFlow(
		typedResource = TypedResource.Boolean(id),
		getResource = ::getBoolean,
	)

	override fun getColorStateFlow(@ColorRes id: Int) = getOrCreateResourceStateFlow(
		typedResource = TypedResource.Color(id),
		getResource = ::getColor,
	)

	override fun getDimensionStateFlow(@DimenRes id: Int) = getOrCreateResourceStateFlow(
		typedResource = TypedResource.Dimension(id),
		getResource = ::getDimension,
	)

	override fun getDimensionPixelOffsetStateFlow(@DimenRes id: Int) = getOrCreateResourceStateFlow(
		typedResource = TypedResource.DimensionPixelOffset(id),
		getResource = ::getDimensionPixelOffset,
	)

	override fun getDimensionPixelSizeStateFlow(@DimenRes id: Int) = getOrCreateResourceStateFlow(
		typedResource = TypedResource.DimensionPixelSize(id),
		getResource = ::getDimensionPixelSize,
	)

	@RequiresApi(Build.VERSION_CODES.Q)
	override fun getFloatStateFlow(@DimenRes id: Int) = getOrCreateResourceStateFlow(
		typedResource = TypedResource.Float(id),
		getResource = ::getFloat,
	)

	override fun getStringStateFlow(@StringRes id: Int) = getOrCreateResourceStateFlow(
		typedResource = TypedResource.String(id),
		getResource = ::getString,
	)

	override fun getQuantityStringStateFlow(
		@PluralsRes
		id: Int,
		quantity: Int,
	) = getOrCreateResourceStateFlow(
		typedResource = TypedResource.QuantityString(id, quantity),
		getResource = { getQuantityString(id, quantity) },
	)

	override fun getTextStateFlow(@StringRes id: Int) = getOrCreateResourceStateFlow(
		typedResource = TypedResource.Text(id),
		getResource = ::getText,
	)

	override fun getQuantityTextStateFlow(
		@PluralsRes
		id: Int,
		quantity: Int,
	) = getOrCreateResourceStateFlow(
		typedResource = TypedResource.QuantityText(id, quantity),
		getResource = { getQuantityText(id, quantity) },
	)

	override fun getIntArrayStateFlow(@ArrayRes id: Int) = getOrCreateResourceStateFlow(
		typedResource = TypedResource.IntArray(id),
		getResource = ::getIntArray,
	)

	override fun getStringArrayStateFlow(@ArrayRes id: Int) = getOrCreateResourceStateFlow(
		typedResource = TypedResource.StringArray(id),
		getResource = ::getStringArray,
	)

	override fun getTextArrayStateFlow(@ArrayRes id: Int) = getOrCreateResourceStateFlow(
		typedResource = TypedResource.TextArray(id),
		getResource = ::getTextArray,
	)

	override fun getDrawableStateFlow(@DrawableRes id: Int) = getOrCreateResourceStateFlow(
		typedResource = TypedResource.Drawable(id),
		getResource = ::getDrawable,
	)


	private fun update() {
		_stateFlowByResource.forEach { (typedResource, stateFlow) ->
			val id = typedResource.id

			stateFlow.value = when (typedResource) {
				is TypedResource.Integer              -> getInt(id)
				is TypedResource.Boolean              -> getBoolean(id)
				is TypedResource.Color                -> getColor(id)
				is TypedResource.Dimension            -> getDimension(id)
				is TypedResource.DimensionPixelOffset -> getDimensionPixelOffset(id)
				is TypedResource.DimensionPixelSize   -> getDimensionPixelSize(id)
				is TypedResource.Float                -> {
					if (Build.VERSION.SDK_INT < Build.VERSION_CODES.Q) {
						return
					}
					getFloat(id)
				}
				is TypedResource.String               -> getString(id)
				is TypedResource.QuantityString       -> getQuantityString(id, typedResource.quantity)
				is TypedResource.Text                 -> getText(id)
				is TypedResource.QuantityText         -> getQuantityText(id, typedResource.quantity)
				is TypedResource.IntArray             -> getIntArray(id)
				is TypedResource.StringArray          -> getStringArray(id)
				is TypedResource.TextArray            -> getTextArray(id)
				is TypedResource.Drawable             -> getDrawable(id)
			}
		}
	}

	private inline fun <T> getOrCreateResourceStateFlow(
		typedResource: TypedResource,
		getResource: (id: Int) -> T,
	): StateFlow<T> {
		if (typedResource in _stateFlowByResource) {
			return getResourceStateFlow(typedResource)
		}

		val value = getResource(typedResource.id)

		val stateFlow = MutableStateFlow(value)

		addResourceStateFlow(typedResource, stateFlow)

		return stateFlow
	}

	@Suppress("NOTHING_TO_INLINE", "UNCHECKED_CAST")
	private inline fun addResourceStateFlow(typedResource: TypedResource, stateFlow: MutableStateFlow<*>) {
		_stateFlowByResource[typedResource] = stateFlow as MutableStateFlow<in Any?>
	}

	@Suppress("NOTHING_TO_INLINE", "UNCHECKED_CAST")
	private inline fun <T> getResourceStateFlow(typedResource: TypedResource): StateFlow<T> {
		return _stateFlowByResource[typedResource] as StateFlow<T>
	}
}


private sealed interface TypedResource {

	val id: Int

	class Integer(@IntegerRes override val id: Int) : TypedResource

	class Boolean(@BoolRes override val id: Int) : TypedResource

	class Color(@ColorRes override val id: Int) : TypedResource

	class Dimension(@DimenRes override val id: Int) : TypedResource

	class DimensionPixelOffset(@DimenRes override val id: Int) : TypedResource

	class DimensionPixelSize(@DimenRes override val id: Int) : TypedResource

	class Float(@DimenRes override val id: Int) : TypedResource

	class String(@StringRes override val id: Int) : TypedResource

	class QuantityString private constructor(
		private val packedValue: Long
	) : TypedResource {

		@get:PluralsRes
		override val id: Int get() = packedValue.toInt()

		val quantity: Int get() = (packedValue shr 32).toInt()

		constructor(
			@PluralsRes
			id: Int,
			quantity: Int,
		) : this(
			packedValue = id.toLong() shl 32 or quantity.toLong(),
		)
	}

	class Text(@StringRes override val id: Int) : TypedResource

	class QuantityText private constructor(
		private val packedValue: Long
	) : TypedResource {

		@get:PluralsRes
		override val id: Int get() = packedValue.toInt()

		val quantity: Int get() = (packedValue shr 32).toInt()

		constructor(
			@PluralsRes
			id: Int,
			quantity: Int,
		) : this(
			packedValue = id.toLong() shl 32 or quantity.toLong(),
		)
	}

	class IntArray(@ArrayRes override val id: Int) : TypedResource

	class StringArray(@ArrayRes override val id: Int) : TypedResource

	class TextArray(@ArrayRes override val id: Int) : TypedResource

	class Drawable(@DrawableRes override val id: Int) : TypedResource
}