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”.

<LinearLayout   android:layout_width=“match_parent”   android:layout_height=“wrap_content”   android:orientation=“vertical”>   <TextView       android:layout_width=“wrap_content”       android:layout_height=“wrap_content”       android:layout_marginLeft=“@dimen/spacing_normal”       android:layout_marginStart=“@dimen/spacing_normal”       android:layout_marginTop=“@dimen/spacing_normal”       android:text=“@string/check_in_summary”       android:textAllCaps=“true”       android:textSize=“@dimen/text_size_small” />   <com.github.mikephil.charting.charts.LineChart       android:id=“@+id/chartCheckIn”       android:layout_width=“match_parent”       android:layout_height=“200dp”       android:layout_marginEnd=“@dimen/spacing_normal”       android:layout_marginLeft=“@dimen/spacing_normal”       android:layout_marginRight=“@dimen/spacing_normal”       android:layout_marginStart=“@dimen/spacing_normal” />   <TextView       android:layout_width=“wrap_content”       android:layout_height=“wrap_content”       android:layout_gravity=“center”       android:layout_marginBottom=“8dp”       android:layout_marginTop=“8dp”       android:text=“@string/check_in_time”       android:textSize=“10sp” />   <LinearLayout       android:layout_width=“match_parent”       android:layout_height=“wrap_content”       android:orientation=“vertical”>       <FrameLayout           android:layout_width=“match_parent”           android:layout_height=“1dp”           android:background=“@color/color_shadow” />       <FrameLayout           android:layout_width=“match_parent”           android:layout_height=“@dimen/spacing_small”           android:background=“@color/color_bottom_surface” />   </LinearLayout> </LinearLayout>

• 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() {   chartAnalyser.showChart(getView().getCheckinTimeChartView());   chartAnalyser.loadDataCheckIn(getId())       .compose(disposeCompletable(getDisposable()))       .subscribe(() -> {           getView().showChartCheckIn(true);           chartAnalyser.showChart(getView().getCheckinTimeChartView());       }, 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) {   clearData();   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);   })     .toList()     .doAfterSuccess(attendees -> this.attendees = attendees)     .toCompletable()     .doOnComplete(() -> {         if (error)             throw new IllegalAccessException(“No checkin’s found”);         checkInDataSet = setDataForCheckIn(checkInTimeMap, “check-in time”);         prepare();     }); }

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);   else       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);       lineData.addDataSet(checkInDataSet);   } 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);       lineData.addDataSet(freeSet);       lineData.addDataSet(paidSet);       lineData.addDataSet(donationSet);       lineData.setDrawValues(false);   } lineData.setDrawValues(false); }

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 {   @Override   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) {   lineChart.setData(lineData);   lineChart.getXAxis().setEnabled(true);   lineChart.getAxisRight().setEnabled(false);   lineChart.getDescription().setEnabled(false);   lineChart.getLegend().setEnabled(false);   YAxis yAxis = lineChart.getAxisLeft();   yAxis.setGridLineWidth(1);   yAxis.setGridColor(Color.parseColor(“#992ecc71”));   if (!isCheckinChart)       if (maxTicketSale > TICKET_SALE_THRESHOLD)           yAxis.setGranularity(maxTicketSale / TICKET_SALE_THRESHOLD);   else {       XAxis xAxis = lineChart.getXAxis();       xAxis.setValueFormatter(new MyAxisValueFormatter());       yAxis.setGranularity(1);       lineChart.getXAxis().setPosition(XAxis.XAxisPosition.BOTTOM);       lineChart.getXAxis().setGranularity(1f);   }   Description description = new Description();   description.setText(“”);   lineChart.setDescription(description);   lineChart.animateY(1000); }