Tech Team Lead News: April 2013

Recently I had to investigate if it is possible to show other data than the X and Y value when hovering over a stacked bar graph in the Vaadin Charts add-on. And yes it is possible!
Nowhere I could find an example on how to do this, so that's why I wrote this blogpost. Hope it helps some people :)

Setup:
- Vaadin 7.0.1
- Charts add-on 1.0.1. In version 1.0.0 you can't set the color of the stacked bars using PlotOptions and ContainerDataSeries. This version has a fix for that.
- Note: I had to manually modify some labels of the hover in the screenshot since I can't use the real data used in the project. Same goes for the code, did not check if it still compiles. Let me know if something essential is missing :) Oh yeah and this is all demo-code so no quality complaints please....

Goal:
- Be able to add a custom field to the hover. And even better: be able to add an array to the hover tooltip.

Here's a screenshot of what the goal was. Click on it for a larger image:

The code:
Notice the Grapes ok: 7 Total: 16 in the hover text. These are the standard x and y values you can show easily via:



        Tooltip tooltip = new Tooltip();
        tooltip.setFormatter("function() { return ''+ this.x +'"+ " '+ this.series.name +': '+ this.y

+' '+'Total: '+ this.point.stackTotal;}");

        conf2.setTooltip(tooltip);

But also note the extra this.point.custom = 708. That's an example of adding a custom value. The tooltip code then looks like:



tooltip.setFormatter("function() {"return ''+ this.x +'"+ " '+this.series.name +': '+ this.y +' '+

'Total: '+ this.point.stackTotal + ' this.point.custom = ' + this.point.custom + "''"

And then below that line you see a set of table-like data: Quality 1: 2 Stored: 3 Interesting: 4. This is the data that comes from three arrays. The tooltip code then looks like this:



tooltip.setFormatter("function() { var qualityValuesArray = JSON.parse(this.point.qualities); " +
        "var storedValuesArray = JSON.parse(this.point.stored); " + 
        "var interestingValuesArray = JSON.parse(this.point.interesting); " + 
        "return ''+ this.x +'"+ " '+this.series.name +': '+ this.y +' '+
        'Total: '+ this.point.stackTotal + ' this.point.custom = ' + this.point.custom + " +
        "'
Quality 1: ' + qualityValuesArray[0]  + " + "'Stored: ' + storedValuesArray[0]  + " + "'Interesting: ' + interestingValuesArray[0]  + " +
        "'
Quality 2: ' + qualityValuesArray[1]  + " + "'Stored: ' + storedValuesArray[1]  + " + "'Interesting: ' + interestingValuesArray[1]  + " +
        "'
Quality 3: ' + qualityValuesArray[2]  + " + "'Stored: ' + storedValuesArray[2]  + " + "'Interesting: ' + interestingValuesArray[2]  + " +
        "'
Quality 4: ' + qualityValuesArray[3]  + " + "'Stored: ' + storedValuesArray[3]  + " + "'Interesting: ' + interestingValuesArray[3]  + " +
        "'
Quality 5: ' + qualityValuesArray[4]  + " + "'Stored: ' + storedValuesArray[4]  + " + "'Interesting: ' + interestingValuesArray[4]  + " +
        "'
Quality 6: ' + qualityValuesArray[5]  + " + "'Stored: ' + storedValuesArray[5]  + " + "'Interesting: ' + interestingValuesArray[5]  + " +
        "'
Quality 7: ' + qualityValuesArray[6]  + " + "'Stored: ' + storedValuesArray[6]  + " + "'Interesting: ' + interestingValuesArray[6]  + " +
        "'
Quality 8: ' + qualityValuesArray[7]  + " + "'Stored: ' + storedValuesArray[7]  + " + "'Interesting: ' + interestingValuesArray[7]  + " +
        "'.';}");

The span can also be replaced by a HTML b tag of course.

Too bad you can't use the setHTML() for better formatting, like putting in a HTML table tag. This is a known issue, see here.

Essential in constructing the data is to use the BeanItemContainer, ContainerDataSeries and the addAttributeToPropertyIdMapping() in which you can put custom class (bean) OrderChartItem:




 /**
  * Class with custom value and 3 arrays to be displayed in tooltip
  */
    public class OrderChartItem {

     private static final int NR_QUALITIES = 8;
     
     private final String name;
  private final int x;
  private final Number y;
  private final int someValue;
  
  private final Number[] quality = new Number[NR_QUALITIES];
  private final Number[] stored = new Number[NR_QUALITIES];
  private final Number[] interesting = new Number[NR_QUALITIES];

  public OrderChartItem(String name, int x, Number y, int someValue) {
   this.name = name;
   this.x = x;
   this.y = y;
   this.someValue = someValue;
   
   for (int i = 0; i < NR_QUALITIES; i++) {
    quality[i] = i + 2;
    stored[i] = i + 3;
    interesting[i] = i + 4;
   }
  }

  public String getName() {
   return name;
  }

  public int getX() {
   return x;
  }

  public Number getY() {
   return y;
  }

  public int getSomeValue() {
   return someValue;
  }

  public List getQualities() {
   return java.util.Arrays.asList(quality);
  }
  public List getStored() {
   return java.util.Arrays.asList(stored);
  }
  public List getInteresting() {
   return java.util.Arrays.asList(interesting);
  }
    }

I made the arrays the same size because of its table data, but that doesn't have to be of course.

The basic mechanism is:

Set up a BeanItemContainer with values of OrderChartItem. Take special care when putting in 0 values. The graph then shows the number 0. To avoid that, put in 'null' as a value.
BeanItemContainer containerGood = new BeanItemContainer(OrderChartItem.class); containerGood.addBean(new OrderChartItem("some name good", 1, null, 701));
So the OrderChartItem has the properties that can be reached from the tooltip Javascript. Note the OrderChartItem just gets some name, later it is overwritten by setting the ContainerDataSeries names:
seriesGood.setName("good");

Then wrap each BeanItemContainer in a ContainerDataSeries:



ContainerDataSeries seriesGood = new ContainerDataSeries(containerGood);

Then add the custom properties for each container. First the one value:



seriesGood.addAttributeToPropertyIdMapping("custom", "someValue");

Then the arrays:



seriesGood.addAttributeToPropertyIdMapping("qualities", "qualities");

And add the series to the configuration:
conf2.addSeries(seriesGood);

In summary: the OrderChartItem is used as data-provider by adding them to the ContainerDataSeries. The properties-mappings of the custom OrderChartItem are then added to the series, after which they are accessible in the tooltip Javascript. Note the "trick" of using JSON.parse() in the formatter and the List getQualities() to get the arrays in the correct format.

Full source code can be found here.

The widgetsets directory has been cleared out because of distribution issues.