fix: update columns headers on attach

Close #43

enhanced-grid-flow-demo/src/main/java/com/vaadin/componentfactory/enhancedgrid/GridInDialogView.java

@@ -0,0 +1,42 @@
+package com.vaadin.componentfactory.enhancedgrid;
+
+import com.vaadin.componentfactory.enhancedgrid.bean.Person;
+import com.vaadin.componentfactory.enhancedgrid.filtering.TextFilterField;
+import com.vaadin.componentfactory.enhancedgrid.service.PersonService;
+import com.vaadin.flow.component.button.Button;
+import com.vaadin.flow.component.dialog.Dialog;
+import com.vaadin.flow.component.html.Div;
+import com.vaadin.flow.component.html.Paragraph;
+import com.vaadin.flow.component.icon.VaadinIcon;
+import com.vaadin.flow.router.Route;
+import java.util.List;
+
+/**
+ * Opening grid in a dialog.
+ */
+@Route(value = "in-dialog", layout = MainLayout.class)
+public class GridInDialogView extends Div {
+
+  public GridInDialogView() {
+    add(new Paragraph("Opening grid in a dialog"));
+
+    EnhancedGrid<Person> grid = new EnhancedGrid<>();
+    grid.setItems(getItems());
+    grid.addColumn(Person::getFirstName).setHeader("First Name", new TextFilterField());
+    grid.addColumn(Person::getLastName).setHeader("Last Name").setSortable(true);    
+    grid.setFilterIcon(VaadinIcon.FILTER.create());
+
+    Dialog dialog = new Dialog();
+    dialog.add(grid);
+    dialog.setWidth("800px");
+    dialog.setWidth("600px");
+
+    Button button = new Button("Open dialog to see grid", e -> dialog.open());
+    add(button);
+  }
+
+  private List<Person> getItems() {
+    PersonService personService = new PersonService();
+    return personService.fetchAll();
+  }
+}

enhanced-grid-flow-demo/src/main/java/com/vaadin/componentfactory/enhancedgrid/MainLayout.java

@@ -18,10 +18,11 @@ public MainLayout() {
         final RouterLink multiTree = new RouterLink("Multiple Selection Tree Grid", MultiTreeGridView.class);
         final RouterLink lazySingleTree = new RouterLink("Lazy Single Selection Tree Grid", LazySingleTreeGridView.class);        
         final RouterLink lazyMultiTree = new RouterLink("Lazy Multiple Selection Tree Grid", LazyMultiTreeGridView.class);   
-        final RouterLink customFilterIcon = new RouterLink("Custom filter icon grid", CustomFilterIconView.class);   
+        final RouterLink customFilterIcon = new RouterLink("Custom filter icon grid", CustomFilterIconView.class);
+        final RouterLink gridInDialog = new RouterLink("Open Grid in Dialog", GridInDialogView.class);
 
         final VerticalLayout menuLayout = new VerticalLayout(simpleSingleGrid, simpleMultiGrid, lazySingleGrid, lazyMultiGrid, 
-        		singleTree, multiTree, lazySingleTree, lazyMultiTree, customFilterIcon);
+        		singleTree, multiTree, lazySingleTree, lazyMultiTree, customFilterIcon, gridInDialog);
         addToDrawer(menuLayout);
         addToNavbar(drawerToggle);
     }

enhanced-grid-flow/src/main/java/com/vaadin/componentfactory/enhancedgrid/EnhancedColumn.java

@@ -22,7 +22,6 @@
 
 import java.util.Comparator;
 import java.util.Optional;
-
 import com.vaadin.flow.component.Component;
 import com.vaadin.flow.component.HasValueAndElement;
 import com.vaadin.flow.component.dependency.JsModule;
@@ -91,14 +90,19 @@ public EnhancedColumn<T> setHeader(Component headerComponent, HasValueAndElement
 	}
 
 	/** @see Column#setHeader(Component) */
-	@Override
-	public EnhancedColumn<T> setHeader(Component headerComponent) {
-		if (this.isFilterable()) {
-			this.grid.getElement().executeJs("monkeyPatchHeaderRenderer(this.$connector, $0)", getInternalId());
-		}
-		return (EnhancedColumn<T>) super.setHeader(headerComponent);
-	}
+    @Override
+    public EnhancedColumn<T> setHeader(Component headerComponent) {
+      this.renderHeader();
+      return (EnhancedColumn<T>) super.setHeader(headerComponent);
+    }
 
+    protected void renderHeader() {
+      if (this.isFilterable()) {
+        this.grid.getElement().executeJs("monkeyPatchHeaderRenderer(this.$connector, $0)",
+            getInternalId());
+      }
+    }
+
 	/**
 	 * @see Column#setHeader(String)
 	 * 

enhanced-grid-flow/src/main/java/com/vaadin/componentfactory/enhancedgrid/EnhancedGrid.java

@@ -564,6 +564,11 @@ private void updateFilterIcon() {
     @Override
     protected void onAttach(AttachEvent attachEvent) {
     	super.onAttach(attachEvent);
+    	for(Column<T> column : getColumns()) {
+          EnhancedColumn<T> enhancedColumn = (EnhancedColumn<T>)column;
+          enhancedColumn.renderHeader();
+          enhancedColumn.updateFilterButtonStyle();
+        }
     	this.updateFilterIcon();
     }
 }