vaadin-framework/uitest/src/main/java/com/vaadin/tests/components/grid/GridAddColumn.java

package com.vaadin.tests.components.grid;

import com.vaadin.annotations.Widgetset;
import com.vaadin.data.ValueProvider;
import com.vaadin.server.VaadinRequest;
import com.vaadin.tests.components.AbstractTestUI;
import com.vaadin.ui.Button;
import com.vaadin.ui.Grid;
import com.vaadin.ui.Grid.Column;
import com.vaadin.ui.Label;
import com.vaadin.ui.Notification;
import com.vaadin.ui.renderers.NumberRenderer;

@Widgetset("com.vaadin.DefaultWidgetSet")
public class GridAddColumn extends AbstractTestUI {

    @Override
    protected void setup(VaadinRequest request) {
        Grid<String> grid = new Grid<>();
        createColumns(grid);
        grid.setItems("a", "aa", "aaa");
        addComponent(grid);

        addComponent(new Button("Replace columns", event -> {
            grid.removeAllColumns();
            createColumns(grid);
            Notification.show("Columns replaced.");
        }));
    }

    private void createColumns(Grid<String> grid) {
        Column<String, String> col0 = grid.addColumn(ValueProvider.identity())
                .setCaption("First column");
        grid.getDefaultHeaderRow().getCell(col0)
                .setComponent(new Label("Label Header"));
        grid.addColumn(String::length, new NumberRenderer());
        grid.addColumn(String::length);
        grid.addColumn(string -> -string.length());
        grid.addColumn(string -> new Object());
    }
}