Android添加书签(二)(19)

        createdColumnIndex = columns.length - 1; 
        columns[createdColumnIndex] = Browser.BookmarkColumns.CREATED; 
 
        String whereClause = Browser.BookmarkColumns.BOOKMARK + " == 1"; 
        String orderBy = Browser.BookmarkColumns.CREATED + " DESC"; 
        String[] selectionArgs = null; 
        mCursor = mContentResolver.query(Browser.BOOKMARKS_URI, columns, 
                whereClause, selectionArgs, orderBy); 
        mCursor.registerContentObserver(mChangeObserver); 
        mCursor.registerDataSetObserver(mDataSetObserver); 
 
        mDataValid = true; 
        notifyDataSetChanged(); 
 
        mCount = mCursor.getCount(); 
    } 
 
    /**
     * How many items should be displayed in the list.
     * 
     * @return Count of items.
     */ 
    public int getCount() { 
        if (mDataValid) { 
            return mCount; 
        } else { 
            return 0; 
        } 
    } 
 
    public boolean areAllItemsEnabled() { 
        return true; 
    } 
 
    public boolean isEnabled(int position) { 
        return true; 
    } 
 
    /**
     * Get the data associated with the specified position in the list.
     * 
     * @param position
     *            Index of the item whose data we want.
     * @return The data at the specified position.
     */ 
    public Object getItem(int position) { 
        return null;