com.ocs.dynamo.ui.composite.layout.LazyTabLayout.java Source code

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Here is the source code for com.ocs.dynamo.ui.composite.layout.LazyTabLayout.java

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/*
   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.ocs.dynamo.ui.composite.layout;

import java.io.Serializable;
import java.util.HashSet;
import java.util.Set;

import com.ocs.dynamo.domain.AbstractEntity;
import com.ocs.dynamo.ui.Reloadable;
import com.ocs.dynamo.ui.component.DefaultVerticalLayout;
import com.vaadin.ui.Component;
import com.vaadin.ui.Layout;
import com.vaadin.ui.Panel;
import com.vaadin.ui.TabSheet;
import com.vaadin.ui.TabSheet.SelectedTabChangeEvent;
import com.vaadin.ui.TabSheet.Tab;
import com.vaadin.ui.VerticalLayout;

/**
 * A layout that contains a tab sheet with tabs that are lazily loaded
 * 
 * @author bas.rutten
 * @param <ID>
 *            type of the primary key
 * @param <T>
 *            type of the entity
 */
@SuppressWarnings("serial")
public abstract class LazyTabLayout<ID extends Serializable, T extends AbstractEntity<ID>>
        extends BaseCustomComponent {

    private static final long serialVersionUID = 3788799136302802727L;

    // the entity whose details are being shown
    private T entity;

    // the set of tabs that have already been loaded
    private Set<String> replacedTabs = new HashSet<>();

    private TabSheet tabs;

    /**
     * Constructor
     * 
     * @param entity
     */
    public LazyTabLayout(T entity) {
        this.entity = entity;
    }

    @Override
    public void attach() {
        super.attach();
        build();
    }

    @Override
    public void build() {
        Panel panel = new Panel();
        panel.setCaptionAsHtml(true);
        panel.setCaption(createTitle());

        VerticalLayout main = new DefaultVerticalLayout(true, true);
        panel.setContent(main);

        tabs = new TabSheet();
        tabs.setSizeFull();

        main.addComponent(tabs);
        setupLazySheet(tabs);
        setCompositionRoot(panel);
    }

    /**
     * Returns the captions of the tabs
     * 
     * @return
     */
    protected abstract String[] getTabCaptions();

    /**
     * Lazily creates a certain tab
     * 
     * @param index
     *            the index of the tab to create
     * @return
     */
    protected abstract Component initTab(int index);

    /**
     * Constructs the lazy tab sheet by setting up empty dummy tabs
     * @param tabs
     */
    private void setupLazySheet(final TabSheet tabs) {

        // build up placeholder tabs that only contain an empty layout
        for (String caption : getTabCaptions()) {
            tabs.addTab(new DefaultVerticalLayout(false, false), caption);
        }

        // load the first tab
        ((Layout) tabs.getTab(0).getComponent()).addComponent(initTab(0));
        replacedTabs.add(tabs.getTab(0).getCaption());

        // respond to a tab change by actually loading the sheet
        tabs.addSelectedTabChangeListener(new TabSheet.SelectedTabChangeListener() {

            @Override
            public void selectedTabChange(SelectedTabChangeEvent event) {
                Component selectedTab = event.getTabSheet().getSelectedTab();
                Tab tab = event.getTabSheet().getTab(selectedTab);

                // lazily load a tab
                if (!replacedTabs.contains(tab.getCaption())) {
                    replacedTabs.add(tab.getCaption());

                    // look up the tab in the copies
                    int index = 0;
                    for (int i = 0; i < tabs.getComponentCount(); i++) {
                        Tab t = tabs.getTab(i);
                        if (t.getCaption().equals(tab.getCaption())) {
                            index = i;
                            break;
                        }
                    }

                    // paste the real tab into the placeholder
                    Component realTab = initTab(index);
                    ((Layout) selectedTab).addComponent(realTab);

                } else {
                    // reload the tab if needed
                    Layout layout = (Layout) selectedTab;
                    Component next = layout.iterator().next();
                    if (next instanceof Reloadable) {
                        ((Reloadable) next).reload();
                    }
                }

            }
        });
    }

    /**
     * Constructs the title of the page
     * 
     * @return
     */
    protected abstract String createTitle();

    public T getEntity() {
        return entity;
    }

    public void setEntity(T entity) {
        this.entity = entity;
    }

    public void selectTab(int index) {
        tabs.setSelectedTab(index);
    }
}