com.google.gwt.sample.feedreader.client.ManifestPanel.java Source code

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Here is the source code for com.google.gwt.sample.feedreader.client.ManifestPanel.java

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/*
 * Copyright 2007 Google Inc.
 * 
 * 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.google.gwt.sample.feedreader.client;

import com.google.gwt.user.client.Command;
import com.google.gwt.user.client.History;
import com.google.gwt.user.client.Timer;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;

/**
 * The main view; a list of all of the configured feeds.
 */
public class ManifestPanel extends WallToWallPanel {
    /**
     * This class serves as a synchronization point for downloading the contents
     * of a feed. If it contains any elements and there is no currently-loading
     * feed, the first feed in the list will be loaded every 100ms.
     */
    private static class LoaderList extends ArrayList {
        final Timer t = new Timer() {
            public void run() {
                if (loadingFeed != null && !loadingFeed.isLoadFinished()) {
                    return;
                }

                if (size() == 0) {
                    return;
                }

                FeedPanel p = (FeedPanel) get(0);
                if (p.isLoadFinished()) {
                    remove(0);
                } else if (!p.isLoadStarted()) {
                    loadingFeed = p;
                    p.loadFeed();
                }
            }
        };

        public LoaderList() {
            t.scheduleRepeating(100);
        }

        public boolean add(Object o) {
            if (contains(o)) {
                return false;
            }
            return super.add(o);
        }
    }

    /**
     * The list of feeds that need to be loaded.
     */
    private static final List toLoad = new LoaderList();

    /**
     * Used to prevent more than one FeedPanel from being automatically loaded at
     * a time.
     */
    private static FeedPanel loadingFeed;

    private final Configuration configuration;
    private final HashMap/* <Feed, FeedPanel> */ feedPanelMap = new HashMap();

    private boolean dirty = true;

    public ManifestPanel(final Configuration configuration) {
        super("Feeds", null);
        this.configuration = configuration;

        setEditCommand("Edit", "Edits feeds", new Command() {
            public void execute() {
                History.newItem("configuration");
            }
        });

        // Start a timer to refresh the feed data.
        (new Timer() {
            public void run() {
                refresh();
            }
        }).scheduleRepeating(5 * 60 * 1000);

        addStyleName("ManifestPanel");
    }

    public void enter() {
        if (dirty) {
            refresh();
        }

        super.enter();
        History.newItem("manifest");
    }

    public PanelLabel getLabel() {
        throw new RuntimeException("This should not be called on the root panel");
    }

    public void showFeed(Configuration.Feed feed, String entryUrl) {
        FeedPanel p = (FeedPanel) feedPanelMap.get(feed);
        if (p == null) {
            // We don't want to take the hit of reloading everything, so defer this
            // until the panel is re-shown.
            setDirty();
            p = new FeedPanel(feed, this);
            feedPanelMap.put(feed, p);
        }

        if (entryUrl == null) {
            p.enter();
        } else {
            p.showEntry(entryUrl);
        }
    }

    protected String getShortTitle() {
        return "Feeds";
    }

    void setDirty() {
        dirty = true;
    }

    private void refresh() {
        dirty = false;
        clear();
        feedPanelMap.clear();

        for (Iterator i = configuration.getFeeds().iterator(); i.hasNext();) {
            Configuration.Feed feed = (Configuration.Feed) i.next();

            FeedPanel panel = new FeedPanel(feed, this);
            feedPanelMap.put(feed, panel);
            add(panel.getLabel());
            toLoad.add(panel);
        }
    }
}