doc/src/examples/fetchmore.qdoc
branchRCL_3
changeset 7 3f74d0d4af4c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/doc/src/examples/fetchmore.qdoc	Thu Apr 08 14:19:33 2010 +0300
@@ -0,0 +1,125 @@
+/****************************************************************************
+**
+** Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).
+** All rights reserved.
+** Contact: Nokia Corporation (qt-info@nokia.com)
+**
+** This file is part of the documentation of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** No Commercial Usage
+** This file contains pre-release code and may not be distributed.
+** You may use this file in accordance with the terms and conditions
+** contained in the Technology Preview License Agreement accompanying
+** this package.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Nokia gives you certain additional
+** rights.  These rights are described in the Nokia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** If you have questions regarding the use of this file, please contact
+** Nokia at qt-info@nokia.com.
+**
+**
+**
+**
+**
+**
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+/*!
+    \example itemviews/fetchmore
+    \title Fetch More Example
+
+    The Fetch More example shows how two add items to an item view
+    model on demand.
+
+    \image fetchmore-example.png
+
+    The user of the example can enter a directory in the \gui
+    Directory line edit. The contents of the directory will
+    be listed in the list view below.
+
+    When you have large - or perhaps even infinite - data sets, you
+    will need to add items to the model in batches, and preferably only
+    when the items are needed by the view (i.e., when they are visible
+    in the view).
+
+    In this example, we implement \c FileListModel - an item view
+    model containing the entries of a directory. We also have \c
+    Window, which sets up the GUI and feeds the model with
+    directories.
+
+    Let's take a tour of \c {FileListModel}'s code.
+
+    \section1 FileListModel Class Definition
+
+    The \c FileListModel inherits QAbstractListModel and contains the
+    contents of a directory. It will add items to itself only when
+    requested to do so by the view.
+
+    \snippet examples/itemviews/fetchmore/filelistmodel.h 0
+
+    The secret lies in the reimplementation of
+    \l{QAbstractItemModel::}{fetchMore()} and
+    \l{QAbstractItemModel::}{canFetchMore()} from QAbstractItemModel.
+    These functions are called by the item view when it needs more
+    items. 
+
+    The \c setDirPath() function sets the directory the model will
+    work on. We emit \c numberPopulated() each time we add a batch of
+    items to the model.
+
+    We keep all directory entries in \c fileList. \c fileCount is the
+    number of items that have been added to the model.
+
+    \section1 FileListModel Class Implementation
+
+    We start by checking out the \c setDirPath().
+
+    \snippet examples/itemviews/fetchmore/filelistmodel.cpp 0
+
+    We use a QDir to get the contents of the directory. We need to
+    inform QAbstractItemModel that we want to remove all items - if
+    any - from the model.
+
+    \snippet examples/itemviews/fetchmore/filelistmodel.cpp 1
+
+    The \c canFetchMore() function is called by the view when it needs
+    more items. We return true if there still are entries that we have
+    not added to the model; otherwise, we return false.
+
+    And now, the \c fetchMore() function itself:
+
+    \snippet examples/itemviews/fetchmore/filelistmodel.cpp 2
+
+    We first calculate the number of items to fetch.
+    \l{QAbstractItemModel::}{beginInsertRows()} and
+    \l{QAbstractItemModel::}{endInsertRows()} are mandatory for
+    QAbstractItemModel to keep up with the row insertions. Finally, we
+    emit \c numberPopulated(), which is picked up by \c Window.
+
+    To complete the tour, we also look at \c rowCount() and \c data().
+
+    \snippet examples/itemviews/fetchmore/filelistmodel.cpp 4
+
+    Notice that the row count is only the items we have added so far,
+    i.e., not the number of entries in the directory.
+
+    In \c data(), we return the appropriate entry from the \c
+    fileList. We also separate the batches with a different background
+    color.
+*/
+