Implementing Check-in time chart in Orga App

Earlier in the Open event orga app there were no charts present to track the check-in time of the attendees. Hence it was quite cumbersome for the organiser to track the people and at what time they have checked-in. Using this feature of check-in time chart, the process has become quite easier.

Whenever an attendee checks-in, the data point is added to the chart and a chart is plotted. The Y-axis shows the number of attendees and the X-axis shows the time at which they have checked-in.

To implement this feature I have taken use of the MPAndroidCharts library which makes the job a lot easier. Following steps were followed to implement the charts:

  • Adding the following Library dependency in the build.gradle file
implementation “com.github.PhilJay:MPAndroidChart:v3.0.3”
  • Now the following code is added to the ticket_analytics.xml file. This is done so that the UI of the charts can be created. The following XML file consists of the LineChart XML tag which shows the check-in time chart on screen. Also the labelling of the axis needs to be done, so the X-axis is explicitly named as “TIME”.

      android:textSize=“@dimen/text_size_small” />

      android:layout_marginStart=“@dimen/spacing_normal” />

      android:textSize=“10sp” />


          android:background=“@color/color_shadow” />

          android:background=“@color/color_bottom_surface” />
  • Now the a method loadCheckIn( )  chart needs to added to the EventsDashboardPresenter. This is called from the EventsDashboardFragment. The loadDataCheckIn( ) is created in the ChartAnalyzer class. We pass getId( ) as the parameter.
private void loadCheckInTimesChart() {
      .subscribe(() -> {
      }, throwable -> getView().showChartCheckIn(false));
  • Now we add the method loadDataCheckIn( ) in the ChartAnalyzer class. This method returns a Completable and takes eventId as the single parameter.
public Completable loadDataCheckIn(long eventId) {
  isCheckinChart = true;
  return getAttendeeSource(eventId).doOnNext(attendee -> {
     String checkInTime = attendee.getCheckinTimes();
     int length = checkInTime.split(“,”).length;
     String latestCheckInTime = checkInTime.split(“,”)[length – 1];
     error = checkInTime == null ? true : false;
     addDataPointForCheckIn(checkInTimeMap, latestCheckInTime);
    .doAfterSuccess(attendees -> this.attendees = attendees)
    .doOnComplete(() -> {
        if (error)
            throw new IllegalAccessException(“No checkin’s found”);
        checkInDataSet = setDataForCheckIn(checkInTimeMap, “check-in time”);

It calls the getAttendeeSource( ) which further gives a call to the method getAttendees( ) from the AttendeeRepository. All the inormation related to the attendees is returned from which the check-in times is extracted. The check-in times are returned in comma separated form and hence we need to extract the first element of the sequence.

private Observable<Attendee> getAttendeeSource(long eventId) {
  if (attendees == null || attendees.isEmpty())
      return attendeeRepository.getAttendees(eventId, false);
      return Observable.fromIterable(attendees);
  • After the success of loading the attendees, the method addDataPointForCheckIn is called. We call it by inserting the parameters Map<Integer, Long> and the dateString which we had passed from the loadDataCheckIn( ). Following is the code for it. A map is created out of the data. The key in the map is the time and value is the number of people who have checked-in at that time.
private void addDataPointForCheckIn(Map<Integer, Long> map, String dateString) {
  int hour = DateUtils.getDate(dateString).getHour();
  Long numberOfCheckins = map.get(hour);

  if (numberOfCheckins == null)
      numberOfCheckins = 0L;

  map.put(hour, ++numberOfCheckins);
  • After the map is created it is passed on to the setDataForCheckIn( ) and the label is provided as “check-in times”. Following is the code for setDataForCheckIn( ). All the values of the map are parsed and a new entry object is made in which the value of the key and value pairs are passed. This object is then added to the ArrayList.
private LineDataSet setDataForCheckIn(Map<Integer, Long> map, String label) throws ParseException {
  List<Entry> entries = new ArrayList<>();
  for (Map.Entry<Integer, Long> entry : map.entrySet()) {
      entries.add(new Entry(entry.getKey(), entry.getValue()));
  Collections.sort(entries, new EntryXComparator());

  // Add a starting point 2 hrs ago
  entries.add(0, new Entry(entries.get(0).getX() – 2, 0));
  return new LineDataSet(entries, label);
  • The object LineDataSet is returned with all the entries stored in the ArrayList. Now the prepare( ) is called. It is in this method that we add the code for the UI of the chart.
private void prepare() {
  if (isCheckinChart) {
      initializeLineSet(checkInDataSet, R.color.light_blue_500, R.color.light_blue_100);
  } else {
      initializeLineSet(freeSet, R.color.light_blue_500, R.color.light_blue_100);
      initializeLineSet(paidSet, R.color.purple_500, R.color.purple_100);
      initializeLineSet(donationSet, R.color.red_500, R.color.red_100);

initializeLineSet( ) is the method where we add the color which will be used for plotting the data set.In our case the color is blue.

  • We also need to plot the time stamps in the X-axis. Unfortunately MPAndroidCharts doesn’t have a functionality for that. So to handle it an inner class MyMyAxisValueFormatter is created which extends IAxisValueFormatter. Following is the code for it.
public class MyAxisValueFormatter implements IAxisValueFormatter {

  public String getFormattedValue(float value, AxisBase axis) {
      if (value < 0)
          return values[24 + (int) value];
      return values[(int) value];

The values array list consists of the time stamps that will be present on the X-Axis.

String[] values = new String[] {“00:00”, “1:00”, “2:00”, “3:00”, “4:00”, “5:00”, “6:00”, “7:00”, “8:00”, “9:00”, “10:00”, “11:00”, “12:00”, “13:00”, “14:00”, “15:00”, “16:00”, “17:00”, “18:00”, “19:00”, “20:00”, “21:00”, “22:00”, “23:00”};
  • Finally the showChart( ) is called in which we specify details regarding the grid color, legend, visibility of X and Y axis etc. We also specify the animation that needs to be done whenever the chart is on screen.


public void showChart(LineChart lineChart) {

  YAxis yAxis = lineChart.getAxisLeft();
  if (!isCheckinChart)
      if (maxTicketSale > TICKET_SALE_THRESHOLD)
          yAxis.setGranularity(maxTicketSale / TICKET_SALE_THRESHOLD);
  else {
      XAxis xAxis = lineChart.getXAxis();
      xAxis.setValueFormatter(new MyAxisValueFormatter());

  Description description = new Description();