Grid ValueProvider


Column<T> column;
T item;

How can I get the column-value for the item (in Vaadin 10.0.4)?
In Vaadin 8 this was:

By checking the source code, I can confirm that reference to ValueProvider is not saved in the Column class. This is probably because Column can be created without a ValueProvider also (For example, directly passing a Renderer).

I assume you could still save a reference to the ValueProvider when you’re creating the Column, and use that saved reference later.

I’m not sure how to do this. In my case I have an ExcelExporter that exports a grid to an excel file.
The ExcelExporter takes only the grid as an argument and runs the following code:

ListDataProvider<T> listDataProvider = (ListDataProvider<T>) grid.getDataProvider();
Collection<T> items = listDataProvider.getItems();
for (T item : items) {
    // if not defined, visibleColumns = grid.getColumns();
	for (Column<T> column : visibleColumns) {
		// FIXME this line I would like to do....
		Object value = column.getValueProvider().apply(item);

A generic workaround is to build a Map of (Column, ValueProvider) when you add columns. This could be in your extended Grid.

Then the ExcelExporter would need a grid and a valueProviderMap as arguments?
If that’s the solution, I think there is missing something in the framework.
The grid knows how to show the (formated) values when given the items, so why not implement
a public method that returns the (formated) values (similar to Vaadin 8)? This method could
also check if there is a ValueProvider or a Renderer available for the specific column.

V10 Grid is using a Renderer in all the cases. Even if you use a ValueProvider to create a Column, it internally uses a TemplateRenderer.

Also, a Grid cell may contain more that one value (you can render complex structures using TemplateRenderer). So, one-to-one mapping between a Grid and an Excel sheet is not always possible.

A dirty hack for getting the cell content would be to get the cell json representation by reflection

 Method generateJsonMethod = DataCommunicator.class.getDeclaredMethod("generateJson", Object.class);
 JsonValue jsonValue = (JsonValue) generateJsonMethod.invoke(grid.getDataCommunicator(), item);

and then parse the jsonValue.
This is not a general solution to the problem, but works for me.

Hello, is there any other way to read the values of the cells from a grid? Unfortunately I can’t really find any example code on this.

Hi, I also need a way to access particular cell in Grid.
Need to set/get value to the cell based on event listener.

Vikas Rana:
Hi, I also need a way to access particular cell in Grid.
Need to set/get value to the cell based on event listener.

Hi Vikas,

Can you explain a little bit your use case? It can probably be done with a component renderer or a template renderer but without any detail it’s hard to say.