rename from Pixiview to Gallery

Gallery.Android/Renderers/AppShellSection/AppColorChangeRevealDrawable.cs

@@ -0,0 +1,98 @@
+using Android.Animation;
+using Android.Graphics;
+using Android.Graphics.Drawables;
+using System;
+using AColor = Android.Graphics.Color;
+
+namespace Gallery.Droid.Renderers.AppShellSection
+{
+    public class AppColorChangeRevealDrawable : AnimationDrawable
+    {
+        readonly Point _center;
+        float _progress;
+        bool _disposed;
+        ValueAnimator _animator;
+
+        internal AColor StartColor { get; }
+        internal AColor EndColor { get; }
+
+        public AppColorChangeRevealDrawable(AColor startColor, AColor endColor, Point center) : base()
+        {
+            StartColor = startColor;
+            EndColor = endColor;
+
+            if (StartColor != EndColor)
+            {
+                _animator = ValueAnimator.OfFloat(0, 1);
+                _animator.SetInterpolator(new Android.Views.Animations.DecelerateInterpolator());
+                _animator.SetDuration(500);
+                _animator.Update += OnUpdate;
+                _animator.Start();
+                _center = center;
+            }
+            else
+            {
+                _progress = 1;
+            }
+        }
+
+        public override void Draw(Canvas canvas)
+        {
+            if (_disposed)
+                return;
+
+            if (_progress == 1)
+            {
+                canvas.DrawColor(EndColor);
+                return;
+            }
+
+            canvas.DrawColor(StartColor);
+            var bounds = Bounds;
+            float centerX = _center.X;
+            float centerY = _center.Y;
+
+            float width = bounds.Width();
+            float distanceFromCenter = Math.Abs(width / 2 - _center.X);
+            float radius = (width / 2 + distanceFromCenter) * 1.1f;
+
+            var paint = new Paint
+            {
+                Color = EndColor
+            };
+
+            canvas.DrawCircle(centerX, centerY, radius * _progress, paint);
+        }
+
+        void OnUpdate(object sender, ValueAnimator.AnimatorUpdateEventArgs e)
+        {
+            _progress = (float)e.Animation.AnimatedValue;
+
+            InvalidateSelf();
+        }
+
+        protected override void Dispose(bool disposing)
+        {
+            if (_disposed)
+                return;
+
+            _disposed = true;
+
+            if (disposing)
+            {
+                if (_animator != null)
+                {
+                    _animator.Update -= OnUpdate;
+
+                    _animator.Cancel();
+
+                    _animator.Dispose();
+
+                    _animator = null;
+                }
+            }
+
+            base.Dispose(disposing);
+        }
+    }
+}