Drawing Lines on Chart by User Interaction

Hi Ray,

Unfortunately we don’t support such functionality out of the box for now but we’re planning to add such functionality in one of our future releases. For now you can create and use custom modifier which implements desired functionality.

I have created a simple prototype which creates LineAnnotation on drag. Here is my code:

public class LineDrawingModifier extends TouchModifierBase {
    private final PenStyle srokeStyle = new PenStyle(Color.RED, true, 10);
    private LineAnnotation lineAnnotation;

    @Override
    protected boolean onTouchDown(ModifierTouchEventArgs args) {
        final float x = args.e.getX();
        final float y = args.e.getY();

        lineAnnotation = new LineAnnotation(getContext());

        lineAnnotation.setStroke(srokeStyle);

        getParentSurface().getAnnotations().add(lineAnnotation);

        setLineStart(lineAnnotation, x, y);
        setLineEnd(lineAnnotation, x, y);

        return true;
    }

    @Override
    protected boolean onTouchMove(ModifierTouchEventArgs args) {
        if (lineAnnotation != null) {
            final float x = args.e.getX();
            final float y = args.e.getY();

            setLineEnd(lineAnnotation, x, y);

            return true;
        } else
            return super.onTouchMove(args);
    }

    @Override
    protected boolean onTouchUp(ModifierTouchEventArgs args) {
        if (lineAnnotation != null) {
            final float x = args.e.getX();
            final float y = args.e.getY();

            setLineEnd(lineAnnotation, x, y);

            return true;
        } else
            return super.onTouchUp(args);
    }

    private static void setLineStart(@NonNull LineAnnotation lineAnnotation, float xStart, float yStart) {
        final Comparable xValue = lineAnnotation.getXAxis().getDataValue(xStart);
        final Comparable yValue = lineAnnotation.getYAxis().getDataValue(yStart);

        lineAnnotation.setX1(xValue);
        lineAnnotation.setY1(yValue);
    }

    private static void setLineEnd(@NonNull LineAnnotation lineAnnotation, float xEnd, float yEnd) {
        final Comparable xValue = lineAnnotation.getXAxis().getDataValue(xEnd);
        final Comparable yValue = lineAnnotation.getYAxis().getDataValue(yEnd);

        lineAnnotation.setX2(xValue);
        lineAnnotation.setY2(yValue);
    }

}

Hope this will help you!

Best regards,
Yura.