How can i plot a linechart using the data in textview and this data is being generated by a heart rate measurment instrument

Question

As per now i have added values manually in this piece of code. But I need a graph according to the values I get from the instrument.This textview data is called from textview data in devicecontrolactivity class using intent. Have used MPandroidchartv3.0.3.

Thank you _/\_

public class GraphView extends Activity {
    LineChart lineChart;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.streaming);
        TextView textView = (TextView) findViewById(R.id.textview1);
        Bundle b = getIntent().getExtras();
        String received = b.getString("value");
        //this textview contains the data which needs to be plotted
        textView.setText(received);
        //back button to get back to devicecontrolactivity
        Button button = (Button) findViewById(R.id.buttoni);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                backActivity();
            }
        });
        lineChart = (LineChart) findViewById(R.id.linegraph);
        LineDataSet lineDataSet = new LineDataSet(datavalues(), "Data Set");
        //Arraylist of linedatasets
        ArrayList < ILineDataSet > dataSets = new ArrayList < > ();
        dataSets.add(lineDataSet);
        LineData Data = new LineData(dataSets);
        lineChart.setData(Data);
        lineChart.invalidate();
    }
    //intent method to get back to devicecontrolactivity
    public void backActivity() {
        Intent intent1 = new Intent(this, DeviceControlActivity.class);
        startActivity(intent1);
    }
    //Array for dataentries for plotting data as linechart
    public ArrayList < Entry > datavalues() {
        ArrayList < Entry > datavals = new ArrayList < Entry > ();
        datavals.add(new Entry(0, 20));
        datavals.add(new Entry(1, 25));
        datavals.add(new Entry(2, 30));
        datavals.add(new Entry(3, 15));
        return datavals;
    }
}