The ECG Monitor Demo showcases a real-time Android ECG/EKG heart-rate monitor app. A ECG trace is drawn from the left of the screen and when it reaches the right, it sweeps around: an effect which is common in ECG monitors. The example can run indefinitely as the FIFO chart series automatically discards points that are outside the viewport.

Tip!

Sweeping is achieved by overlaying two series, so that when the trace reaches the right edge, it wraps around again to the beginning.

// example_single_chart_fragment.xml

<?xml version="1.0" encoding="utf-8"?><!--*************************************************************************-->
<!-- SCICHART® Copyright SciChart Ltd. 2011-2016. All rights reserved. -->
<!--   -->
<!-- Web: http://www.scichart.com -->
<!-- Support: support@scichart.com -->
<!-- Sales:   sales@scichart.com -->
<!--  -->
<!-- example_single_chart_fragment.xml is part of the SCICHART® Examples. Permission is hereby granted -->
<!-- to modify, create derivative works, distribute and publish any part of this source -->
<!-- code whether for commercial, private or personal use. -->
<!--  -->
<!-- The SCICHART® examples are distributed in the hope that they will be useful, but -->
<!-- without any warranty. It is provided "AS IS" without warranty of any kind, either -->
<!-- expressed or implied. -->
<!--*************************************************************************-->

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <com.scichart.charting.visuals.SciChartSurface
        android:id="@+id/chart"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent" />

</LinearLayout>

// ECGMonitorFragment.java

//******************************************************************************
// SCICHART® Copyright SciChart Ltd. 2011-2017. All rights reserved.
//
// Web: http://www.scichart.com
// Support: support@scichart.com
// Sales:   sales@scichart.com
//
// ECGMonitorFragment.java is part of the SCICHART® Examples. Permission is hereby granted
// to modify, create derivative works, distribute and publish any part of this source
// code whether for commercial, private or personal use.
//
// The SCICHART® examples are distributed in the hope that they will be useful, but
// without any warranty. It is provided "AS IS" without warranty of any kind, either
// expressed or implied.
//******************************************************************************

package com.scichart.examples.fragments;

import android.os.Bundle;
import android.view.View;

import com.scichart.charting.model.dataSeries.IXyDataSeries;
import com.scichart.charting.visuals.SciChartSurface;
import com.scichart.charting.visuals.axes.AutoRange;
import com.scichart.charting.visuals.axes.IAxis;
import com.scichart.charting.visuals.renderableSeries.IRenderableSeries;
import com.scichart.core.framework.UpdateSuspender;
import com.scichart.data.model.DoubleRange;
import com.scichart.data.model.ISciList;
import com.scichart.examples.R;
import com.scichart.examples.data.DataManager;
import com.scichart.examples.fragments.base.ExampleBaseFragment;
import com.scichart.examples.utils.widgetgeneration.ImageViewWidget;
import com.scichart.examples.utils.widgetgeneration.Widget;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.TimeUnit;

import butterknife.BindView;

public class ECGMonitorFragment extends ExampleBaseFragment {

    private final static long TIME_INTERVAL = 20;

    private final IXyDataSeries<Double, Double> series0 = sciChartBuilder.newXyDataSeries(Double.class, Double.class).withFifoCapacity(3850).build();
    private final IXyDataSeries<Double, Double> series1 = sciChartBuilder.newXyDataSeries(Double.class, Double.class).withFifoCapacity(3850).build();

    private double[] sourceData;

    private int _currentIndex;
    private int _totalIndex;

    private TraceAOrB whichTrace = TraceAOrB.TraceA;

    private final ScheduledExecutorService scheduledExecutorService = Executors.newSingleThreadScheduledExecutor();
    private ScheduledFuture<?> schedule;

    private volatile boolean isRunning = true;

    @BindView(R.id.chart)
    SciChartSurface surface;

    @Override
    public List<Widget> getToolbarItems() {
        return new ArrayList<Widget>() {
            {
                add(new ImageViewWidget.Builder().setId(R.drawable.example_toolbar_play).setListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        isRunning = true;
                    }
                }).build());
                add(new ImageViewWidget.Builder().setId(R.drawable.example_toolbar_pause).setListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        isRunning = false;
                    }
                }).build());
            }
        };
    }

    @Override
    public boolean showDefaultModifiersInToolbar() {
        return false;
    }

    @Override
    protected int getLayoutId() {
        return R.layout.example_single_chart_fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        sourceData = DataManager.getInstance().loadWaveformData(getActivity());
    }

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        if (savedInstanceState != null) {
            _currentIndex = savedInstanceState.getInt("currentIndex");
            _totalIndex = savedInstanceState.getInt("totalIndex");
            final ISciList<Double> xValues0 = savedInstanceState.getParcelable("xValues0");
            final ISciList<Double> yValues0 = savedInstanceState.getParcelable("yValues0");
            final ISciList<Double> xValues1 = savedInstanceState.getParcelable("xValues1");
            final ISciList<Double> yValues1 = savedInstanceState.getParcelable("yValues1");
            series0.append(xValues0, yValues0);
            series1.append(xValues1, yValues1);
        }
    }

    @Override
    protected void initExample() {
        UpdateSuspender.using(surface, new Runnable() {
            @Override
            public void run() {
                final IAxis xBottomAxis = sciChartBuilder.newNumericAxis()
                        .withVisibleRange(new DoubleRange(0d, 10d))
                        .withAutoRangeMode(AutoRange.Never)
                        .withAxisTitle("Time (seconds)")
                        .build();

                final IAxis yRightAxis = sciChartBuilder.newNumericAxis()
                        .withVisibleRange(new DoubleRange(-0.5d, 1.5d))
                        .withAxisTitle("Voltage (mV)")
                        .build();

                final IRenderableSeries rs1 = sciChartBuilder.newLineSeries()
                        .withDataSeries(series0)
                        .build();

                final IRenderableSeries rs2 = sciChartBuilder.newLineSeries()
                        .withDataSeries(series1)
                        .build();

                Collections.addAll(surface.getXAxes(), xBottomAxis);
                Collections.addAll(surface.getYAxes(), yRightAxis);
                Collections.addAll(surface.getRenderableSeries(), rs1, rs2);
            }
        });

        schedule = scheduledExecutorService.scheduleWithFixedDelay(new Runnable() {
            @Override
            public void run() {
                UpdateSuspender.using(surface, appendDataRunnable);
            }
        }, 0, TIME_INTERVAL, TimeUnit.MILLISECONDS);
    }

    @Override
    public void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        isRunning = false;

        outState.putInt("currentIndex", _currentIndex);
        outState.putInt("totalIndex", _totalIndex);
        outState.putParcelable("xValues0", series0.getXValues());
        outState.putParcelable("yValues0", series0.getYValues());
        outState.putParcelable("xValues1", series1.getXValues());
        outState.putParcelable("yValues1", series1.getYValues());
    }

    private final Runnable appendDataRunnable = new Runnable() {
        @Override
        public synchronized void run() {
            if (isRunning) {
                for (int i = 0; i < 10; i++) {
                    appendPoint(400);
                }
            }
        }
    };

    private synchronized void appendPoint(double sampleRate) {
        if (_currentIndex >= sourceData.length) {
            _currentIndex = 0;
        }

        // Get the next voltage and time, and append to the chart
        double voltage = sourceData[_currentIndex];
        double time = (_totalIndex / sampleRate) % 10;

        if (whichTrace == TraceAOrB.TraceA) {
            series0.append(time, voltage);
            series1.append(time, Double.NaN);
        } else {
            series0.append(time, Double.NaN);
            series1.append(time, voltage);
        }

        _currentIndex++;
        _totalIndex++;

        if (_totalIndex % 4000 == 0) {
            whichTrace = whichTrace == TraceAOrB.TraceA ? TraceAOrB.TraceB : TraceAOrB.TraceA;
        }
    }

    @Override
    public void onDestroyView() {
        super.onDestroyView();

        if (schedule != null) {
            schedule.cancel(true);
        }
    }

    enum TraceAOrB {
        TraceA,
        TraceB
    }
}

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