Override calcuate method for Summary Row to handle Dates

[nstokoe]

I have a grid similar patterned after the Live Group Summary example in the 3.x showcase. Two of my columns contain dates and I would like to be able to have the latest date from each column appear in the summary row for each group. I wrote this code to override the caculate method:

SummaryColumnConfig<GranuleThroughputByProduct, Date> lastIngestedCol = new SummaryColumnConfig<GranuleThroughputByProduct, Date>(
                props.lastIngestedTime(), 100, "Last Ingested Time");
        lastIngestedCol.setCell(new DateCell(DateTimeFormat.getFormat(CommonConstants.DATE_TIME_ISO8601)));
        lastIngestedCol.setSummaryType(new SummaryType<GranuleThroughputByProduct, Date, Number>() {
            @Override
            public Number calculate(
                    List<GranuleThroughputByProduct> m,
                    ValueProvider<GranuleThroughputByProduct, Date> valueProvider) { 
                int dummyVal = 21;
                Date latest = null;
                for (int i = 0; i < m.size(); i++) {
                    GranuleThroughputByProduct t = m.get(i);
                     if (latest == null) {
                         latest = t.getLastIngestedTime();
                     } else if (latest.before(t.getLastIngestedTime())) {
                         latest = t.getLastIngestedTime();
                     }
                }
                return dummyVal;
            }  
        });

When I do this I get the error:

Caused by: java.lang.ClassCastException: java.lang.String cannot be cast to java.lang.Number
    at com.sencha.gxt.widget.core.client.grid.GroupSummaryView.calculate(GroupSummaryView.java:90)

Now the calculate method itself doesn't tip you off that it needs to return a Number but the render method obviously needs to take a Number to work correctly. This is where I assume the problem lies.

Is there anyway to get this to work? It seems that Summary columns should be compatible with more date types than just Numbers since it is a fairly common query to ask for the latest date (for example in a SQL query or excel spreadsheet).

[PhiLho]

I discover this (interesting) feature, so I don't know if my remarks can be helpful.
I don't understand how your code is related to your description and how the error message is related to your code. (Probably my fault.)

From what I see in SummaryType description, you can define the input type and the output type. Apparently, you need that both be dates. So perhaps your code could look like:

lastIngestedCol.setSummaryType(new SummaryType<GranuleThroughputByProduct, Date, Date>() {
  @Override
  public Date calculate(
      List<GranuleThroughputByProduct> m,
      ValueProvider<GranuleThroughputByProduct, Date> valueProvider) { 
    Date latest = null;
    for (GranuleThroughputByProduct t : m) {
      if (latest == null || latest.before(t.getLastIngestedTime())) {
        latest = t.getLastIngestedTime();
      }
    }
    return latest;
  }  
});

Obviously untested...

[nstokoe]

Unfortuately I have already tried your exact suggestion several times, each resulting with the following error:

Caused by: java.lang.ClassCastException: java.util.Date cannot be cast to java.lang.Number
    at com.sencha.gxt.widget.core.client.grid.GroupSummaryView.calculate(GroupSummaryView.java:90)
    at com.sencha.gxt.widget.core.client.grid.GroupSummaryView.renderGroupSummary(GroupSummaryView.java:156)
    at com.sencha.gxt.widget.core.client.grid.GroupingView.renderGroup(GroupingView.java:542)

The problem is that the renderGroupSummary method that calls the overriden calculate method is expecting a Number. Unfortuately it appears there is no way to override the renderGroupSummary (and the renderSummary) method for just a single column.

[nstokoe]

So I figured it out. I wouldn't have got it if I didn't go back to the code today after seeing your reply so thanks!

Basically I knew I had to work within the confines of the provided method signatures of calculate and render when setting new SummaryTypes and SummaryRenders. Essentially in calculate I find the latest date, but then return it as a long using the Date.getTime() method. Then in render I had to take that long and convert it back to a Date before formatting it as a String.

SummaryColumnConfig<GranuleThroughputByProduct, Date> lastIngestedCol = new SummaryColumnConfig<GranuleThroughputByProduct, Date>(
                props.lastIngestedTime(), 100, "Last Ingested Time");
        lastIngestedCol.setCell(new AbstractCell<Date>() {
            @Override
            public void render(com.google.gwt.cell.client.Cell.Context context,
                    Date value, SafeHtmlBuilder sb) {
                sb.appendHtmlConstant((DateTimeFormat.getFormat(CommonConstants.DATE_TIME_ISO8601).format(value)));
            }
        });
        lastIngestedCol.setSummaryType(new SummaryType<GranuleThroughputByProduct, Date, Long>() {
            @Override
            public Long calculate(
                    List<GranuleThroughputByProduct> m,
                    ValueProvider<GranuleThroughputByProduct, Date> valueProvider) {
                Date latest = null;
                for (GranuleThroughputByProduct t : m) {
                    if (latest == null || latest.before(t.getLastIngestedTime())) {
                        latest = t.getLastIngestedTime();
                    }
                }
    
                return latest.getTime();
            }
        });
        lastIngestedCol.setSummaryRenderer(new SummaryRenderer<GranuleThroughputByProduct>() {

            @Override
            public SafeHtml render(
                    Number value,
                    Map<ValueProvider<GranuleThroughputByProduct, ?>, Number> data) {
                
                Date  latest = new Date(value.longValue());
                
                return SafeHtmlUtils.fromTrustedString((DateTimeFormat.getFormat(CommonConstants.DATE_TIME_ISO8601).format(latest)));
            }
        });

I can't believe I didn't try this sooner. In retrospect the answer is so obvious.