Android : how to draw a line without spikes using AChartEngine with fast incoming data

Overview

Three signals should be drawn as lines in a graph in a very fast way (10ms). Most of the time the graph shows three ramps without any error. Sometimes there are spikes in these ramps. This is what I have created:

• activity_temp_linegraph.xml: contains the attributes for the graph


• DynamicLineGraphActivity: which register the DynmicLineGraphPresenter and setContentView() to activity_temp_linegraph

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Problem

As it turns out most of the time the ramps are just looking fine. Sometimes there seems to be a race condition and there are spikes in the ramps. Where are these spikes coming from?

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DynmicLineGraph

private void initDataset() {
    mData0 = new TimeSeries(graphName1);
    ... // add more grapNames

    mDatasets = new XYMultipleSeriesDataset();
    mDatasets.addSeries(mData0);
    ... // add mData1 and mData2
}

private void initRenderer(Context context) {

   mRenderer0 = new XYSeriesRenderer();
   ... //setAttributes for example: setColor()

   mMultiRenderer = new XYMultipleSeriesRenderer();
   ... // setAttributes for example: setXTitle()

  mMultiRenderer.addSeriesRenderer(mRenderer0);
}

 // the code in the other addPointAndRepaint1-2 is the same
 public void addPointAndRepaint(PointXY p) {
   addPoint(p, mData2);
        repaint();

}

private synchronized void addPoint(PointXY p, TimeSeries mData) {

    mData.add(p.getX(), p.getY());

    // move XAxis boundaries if plot would exceed the right border
    if (p.getX() >= mXAxisMax) {  

        mXAxisMin = mXAxisMin + (p.getX() - mLastXvalue);
        mMultiRenderer.setXAxisMin(mXAxisMin);

        mXAxisMax = mXAxisMax + (p.getX() - mLastXvalue);
        mMultiRenderer.setXAxisMax(mXAxisMax);

    }
    mLastXvalue = p.getX();
   }

} // end addPoint 

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Simulated Data with a Thread

I have tried it with a thread, that draws linear rising lines. But even than, there are spikes.

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

    Thread thread = new Thread() {

        long initTimestamp = System.currentTimeMillis();

        public void run() {
            for (int i = 0; i < 10000; ++i) {
                try {
                    Thread.sleep(10);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }

                if (runB) {
                    t += 0.1;
                    t = (System.currentTimeMillis()- initTimestamp)/1000.0;

                    simVal+=0.1;

                    if (simVal>9) 
                        simVal=-6;

                    PointXY p0 = new PointXY(t     , simVal-2);
                    PointXY p1 = new PointXY(t+0.02, simVal-1);
                    PointXY p2 = new PointXY(t+0.04, simVal);

                    mLineGraph.addPointAndRepaint(p0);
                    mLineGraph.addPointAndRepaint1(p1);
                    mLineGraph.addPointAndRepaint2(p2);
                } } } };
    thread.start();
}

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What can I do? Where is the fault?