This example demonstrates the difference between FIFO DataSeries and standard DataSeries.
A FIFO series discards old data-points once a predefined number of points is met. This type of data-series is extremely efficient for scrolling charts, where you do not care about discarded (off-screen) data.

FIFO Series can be used in more ways than just scrolling a chart. For instance, reload the entire FIFO buffer each frame to get a Spectrum Analyzer style chart. Or, use FIFO series and set the XAxis.VisibleRange to achieve an ECG style chart.

To learn more, read the tutorials on Xamarin.Android adding realtime updates and Xamarin.iOS adding realtime updates.

Tip!
To switch to FIFO series just need to set FifoCapacity for DataSeries.

// FifoChartViewController.cs (Xamarin.iOS)

// FifoChartFragment.cs (Xamarin.Android)

using System;
using System.Timers;
using Android.Widget;
using SciChart.Charting.Model.DataSeries;
using SciChart.Charting.Visuals;
using SciChart.Charting.Visuals.Axes;
using SciChart.Charting.Visuals.RenderableSeries;
using SciChart.Data.Model;
using SciChart.Drawing.Common;
using Xamarin.Examples.Demo;
using Xamarin.Examples.Demo.Droid.Extensions;
using Xamarin.Examples.Demo.Droid.Fragments.Base;

namespace Xamarin.Examples.Demo.Droid.Fragments.Examples
{
    [ExampleDefinition("FIFO Chart", description:"Demonstrates a scrolling FIFO chart", icon: ExampleIcon.RealTime)]
    public class FifoChartFragment : ExampleBaseFragment
    {
        private const int FifoCapacity = 50;
        private const long TimerInterval = 30;
        private const double OneOverTimeInteval = 1.0/TimerInterval;
        private const double VisibleRangeMax = FifoCapacity*OneOverTimeInteval;
        private const double GrowBy = VisibleRangeMax*0.1;

        public override int ExampleLayoutId => Resource.Layout.Example_Single_Realtime_Chart_Fragment;

        private SciChartSurface Surface => View.FindViewById<SciChartSurface>(Resource.Id.chart);

        private readonly Random _random = new Random(42);

        private readonly XyDataSeries<double, double> _ds1 = new XyDataSeries<double, double> {FifoCapacityValue = FifoCapacity};
        private readonly XyDataSeries<double, double> _ds2 = new XyDataSeries<double, double> {FifoCapacityValue = FifoCapacity};
        private readonly XyDataSeries<double, double> _ds3 = new XyDataSeries<double, double> {FifoCapacityValue = FifoCapacity};

        private readonly DoubleRange _xVisibleRange = new DoubleRange(-GrowBy, VisibleRangeMax + GrowBy);

        private double _t = 0;
        private volatile bool _isRunning = false;
        private readonly object _syncRoot = new object();
        private Timer _timer;

        protected override void InitExample()
        {
            View.FindViewById<Button>(Resource.Id.start).Click += (sender, args) => Start();
            View.FindViewById<Button>(Resource.Id.pause).Click += (sender, args) => Pause();
            View.FindViewById<Button>(Resource.Id.reset).Click += (sender, args) => Reset();

            var xAxis = new NumericAxis(Activity) {VisibleRange = _xVisibleRange, AutoRange = AutoRange.Never};
            var yAxis = new NumericAxis(Activity) {GrowBy = new DoubleRange(0.1, 0.1), AutoRange = AutoRange.Always};

            var rs1 = new FastLineRenderableSeries {DataSeries = _ds1, StrokeStyle = new SolidPenStyle(0xFF4083B7, 2f.ToDip(Activity))};
            var rs2 = new FastLineRenderableSeries {DataSeries = _ds2, StrokeStyle = new SolidPenStyle(0xFFFFA500, 2f.ToDip(Activity))};
            var rs3 = new FastLineRenderableSeries {DataSeries = _ds3, StrokeStyle = new SolidPenStyle(0xFFE13219, 2f.ToDip(Activity))};

            using (Surface.SuspendUpdates())
            {
                Surface.XAxes.Add(xAxis);
                Surface.YAxes.Add(yAxis);
                Surface.RenderableSeries.Add(rs1);
                Surface.RenderableSeries.Add(rs2);
                Surface.RenderableSeries.Add(rs3);
            }
            Start();
        }

        private void Start()
        {
            if (!_isRunning)
            {
                _isRunning = true;
                _timer = new Timer(TimerInterval);
                _timer.Elapsed += OnTick;
                _timer.AutoReset = true;
                _timer.Start();
            }
        }

        private void Pause()
        {
            if (_isRunning)
            {
                _isRunning = false;
                _timer.Stop();
                _timer.Elapsed -= OnTick;
                _timer = null;
            }
        }

        private void Reset()
        {
            if (_isRunning)
            {
                Pause();
            }

            using (Surface.SuspendUpdates())
            {
                _t = 0;
                _xVisibleRange.SetMinMaxDouble(-GrowBy, VisibleRangeMax + GrowBy);

                _ds1.Clear();
                _ds2.Clear();
                _ds3.Clear();
            }
        }

        private void OnTick(object sender, ElapsedEventArgs e)
        {
            lock (_syncRoot)
            {
                if(!_isRunning) return;

                AppendData(_random);
            }
        }

        private void AppendData(Random random)
        {
            var y1 = 3.0*Math.Sin(2*Math.PI*1.4*_t) + random.NextDouble()*0.5;
            var y2 = 2.0*Math.Cos(2*Math.PI*0.8*_t) + random.NextDouble()*0.5;
            var y3 = 1.0*Math.Sin(2*Math.PI*2.2*_t) + random.NextDouble()*0.5;

            _ds1.Append(_t, y1);
            _ds2.Append(_t, y2);
            _ds3.Append(_t, y3);

            _t += OneOverTimeInteval;
            if (_t > VisibleRangeMax)
            {
                _xVisibleRange.SetMinMax(_xVisibleRange.Min + OneOverTimeInteval, _xVisibleRange.Max + OneOverTimeInteval);
            }
        }

        public override void OnDestroyView()
        {
            base.OnDestroyView();

            Reset();
        }

        public override void InitExampleForUiTest()
        {
            base.InitExampleForUiTest();

            lock (_syncRoot)
            {
                Reset(); 

                var random = new Random(42);
                for (var i = 0; i < FifoCapacity; i++)
                {
                    AppendData(random);
                }
            }
        }
    }
}

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