QuestMapView.cs

class QuestMapView : View
{
	const int BaseRadius = 5;

	Paint mainPaint;
	Paint linePaint;
	Drawable ripple;

	int radius;
	int textMargin;

	MapPinPosition[] pins;

	int[] shiverOffsets;
	ValueAnimator shiverAnimator;
	int shiverIndex;
	float currentShiverInterpolation;

	int[] heightVariants;

	public QuestMapView (Context context) :
		base (context)
	{
		Initialize ();
	}

	public QuestMapView (Context context, IAttributeSet attrs) :
		base (context, attrs)
	{
		Initialize ();
	}

	public QuestMapView (Context context, IAttributeSet attrs, int defStyle) :
		base (context, attrs, defStyle)
	{
		Initialize ();
	}

	public int CurrentPin { get; set; }

	void Initialize ()
	{
		var display = Resources.DisplayMetrics;
		// Numbers and dots
		mainPaint = new Paint {
			AntiAlias = true,
			Color = Color.White,
			TextSize = TypedValue.ApplyDimension (ComplexUnitType.Sp, 12, display),
		};
		linePaint = new Paint {
			AntiAlias = true,
			Color = Color.Argb (0xaa, 0xff, 0xff, 0xff),
		};
		linePaint.SetStyle (Paint.Style.Stroke);
		ripple = Context.Resources.GetDrawable (Resource.Drawable.ripple_background);

		radius = (int)TypedValue.ApplyDimension (ComplexUnitType.Dip, BaseRadius, display);
		textMargin = (int)TypedValue.ApplyDimension (ComplexUnitType.Dip, 10, display);

		heightVariants = new [] {
			0,
			(int)TypedValue.ApplyDimension (ComplexUnitType.Dip, 16, display),
			-(int)TypedValue.ApplyDimension (ComplexUnitType.Dip, 14, display),
			(int)TypedValue.ApplyDimension (ComplexUnitType.Dip, 9, display),
		};

		shiverOffsets = new [] {
			(int)TypedValue.ApplyDimension (ComplexUnitType.Dip, 9, display),
			(int)TypedValue.ApplyDimension (ComplexUnitType.Dip, 3, display),
			-(int)TypedValue.ApplyDimension (ComplexUnitType.Dip, 8, display),
			(int)TypedValue.ApplyDimension (ComplexUnitType.Dip, 4, display),
			-(int)TypedValue.ApplyDimension (ComplexUnitType.Dip, 7, display),
			(int)TypedValue.ApplyDimension (ComplexUnitType.Dip, 6, display),
		};
		shiverAnimator = ObjectAnimator.OfFloat (this, "scaleX", 0, 1);
		shiverAnimator.SetInterpolator (new TriangleWave ());
		shiverAnimator.SetDuration (8000);
		shiverAnimator.RepeatCount = ValueAnimator.Infinite;
		shiverAnimator.AnimationRepeat += (sender, e) => shiverIndex++;
	}

	public void SetPins (MapPinPosition[] pins)
	{
		this.pins = pins;
		Invalidate ();
		if (!shiverAnimator.IsStarted)
			shiverAnimator.Start ();
	}

	protected override void OnMeasure (int widthMeasureSpec, int heightMeasureSpec)
	{
		var height = PaddingTop + PaddingBottom;
		var vspace = Resources.DisplayMetrics.HeightPixels / 5;
		heightMeasureSpec = MeasureSpec.MakeMeasureSpec (height + vspace * (pins.Length - 1), MeasureSpecMode.Exactly);

		base.OnMeasure (widthMeasureSpec, heightMeasureSpec);
	}

	public override void Draw (Canvas canvas)
	{
		if (pins == null)
			return;

		var xcoords = new int [] {
			PaddingLeft,   // Left
			Width / 2,    // Center
			Width - PaddingRight // Right
		};

		var vspace = (Height - PaddingTop - PaddingBottom) / (pins.Length - 1);
		var currY = PaddingTop;

		for (int i = 0; i < pins.Length; i++) {
			var pin = pins [i];
			var x = xcoords [(int)pin];
			var y = currY + heightVariants[i % heightVariants.Length];

			// Apply shivering
			x = ApplyShivering (i, x);
			y = ApplyShivering (i + 1, y);

			// First draw joint line if needed
			if (i < pins.Length - 1) {
				var x1 = xcoords [(int)pins[i + 1]];
				var y1 = currY + vspace + heightVariants[(i + 1) % heightVariants.Length];
				x1 = ApplyShivering (i + 1, x1);
				y1 = ApplyShivering (i + 2, y1);
				canvas.DrawLine (x, y, x1, y1, linePaint);
			}

			// If the point is currently the selected one, draw the ripple current state
			if (CurrentPin == i) {
				var dur = shiverAnimator.Duration / 4;
				var fraction = (float)(shiverAnimator.CurrentPlayTime % dur) / dur;
				// Cheap interpolation
				fraction *= fraction;
				var rippleRadius = (int)(radius * (5 * fraction + 1)) - 8;
				var color = Color.Argb ((int)Math.Round (0x99 * (1 - fraction)),
				                        0xFF, 0xFF, 0xFF);
				((GradientDrawable)ripple).SetColor (color.ToArgb ());
				ripple.SetBounds (x - rippleRadius, y - rippleRadius, x + rippleRadius, y + rippleRadius);
				ripple.Draw (canvas);
			}

			// Then draw our point
			canvas.DrawCircle (x, y, radius, mainPaint);

			// Finally draw the step number
			var ty = y;
			var tx = x;

			if (pin == MapPinPosition.Right)
				tx += textMargin;
			else if (pin == MapPinPosition.Left)
				tx -= textMargin * 2;
			else {
				if (i == 0 || i == pins.Length - 1)
					ty += (i == 0) ? -textMargin : 2 * textMargin;
				else {
					var prev = pins [i - 1];
					var next = pins [i + 1];

					if (prev != next)
						ty -= textMargin;
					tx += prev == MapPinPosition.Left ? textMargin : -textMargin;
				}
			}
			canvas.DrawText ((i + 1).ToString (), tx, ty, mainPaint);

			currY += vspace;
		}
	}

	int ApplyShivering (int i, int value)
	{
		value += (int)Math.Round (shiverOffsets [(i + shiverIndex) % shiverOffsets.Length] * currentShiverInterpolation);
		return value;
	}

	public override float ScaleX {
		get {
			return currentShiverInterpolation;
		}
		set {
			currentShiverInterpolation = value;
			Invalidate ();
		}
	}
}