LivingCells color picker activity

color_picker.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="@dimen/margin_edge"
    >

    <View
        android:id="@+id/colorPickerSaturationNone"
        android:layout_width="@dimen/color_picker_strip_short_side"
        android:layout_height="0dp"
        app:layout_constraintBottom_toBottomOf="@id/colorPickerSaturationStrip"
        app:layout_constraintEnd_toStartOf="@id/colorPickerSaturationStrip"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="@id/colorPickerSaturationStrip"
        tools:background="@android:color/black"
        />

    <View
        android:id="@+id/colorPickerSaturationStrip"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:layout_margin="@dimen/margin_between_elements"
        app:layout_constraintBottom_toTopOf="@id/colorPickerHueWheel"
        app:layout_constraintEnd_toStartOf="@id/colorPickerSaturationFull"
        app:layout_constraintStart_toEndOf="@id/colorPickerSaturationNone"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_weight="1"
        tools:background="@android:color/holo_red_dark"
        />

    <View
        android:id="@+id/colorPickerSaturationFull"
        android:layout_width="@dimen/color_picker_strip_short_side"
        android:layout_height="0dp"
        app:layout_constraintBottom_toBottomOf="@id/colorPickerSaturationStrip"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toEndOf="@id/colorPickerSaturationStrip"
        app:layout_constraintTop_toTopOf="@id/colorPickerSaturationStrip"
        tools:background="@android:color/black"
        />

    <View
        android:id="@+id/colorPickerHueWheel"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:layout_margin="@dimen/margin_between_elements"
        app:layout_constraintBottom_toTopOf="@+id/colorPickerBrightnessStrip"
        app:layout_constraintDimensionRatio="1:1"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@id/colorPickerSaturationStrip"
        app:layout_constraintVertical_weight="4"
        tools:background="@android:color/holo_green_dark"
        />

    <View
        android:id="@+id/colorPickerBrightnessNone"
        android:layout_width="@dimen/color_picker_strip_short_side"
        android:layout_height="0dp"
        app:layout_constraintBottom_toBottomOf="@+id/colorPickerBrightnessStrip"
        app:layout_constraintEnd_toStartOf="@id/colorPickerBrightnessStrip"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="@+id/colorPickerBrightnessStrip"
        tools:background="@android:color/black"
        />

    <View
        android:id="@+id/colorPickerBrightnessStrip"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:layout_margin="@dimen/margin_between_elements"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toStartOf="@id/colorPickerBrightnessFull"
        app:layout_constraintStart_toEndOf="@+id/colorPickerBrightnessNone"
        app:layout_constraintTop_toBottomOf="@id/colorPickerHueWheel"
        app:layout_constraintVertical_weight="1"
        tools:background="@android:color/holo_red_dark"
        />

    <View
        android:id="@+id/colorPickerBrightnessFull"
        android:layout_width="@dimen/color_picker_strip_short_side"
        android:layout_height="0dp"
        app:layout_constraintBottom_toBottomOf="@+id/colorPickerBrightnessStrip"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toEndOf="@id/colorPickerBrightnessStrip"
        app:layout_constraintTop_toTopOf="@+id/colorPickerBrightnessStrip"
        tools:background="@android:color/black"
        />

    <View
        android:id="@+id/colorPickerSelectedColor"
        android:layout_width="48dp"
        android:layout_height="48dp"
        app:layout_constraintBottom_toBottomOf="@+id/colorPickerHueWheel"
        app:layout_constraintEnd_toEndOf="@+id/colorPickerHueWheel"
        app:layout_constraintStart_toStartOf="@+id/colorPickerHueWheel"
        app:layout_constraintTop_toTopOf="@+id/colorPickerHueWheel"
        tools:background="@android:color/holo_blue_dark"
        />
</androidx.constraintlayout.widget.ConstraintLayout>

ColorPickerActivity.kt

package com.malcolmsoft.livingcells

import android.app.Activity
import android.content.Intent
import android.content.res.Configuration
import android.graphics.Color
import android.graphics.SweepGradient
import android.graphics.drawable.ColorDrawable
import android.graphics.drawable.Drawable
import android.graphics.drawable.GradientDrawable
import android.graphics.drawable.GradientDrawable.Orientation
import android.graphics.drawable.InsetDrawable
import android.graphics.drawable.LayerDrawable
import android.graphics.drawable.ShapeDrawable
import android.graphics.drawable.shapes.OvalShape
import android.os.Bundle
import android.view.Menu
import android.view.MenuItem
import android.view.MotionEvent
import android.view.View
import androidx.appcompat.app.AppCompatActivity
import androidx.core.content.res.ResourcesCompat
import androidx.core.view.doOnLayout
import androidx.lifecycle.Observer
import androidx.lifecycle.ViewModelProviders
import kotlin.math.PI
import kotlin.math.atan2
import kotlin.math.hypot

class ColorPickerActivity : AppCompatActivity() {
    private lateinit var model: ColorPickerModel

    private val saturationNoneViewDrawable = ColorDrawable()
    private val saturationStripViewDrawable = GradientDrawable()
    private val saturationFullViewDrawable = ColorDrawable()
    private val brightnessNoneViewDrawable = ColorDrawable()
    private val brightnessStripViewDrawable = GradientDrawable()
    private val brightnessFullViewDrawable = ColorDrawable()
    private val selectedColorViewDrawable = ShapeDrawable(OvalShape())

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.color_picker)

        model = ViewModelProviders.of(this)[ColorPickerModel::class.java]
        model.setInitialColor(intent.getIntExtra(EXTRA_COLOR, 0xFFFFFF))

        val saturationNoneView: View = findViewById(R.id.colorPickerSaturationNone)
        saturationNoneView.setOnClickListener {
            model.setSaturation(0F)
        }
        saturationNoneView.background = saturationNoneViewDrawable.makeOutlined()

        val saturationStripView: View = findViewById(R.id.colorPickerSaturationStrip)
        saturationStripView.setOnTouchListener { v, event ->
            model.setSaturation(getStripPositionFraction(v, event))
            true
        }
        saturationStripView.background = saturationStripViewDrawable.makeOutlined()

        val saturationFullView: View = findViewById(R.id.colorPickerSaturationFull)
        saturationFullView.setOnClickListener {
            model.setSaturation(1F)
        }
        saturationFullView.background = saturationFullViewDrawable.makeOutlined()

        val brightnessNoneView: View = findViewById(R.id.colorPickerBrightnessNone)
        brightnessNoneView.setOnClickListener {
            model.setBrightness(0F)
        }
        brightnessNoneView.background = brightnessNoneViewDrawable.makeOutlined()

        val brightnessStripView: View = findViewById(R.id.colorPickerBrightnessStrip)
        brightnessStripView.background = brightnessStripViewDrawable.makeOutlined()
        brightnessStripView.setOnTouchListener { v, event ->
            model.setBrightness(getStripPositionFraction(v, event))
            true
        }

        val brightnessFullView: View = findViewById(R.id.colorPickerBrightnessFull)
        brightnessFullView.setOnClickListener {
            model.setBrightness(1F)
        }
        brightnessFullView.background = brightnessFullViewDrawable.makeOutlined()

        val hueWheelView: View = findViewById(R.id.colorPickerHueWheel)
        hueWheelView.doOnLayout {
            it.background = ShapeDrawable(OvalShape()).apply {
                paint.apply {
                    val colors = listOf(0xFFFF0000, 0xFFFF00FF, 0xFF0000FF, 0xFF00FFFF, 0xFF00FF00, 0xFFFFFF00, 0xFFFF0000)
                        .map(Number::toInt)
                        .toIntArray()
                    shader = SweepGradient(it.width.toFloat() / 2, it.height.toFloat() / 2, colors, null)
                }
            }
        }
        hueWheelView.setOnTouchListener { v, event ->
            val radius = v.width.toFloat() / 2
            val x = event.x - radius
            val y = event.y - radius
            if (hypot(x, y) > radius) return@setOnTouchListener false

            val angle = -atan2(y, x)
            var angleDegrees = angle * 360 / (2 * PI.toFloat())
            if (angleDegrees < 0) angleDegrees += 360F

            model.setHue(angleDegrees)

            true
        }

        val selectedColorView: View = findViewById(R.id.colorPickerSelectedColor)
        selectedColorView.background = selectedColorViewDrawable.makeOutlined()

        model.colorComponentsLiveData.observe(this, Observer(::generateBackgrounds))
    }

    private fun Drawable.makeOutlined(): LayerDrawable {
        val outlineColor = ResourcesCompat.getColor(resources, R.color.color_picker_element_outline, null)
        val outlineDrawable = when (this) {
            is ShapeDrawable -> ShapeDrawable(shape.clone()).apply {
                paint.color = outlineColor
            }
            else -> ColorDrawable(outlineColor)
        }

        return LayerDrawable(
            arrayOf(
                outlineDrawable,
                InsetDrawable(this, resources.getDimensionPixelSize(R.dimen.color_picker_element_stroke_width))
            )
        )
    }

    private fun getStripPositionFraction(view: View, event: MotionEvent): Float {
        val value = if (resources.configuration.orientation == Configuration.ORIENTATION_LANDSCAPE) {
            1F - event.y / view.height
        } else {
            event.x / view.width
        }
        return value.coerceIn(0F, 1F)
    }

    private fun generateBackgrounds(colorComponents: FloatArray) {
        fun getComponentExtremes(index: Int): Pair<Int, Int> {
            val buf = colorComponents.clone()
            buf[index] = 0F
            val zeroComponentColor = Color.HSVToColor(buf)
            buf[index] = 1F
            val fullComponentColor = Color.HSVToColor(buf)

            return Pair(zeroComponentColor, fullComponentColor)
        }

        val gradientOrientation = if (resources.configuration.orientation == Configuration.ORIENTATION_LANDSCAPE) {
            Orientation.BOTTOM_TOP
        } else {
            Orientation.LEFT_RIGHT
        }

        val (zeroSaturationColor, fullSaturationColor) = getComponentExtremes(1)
        saturationNoneViewDrawable.color = zeroSaturationColor
        saturationFullViewDrawable.color = fullSaturationColor

        saturationStripViewDrawable.orientation = gradientOrientation
        saturationStripViewDrawable.colors = intArrayOf(zeroSaturationColor, fullSaturationColor)

        val (zeroBrightnessColor, fullBrightnessColor) = getComponentExtremes(2)
        brightnessNoneViewDrawable.color = zeroBrightnessColor
        brightnessFullViewDrawable.color = fullBrightnessColor

        brightnessStripViewDrawable.orientation = gradientOrientation
        brightnessStripViewDrawable.colors = intArrayOf(zeroBrightnessColor, fullBrightnessColor)

        selectedColorViewDrawable.paint.color = Color.HSVToColor(colorComponents)

        for (drawable in listOf(
            saturationNoneViewDrawable,
            saturationStripViewDrawable,
            saturationFullViewDrawable,
            brightnessNoneViewDrawable,
            brightnessStripViewDrawable,
            brightnessFullViewDrawable,
            selectedColorViewDrawable
        )) {
            drawable.invalidateSelf()
        }
    }

    override fun onCreateOptionsMenu(menu: Menu): Boolean {
        menuInflater.inflate(R.menu.color_picker, menu)
        return true
    }

    override fun onOptionsItemSelected(item: MenuItem) = when (item.itemId) {
        R.id.menu_color_picker_confirm -> {
            returnResult()
            true
        }
        else -> false
    }

    private fun returnResult() {
        setResult(Activity.RESULT_OK, Intent().apply {
            putExtra(EXTRA_COLOR, model.color)
        })
        finish()
    }

    companion object {
        const val CATEGORY_COLOR = "org.openintents.category.COLOR"
        const val INTENT_PICK_COLOR = "org.openintents.action.PICK_COLOR"
        const val EXTRA_COLOR = "org.openintents.extra.COLOR"
    }
}

ColorPickerModel.kt

package com.malcolmsoft.livingcells

import android.app.Application
import android.graphics.Color
import androidx.annotation.ColorInt
import androidx.lifecycle.AndroidViewModel
import androidx.lifecycle.LiveData
import androidx.lifecycle.MutableLiveData
import com.malcolmsoft.utils.LiveDataPublishingProperty

class ColorPickerModel(application: Application) : AndroidViewModel(application) {
    private var initialized = false

    val colorComponentsLiveData: LiveData<FloatArray> = MutableLiveData<FloatArray>()
    private var colorComponents: FloatArray by LiveDataPublishingProperty(FloatArray(3), colorComponentsLiveData)

    val color
        get() = Color.HSVToColor(colorComponents)

    fun setInitialColor(@ColorInt color: Int) {
        if (initialized) return

        colorComponents = FloatArray(3).apply {
            Color.colorToHSV(color, this)
        }
        initialized = true
    }

    fun setHue(value: Float) = setComponent(0, value)

    fun setSaturation(value: Float) = setComponent(1, value)

    fun setBrightness(value: Float) = setComponent(2, value)

    private fun setComponent(index: Int, value: Float) {
        colorComponents = colorComponents.clone().apply {
            this[index] = value
        }
    }
}

LiveDataPublishingProperty.kt

package com.malcolmsoft.utils

import androidx.lifecycle.LiveData
import androidx.lifecycle.MutableLiveData
import kotlin.properties.ReadWriteProperty
import kotlin.reflect.KProperty

class LiveDataPublishingProperty<T>(private var value: T, liveData: LiveData<T>) : ReadWriteProperty<Any, T> {
    private val mutableLiveData = liveData as MutableLiveData<T>

    init {
        mutableLiveData.setValueFromAnyThread(value)
    }

    override fun getValue(thisRef: Any, property: KProperty<*>): T = synchronized(thisRef) {
        value
    }

    override fun setValue(thisRef: Any, property: KProperty<*>, value: T) = synchronized(thisRef) {
        this.value = value
        mutableLiveData.setValueFromAnyThread(value)
    }
}

LiveDataUtils.kt

package com.malcolmsoft.utils

import android.os.Looper
import androidx.lifecycle.LiveData
import androidx.lifecycle.MediatorLiveData
import androidx.lifecycle.MutableLiveData
import androidx.lifecycle.Transformations
import java.util.concurrent.ExecutorService
import java.util.concurrent.atomic.AtomicReference

private fun <T, R> makeInputNullable(fn: (T) -> R?): (T?) -> R? = { input -> input?.let { fn(input) } }

fun <T, R> LiveData<T>.map(fn: (T) -> R?): LiveData<R> = Transformations.map(this, makeInputNullable(fn))

fun <T, R> LiveData<T>.switchMap(fn: (T) -> LiveData<R>): LiveData<R> = Transformations.switchMap(this, makeInputNullable(fn))

fun <T> MutableLiveData<T>.setValueFromAnyThread(value: T?) {
    if (Looper.getMainLooper() == Looper.myLooper()) {
        this.value = value
    } else {
        postValue(value)
    }
}

fun <T, U, R> combine(first: LiveData<T>, second: LiveData<U>, executor: ExecutorService? = null, merger: (T?, U?) -> R?): MediatorLiveData<R> =
    combine<T, U, Nothing, Nothing, R>(first, second, executor = executor) { firstValue, secondValue, _, _ ->
        merger(firstValue, secondValue)
    }

fun <T, U, V, W, R> combine(
    first: LiveData<T>,
    second: LiveData<U>,
    third: LiveData<V>? = null,
    fourth: LiveData<W>? = null,
    executor: ExecutorService? = null,
    merger: (T?, U?, V?, W?) -> R?
): MediatorLiveData<R> {
    fun MediatorLiveData<R>.calculate(firstValue: T?, secondValue: U?, thirdValue: V?, fourthValue: W?) {
        if (executor != null) {
            executor.submit {
                merger(firstValue, secondValue, thirdValue, fourthValue)?.let { result ->
                    postValue(result)
                }
            }
        } else {
            merger(firstValue, secondValue, thirdValue, fourthValue)?.let { result ->
                value = result
            }
        }
    }

    return MediatorLiveData<R>().apply {
        addSource(first) { calculate(it, second.value, third?.value, fourth?.value) }
        addSource(second) { calculate(first.value, it, third?.value, fourth?.value) }
        third?.let {
            addSource(third) { calculate(first.value, second.value, it, fourth?.value) }
        }
        fourth?.let {
            addSource(fourth) { calculate(first.value, second.value, third?.value, it) }
        }
    }
}

class UiMessage<T>(value: T) {
    private val reference = AtomicReference<T>(value)

    fun takeValue(): T? = reference.getAndSet(null)
}