Java tutorial
/* * Copyright 2000-2018 Vaadin Ltd. * * Licensed under the Apache License, Version 2.0 (the "License"); you may not * use this file except in compliance with the License. You may obtain a copy of * the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the * License for the specific language governing permissions and limitations under * the License. */ package com.vaadin.client.ui; import java.util.Collections; import java.util.List; import com.google.gwt.event.shared.HandlerRegistration; import com.vaadin.client.ComponentConnector; import com.vaadin.client.ConnectorHierarchyChangeEvent; import com.vaadin.client.ConnectorHierarchyChangeEvent.ConnectorHierarchyChangeHandler; import com.vaadin.client.HasComponentsConnector; public abstract class AbstractHasComponentsConnector extends AbstractComponentConnector implements HasComponentsConnector, ConnectorHierarchyChangeHandler { List<ComponentConnector> childComponents; /** * Default constructor. */ public AbstractHasComponentsConnector() { addConnectorHierarchyChangeHandler(this); } /* * (non-Javadoc) * * @see com.vaadin.client.HasComponentsConnector#getChildren() */ @Override public List<ComponentConnector> getChildComponents() { if (childComponents == null) { return Collections.emptyList(); } return childComponents; } /* * (non-Javadoc) * * @see com.vaadin.client.HasComponentsConnector#setChildren * (java.util.Collection) */ @Override public void setChildComponents(List<ComponentConnector> childComponents) { this.childComponents = childComponents; } @Override public HandlerRegistration addConnectorHierarchyChangeHandler(ConnectorHierarchyChangeHandler handler) { return ensureHandlerManager().addHandler(ConnectorHierarchyChangeEvent.TYPE, handler); } }