如何在由graphview库绘制的图形中的特定点上添加注释？

Question

我正在研究从服务器获取ECG值并在Android中绘制ECG图的项目。现在，我能够绘制图形，但是无法在其上添加注释。就像我想在特定数据点上添加“ NP”（正常脉冲）和AP（异常脉冲）。 我正在使用这段代码从服务器获取数据并绘制图形。  私有无效GetECGProcessedData（）{

    final ProgressDialog progressDialog = new ProgressDialog(this);
    progressDialog.setMessage("Send Report for Processing....!!!");
    progressDialog.show();
    progressDialog.setCancelable(true);


    StringRequest stringRequest = new StringRequest(Request.Method.POST, "http://20.188.98.39/cardiccare/get_p.php",
            new Response.Listener<String>() {
                @Override
                public void onResponse(String response) {
                    progressDialog.dismiss();

                    try {
                        JSONObject obj = new JSONObject(response);
                        JSONArray array = obj.getJSONArray("response_array");
                        for (int i = 0; i < array.length(); i++) {
                            JSONObject jsonObject = array.getJSONObject(i);
                            Pdata = jsonObject.getString("pdata");
                        }

                        // Storing value in array after removing the comma in the string.
                        final String[] elements = Pdata.split(",");
                        fixedLenghtList = Arrays.asList(elements);
                        listOfString = new ArrayList<String>(fixedLenghtList);


                        // we get graph view instance
                        GraphView graph = (GraphView) findViewById(R.id.graphview);
                        // set manual X bounds
                        graph.getViewport().setYAxisBoundsManual(true);

                        // first series is a line
                        DataPoint[] points = new DataPoint[listOfString.size()];
                        for (int i = 0; i < points.length; i++) {
                            points[i] = new DataPoint(i, Double.parseDouble(listOfString.get(i)));
                        }
                        LineGraphSeries<DataPoint> series = new LineGraphSeries<>(points);

                        // set manual X bounds
                        graph.getViewport().setYAxisBoundsManual(true);
                        graph.getViewport().setMinY(-20);
                        graph.getViewport().setMaxY(20);

                        graph.getViewport().setXAxisBoundsManual(true);
                        graph.getViewport().setMinX(4);
                        graph.getViewport().setMaxX(3700);

                        // enable scaling and scrolling
                        graph.getViewport().setScalable(true);
                        graph.getViewport().setScalableY(true);
                        graph.addSeries(series);

                    } catch (JSONException e) {
                        e.printStackTrace();
                    }
                }
            },
            new Response.ErrorListener() {
                @Override
                public void onErrorResponse(VolleyError error) {
                    progressDialog.dismiss();
                    Toast.makeText(MainActivity.this, error.getMessage(), Toast.LENGTH_LONG).show();
                }
            }) {

        @Override
        protected Map<String, String> getParams() throws AuthFailureError {
            Map<String, String> params = new HashMap<>();
            params.put("rid", String.valueOf(1143));


            return params;
        }
    };
    RequestQueue requestQueue = Volley.newRequestQueue(this);
    requestQueue.add(stringRequest);
    PlotECG();
}