documentation/summary_row.html

<div id="midcolumn">
	<h3>Summary row</h3>
	<div id="doccontent">
		<div class="chapter">
			<div class="content">
				<p>
					You can add a summary row to your NatTable easily by adding and configuring the
					<span class="code">SummaryRowLayer</span>. 
				</p>
				<p style="text-align: center;">
					<img align="middle" src="images/summary_row.png" border="0" alt="Summary Row Example"/>
				</p>
				<p>
					The <span class="code">Creating_a_summary_row</span> and <span class="code">CalculatingGridExample</span>
					examples are the best places to look at. 
				</p>
			</div>
		</div>
		<div class="chapter">
			<h5>Adding the SummaryRowLayer to the body layer stack</h5>
			<div class="content">
				<p>
					To add a summary row to your NatTable, you have to add the <span class="code">SummaryRowLayer</span>
					to your body layer stack. As it should deal directly to the data shown in the NatTable, it should 
					be added to the body layer close to the <span class="code">DataLayer</span>. As with all layers this 
					can easily be done with the following code snippet: 
				</p>
				<div class="codeBlock">IConfigRegistry configRegistry = new ConfigRegistry();
IUniqueIndexLayer dataLayer = new DataLayer(myDataProvider);

// Plug in the SummaryRowLayer
IUniqueIndexLayer summaryRowLayer = 
	new SummaryRowLayer(dataLayer, configRegistry, false);
ViewportLayer viewportLayer = new ViewportLayer(summaryRowLayer);</div>
				<p class="subline">Snippet from Creating_a_summary_row example</p>
			<p>
				Note that the <span class="code">SummaryRowLayer</span> needs the <span class="code">ConfigRegistry</span>
				to access the summary row specific configurations.
			</p>
			</div>
		</div>
		<div class="chapter">
			<h5>Configuring the summary data</h5>
			<div class="content">
				<p>
					The next step on adding a summary row to a NatTable is to configure the content that should
					be showed within the summary row. This is done by <span class="code">ISummaryProvider</span> 
					that need to be configured via <span class="code">ConfigRegistry</span>.
				</p>
				<p>
					NatTable comes with three default <span class="code">ISummaryProvider</span>
					<ul>
						<li>ISummaryProvider.DEFAULT<br>
						always returns the String ...</li>
						<li>ISummaryProvider.NONE<br>
						always returns null which skips calls to the <span class="code">ISummaryProvider</span> and 
						is a performance tweak</li>
						<li>SummationSummaryProvider<br>
						needs the body data provider so it can iterate over all values for the column it is 
						configured to and summarize all the number values to a resulting float value</li>
					</ul>
					
					Creating your own <span class="code">ISummaryProvider</span> is quite easy. The following 
					snippet shows how to implement one to calculate the average value instead of the sum.
					<div class="codeBlock">class AverageSummaryProvider implements ISummaryProvider {
	public Object summarize(int columnIndex) {
		int total = 0;
		int rowCount = myDataProvider.getRowCount();

		for (int rowIndex = 0; rowIndex < rowCount; rowIndex++) {
			Object dataValue = 
				myDataProvider.getDataValue(columnIndex, rowIndex);
			total = total + Integer.parseInt(dataValue.toString());
		}
		return "Average: " + total / rowCount;
	}
}</div>
				<p class="subline">Snippet from Creating_a_summary_row example</p>
				<p>
					To be able to configure the <span class="code">SummaryRowLayer</span> in detail, it introduces
					two new labels for which the specific configurations can be added:
					<ul>
						<li>SummaryRowLayer#DEFAULT_SUMMARY_ROW_CONFIG_LABEL to all cells in the row</li>
						<li>SummaryRowLayer#DEFAULT_SUMMARY_COLUMN_CONFIG_LABEL_PREFIX + column index per column</li>
					</ul>
				</p>
				<p>
					There is a <span class="code">DefaultSummaryRowConfiguration</span>
					to configure the style and the summary formulas of the summary row. You can extend that or
					create your own configuration. In this configuration you should add your <span class="code">ISummaryProvider</span>
					as you like the <span class="code">SummaryRowLayer</span> to be configured.
					<div class="codeBlock">// Default summary provider
configRegistry.registerConfigAttribute(
	SummaryRowConfigAttributes.SUMMARY_PROVIDER,
	new SummationSummaryProvider(myDataProvider),
	DisplayMode.NORMAL,
	SummaryRowLayer.DEFAULT_SUMMARY_ROW_CONFIG_LABEL);

// Average summary provider for column index 2
configRegistry.registerConfigAttribute(
	SummaryRowConfigAttributes.SUMMARY_PROVIDER,
	new AverageSummaryProvider(),
	DisplayMode.NORMAL,
	SummaryRowLayer.DEFAULT_SUMMARY_COLUMN_CONFIG_LABEL_PREFIX + 2);</div>
				<p class="subline">Snippet from MySummaryRowConfig of the Creating_a_summary_row example</p>
				</p>
				
			</div>
		</div>
		<div class="chapter">
			<h5>Summary row label in the row header</h5>
			<div class="content">
				<p>
					To reflect the summary row within the row header of a grid, you should consider using
					the <span class="code">DefaultSummaryRowHeaderDataProvider</span> to create the 
					<span class="code">DataLayer</span> of your <span class="code">DefaultSummaryRowHeaderDataProvider</span>
					or something custom that looks like it. Using this the row header will show incrementing line numbers 
					for all data rows and by default the word <i>Summary</i> for the summary row. The 
					<span class="code">DefaultSummaryRowHeaderDataProvider</span> also has a constructor that
					accepts a parameter that allows you to specify your own row header label for the summary row.
					<div class="codeBlock">IDataProvider rowHeaderDataProvider = new DefaultSummaryRowHeaderDataProvider(
	bodyLayer.getDataLayer().getDataProvider(), 
	"\u2211");
ILayer rowHeaderLayer = new RowHeaderLayer(
	new DefaultRowHeaderDataLayer(rowHeaderDataProvider), 
	bodyLayer, 
	selectionLayer);</div>
				<p class="subline">Snippet from CalculatingGridLayer of the CalculatingGridExample</p>
				</p>
			</div>
		</div>
	</div>
</div>