Supporting Multiple Screens

public class ArticleActivity extends FragmentActivity {
    // The news category index and the article index for the article we are to display
    int mCatIndex, mArtIndex;

    /**
     * Sets up the activity.
     *
     * Setting up the activity means reading the category/article index from the Intent that
     * fired this Activity and loading it onto the UI. We also detect if there has been a
     * screen configuration change (in particular, a rotation) that makes this activity
     * unnecessary, in which case we do the honorable thing and get out of the way.
     */
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        mCatIndex = getIntent().getExtras().getInt("catIndex", 0);
        mArtIndex = getIntent().getExtras().getInt("artIndex", 0);

        // If we are in two-pane layout mode, this activity is no longer necessary
        if (getResources().getBoolean(R.bool.has_two_panes)) {
            finish();
            return;
        }

        // Place an ArticleFragment as our content pane
        ArticleFragment f = new ArticleFragment();
        getSupportFragmentManager().beginTransaction().add(android.R.id.content, f).commit();

        // Display the correct news article on the fragment
        NewsArticle article = NewsSource.getInstance().getCategory(mCatIndex).getArticle(mArtIndex);
        f.displayArticle(article);
    }
}

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/**
 * Fragment that displays a news article.
 */
public class ArticleFragment extends Fragment {
    // The webview where we display the article (our only view)
    WebView mWebView;

    // The article we are to display
    NewsArticle mNewsArticle = null;

    // Parameterless constructor is needed by framework
    public ArticleFragment() {
        super();
    }

    /**
     * Sets up the UI. It consists if a single WebView.
     */
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        mWebView = new WebView(getActivity());
        loadWebView();
        return mWebView;
    }

    /**
     * Displays a particular article.
     *
     * @param article the article to display
     */
    public void displayArticle(NewsArticle article) {
        mNewsArticle = article;
        loadWebView();
    }

    /**
     * Loads article data into the webview.
     *
     * This method is called internally to update the webview's contents to the appropriate
     * article's text.
     */
    void loadWebView() {
        if (mWebView != null) {
            mWebView.loadData(mNewsArticle == null ? "" : mNewsArticle.getBody(), "text/html",
                        "utf-8");
        }
    }
}

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public class CompatActionBarNavHandler implements TabListener,
        OnNavigationListener {
    // The listener that we notify of navigation events
    CompatActionBarNavListener mNavListener;

    /**
     * Constructs an instance with the given listener.
     *
     * @param listener
     *            the listener to notify when a navigation event occurs.
     */
    public CompatActionBarNavHandler(CompatActionBarNavListener listener) {
        mNavListener = listener;
    }

    /**
     * Called by framework when a tab is selected.
     *
     * This will cause a navigation event to be delivered to the configured
     * listener.
     */
    @Override
    public void onTabSelected(Tab tab, FragmentTransaction ft) {
        // TODO Auto-generated method stub
        mNavListener.onCategorySelected(tab.getPosition());
    }

    /**
     * Called by framework when a item on the navigation menu is selected.
     *
     * This will cause a navigation event to be delivered to the configured
     * listener.
     */
    @Override
    public boolean onNavigationItemSelected(int itemPosition, long itemId) {
        mNavListener.onCategorySelected(itemPosition);
        return true;
    }

    /**
     * Called by framework when a tab is re-selected. That is, it was already
     * selected and is tapped on again. This is not used in our app.
     */
    @Override
    public void onTabReselected(Tab tab, FragmentTransaction ft) {
        // we don't care
    }

    /**
     * Called by framework when a tab is unselected. Not used in our app.
     */
    @Override
    public void onTabUnselected(Tab tab, FragmentTransaction ft) {
        // we don't care
    }

}
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public interface CompatActionBarNavListener {
    /**
     * Signals that the given news category was selected.
     * @param catIndex the selected category's index.
     */
    public void onCategorySelected(int catIndex);
}

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public class HeadlinesFragment extends ListFragment implements OnItemClickListener {
    // The list of headlines that we are displaying
    List<String> mHeadlinesList = new ArrayList<String>();

    // The list adapter for the list we are displaying
    ArrayAdapter<String> mListAdapter;

    // The listener we are to notify when a headline is selected
    OnHeadlineSelectedListener mHeadlineSelectedListener = null;

    /**
     * Represents a listener that will be notified of headline selections.
     */
    public interface OnHeadlineSelectedListener {
        /**
         * Called when a given headline is selected.
         * @param index the index of the selected headline.
         */
        public void onHeadlineSelected(int index);
    }

    /**
     * Default constructor required by framework.
     */
    public HeadlinesFragment() {
        super();
    }

    @Override
    public void onStart() {
        super.onStart();
        setListAdapter(mListAdapter);
        getListView().setOnItemClickListener(this);
        loadCategory(0);
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        mListAdapter = new ArrayAdapter<String>(getActivity(), R.layout.headline_item,
                mHeadlinesList);
    }

    /**
     * Sets the listener that should be notified of headline selection events.
     * @param listener the listener to notify.
     */
    public void setOnHeadlineSelectedListener(OnHeadlineSelectedListener listener) {
        mHeadlineSelectedListener = listener;
    }

    /**
     * Load and display the headlines for the given news category.
     * @param categoryIndex the index of the news category to display.
     */
    public void loadCategory(int categoryIndex) {
        mHeadlinesList.clear();
        int i;
        NewsCategory cat = NewsSource.getInstance().getCategory(categoryIndex);
        for (i = 0; i < cat.getArticleCount(); i++) {
            mHeadlinesList.add(cat.getArticle(i).getHeadline());
        }
        mListAdapter.notifyDataSetChanged();
    }

    /**
     * Handles a click on a headline.
     *
     * This causes the configured listener to be notified that a headline was selected.
     */
    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
        if (null != mHeadlineSelectedListener) {
            mHeadlineSelectedListener.onHeadlineSelected(position);
        }
    }

    /** Sets choice mode for the list
     *
     * @param selectable whether list is to be selectable.
     */
    public void setSelectable(boolean selectable) {
        if (selectable) {
            getListView().setChoiceMode(ListView.CHOICE_MODE_SINGLE);
        }
        else {
            getListView().setChoiceMode(ListView.CHOICE_MODE_NONE);
        }
    }
}
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public class NewsArticle {
    // How many sentences in each paragraph?
    final int SENTENCES_PER_PARAGRAPH = 20;

    // How many paragraphs in each article?
    final int PARAGRAPHS_PER_ARTICLE = 5;

    // Headline and body
    String mHeadline, mBody;

    /**
     * Create a news article with randomly generated text.
     * @param ngen the nonsense generator to use.
     */
    public NewsArticle(NonsenseGenerator ngen) {
        mHeadline = ngen.makeHeadline();

        StringBuilder sb = new StringBuilder();
        sb.append("<html><body>");
        sb.append("<h1>" + mHeadline + "</h1>");
        int i;
        for (i = 0; i < PARAGRAPHS_PER_ARTICLE; i++) {
            sb.append("<p>").append(ngen.makeText(SENTENCES_PER_PARAGRAPH)).append("</p>");
        }

        sb.append("</body></html>");
        mBody = sb.toString();
    }

    /** Returns the headline. */
    public String getHeadline() {
        return mHeadline;
    }

    /** Returns the article body (HTML)*/
    public String getBody() {
        return mBody;
    }
}
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public class NewsCategory {
    // how many articles?
    final int ARTICLES_PER_CATEGORY = 20;

    // array of our articles
    NewsArticle[] mArticles;

    /**
     * Create a news category.
     *
     * The articles are dynamically generated with fun and random nonsense.
     */
    public NewsCategory() {
        NonsenseGenerator ngen = new NonsenseGenerator();
        mArticles = new NewsArticle[ARTICLES_PER_CATEGORY];
        int i;
        for (i = 0; i < mArticles.length; i++) {
            mArticles[i] = new NewsArticle(ngen);
        }
    }

    /** Returns how many articles exist in this category. */
    public int getArticleCount() {
        return mArticles.length;
    }

    /** Gets a particular article by index. */
    public NewsArticle getArticle(int index) {
        return mArticles[index];
    }
}