Smartgwt listgrid on the fly / dynamic highlighting

Question

I have a smartGwt ListGrid which i use for showing stock market data. I want to be able to highlight the value of a cell. For example - if its current value is greater than the last value, turn green and turn red if it is lower. I looked at the showcase for smartGWT for any such capability but i only found this sample code for highlighting.

        new Hilite() {{  
            setFieldNames("area", "gdp");  
            setTextColor("#FFFFFF");  
            setBackgroundColor("#639966");  
            setCriteria(new AdvancedCriteria(OperatorId.AND, new Criterion[] {  
                            new Criterion("gdp", OperatorId.GREATER_THAN, 1000000),  
                            new Criterion("area", OperatorId.LESS_THAN, 500000)}));  
            setCssText("color:#3333FF;background-color:#CDEB8B;");  
            setHtmlAfter(" " + Canvas.imgHTML("[SKIN]/actions/back.png"));  
            setId("1");  
        }} 

Here the "gdp" or "area" fields are highlighted if their values are greater or less than a fixed number. Is it possible to use similar highlighting but the value should be compared to the previous value in the cell?

Thanks and regards Mukul

Answer 1

Previous values are not stored anywhere in the model. So the comparison cannot be made out of the box.

A possible solution to this is to create duplicate hidden list grid fields like areaPrevious or gdpPrevious. When the data changes you populate gdp/area and gdpPrevious/areaPrevious fields. Instead of using hilites you use cellFormatters.

gdpField.setCellFormatter(new CellFormatter(){
    public String format(Object value, ListGridRecord record, int rowNum, int colNum){
        if( record.getAttribute("gdpPrevious") < record.getAttribute("gdp")){
             return "<div style=\"width:14px;height:14px;background-color:green;\">+value+        "</div>";
        }else{
              return "<div style=\"width:14px;height:14px;background-color:red;\">"+value+        "</div>";
        }
    }
});

Answer 2

In addition to Abhijith's method, Found an alternative method for doing this in the SmartGWT Enterprise showcase - Pasting here for future reference. They accomplished this by overriding the getCellCSSText method -

            stockQuotesGrid = new ListGrid() {  
            private int blinkPeriod = 2000;  

            // Cell animation - go bright green or red on a change, then fades.  
            protected String getCellCSSText(ListGridRecord record, final int rowNum,  
                    final int colNum) {  
                // changeValue column  
                Date lastUpdated = record.getAttributeAsDate("lastUpdated");  
                if (colNum == 2 && lastUpdated != null) {  
                    long delta = System.currentTimeMillis() - lastUpdated.getTime();  
                    if (delta < blinkPeriod) {  
                        // refresh 10x / second  
                        new Timer() {  
                            public void run() {  
                                stockQuotesGrid.refreshCell(rowNum, colNum);  
                            }  
                        }.schedule(100);  
                        float changeValue = record.getAttributeAsFloat("changeValue");  

                        float ratio = ((float) (blinkPeriod - delta)) / blinkPeriod;  
                        int color = 255 - Math.round(200 * ratio);  

                        if (changeValue > 0) {  
                            return "background-color:#" + Integer.toHexString(color) + "FF"  
                                    + Integer.toHexString(color);  
                        } else if (changeValue < 0) {  
                            return "background-color:#FF" + Integer.toHexString(color)  
                                    + Integer.toHexString(color);  
                        }  
                    } else {  
                        record.setAttribute("lastUpdated", (Date) null);  
                    }  
                }  
                // no style override  
                return null;  
            };  
        };