Androidでのオブザーバーモードの応用

Androidでのオブザーバーモードの応用
例:BrowserにはTabがたくさんあり、今流行っているラベルページを閲覧しています.BrowserのBrowserSettings(共通)が変化するたびに
BrowserのTabはすぐに有効です.ここでTAbはオブザーバー、BrowserSettingsはオブザーバーです.

class BrowserSettings extends Observable {


    /**
     * Add a WebSettings object to the list of observers that will be updated
     * when update() is called.
     *
     * @param s A WebSettings object that is strictly tied to the life of a
     *            WebView.
     */
    public Observer addObserver(WebSettings s) {
        Observer old = mWebSettingsToObservers.get(s);
        if (old != null) {
            super.deleteObserver(old);
        }
        Observer o = new Observer(s);
        mWebSettingsToObservers.put(s, o);
        super.addObserver(o);
        return o;
    }

    /**
     * Delete the given WebSettings observer from the list of observers.
     * @param s The WebSettings object to be deleted.
     */
    public void deleteObserver(WebSettings s) {
        Observer o = mWebSettingsToObservers.get(s);
        if (o != null) {
            mWebSettingsToObservers.remove(s);
            super.deleteObserver(o);
        }
    }

    /*
     * Package level method for obtaining a single app instance of the
     * BrowserSettings.
     */
    /*package*/ static BrowserSettings getInstance() {
        if (sSingleton == null ) {
            sSingleton = new BrowserSettings();
        }
        return sSingleton;
    }

    void update() {
        setChanged();
        notifyObservers();
    }


    /*
     * An observer wrapper for updating a WebSettings object with the new
     * settings after a call to BrowserSettings.update().
     */
    static class Observer implements java.util.Observer {
        // Private WebSettings object that will be updated.
        private WebSettings mSettings;

        Observer(WebSettings w) {
            mSettings = w;
        }

        public void update(Observable o, Object arg) {
    }
    }
}