title: MPAndroidChart is not updating
body: <p>I have a hashmap like this </p>
  
  <pre><code>LinkedHashMap&lt;String, String&gt; hash = new LinkedHashMap&lt;&gt;();
  hash.put("2015-05-03", 100);
  hash.put("2015-05-04", 110);
  hash.put("2015-05-05", 90);
  hash.put("2015-05-06", 40);
  </code></pre>
  
  <p>I want to design a LineChart via <a href="https://github.com/PhilJay/MPAndroidChart" rel="noreferrer">MPAndroidChart</a> but it is not working, diagram is not valid, nothing to show!it seems my codes are invalid.<br>
  here are my codes :  </p>
  
  <pre><code>private void setChartData(LinkedHashMap&lt;String, String&gt; lastMonthMediaLikes)
      {
  
          ArrayList&lt;String&gt; xVals = new ArrayList&lt;&gt;();
  
          for(Map.Entry&lt;String, String&gt; entry : lastMonthMediaLikes.entrySet())
          {
              xVals.add(entry.getKey());
          }
  
  
  
          ArrayList&lt;Entry&gt; vals1 = new ArrayList&lt;&gt;();
          int i = 0;
          for(Map.Entry&lt;String, String&gt; entry : lastMonthMediaLikes.entrySet())
          {
              vals1.add(new Entry(Float.valueOf(entry.getValue()), i));
              i++;
          }
  
          // create a dataset and give it a type
          LineDataSet set1 = new LineDataSet(vals1, "DataSet 1");
          set1.setDrawCubic(true);
          set1.setCubicIntensity(0.2f);
          //set1.setDrawFilled(true);
          set1.setDrawCircles(false);
          set1.setLineWidth(1.8f);
          set1.setCircleSize(4f);
          set1.setCircleColor(Color.WHITE);
          set1.setHighLightColor(Color.rgb(244, 117, 117));
          set1.setColor(Color.WHITE);
          set1.setFillColor(Color.WHITE);
          set1.setFillAlpha(100);
          set1.setDrawHorizontalHighlightIndicator(false);
          set1.setFillFormatter(new FillFormatter()
          {
              @Override
              public float getFillLinePosition(LineDataSet dataSet, LineDataProvider dataProvider)
              {
                  return -10;
              }
          });
  
          // create a data object with the datasets
          LineData data = new LineData(xVals, set1);
          //data.setValueTypeface(tf);
          data.setValueTextSize(9f);
          data.setDrawValues(false);
  
          // set data
          chart.setData(data);
      }
  </code></pre>
  
  <p>Please advice, what should i do?</p>