andrei-fedorov · June 3, 2022 17:30 · Dec 5, 2017 · Dec 5, 2017 · Dec 4, 2017 · Dec 4, 2017
diff --git a/IconView.kt b/IconView.kt
@@ -15,18 +15,32 @@
 package com.example.playgamesshadows
 
 import android.content.Context
-import android.graphics.*
+import android.graphics.Bitmap
+import android.graphics.Bitmap.Config.*
+import android.graphics.Canvas
+import android.graphics.Color
+import android.graphics.ColorMatrix
+import android.graphics.ColorMatrixColorFilter
+import android.graphics.Paint
+import android.graphics.Rect
+import android.graphics.RectF
 import android.graphics.drawable.Drawable
 import android.renderscript.Allocation
 import android.renderscript.Element
 import android.renderscript.RenderScript
 import android.renderscript.ScriptIntrinsicBlur
-import android.support.annotation.FloatRange
+import android.support.annotation.AttrRes
+import android.support.annotation.StyleRes
 import android.support.v4.view.animation.FastOutSlowInInterpolator
 import android.util.AttributeSet
 import android.view.View
 
-class IconView(context: Context, attrs: AttributeSet) : View(context, attrs) {
+class IconView @JvmOverloads constructor(
+        context: Context,
+        attrs: AttributeSet,
+        @AttrRes defStyleAttr: Int = R.attr.iconViewStyle,
+        @StyleRes defStyleRes: Int = R.style.Widget_ShadowPlay_IconView)
+    : View(context, attrs, defStyleAttr, defStyleRes) {
 
     var icon: Drawable? = null
         set(value) {
@@ -38,29 +52,48 @@ class IconView(context: Context, attrs: AttributeSet) : View(context, attrs) {
     var offset = 0f
         set(value) {
             field = interp.getInterpolation(value.coerceIn(0f, 1f))
-            val scale = 0.85f + 0.15f * (1f - field)
+            val scale = scaleDown + (1f - scaleDown) * (1f - field)
             scaleX = scale
             scaleY = scale
             smallBlurShadowAlpha = (field * 255).toInt()
             bigBlurShadowAlpha = 255 - smallBlurShadowAlpha
-            // todo this should be in dps
-            shadowTranslate = 8f + 16f * (1f - field)
+            shadowTranslate = constantShadowTranslationY + variableShadowTranslationY * (1f - field)
             postInvalidateOnAnimation()
         }
 
-    private val padding = BIG_BLUR_RADIUS.toInt()
+    private var bigBlurShadow: Bitmap? = null
+    private var smallBlurShadow: Bitmap? = null
+    private var smallBlurShadowAlpha = 255
+    private var bigBlurShadowAlpha = 255
+    private var shadowTranslate = 0f
+    private var constantShadowTranslationY = 8f
+    private var variableShadowTranslationY = 16f
+    private var scaleDown = 0.85f
+    private var bigBlurRadius = 24f
+    private var smallBlurRadius = 8f
+    private var padding = bigBlurRadius.toInt()
     private val iconBounds = Rect()
     private val shadowBounds = RectF()
     private val shadowPaint = Paint(Paint.ANTI_ALIAS_FLAG).apply {
         colorFilter = ColorMatrixColorFilter(ColorMatrix().apply {
             setScale(SHADOW_SCALE_RGB, SHADOW_SCALE_RGB, SHADOW_SCALE_RGB, SHADOW_SCALE_ALPHA)
         })
     }
-    private var bigBlurShadow: Bitmap? = null
-    private var smallBlurShadow: Bitmap? = null
-    private var smallBlurShadowAlpha = 255
-    private var bigBlurShadowAlpha = 255
-    private var shadowTranslate = 0f
+
+    init {
+        val a = context.obtainStyledAttributes(attrs, R.styleable.IconView, defStyleAttr, defStyleRes)
+        constantShadowTranslationY = a.getDimension(R.styleable.IconView_constantShadowTranslationY,
+                constantShadowTranslationY)
+        variableShadowTranslationY = a.getDimension(R.styleable.IconView_variableShadowTranslationY,
+                variableShadowTranslationY)
+        scaleDown = a.getFloat(R.styleable.IconView_scaleDown, scaleDown).coerceIn(0f, 1f)
+        bigBlurRadius = a.getFloat(R.styleable.IconView_bigBlurRadius, bigBlurRadius)
+                .coerceIn(0f, 25f)
+        padding = bigBlurRadius.toInt()
+        smallBlurRadius = a.getFloat(R.styleable.IconView_smallBlurRadius, smallBlurRadius)
+                .coerceIn(0f, 25f)
+        a.recycle()
+    }
 
     override fun onSizeChanged(w: Int, h: Int, oldw: Int, oldh: Int) {
         val shadowTop = (h - w) / 2
@@ -91,31 +124,32 @@ class IconView(context: Context, attrs: AttributeSet) : View(context, attrs) {
     private fun createShadows() {
         if (icon == null || shadowBounds.width() == 0f) return
         if (bigBlurShadow == null) {
-            bigBlurShadow = Bitmap.createBitmap(shadowBounds.width().toInt(),
-                    shadowBounds.height().toInt(), Bitmap.Config.ARGB_8888)
+            bigBlurShadow = Bitmap.createBitmap(
+                    shadowBounds.width().toInt(), shadowBounds.height().toInt(), ARGB_8888)
         } else {
             bigBlurShadow?.eraseColor(Color.TRANSPARENT)
         }
-        createShadow(bigBlurShadow, BIG_BLUR_RADIUS)
         if (smallBlurShadow == null) {
-            smallBlurShadow = Bitmap.createBitmap(shadowBounds.width().toInt(),
-                    shadowBounds.height().toInt(), Bitmap.Config.ARGB_8888)
+            smallBlurShadow = Bitmap.createBitmap(
+                    shadowBounds.width().toInt(), shadowBounds.height().toInt(), ARGB_8888)
         } else {
             smallBlurShadow?.eraseColor(Color.TRANSPARENT)
         }
-        createShadow(smallBlurShadow, SMALL_BLUR_RADIUS)
+        val c = Canvas()
+        createShadow(bigBlurShadow, c, bigBlurRadius)
+        createShadow(smallBlurShadow, c, smallBlurRadius)
     }
 
-    private fun createShadow(bitmap: Bitmap?, @FloatRange(from = 0.0, to = 25.0) blurRadius: Float) {
-        val canvas = Canvas(bitmap)
+    private fun createShadow(bitmap: Bitmap?, canvas: Canvas, blurRadius: Float) {
+        canvas.setBitmap(bitmap)
         canvas.translate(padding - iconBounds.left.toFloat(),
                 padding - iconBounds.top.toFloat())
         icon?.draw(canvas)
         val rs = getRS(context)
         val blur = getBlur(context)
         val input = Allocation.createFromBitmap(rs, bitmap)
         val output = Allocation.createTyped(rs, input.type)
-        blur.setRadius(blurRadius)
+        blur.setRadius(blurRadius.coerceIn(0f, 25f))
         blur.setInput(input)
         blur.forEach(output)
         output.copyTo(bitmap)
@@ -126,8 +160,6 @@ class IconView(context: Context, attrs: AttributeSet) : View(context, attrs) {
     companion object {
         private const val SHADOW_SCALE_RGB = 0.85f
         private const val SHADOW_SCALE_ALPHA = 0.6f
-        private const val BIG_BLUR_RADIUS = 24f
-        private const val SMALL_BLUR_RADIUS = 16f
         private val interp = FastOutSlowInInterpolator()
 
         private var rs: RenderScript? = null

diff --git a/MainActivity.kt b/MainActivity.kt
@@ -38,8 +38,7 @@ class MainActivity : AppCompatActivity() {
         LinearSnapHelper().attachToRecyclerView(carousel)
         carousel.addOnScrollListener(object : RecyclerView.OnScrollListener() {
             override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
-                val w = recyclerView.width
-                val center = w / 2
+                val center = recyclerView.width / 2
                 (0 until recyclerView.childCount).forEach { i ->
                     val child = recyclerView.getChildAt(i) as? IconView ?: return@forEach
                     val cx = (child.left + child.right) / 2
@@ -49,15 +48,16 @@ class MainActivity : AppCompatActivity() {
             }
         })
 
-        loaderManager.initLoader(0, Bundle.EMPTY, object : LoaderManager.LoaderCallbacks<List<Drawable>> {
+        loaderManager.initLoader(0, Bundle.EMPTY,
+                object : LoaderManager.LoaderCallbacks<List<Drawable>> {
             override fun onCreateLoader(id: Int, args: Bundle?) = AppIconLoader(applicationContext)
 
             override fun onLoadFinished(loader: Loader<List<Drawable>>, icons: List<Drawable>) {
                 loading.visibility = View.GONE
                 carousel.adapter = AppAdapter(icons)
             }
 
-            override fun onLoaderReset(p0: Loader<List<Drawable>>?) {}
+            override fun onLoaderReset(loader: Loader<List<Drawable>>?) {}
         })
     }
 
@@ -80,7 +80,7 @@ class MainActivity : AppCompatActivity() {
             pm.getInstalledApplications(0).forEach { appInfo ->
                 launcherIntent.`package` = appInfo.packageName
                 // only show launch-able apps
-                if (pm.queryIntentActivities(launcherIntent, 0).size > 0) {
+                if (pm.queryIntentActivities(launcherIntent, 0).isNotEmpty()) {
                     launchableAppIcons += appInfo.loadUnbadgedIcon(pm)
                 }
             }
@@ -96,7 +96,7 @@ class MainActivity : AppCompatActivity() {
     class AppAdapter(private val icons: List<Drawable>) : RecyclerView.Adapter<AppViewHolder>() {
         override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): AppViewHolder {
             return AppViewHolder(LayoutInflater.from(parent.context)
-                    .inflate(R.layout.app_item, parent, false))
+                    .inflate(R.layout.app_item, parent, false) as IconView)
         }
 
         override fun onBindViewHolder(holder: AppViewHolder, position: Int) {
@@ -106,7 +106,5 @@ class MainActivity : AppCompatActivity() {
         override fun getItemCount() = icons.size
     }
 
-    class AppViewHolder(view: View) : RecyclerView.ViewHolder(view) {
-        val iconView = view as IconView
-    }
+    class AppViewHolder(val iconView: IconView) : RecyclerView.ViewHolder(iconView)
 }
diff --git a/attrs.xml b/attrs.xml
@@ -0,0 +1,27 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  Copyright (c) 2017 Google Inc.
+
+  Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
+  in compliance with the License. You may obtain a copy of the License at
+
+  http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software distributed under the License
+  is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
+  or implied. See the License for the specific language governing permissions and limitations under
+  the License.
+  -->
+<resources>
+    <declare-styleable name="AppTheme">
+        <attr name="iconViewStyle" format="reference" />
+    </declare-styleable>
+
+    <declare-styleable name="IconView">
+        <attr name="constantShadowTranslationY" format="dimension" />
+        <attr name="variableShadowTranslationY" format="dimension" />
+        <attr name="scaleDown" format="float" />
+        <attr name="bigBlurRadius" format="float" />
+        <attr name="smallBlurRadius" format="float" />
+    </declare-styleable>
+</resources>
diff --git a/blur_shadows.gif b/blur_shadows.gif
diff --git a/styles.xml b/styles.xml
@@ -0,0 +1,35 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  Copyright (c) 2017 Google Inc.
+
+  Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
+  in compliance with the License. You may obtain a copy of the License at
+
+  http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software distributed under the License
+  is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
+  or implied. See the License for the specific language governing permissions and limitations under
+  the License.
+  -->
+<resources>
+    <style name="AppTheme" parent="@style/Theme.AppCompat.Light.NoActionBar">
+        <item name="colorPrimary">@color/colorPrimary</item>
+        <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
+        <item name="colorAccent">@color/colorAccent</item>
+        <item name="android:windowBackground">@color/background</item>
+        <item name="android:windowLightStatusBar">true</item>
+        <item name="android:navigationBarColor">@color/colorPrimaryDark</item>
+        <item name="android:windowLightNavigationBar">true</item>
+    </style>
+
+    <style name="Widget.ShadowPlay" parent="@android:style/Widget" />
+
+    <style name="Widget.ShadowPlay.IconView">
+        <item name="constantShadowTranslationY">4dp</item>
+        <item name="variableShadowTranslationY">8dp</item>
+        <item name="scaleDown">0.85</item>
+        <item name="bigBlurRadius">25</item>
+        <item name="smallBlurRadius">8</item>
+    </style>
+</resources>
diff --git a/MainActivity.kt b/MainActivity.kt
@@ -22,6 +22,7 @@ import android.content.Loader
 import android.graphics.drawable.Drawable
 import android.os.Bundle
 import android.support.v7.app.AppCompatActivity
+import android.support.v7.widget.LinearSnapHelper
 import android.support.v7.widget.RecyclerView
 import android.view.LayoutInflater
 import android.view.View
@@ -34,6 +35,7 @@ class MainActivity : AppCompatActivity() {
         super.onCreate(savedInstanceState)
         setContentView(R.layout.activity_main)
         carousel.setHasFixedSize(true)
+        LinearSnapHelper().attachToRecyclerView(carousel)
         carousel.addOnScrollListener(object : RecyclerView.OnScrollListener() {
             override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
                 val w = recyclerView.width

diff --git a/blur_shadows.gif b/blur_shadows.gif
diff --git a/blur_shadows.gif b/blur_shadows.gif
diff --git a/IconView.kt b/IconView.kt
@@ -0,0 +1,150 @@
+/*
+ *  Copyright 2017 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file
+ * except in compliance with the License. You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the
+ * License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the specific language governing
+ * permissions and limitations under the License.
+ */
+
+package com.example.playgamesshadows
+
+import android.content.Context
+import android.graphics.*
+import android.graphics.drawable.Drawable
+import android.renderscript.Allocation
+import android.renderscript.Element
+import android.renderscript.RenderScript
+import android.renderscript.ScriptIntrinsicBlur
+import android.support.annotation.FloatRange
+import android.support.v4.view.animation.FastOutSlowInInterpolator
+import android.util.AttributeSet
+import android.view.View
+
+class IconView(context: Context, attrs: AttributeSet) : View(context, attrs) {
+
+    var icon: Drawable? = null
+        set(value) {
+            field = value
+            setIconBounds()
+            createShadows()
+        }
+
+    var offset = 0f
+        set(value) {
+            field = interp.getInterpolation(value.coerceIn(0f, 1f))
+            val scale = 0.85f + 0.15f * (1f - field)
+            scaleX = scale
+            scaleY = scale
+            smallBlurShadowAlpha = (field * 255).toInt()
+            bigBlurShadowAlpha = 255 - smallBlurShadowAlpha
+            // todo this should be in dps
+            shadowTranslate = 8f + 16f * (1f - field)
+            postInvalidateOnAnimation()
+        }
+
+    private val padding = BIG_BLUR_RADIUS.toInt()
+    private val iconBounds = Rect()
+    private val shadowBounds = RectF()
+    private val shadowPaint = Paint(Paint.ANTI_ALIAS_FLAG).apply {
+        colorFilter = ColorMatrixColorFilter(ColorMatrix().apply {
+            setScale(SHADOW_SCALE_RGB, SHADOW_SCALE_RGB, SHADOW_SCALE_RGB, SHADOW_SCALE_ALPHA)
+        })
+    }
+    private var bigBlurShadow: Bitmap? = null
+    private var smallBlurShadow: Bitmap? = null
+    private var smallBlurShadowAlpha = 255
+    private var bigBlurShadowAlpha = 255
+    private var shadowTranslate = 0f
+
+    override fun onSizeChanged(w: Int, h: Int, oldw: Int, oldh: Int) {
+        val shadowTop = (h - w) / 2
+        val iconTop = shadowTop + padding
+        val iconSize = w - padding - padding
+        iconBounds.set(padding, iconTop, padding + iconSize, iconTop + iconSize)
+        shadowBounds.set(0f, shadowTop.toFloat(), w.toFloat(), (shadowTop + w).toFloat())
+        setIconBounds()
+        createShadows()
+    }
+
+    override fun onDraw(canvas: Canvas) {
+        super.onDraw(canvas)
+        val saveCount = canvas.save()
+        canvas.translate(shadowBounds.left, shadowBounds.top + shadowTranslate)
+        shadowPaint.alpha = bigBlurShadowAlpha
+        canvas.drawBitmap(bigBlurShadow, 0f, 0f, shadowPaint)
+        shadowPaint.alpha = smallBlurShadowAlpha
+        canvas.drawBitmap(smallBlurShadow, 0f, 0f, shadowPaint)
+        canvas.restoreToCount(saveCount)
+        icon?.draw(canvas)
+    }
+
+    private fun setIconBounds() {
+        icon?.bounds = iconBounds
+    }
+
+    private fun createShadows() {
+        if (icon == null || shadowBounds.width() == 0f) return
+        if (bigBlurShadow == null) {
+            bigBlurShadow = Bitmap.createBitmap(shadowBounds.width().toInt(),
+                    shadowBounds.height().toInt(), Bitmap.Config.ARGB_8888)
+        } else {
+            bigBlurShadow?.eraseColor(Color.TRANSPARENT)
+        }
+        createShadow(bigBlurShadow, BIG_BLUR_RADIUS)
+        if (smallBlurShadow == null) {
+            smallBlurShadow = Bitmap.createBitmap(shadowBounds.width().toInt(),
+                    shadowBounds.height().toInt(), Bitmap.Config.ARGB_8888)
+        } else {
+            smallBlurShadow?.eraseColor(Color.TRANSPARENT)
+        }
+        createShadow(smallBlurShadow, SMALL_BLUR_RADIUS)
+    }
+
+    private fun createShadow(bitmap: Bitmap?, @FloatRange(from = 0.0, to = 25.0) blurRadius: Float) {
+        val canvas = Canvas(bitmap)
+        canvas.translate(padding - iconBounds.left.toFloat(),
+                padding - iconBounds.top.toFloat())
+        icon?.draw(canvas)
+        val rs = getRS(context)
+        val blur = getBlur(context)
+        val input = Allocation.createFromBitmap(rs, bitmap)
+        val output = Allocation.createTyped(rs, input.type)
+        blur.setRadius(blurRadius)
+        blur.setInput(input)
+        blur.forEach(output)
+        output.copyTo(bitmap)
+        input.destroy()
+        output.destroy()
+    }
+
+    companion object {
+        private const val SHADOW_SCALE_RGB = 0.85f
+        private const val SHADOW_SCALE_ALPHA = 0.6f
+        private const val BIG_BLUR_RADIUS = 24f
+        private const val SMALL_BLUR_RADIUS = 16f
+        private val interp = FastOutSlowInInterpolator()
+
+        private var rs: RenderScript? = null
+        fun getRS(context: Context): RenderScript {
+            if (rs == null) {
+                rs = RenderScript.create(context.applicationContext)
+            }
+            return rs!!
+        }
+
+        private var blur: ScriptIntrinsicBlur? = null
+        fun getBlur(context: Context): ScriptIntrinsicBlur {
+            if (blur == null) {
+                val rs = getRS(context)
+                blur = ScriptIntrinsicBlur.create(rs, Element.U8_4(rs))
+            }
+            return blur!!
+        }
+    }
+}
diff --git a/LICENSE b/LICENSE
@@ -0,0 +1,202 @@
+                                 Apache License
+                           Version 2.0, January 2004
+                        http://www.apache.org/licenses/
+
+   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
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+   APPENDIX: How to apply the Apache License to your work.
+
+      To apply the Apache License to your work, attach the following
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+   Copyright 2015 Google Inc.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
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+   See the License for the specific language governing permissions and
+   limitations under the License.
+
diff --git a/MainActivity.kt b/MainActivity.kt
@@ -0,0 +1,110 @@
+/*
+ *  Copyright 2017 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file
+ * except in compliance with the License. You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the
+ * License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the specific language governing
+ * permissions and limitations under the License.
+ */
+
+package com.example.playgamesshadows
+
+import android.app.LoaderManager
+import android.content.AsyncTaskLoader
+import android.content.Context
+import android.content.Intent
+import android.content.Loader
+import android.graphics.drawable.Drawable
+import android.os.Bundle
+import android.support.v7.app.AppCompatActivity
+import android.support.v7.widget.RecyclerView
+import android.view.LayoutInflater
+import android.view.View
+import android.view.ViewGroup
+import kotlinx.android.synthetic.main.activity_main.*
+
+class MainActivity : AppCompatActivity() {
+
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        setContentView(R.layout.activity_main)
+        carousel.setHasFixedSize(true)
+        carousel.addOnScrollListener(object : RecyclerView.OnScrollListener() {
+            override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
+                val w = recyclerView.width
+                val center = w / 2
+                (0 until recyclerView.childCount).forEach { i ->
+                    val child = recyclerView.getChildAt(i) as? IconView ?: return@forEach
+                    val cx = (child.left + child.right) / 2
+                    val offsetPx = Math.abs(center - cx)
+                    child.offset = offsetPx / center.toFloat()
+                }
+            }
+        })
+
+        loaderManager.initLoader(0, Bundle.EMPTY, object : LoaderManager.LoaderCallbacks<List<Drawable>> {
+            override fun onCreateLoader(id: Int, args: Bundle?) = AppIconLoader(applicationContext)
+
+            override fun onLoadFinished(loader: Loader<List<Drawable>>, icons: List<Drawable>) {
+                loading.visibility = View.GONE
+                carousel.adapter = AppAdapter(icons)
+            }
+
+            override fun onLoaderReset(p0: Loader<List<Drawable>>?) {}
+        })
+    }
+
+    private class AppIconLoader(context: Context) : AsyncTaskLoader<List<Drawable>>(context) {
+
+        private val icons = mutableListOf<Drawable>()
+
+        override fun onStartLoading() {
+            if (icons.isNotEmpty()) {
+                deliverResult(icons)
+            } else {
+                forceLoad()
+            }
+        }
+
+        override fun loadInBackground(): List<Drawable>? {
+            val pm = context.packageManager
+            val launchableAppIcons = mutableListOf<Drawable>()
+            val launcherIntent = Intent().apply { addCategory(Intent.CATEGORY_LAUNCHER) }
+            pm.getInstalledApplications(0).forEach { appInfo ->
+                launcherIntent.`package` = appInfo.packageName
+                // only show launch-able apps
+                if (pm.queryIntentActivities(launcherIntent, 0).size > 0) {
+                    launchableAppIcons += appInfo.loadUnbadgedIcon(pm)
+                }
+            }
+            return launchableAppIcons
+        }
+
+        override fun deliverResult(data: List<Drawable>) {
+            icons += data
+            super.deliverResult(data)
+        }
+    }
+
+    class AppAdapter(private val icons: List<Drawable>) : RecyclerView.Adapter<AppViewHolder>() {
+        override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): AppViewHolder {
+            return AppViewHolder(LayoutInflater.from(parent.context)
+                    .inflate(R.layout.app_item, parent, false))
+        }
+
+        override fun onBindViewHolder(holder: AppViewHolder, position: Int) {
+            holder.iconView.icon = icons[position]
+        }
+
+        override fun getItemCount() = icons.size
+    }
+
+    class AppViewHolder(view: View) : RecyclerView.ViewHolder(view) {
+        val iconView = view as IconView
+    }
+}
diff --git a/activity_main.xml b/activity_main.xml
@@ -0,0 +1,42 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  Copyright (c) 2017 Google Inc.
+
+  Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
+  in compliance with the License. You may obtain a copy of the License at
+
+  http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software distributed under the License
+  is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
+  or implied. See the License for the specific language governing permissions and limitations under
+  the License.
+  -->
+<FrameLayout
+    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"
+    tools:context=".MainActivity">
+
+    <ProgressBar
+        android:id="@+id/loading"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_gravity="center"
+        android:indeterminate="true" />
+
+    <android.support.v7.widget.RecyclerView
+        android:id="@+id/carousel"
+        android:layout_width="match_parent"
+        android:layout_height="match_parent"
+        android:clipToPadding="false"
+        android:orientation="horizontal"
+        android:paddingStart="96dp"
+        android:scrollbarStyle="insideOverlay"
+        android:scrollbars="horizontal"
+        app:layoutManager="LinearLayoutManager"
+        tools:context=".MainActivity" />
+
+</FrameLayout>
diff --git a/app_item.xml b/app_item.xml
@@ -0,0 +1,18 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  Copyright (c) 2017 Google Inc.
+
+  Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
+  in compliance with the License. You may obtain a copy of the License at
+
+  http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software distributed under the License
+  is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
+  or implied. See the License for the specific language governing permissions and limitations under
+  the License.
+  -->
+<com.example.playgamesshadows.IconView
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="224dp"
+    android:layout_height="match_parent" />