Anyone know why I'm getting a NPE from running this code?
Basically it appears to call to indicatorsProvder.getIndicator("SAR") fails - don't understand why - I also have the same issue with "ATR" (average true range) - wondering if the these base indicators can be called in a strategy but not through the indicator framework because they come direct from ta-lib and haven't been wrapped...

I'm raising this as a bug because I haven't got any traction on this issue for months.

 private IIndicatorContext context = null;
    private IIndicator PSAR = null;  

    private InputParameterInfo inputParas;
    
    private double accFactor = 0.1;
    private double accLimit = 0.1;
    
    public void onStart(IIndicatorContext context) 
    {        
        this.context = context;
        IIndicatorsProvider indicatorsProvider = context.getIndicatorsProvider();
        
        PSAR = indicatorsProvider.getIndicator("SAR");
                
        indicatorInfo = new IndicatorInfo("PSAR2", "Parabolic SAR", "Overlap Studies", true, false, true, 1, 2, 1);
        
        inputParas = new InputParameterInfo("PSAR Applied Price", InputParameterInfo.Type.DOUBLE);
        inputParas.setAppliedPrice(IIndicators.AppliedPrice.CLOSE);
        
        inputParameterInfos = new InputParameterInfo[] { inputParas };
       
        optInputParameterInfos = new OptInputParameterInfo[] 
        {
            new OptInputParameterInfo("Acceleration Factor", OptInputParameterInfo.Type.OTHER, new DoubleRangeDescription(accFactor, 0.001, 0.50, 0.001, 2)),
            new OptInputParameterInfo("Acceleration Limit", OptInputParameterInfo.Type.OTHER, new DoubleRangeDescription(accLimit, 0.1, 0.50, 0.005, 2))
        };
        
        outputParameterInfos = new OutputParameterInfo[] 
        {
            new OutputParameterInfo("PSAR", OutputParameterInfo.Type.DOUBLE, OutputParameterInfo.DrawingStyle.LINE) 
            {{
                setColor(Color.YELLOW);
            }}
           
        };
    }
    
    public IndicatorResult calculate(int startIndex, int endIndex) 
    {

        if (startIndex - getLookback() < 0) 
        {
            startIndex -= startIndex - getLookback();
        }
        
        if (startIndex > endIndex) 
        {
            return new IndicatorResult(0, 0);
        }   
        
        // next line throws Null Pointer Exception when the indicator is run   
        PSAR.setInputParameter(0, inputs);
        PSAR.setOutputParameter(0, outputs[0]);
        PSAR.setOptInputParameter(0, accFactor);
        PSAR.setOptInputParameter(1, accLimit); 
        
        IndicatorResult lrPSAR = PSAR.calculate(startIndex, endIndex);

It does not, you can check it by adding the following lines in the onStart method:

        IIndicatorsProvider ip = context.getIndicatorsProvider();
        context.getConsole().getOut().println(String.format("%s %s", ip.getIndicator("SAR"), ip.getIndicator("ATR")));

Make sure you assign the inputs value in IIndicator.setInputParameter
If you still face some problems, then please provide a full indicator which replicates the issue.

I have found the issue - ATR and SAR indicators require input of type PRICE (i.e. double[][] = new inputs[5][]) otherwise the indicator will produce NPE.

Might be helpful to list which indicators require price or double input (i.e. cannot accept IBar) in the indicator documentation.

In fact you can find this out programmatically:
https://www.dukascopy.com/wiki/#Indicator_metadata/Retrieve_indicator_metadata

Hi,
I'm facing the same issue as f451.
I'm trying to build a simple MA over ATR indicator but I have a NullPointerException.
Indeed ATR requires PRICE as input and as a consequence I feed the function setInputParameter with a double[5][] but it still causes the error.
I really don't understand why. Please help me!

public class SMAOverATRIndicator implements IIndicator {
    private IndicatorInfo indicatorInfo;
    private InputParameterInfo[] inputParameterInfos;
    private OptInputParameterInfo[] optInputParameterInfos;
    private OutputParameterInfo[] outputParameterInfos;
    private double[][][] inputs = new double[1][5][];
    private double[][] outputs = new double[2][];
    private IIndicatorContext context;
    private IIndicator atrIndicator;
    private IIndicator smaIndicator;
    private IConsole console; 
    
    public void onStart(IIndicatorContext context) {            
        //getting interfaces of ATR and SMA indicators
        IIndicatorsProvider indicatorsProvider = context.getIndicatorsProvider();
        atrIndicator = indicatorsProvider.getIndicator("ATR");
        if ( atrIndicator== null) {
            print("pb");
        }
        smaIndicator = indicatorsProvider.getIndicator("SMA");
        //inicator with one input, two optional params and two outputs
        indicatorInfo = new IndicatorInfo("SMA_ATR", "SMA over ATR", "My indicators",
                false, false, false, false, 1, 2, 2);
        //one input array of PRICE
        inputParameterInfos = new InputParameterInfo[] {new InputParameterInfo("Input data", InputParameterInfo.Type.PRICE)};
        //two optional params, one for every indicator
        optInputParameterInfos = new OptInputParameterInfo[] {new OptInputParameterInfo("ATR Time Period", OptInputParameterInfo.Type.OTHER,
                new IntegerRangeDescription(14, 2, 5000, 1)), new OptInputParameterInfo("SMA Time Period", OptInputParameterInfo.Type.OTHER,
                new IntegerRangeDescription(14, 2, 5000, 1))};
        //two output arrays, one for ATR and one for SMA over ATR
        outputParameterInfos = new OutputParameterInfo[] {new OutputParameterInfo("ATR line", OutputParameterInfo.Type.DOUBLE,
                OutputParameterInfo.LINE), new OutputParameterInfo("SMA line", OutputParameterInfo.Type.DOUBLE,
                OutputParameterInfo.LINE)};
        this.console = context.getConsole();
        //I check the type of input for ATR, this is PRICE as it is done in InputParamterInfo
        printIndicatorInfos(atrIndicator);
        printIndicatorInfos(smaIndicator);
    }

    public IndicatorResult calculate(int startIndex, int endIndex) {        
        //calculating atr
        int atrLookback = atrIndicator.getLookback();
        //first alocate buffer for atr results
        double[] atrOutput;
        if (startIndex > endIndex || atrLookback > endIndex) {    
            return new IndicatorResult(0, 0);
        } else {
            //take the greater value (startindex/ lookback)
            atrOutput = new double[endIndex - (atrLookback > startIndex ? atrLookback : startIndex) + 1];
        }
        //init atr indicator with input data and array for output
        // next line create a NullPointerException and I don't know : inputs[0] is a double[5][] as required for PRICE type!
        atrIndicator.setInputParameter(0, inputs[0]);
        atrIndicator.setOutputParameter(0, atrOutput);
        IndicatorResult atrResult = atrIndicator.calculate(startIndex, endIndex);

Replace the following code

    
public void setInputParameter(int index, Object array) {
        /*if (index==0) {
            inputs[index] = (double[][]) array;
        }*/
}

with

    
public void setInputParameter(int index, Object array) {
        if (index==0) {
            inputs[index] = (double[][]) array;
        }
}