Parsing 使用ViewPager、PagerAdapter和AsyncTask的活动不'；不要展示内容

我正在尝试构建一个类似于新安卓市场的活动，马赛克风格，在每个马赛克中列出信息。当用户向左或向右滑动时，他们将看到越来越多包含信息的马赛克。信息量是动态的，因为它是通过异步任务从XML文件加载的

我决定使用ViewPager/PagerAdapter来处理视图和控制分页。每个页面都有一个线性布局，与此链接中的图片类似：

马赛克中的每一个方块都是一个带有图像和文本视图的相对物

我遇到的问题是，显示的第一个视图始终为空，当我尝试更改页面时，会显示强制关闭错误。另外，当我调试时，我发现

PagesContentAdapter.java

中的

instantiateItem（）

方法根本没有输入！有什么好处

下面是我的活动（

MosaicMenuActivity.java

）：

异步任务由my

PageContentLoader.java

完成。我从XML中获取所有数据，但未显示：

public class PageContentLoader extends AsyncTask<Void, Integer, Boolean> {
    public static final String TAG = "PageContentLoader";
    private static int SLEEPING_TIME = 2000;

    // The location of the XML file
    private static final String XML_PATH = "/data/nonius/menu/mosaic.xml";

    // XML node keys used to parse xml
    private static final String KEY_PAGE = "page";
    private static final String KEY_PAGE_TEMPLATE = "template";
    private static final String KEY_TILE = "tile";

    // The parent activity. Used to lauch UI items
    private MosaicMenuActivity activity;

    // The content storage
    private PagesContentAdapter content_adapter;

    // The dialog that locks the user interaction
    private LoaderDialog dialog;

    // The array of content (in this demo, Pages!)
    public ArrayList<Page> pages;

    private String language;

    public PageContentLoader(MosaicMenuActivity activity,
            PagesContentAdapter content_adapter, String language) {
        this.activity = activity;
        this.pages = new ArrayList<Page>();
        this.dialog = new LoaderDialog(this.activity);
        this.content_adapter = content_adapter;
        this.language = language;
    }

    public boolean loadXml() {
        Log.d(TAG, "loadXml");
        // Clean the pages array
        this.pages = new ArrayList<Page>();

        // Get the DOM element
        Document doc = XmlHelper.getDomElement(XML_PATH);
        // If the document is null
        if (doc == null) {
            // Return fail
            return false;
        }

        // Get all the nodes with tag KEY_PAGE
        NodeList page_nodelist = doc.getElementsByTagName(KEY_PAGE);
        Log.d(TAG, "getElementsByTagName");

        // looping through all item nodes <item>
        for (int page_i = 0; page_i < page_nodelist.getLength(); page_i++) {
            Page page = new Page();

            Log.d(TAG, "Page " + page_i);
            // Get the element of the node list
            Element page_element = (Element) page_nodelist.item(page_i);

            String page_template = page_element.getAttribute(KEY_PAGE_TEMPLATE);
            page.setTemplate(page_template);

            NodeList tile_nodelist = page_element
                .getElementsByTagName(KEY_TILE);

            for (int tile_i = 0; tile_i < tile_nodelist.getLength(); tile_i++){
                // Create an empty tile
                Tile tile = new Tile();

                Element tile_element = (Element) tile_nodelist.item(tile_i);
                tile.importXmlElement(tile_element);

                page.addTile(tile);

                Log.d(TAG, tile.toString());
            }

            this.pages.add(page);
        }

        // Everything went ok
        return true;
    }

    protected void onPreExecute() {
        this.dialog.setLoadMode(activity.getString(R.string.loading_message));
        this.dialog.show();
    }

    protected Boolean doInBackground(Void... params) {
        // Parse the xml file
        return this.loadXml();
    }

    protected void onPostExecute(Boolean success) {
        // If the loader succeeded
        if (success) {
            // Update the adapter
            content_adapter.updateContent(pages);

            // If the dialog is visible, hide it
            if (dialog.isShowing()) {
                dialog.dismiss();
            }
        }
        // If the loader failed
        else {
            // Start the error dialog
            dialog.setErrorMode(activity
                .getString(R.string.loading_error_message));
        }
    }
}

感谢我能得到的任何帮助。感谢您抽出时间回顾此问题

public class PageContentLoader extends AsyncTask<Void, Integer, Boolean> {
    public static final String TAG = "PageContentLoader";
    private static int SLEEPING_TIME = 2000;

    // The location of the XML file
    private static final String XML_PATH = "/data/nonius/menu/mosaic.xml";

    // XML node keys used to parse xml
    private static final String KEY_PAGE = "page";
    private static final String KEY_PAGE_TEMPLATE = "template";
    private static final String KEY_TILE = "tile";

    // The parent activity. Used to lauch UI items
    private MosaicMenuActivity activity;

    // The content storage
    private PagesContentAdapter content_adapter;

    // The dialog that locks the user interaction
    private LoaderDialog dialog;

    // The array of content (in this demo, Pages!)
    public ArrayList<Page> pages;

    private String language;

    public PageContentLoader(MosaicMenuActivity activity,
            PagesContentAdapter content_adapter, String language) {
        this.activity = activity;
        this.pages = new ArrayList<Page>();
        this.dialog = new LoaderDialog(this.activity);
        this.content_adapter = content_adapter;
        this.language = language;
    }

    public boolean loadXml() {
        Log.d(TAG, "loadXml");
        // Clean the pages array
        this.pages = new ArrayList<Page>();

        // Get the DOM element
        Document doc = XmlHelper.getDomElement(XML_PATH);
        // If the document is null
        if (doc == null) {
            // Return fail
            return false;
        }

        // Get all the nodes with tag KEY_PAGE
        NodeList page_nodelist = doc.getElementsByTagName(KEY_PAGE);
        Log.d(TAG, "getElementsByTagName");

        // looping through all item nodes <item>
        for (int page_i = 0; page_i < page_nodelist.getLength(); page_i++) {
            Page page = new Page();

            Log.d(TAG, "Page " + page_i);
            // Get the element of the node list
            Element page_element = (Element) page_nodelist.item(page_i);

            String page_template = page_element.getAttribute(KEY_PAGE_TEMPLATE);
            page.setTemplate(page_template);

            NodeList tile_nodelist = page_element
                .getElementsByTagName(KEY_TILE);

            for (int tile_i = 0; tile_i < tile_nodelist.getLength(); tile_i++){
                // Create an empty tile
                Tile tile = new Tile();

                Element tile_element = (Element) tile_nodelist.item(tile_i);
                tile.importXmlElement(tile_element);

                page.addTile(tile);

                Log.d(TAG, tile.toString());
            }

            this.pages.add(page);
        }

        // Everything went ok
        return true;
    }

    protected void onPreExecute() {
        this.dialog.setLoadMode(activity.getString(R.string.loading_message));
        this.dialog.show();
    }

    protected Boolean doInBackground(Void... params) {
        // Parse the xml file
        return this.loadXml();
    }

    protected void onPostExecute(Boolean success) {
        // If the loader succeeded
        if (success) {
            // Update the adapter
            content_adapter.updateContent(pages);

            // If the dialog is visible, hide it
            if (dialog.isShowing()) {
                dialog.dismiss();
            }
        }
        // If the loader failed
        else {
            // Start the error dialog
            dialog.setErrorMode(activity
                .getString(R.string.loading_error_message));
        }
    }
}

public class PagesContentAdapter extends PagerAdapter {
public static final String TAG = "PagesContentAdapter";
// The list context
private Context context;

// The content array
public ArrayList<Page> pages;

// The system language
private String language;

/**
 * Class constructor
 * 
 * @param context
 *            The context used to build the ouput views
 */
public PagesContentAdapter(Context context, String language) {
    this.context = context;
    // Create an empty pages array
    this.pages = new ArrayList<Page>();
    this.language = language;
}

/**
 * Update the Adapter pages array and notify the parent
 * that the data was modified
 * @param pages
 */
public void updateContent(ArrayList<Page> pages) {
    this.pages = pages;
    //this.notifyDataSetChanged();
}

public int getCount() {
    return pages.size();
}

public Object getItem(int position) {
    return pages.get(position);
}

public long getItemId(int position) {
    return position;
}

@Override
public void destroyItem(View collection, int position, Object view) {
    ((ViewPager) collection).removeView((View) view);

}

@Override
public void finishUpdate(View arg0) {
    // TODO Auto-generated method stub

}

@Override
public Object instantiateItem(View page_view, int position) {
    Page page = new Page();
    page = pages.get(position);

    LayoutInflater page_layout_inflater = (LayoutInflater) context
        .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    LinearLayout linearlayout_page = (LinearLayout) page_layout_inflater.inflate(R.layout.page_template_5icons_v1, null);

    for(int i=0; i<5; i++) {
        linearlayout_page.addView(layoutTile(linearlayout_page, page, i));
    }

    ((ViewPager) page_view).addView(linearlayout_page, 0);

    return linearlayout_page;
}

public RelativeLayout layoutTile(LinearLayout linearlayout_page, Page page, int index) {
    RelativeLayout relativelayout_tile = null;

    switch(index) {
        case 0: relativelayout_tile = (RelativeLayout) linearlayout_page.findViewById(R.id.item_big_1);
        case 1: relativelayout_tile = (RelativeLayout) linearlayout_page.findViewById(R.id.item_small_1);
        case 2: relativelayout_tile = (RelativeLayout) linearlayout_page.findViewById(R.id.item_small_2);
        case 3: relativelayout_tile = (RelativeLayout) linearlayout_page.findViewById(R.id.item_small_3);
        case 4: relativelayout_tile = (RelativeLayout) linearlayout_page.findViewById(R.id.item_small_4);
    }

    // Inflate it in a layout xml
    LayoutInflater tile1_layout_inflater = (LayoutInflater) context
            .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    tile1_layout_inflater.inflate(R.layout.tile, relativelayout_tile);
    // Get the textview from the inflated layout
    TextView textview_tail = (TextView) relativelayout_tile.findViewById(R.id.textview_tile);
    Tile tile = page.getTiles().get(index);
    // Set its text
    textview_tail.setText(tile.getDescription());

    return relativelayout_tile;
}

@Override
public boolean isViewFromObject(View view, Object object) {
    return view == object;
}

@Override
public void restoreState(Parcelable arg0, ClassLoader arg1) {
    // TODO Auto-generated method stub

}

@Override
public Parcelable saveState() {
    // TODO Auto-generated method stub
    return null;
}

@Override
public void startUpdate(View arg0) {
    // TODO Auto-generated method stub

}

}