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authorRoland Wolf <ext-roland.wolf@nokia.com>2010-07-29 11:51:27 (GMT)
committerRoland Wolf <ext-roland.wolf@nokia.com>2010-07-29 11:51:27 (GMT)
commitda7f8a556c122a31daa11f434d67c8bb96cbd5ec (patch)
tree28d906d034d20c9079cebb75d08bb60bc4d1b8d4 /doc
parent65642dd343bf61510117cd7e13f69e7138247932 (diff)
downloadQt-da7f8a556c122a31daa11f434d67c8bb96cbd5ec.zip
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moving over work from 28b49e42f5bddec2d62e957f158cb848da134db8
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-rw-r--r--[-rwxr-xr-x]doc/src/tutorials/modelview.qdoc661
1 files changed, 357 insertions, 304 deletions
diff --git a/doc/src/tutorials/modelview.qdoc b/doc/src/tutorials/modelview.qdoc
index 98096a0..f771726 100755..100644
--- a/doc/src/tutorials/modelview.qdoc
+++ b/doc/src/tutorials/modelview.qdoc
@@ -34,46 +34,118 @@
\title Model/View Contents
\brief An introduction to ModelView programming
- This tutorial gives an introduction to ModelView programming using the Qt
- cross-platform framework.
+ Every UI developer should know about ModelView programming and the goal of this tutorial is to provide you with an easily understandable introduction to this topic.
- \image treeview.png
+\raw HTML
+<br>
+\endraw
+\raw HTML
+<table style="background-color:white;border:none;font: normal 13px/1.2 Verdana;">
+<tr><td align="left" valign="top" style="background-color:white;border:none;padding:5px;">
+\endraw
+
+Table, list and tree widgets are components frequently used in GUIs. There are 2 different ways how these widgets can access their data. The traditional way involves widgets which include internal containers for storing data. This approach is very intuitive, however, in many non-trivial applications, it leads to data synchronization issues. The second approach is modelview programming, in which widgets do not maintain internal data containers. They access external data through a standardized interface and therefore avoid data dupplication. This may seem complicated at first, but once you take a closer look, it is not only easy to grasp, but the many benefits of modelview programming also become clearer.
+
+\raw HTML
+</td>
+<td width="20px" valign="top"></td>
+<td align="left" valign="top">
+\endraw
+
+\raw HTML
+<table>
+<tr><td>
+\endraw
+
+\raw HTML
+<p style="text-align:center;font: bold 13px/1.2 Verdana;">Contents:</p>
+\endraw
+
+ \list 1
+ \o \l{modelview-part1.html}{Introduction}
+ \o \l{modelview-part2.html}{Developing a Simple Model/View Application}
+ \o \l{modelview-part3.html}{Intermediate Topics}
+ \o \l{modelview-part4.html}{Good Sources of Additional Information}
+ \endlist
+
+\raw HTML
+</td></tr>
+</table>
+\endraw
+
+
+\raw HTML
+</td></tr>
+<tr><td align="left" valign="top" style="background-color:white;border:none;padding:5px;">
+\endraw
+ \raw HTML
+ <br><br>
+ \endraw
\omit
It doesn't cover everything; the emphasis is on teaching the programming
philosophy of Model/View programming, and Qt's features are introduced as
needed. Some commonly used features are never used in this tutorial.
\endomit
- In the process, we will learn about some basic technologies provided by Qt,
- such as:
+ In the process, we will learn about some basic technologies provided by Qt, such as:
\list
\o The difference between standard and model/view widgets
\o Adapters betweeen forms and models
\o Developing a simple model/view application
+ \o Predefined models
\o Intermediate topics such as:
\list
\o Tree views
\o Selection
- \o Predefined models
\o Delegates
\o Debugging with model test
\endlist
\endlist
+
- If you are completely new to Qt, please read \l{How to Learn Qt} if you
- have not already done so.
+ \raw HTML
+ <br>
+ \endraw
+ You will also learn whether your new application can be written easier with ModelView programming or if classic widgets will work just as well.
+ \raw HTML
+ <br>
+ \endraw
+ This tutorial includes example code for you to edit and integrate into your project. The tutorial's source code is located in Qt's \c examples/tutorials/modelview directory.
- The tutorial's source code is located in Qt's \c examples/tutorials/modelview
- directory.
+ \raw HTML
+ <br>
+ \endraw
+ For more detailed information you may also want to look at the \l {model-view-programming.html}{reference documentation}
- \list 1
- \o \l{modelview-part1.html}{Introduction}
- \o \l{modelview-part2.html}{Developing a Simple Model/View Application}
- \o \l{modelview-part3.html}{Intermediate Topics}
- \o \l{modelview-part4.html}{Good Sources of Additional Information}
- \endlist
+
+\raw HTML
+</td>
+<td width="20px" valign="top"></td>
+<td align="right" valign="top">
+\endraw
+
+ \raw HTML
+ <br><br>
+ \endraw
+
+
+
+ \image treeview.png
+
+
+\raw HTML
+</td></tr>
+</table>
+\endraw
+
+
+
+ \raw HTML
+ <br>
+ \endraw
+ If you are completely new to Qt, please read \l{How to Learn Qt} if you have not already done so.
*/
@@ -84,13 +156,12 @@
\previouspage {modelview-index.html}{Model/View Contents}
\nextpage {modelview-part2.html}{Developing a Simple Model/View Application}
\title An Introduction to Model/View Programming
-
+ \raw HTML
+ <br>
+ \endraw
\section1 1. Introduction
- Model/View is a technology used to separate data from views in widgets that
- handle data sets. Standard widgets are not designed for separating data
- from views and this is why Qt 4 has two different types of widgets. Both
- types of widgets look the same, but they interact with data differently.
+ Model/View is a technology used to separate data from views in widgets that handle data sets. Standard widgets are not designed for separating data from views and this is why Qt 4 has two different types of widgets. Both types of widgets look the same, but they interact with data differently.
\table
\row
@@ -103,43 +174,22 @@
\section2 1.1 Standard Widgets
- Let's have a closer look at a standard table widget. A table widget is a 2D
- array of the data elements that the user can change. The table widget can
- be integrated into a program flow by reading and writing the data elements
- that the table widget provides. This method is very intuitive and useful in
- many applications.
+ Let's have a closer look at a standard table widget. A table widget is a 2D array of the data elements that the user can change. The table widget can be integrated into a program flow by reading and writing the data elements that the table widget provides. This method is very intuitive and useful in many applications.
- Displaying and editing a database table with a standard table widget can be
- problematic. Two copies of the data have to be coordinated: one outside the
- widget; one inside the widget. The developer needs to know where up-to-date
- data is so the both copies contain the most recent data. The tight coupling
- of presentation and data makes it harder to write unit tests.
+ Displaying and editing a database table with a standard table widget can be problematic. Two copies of the data have to be coordinated: one outside the widget; one inside the widget. The developer is responsible for synchronizing both versions. The tight coupling of presentation and data makes it harder to write unit tests.
\section2 1.2 Model/View to the Rescue
- Model/view stepped up to provide a solution that uses a more versatile
- architecture. Model/view eliminates the data consistency problems that may
- occur with standard widgets. Model/view also makes it easier to use more
- than one view of the same data because one model can be passed on to many
- views. The most important difference is that model/view widgets do not
- store data behind the table cells. In fact, they operate directly from your
- data. Since view classes do not know your data's structure, you need to
- provide a wrapper to make your data conform to the QAbstractItemModel
- interface. A view uses this interface to read from and write to your data
- and any class that implements QAbstractItemModel is a model. Once the view
- receives a pointer to a model, it will read and display its content and be
- its editor.
+ Model/view stepped up to provide a solution that uses a more versatile architecture. Model/view eliminates the data consistency problems that may occur with standard widgets. Model/view also makes it easier to use more than one view of the same data because one model can be passed on to many views. The most important difference is that model/view widgets do not store data behind the table cells. In fact, they operate directly from your data. Since view classes do not know your data's structure, you need to provide a wrapper to make your data conform to the QAbstractItemModel interface. A view uses this interface to read from and write to your data. Any instance of a class that implements QAbstractItemModel is said to be a model. Once the view receives a pointer to a model, it will read and display its content and be its editor.
\section2 1.3 Overview of the Model/View Widgets
- Here is an overview of the model/view widgets and their corresponding
- standard widgets.
+ Here is an overview of the model/view widgets and their corresponding standard widgets.
\table
\header
\o Widget
- \o Standard Widget (a convenience class with data in
- the widget)
+ \o Standard Widget (an item based convenience class)
\o Model/View View Class (for use with external data)
\row
\o \inlineimage listview.png
@@ -167,23 +217,37 @@
Having adapters between forms and models can come in handy.
- We often prefer editing data stored in tables (e.g. in database tables) in
- forms rather than in tables. There is no direct model/view counterpart for
- separating data and views for widgets that operate on one value instead of
- a dataset, so we need an adapter in order to connect the form to the source
- of data.
+ We can edit data stored in tables directly from within the table itself, but it's much more comfortable to edit data in text fields. There is no direct model/view counterpart that separates data and views for widgets that operate on one value (QLineEdit, QCheckBox ...) instead of a dataset, so we need an adapter in order to connect the form to the source of data.
- \l QDataWidgetMapper is a great solution because it maps form widgets to a
- table row and it makes it very easy to build forms for database tables.
+ \l QDataWidgetMapper is a great solution because it maps form widgets to a table row and makes it very easy to build forms for database tables.
\image widgetmapper.png
-
- Another example of an adapter is QCompleter. Qt has QCompleter for
- providing auto-completions in Qt widgets such as QComboBox and, as shown
- below, QLineEdit. QCompleter uses a model as its data source, so QCompleter,
- in itself, is a very handy adapter.
+
+ Another example of an adapter is \l QCompleter. Qt has \l QCompleter for providing auto-completions in Qt widgets such as \l QComboBox and, as shown below, \l QLineEdit. \l QCompleter uses a model as its data source.
\image qcompleter.png
+
+
+\raw HTML
+<br>
+<br>
+<br>
+<br>
+<br>
+\endraw
+
+\raw HTML
+<p style="position:absolute;left:5px;bottom:5px;">
+<a href="modelview.html">previous page</a>
+</p>
+\endraw
+
+\raw HTML
+<p style="position:absolute;right:5px;bottom:5px;">
+<a href="modelview-part2.html">next page</a>
+</p>
+\endraw
+
*/
/*!
@@ -198,165 +262,143 @@
\previouspage {modelview-part1.html}{Introduction}
\nextpage {modelview-part3.html}{Intermediate Topics}
\title Model/View Chapter 2 - A Simple Model/View Application
-
+ \raw HTML
+ <br>
+ \endraw
\section1 2. A Simple Model/View Application
+ If you want to develop a model/view application, where should you start? We recommend starting with a simple example and extending it step-by-step. This makes understanding the architecture a lot easier. Trying to understand the model/view architecture in detail before invoking the IDE has proven to be less convenient for many developers. It is substantially easier to start with a simple model/view application that has demo data. Give it a try! Simply replace the data in the examples below with your own.
- If you want to develop a model/view application, where should you start? We
- recommend starting with a simple example and extending it step-by-step.
- This makes understanding the architecture a lot easier. Trying to
- understand the model/view architecture in detail before invoking the IDE
- has proven to be less convenient for many developers. It is substantially
- easier to start with a simple model/view application that has demo data.
- Give it a try! Simply replace the data in the examples below with your own.
-
- Below are 7 very simple and independent applications that show different
- sides of model/view programming. The source code can be found inside the
- \c{examples/tutorials/modelview} directory.
+ Below are 7 very simple and independent applications that show different sides of model/view programming. The source code can be found inside the \c{examples/tutorials/modelview} directory.
\section2 2.1 A Read Only Table
-
- We start with an application that uses a QTableView to show data. We will
- add editing capabilities later.
-
+ We start with an application that uses a QTableView to show data. We will add editing capabilities later.
+ \raw HTML
+ <br>
+ \endraw
+ (file source: examples/tutorials/modelview/1_readonly/main.cpp)
\snippet examples/tutorials/modelview/1_readonly/main.cpp Quoting ModelView Tutorial
We have the usual \l {modelview-part2-main-cpp.html}{main()} function:
- \snippet examples/tutorials/modelview/1_readonly/modelview.h Quoting ModelView Tutorial
-
- The application is a \l QMainWindow that holds a \l QTableView.
-
- \snippet examples/tutorials/modelview/1_readonly/modelview.cpp Quoting ModelView Tutorial
-
- Here is the interesting part: We use
- \l{QTableView::setModel()}{tableView->setModel(new MyModel(this));} to
- instantiate the Model and pass its pointer to \l {QTableView}{tableView()}.
- \l{QTableView}{tableView} will invoke the methods of the pointer it has
- received to find out two things:
+ \raw HTML
+ <br>
+ \endraw
+
+ Here is the interesting part: We create an instance of MyModel and use \l{QTableView::setModel()}{tableView.setModel( &myModel );} to pass a pointer of it to to \l {QTableView}{tableView}. \l{QTableView}{tableView} will invoke the methods of the pointer it has received to find out two things:
\list
\o How many rows and columns should be displayed
\o What content should be printed into each cell.
\endlist
- The model needs some code to respond to this.
+ The model needs some code to respond to this.
- We have a table data set, so let's start with QAbstractTableModel since it
- is easier to use.
+ We have a table data set, so let's start with QAbstractTableModel since it is easier to use than the more general QAbstractItemModel.
+
+ \raw HTML
+ <br>
+ \endraw
+ (file source: examples/tutorials/modelview/1_readonly/mymodel.h)
\snippet examples/tutorials/modelview/1_readonly/mymodel.h Quoting ModelView Tutorial
QAbstractTableModel requires the implementation of three abstract methods.
+ \raw HTML
+ <br>
+ \endraw
+ (file source: examples/tutorials/modelview/1_readonly/mymodel.cpp)
\snippet examples/tutorials/modelview/1_readonly/mymodel.cpp Quoting ModelView Tutorial
- The number of rows and columns is set by
- \l{QAbstractItemModel::rowCount()}{MyModel::rowCount()} and
- \l{QAbstractItemModel::columnCount()}{MyModel::columnCount()}.
- When the view has to know what the cell's text is, it calls the method.
- Row and column information is specified with parameter \c index and the
- role is set to \l{Qt::ItemDataRole}{Qt::DisplayRole}. Other roles are
- covered in the next section. In our example, the data that should be
- displayed is generated. In a real application, \c MyModel would have a
- member called \c MyData, which serves as the target for all reading and
- writing operations.
-
- This small example demonstrates the passive nature of a model. The model
- does not know when it will be used or which data is needed. It simply
- provides data each time the view requests it.
-
- What happens when the model 's data needs to be changed? How does the view
- know when data changes and needs to be read again? The model has to emit a
- signal that indicates what range of cells has changed. This will be
- demonstrated in section 2.3.
+ The number of rows and columns is provided by \l{QAbstractItemModel::rowCount()}{MyModel::rowCount()} and \l{QAbstractItemModel::columnCount()}{MyModel::columnCount()}. When the view has to know what the cell's text is, it calls the method \l{QAbstractItemModel::data()}{MyModel::data()}. Row and column information is specified with parameter \c index and the role is set to \l{Qt::ItemDataRole}{Qt::DisplayRole}. Other roles are covered in the next section. In our example, the data that should be displayed is generated. In a real application, \c MyModel would have a member called \c MyData, which serves as the target for all reading and writing operations.
+
+ This small example demonstrates the passive nature of a model. The model does not know when it will be used or which data is needed. It simply provides data each time the view requests it.
+
+ What happens when the model 's data needs to be changed? How does the view realize that data has changed and needs to be read again? The model has to emit a signal that indicates what range of cells has changed. This will be demonstrated in section 2.3.
\section2 2.2 Extending the Read Only Example with Roles
- In addition to controlling what text the view displays, the model also
- controls the text's appearance. When we slightly change the model, we get
- the following result: \image readonlytable_role.png
+ In addition to controlling what text the view displays, the model also controls the text's appearance. When we slightly change the model, we get the following result: \image readonlytable_role.png
+
+ In fact, nothing except for the \l{QAbstractItemModel::}{data()} method needs to be changed to set fonts, background colour, alignment and a checkbox. Below is the \l{QAbstractItemModel::data()}{data()} method that produces the result shown above. The difference is that this time we use parameter int role to return different pieces of information depending on its value.
- In fact, nothing except for the \l{QAbstractItemModel::}{data()}
- method needs to be changed to set fonts, background colour, alignment and a
- checkbox.
- Here is the \l{QAbstractItemModel::data()}{data()} method that produces the
- result shown above:
+ \raw HTML
+ <br>
+ \endraw
+ (file source: examples/tutorials/modelview/2_formatting/mymodel.cpp)
\snippet examples/tutorials/modelview/2_formatting/mymodel.cpp Quoting ModelView Tutorial
- Each formatting property will be requested from the model with a separate
- call to the \l{QAbstractItemModel::data()}{data()} method. The \c role
- parameter is used to let the model know which property is being requested:
+ Each formatting property will be requested from the model with a separate call to the \l{QAbstractItemModel::data()}{data()} method. The \c role parameter is used to let the model know which property is being requested:
\table
\header
- \o Role (enum Qt::ItemDataRole )
+ \o \l{Qt::ItemDataRole}{enum Qt::ItemDataRole}
\o Meaning
\o Type
\row
- \o \l{Qt::ItemDataRole}{Qt::DisplayRole}
+ \o \l{Qt::ItemDataRole}{}Qt::DisplayRole
\o text
\o QString
\row
- \o Qt::FontRole
+ \o \l{Qt::ItemDataRole}{Qt::FontRole}
\o font
\o QFont
\row
- \o Qt::BackgroundRole
+ \o \l{Qt::ItemDataRole}{BackgroundRole}
\o brush for the background of the cell
\o QBrush
\row
- \o Qt::TextAlignmentRole
+ \o \l{Qt::ItemDataRole}{Qt::TextAlignmentRole}
\o text alignment
- \o enum Qt::AlignmentFlag
- \row
- \o {1, 3} Qt::CheckStateRole
- \o {1, 3} suppresses checkboxes with \l{QVariant}{QVariant()},
- sets checkboxes with Qt::Checked or Qt::Unchecked
- \o {1, 3} \l{Qt::ItemDataRole}{enum Qt::ItemDataRole}
+ \o \l{Qt::AlignmentFlag-enum}{enum Qt::AlignmentFlag}
+ \row
+ \o {1, 3} \l{Qt::ItemDataRole}{Qt::CheckStateRole}
+ \o {1, 3} suppresses checkboxes with \l{QVariant}{QVariant()},
+
+ sets checkboxes with \l{Qt::CheckState-enum}{Qt::Checked}
+
+ or \l{Qt::CheckState-enum}{Qt::Unchecked}
+ \o {1, 3} \l{Qt::ItemDataRole}{enum Qt::ItemDataRole}
\endtable
- Refer to the Qt namespace documentation to learn more about the
- Qt::ItemDataRole enum's capabilities.
-
- Now we need to determine how using a seperated model impacts the
- application's performance, so let's trace how often the view calls the
- \l{QAbstractItemModel::}{data()} method. In order to track how often
- the view calls the model, we have put a debug statement in the
- \l{QAbstractItemModel::}{data()} method, which logs onto stdio. In
- our small example, \l{QAbstractItemModel::}{data()} will be called 42
- times.
- Each time you hover the cursor over the field,
- \l{QAbstractItemModel::}{data()} will be called again \mdash 7 times for
- each cell. That's why it is important to make sure that your data is
- available when \l{QAbstractItemModel::}{data()} is invoked and expensive
- lookup operations are cached.
+ Refer to the Qt namespace documentation to learn more about the \l{Qt::ItemDataRole}{Qt::ItemDataRole} enum's capabilities.
+
+ Now we need to determine how using a separated model impacts the application's performance, so let's trace how often the view calls the \l{QAbstractItemModel::}{data()} method. In order to track how often the view calls the model, we have put a debug statement in the \l{QAbstractItemModel::}{data()} method, which logs onto stdio. In our small example, \l{QAbstractItemModel::}{data()} will be called 42 times.
+ Each time you hover the cursor over the field, \l{QAbstractItemModel::}{data()} will be called again \mdash 7 times for each cell. That's why it is important to make sure that your data is available when \l{QAbstractItemModel::}{data()} is invoked and expensive lookup operations are cached.
\section2 2.3 A Clock inside a Table Cell
\image clock.png
- We still have a read only table, but this time the content changes every
- second because we are showing the current time.
+ We still have a read only table, but this time the content changes every second because we are showing the current time.
+
+ \raw HTML
+ <br>
+ \endraw
+ (file source: examples/tutorials/modelview/3_changingmodel/mymodel.cpp)
\snippet examples/tutorials/modelview/3_changingmodel/mymodel.cpp quoting mymodel_QVariant
- Something is missing to make the clock tick. We need to tell the view every
- second that the time has changed and that it needs to be read again. We do
- this with a timer. In the constructor, we set its interval to 1 second and
- connect its timeout signal.
+ Something is missing to make the clock tick. We need to tell the view every second that the time has changed and that it needs to be read again. We do this with a timer. In the constructor, we set its interval to 1 second and connect its timeout signal.
+
+ \raw HTML
+ <br>
+ \endraw
+ (file source: examples/tutorials/modelview/3_changingmodel/mymodel.cpp)
\snippet examples/tutorials/modelview/3_changingmodel/mymodel.cpp quoting mymodel_a
Here is the corresponding slot:
+
+ \raw HTML
+ <br>
+ \endraw
+ (file source: examples/tutorials/modelview/3_changingmodel/mymodel.cpp)
\snippet examples/tutorials/modelview/3_changingmodel/mymodel.cpp quoting mymodel_b
- We ask the view to read the data in the top left cell again by emitting the
- \l{QAbstractItemModel::}{dataChanged()} signal. Note that we did not
- explicitly connect the \l{QAbstractItemModel::}{dataChanged()} signal to
- the view. This happened automatically when we called
- \l{QTableView::}{setModel()}.
+ We ask the view to read the data in the top left cell again by emitting the \l{QAbstractItemModel::}{dataChanged()} signal. Note that we did not explicitly connect the \l{QAbstractItemModel::}{dataChanged()} signal to the view. This happened automatically when we called \l{QTableView::}{setModel()}.
\section2 2.4 Setting up Headers for Columns and Rows
@@ -366,52 +408,75 @@
The header content, however, is set via the model, so we reimplement the
\l{QAbstractItemModel::headerData()}{headerData()} method:
- \snippet examples/tutorials/modelview/4_headers/mymodel.cpp quoting mymodel_c
+ \raw HTML
+ <br>
+ \endraw
+ (file source: examples/tutorials/modelview/4_headers/mymodel.cpp)
+ \snippet examples/tutorials/modelview/4_headers/mymodel.cpp quoting mymodel_c
+ Note that method \l{QAbstractItemModel::headerData()}{headerData()} also has a parameter role which has the same meaning as in \l{QAbstractItemModel::data()}{MyModel::data()}.
\section2 2.5 The Minimal Editing Example
- In this example, we are going to build an application that automatically
- populates a window title with content by repeating values entered into
- table cells.
+ In this example, we are going to build an application that automatically populates a window title with content by repeating values entered into table cells. To be able to access the window title easily we put the QTableView in a QMainWindow.
- The model decides whether editing capabilities are available . We only have
- to modify the model in order for the available editing capabilities to be
- enabled. This is done by reimplementing the following virtual methods:
- \l{QAbstractItemModel::}{setData()} and \l{QAbstractItemModel::}{flags()}.
+ The model decides whether editing capabilities are available . We only have to modify the model in order for the available editing capabilities to be enabled. This is done by reimplementing the following virtual methods: \l{QAbstractItemModel::}{setData()} and \l{QAbstractItemModel::}{flags()}.
- \snippet examples/tutorials/modelview/5_edit/mymodel.h Quoting ModelView Tutorial
- We use \c QStringList m_gridData to store our data. This makes
- \c m_gridData the core of MyModel. The rest of \c MyModel acts like a
- wrapper and adapts \c m_gridData to the QAbstractItemModel interface. We
- have also introduced the \c editCompleted() signal,
- which makes it possible to transfer the modified text to the window title.
- \snippet examples/tutorials/modelview/5_edit/mymodel.cpp quoting mymodel_d
+ \raw HTML
+ <br>
+ \endraw
+ (file source: examples/tutorials/modelview/5_edit/mymodel.h)
+ \snippet examples/tutorials/modelview/5_edit/mymodel.h Quoting ModelView Tutorial
- In the constructor, we fill \c QStringList gridData with 6 items (one item
- for every field in the table):
+ We use \c the two-dimensional array QString m_gridData to store our data. This makes \c m_gridData the core of MyModel. The rest of \c MyModel acts like a wrapper and adapts \c m_gridData to the QAbstractItemModel interface. We have also introduced the \c editCompleted() signal, which makes it possible to transfer the modified text to the window title.
+ \raw HTML
+ <br>
+ \endraw
+ (file source: examples/tutorials/modelview/5_edit/mymodel.cpp)
\snippet examples/tutorials/modelview/5_edit/mymodel.cpp quoting mymodel_e
- \l{QAbstractItemModel::setData()}{setData()} will be called each time the
- user edits a cell. The \c index parameter tells us which field has been
- edited and \c value provides the result of the editing process. The role
- will always be set to \c Qt::EditRole because our cells only contain text.
- If a checkbox were present and user permissions are set to allow the
- checkbox to be selected, calls would also be made with the role set to
- \c Qt::CheckStateRole.
+ \l{QAbstractItemModel::setData()}{setData()} will be called each time the user edits a cell. The \c index parameter tells us which field has been edited and \c value provides the result of the editing process. The role will always be set to \c Qt::EditRole because our cells only contain text. If a checkbox were present and user permissions are set to allow the checkbox to be selected, calls would also be made with the role set to \c Qt::CheckStateRole.
+
+
+ \raw HTML
+ <br>
+ \endraw
+ (file source: examples/tutorials/modelview/5_edit/mymodel.cpp)
\snippet examples/tutorials/modelview/5_edit/mymodel.cpp quoting mymodel_f
- Various properties of a cell can be adjusted with
- \l{QAbstractItemModel::flags()}{flags()}. Returning
- \c Qt::ItemIsEditable | \c Qt::ItemIsEnabled is enough to show an editor
- that a cell has been selected. If editing one cell modifies more data than
- the data in that particular cell, the model must emit a
- \l{QAbstractItemModel::}{dataChanged()} signal in order for the data that
- has been changed to be read.
+ Various properties of a cell can be adjusted with \l{QAbstractItemModel::flags()}{flags()}.
+
+ \raw HTML
+ <p> Returning <a href="qt.html#ItemFlag-enum">Qt::ItemIsEditable | Qt::ItemIsEnabled</a> is enough to show an editor that a cell has been selected.</p>
+ \endraw
+ If editing one cell modifies more data than the data in that particular cell, the model must emit a \l{QAbstractItemModel::dataChanged()}{dataChanged()} signal in order for the data that has been changed to be read.
+
+
+
+\raw HTML
+<br>
+<br>
+<br>
+<br>
+<br>
+\endraw
+
+\raw HTML
+<p style="position:absolute;left:5px;bottom:5px;">
+<a href="modelview-part1.html">previous page</a>
+</p>
+\endraw
+
+\raw HTML
+<p style="position:absolute;right:5px;bottom:5px;">
+<a href="modelview-part3.html">next page</a>
+</p>
+\endraw
+
*/
/*!
@@ -420,21 +485,20 @@
\previouspage {modelview-part2.html}{Developing a Simple Model/View Application}
\nextpage {modelview-part4.html}{Good Sources of Additional Information}
\title Model/View Chapter 3 - Intermediate Topics
-
+\raw HTML
+<br>
+\endraw
\section1 3. Intermediate Topics
-
+\raw HTML
+<br>
+\endraw
\section2 3.1 TreeView
- You can convert the example above into an application with a tree view.
- Simply replace QTableView with QTreeView, which results in a read/write
- tree. No changes have to be made to the model. The tree won't have any
- hierarchies because there aren't any hierarchies in the model itself.
+ You can convert the example above into an application with a tree view. Simply replace QTableView with QTreeView, which results in a read/write tree. No changes have to be made to the model. The tree won't have any hierarchies because there aren't any hierarchies in the model itself.
\image dummy_tree.png
- QListView, QTableView and QTreeView all use a model abstraction, which is a
- merged list, table and tree. This makes it possible to use several different
- types of view classes from the same model.
+ QListView, QTableView and QTreeView all use a model abstraction, which is a merged list, table and tree. This makes it possible to use several different types of view classes from the same model.
\image list_table_tree.png
@@ -442,21 +506,17 @@
\image example_model.png
- We want to present a real tree. We have wrapped our data in the examples
- above in order to make a model. This time we use QStandardItemModel, which
- is a container for hierarchical data that also implements
- QAbstractItemModel. To show a tree, QStandardItemModel must be populated
- with \l{QStandardItem}{QStandardItems}, which are able to hold all the
- standard properties of items like text, fonts, checkboxes or brushes.
- \image tree_2_with_algorithm.png
+ We want to present a real tree. We have wrapped our data in the examples above in order to make a model. This time we use QStandardItemModel, which is a container for hierarchical data that also implements QAbstractItemModel. To show a tree, QStandardItemModel must be populated with \l{QStandardItem}{QStandardItems}, which are able to hold all the standard properties of items like text, fonts, checkboxes or brushes. \image tree_2_with_algorithm.png
+
+
+ \raw HTML
+ <br>
+ \endraw
+ (file source: examples/tutorials/modelview/6_treeview/mainwindow.cpp)
- \snippet examples/tutorials/modelview/6_treeview/modelview.cpp Quoting ModelView Tutorial
+ \snippet examples/tutorials/modelview/6_treeview/mainwindow.cpp Quoting ModelView Tutorial
- We simply instantiate a QStandardItemModel and add a couple of
- \l{QStandardItem}{QStandardItems} to the constructor. We can then make a
- hierarchical data structure because a QStandardItem can hold other
- \l{QStandardItem}{QStandardItems}. Nodes are collapsed and expanded within
- the view.
+ We simply instantiate a QStandardItemModel and add a couple of \l{QStandardItem}{QStandardItems} to the constructor. We can then make a hierarchical data structure because a QStandardItem can hold other \l{QStandardItem}{QStandardItems}. Nodes are collapsed and expanded within the view.
\section2 3.2 Working with Selections
@@ -466,38 +526,29 @@
So let's create a couple of items:
- \snippet examples/tutorials/modelview/7_selections/modelview.cpp quoting modelview_a
- Views manage selections within a separate selection model, which can be
- retrieved with the \l{QAbstractItemView::}{selectionModel()}
- method. We retrieve the selection Model in order to connect a slot to its
- \l{QAbstractItemView::}{selectionChanged()} signal.
+ \raw HTML
+ <br>
+ <p>(file source: examples/tutorials/modelview/7_selections/mainwindow.cpp)</p>
+ \endraw
+ \snippet examples/tutorials/modelview/7_selections/mainwindow.cpp quoting modelview_a
+
+ Views manage selections within a separate selection model, which can be retrieved with the \l{QAbstractItemView::}{selectionModel()} method. We retrieve the selection Model in order to connect a slot to its \l{QAbstractItemView::}{selectionChanged()} signal.
+
- \snippet examples/tutorials/modelview/7_selections/modelview.cpp quoting modelview_b
+ \raw HTML
+ <br>
+ <p>(file source: examples/tutorials/modelview/7_selections/mainwindow.cpp)</p>
+ \endraw
+ \snippet examples/tutorials/modelview/7_selections/mainwindow.cpp quoting modelview_b
- We get the model index that corresponds to the selection by calling
- \l{QItemSelectionModel::currentIndex()}{treeView->selectionModel()->currentIndex()}
- and we get the the field's string by using the model index. Then we just
- calculate the item's \c hierarchyLevel. Top level items do not have
- parents and the \l{QAbstractItemModel::}{parent()} method will return a
- default constructed \l{QModelIndex}{QModelIndex()}. This is why we use the
- \l{QAbstractItemModel::}{parent()} method to iterate to the top level while
- counting the steps performed during iteration.
+ We get the model index that corresponds to the selection by calling \l{QItemSelectionModel::currentIndex()}{treeView->selectionModel()->currentIndex()} and we get the the field's string by using the model index. Then we just calculate the item's \c hierarchyLevel. Top level items do not have parents and the \l{QAbstractItemModel::}{parent()} method will return a default constructed \l{QModelIndex}{QModelIndex()}. This is why we use the \l{QAbstractItemModel::}{parent()} method to iterate to the top level while counting the steps performed during iteration.
- The selection model (as shown above) can be retrieved, but it can also be
- set with \l{QAbstractItemView}{QAbstractItemView::setSelectionModel}. This
- is how it's possible to have 3 view classes with synchronised selections
- because only one instance of a selection model is used. The instance of a
- selection model is retrieved from the first view class with
- \l{QAbstractItemView::}{selectionModel()} and the result is assigned to the
- second and third view class with \l{QAbstractItemView::}{setSelectionModel()}.
+ The selection model (as shown above) can be retrieved, but it can also be set with \l{QAbstractItemView}{QAbstractItemView::setSelectionModel}. This is how it's possible to have 3 view classes with synchronised selections because only one instance of a selection model is used. To share a selection model between 3 views use \l{QAbstractItemView::}{selectionModel()} and assign the result to the second and third view class with \l{QAbstractItemView::}{setSelectionModel()}.
\section2 3.3 Predefined Models
- The typical way to use model/view is to wrap specific data to make it
- usable with view classes. Qt, however, also provides predefined models for
- common underlying data structures. If one of the available data structures
- is suitable for your application, a predefined model can be a good choice.
+ The typical way to use model/view is to wrap specific data to make it usable with view classes. Qt, however, also provides predefined models for common underlying data structures. If one of the available data structures is suitable for your application, a predefined model can be a good choice.
\table
\row
@@ -527,23 +578,14 @@
\section2 3.4 Delegates
- In all examples so far, data is presented as text or a checkbox in a cell
- and is edited as text or a checkbox. The component that provides these
- presentation and editing services is called a \e delegate. We are only just
- beginning to work with the delegate because the view uses a default
- delegate. But imagine that we want to have a different editor.(e.g. a
- slider or a drop down list) Or imagine that we want to present data as
- graphics. Let's take a look at an example called
- \l{Star Delegate Example}{Star Delegate}, in which stars are used to show
- a rating:
+ In all examples so far, data is presented as text or a checkbox in a cell and is edited as text or a checkbox. The component that provides these presentation and editing services is called a \e delegate. We are only just beginning to work with the delegate because the view uses a default delegate. But imagine that we want to have a different editor.(e.g. a slider or a drop down list) Or imagine that we want to present data as graphics. Let's take a look at an example called \l{Star Delegate Example}{Star Delegate}, in which stars are used to show a rating:
+ \raw HTML
+ <p style="">
+ (<a href="itemviews-stardelegate.html">Star Delegate Example</a>)</p>
+ \endraw
\image stardelegate.png
- The view has a method that replaces the default delegate and installs a
- custom delegate. This method is called
- \l{QAbstractItemView::}{setItemDelegate()}. A new delegate can be written
- by creating a class that inherits from QStyledItemDelegate. In order to
- write a delegate that displays stars and has no input capabilities, we only
- need to overwrite 2 methods.
+ The view has a method that replaces the default delegate and installs a custom delegate. This method is called \l{QAbstractItemView::}{setItemDelegate()}. A new delegate can be written by creating a class that inherits from QStyledItemDelegate. In order to write a delegate that displays stars and has no input capabilities, we only need to overwrite 2 methods.
\code
class StarDelegate : public QStyledItemDelegate
@@ -558,36 +600,31 @@
};
\endcode
- \l{QStyledItemDelegate::}{paint()} draws stars depending on the content
- of the underlying data. The data can be looked up with parameter
- \l{QModelIndex::data()}{index.data()}.
- \l{QAbstractItemDelegate::}{sizeHint()} specifies each star's dimensions
- so the the cell will provide enough height and width to accommodate the
- stars.
+ \l{QStyledItemDelegate::}{paint()} draws stars depending on the content of the underlying data. The data can be looked up with parameter \l{QModelIndex::data()}{index.data()}. \l{QAbstractItemDelegate::}{sizeHint()} specifies each star's dimensions so the the cell will provide enough height and width to accommodate the stars.
+
+ Writing custom delegates is the right choice if you want to show your data with a custom graphical representation inside the grid of the view class. If you want to leave the grid, you would not use a custom delegate but a custom view class.
+
+Other references to delegates in Qt Documentation:
+\raw HTML
+<p style="">
+<a href="itemviews-spinboxdelegate.html">Spin Box Delegate Example</a><br>
+<a href="qabstractitemdelegate.html">QAbstractItemDelegate Class Reference</a><br>
+<a href="qsqlrelationaldelegate.html">QSqlRelationalDelegate Class Reference</a><br>
+<a href="qstyleditemdelegate.html">QStyledItemDelegate Class Reference</a><br>
+<a href="qitemdelegate.html">QItemDelegate Class Reference</a><br>
+</p>
+<br><br>
+\endraw
+
- Writing custom delegates is the right choice if you want to show your data
- with a custom graphical representation inside the grid of the view class.
- If you want to leave the grid, you can write a custom view class.
\section2 3.5 Debugging with ModelTest
- The passive nature of models provides new challenges for programmers.
- Inconsistencies in the model can cause the application to crash. Since the
- model is hit by numerous calls from the view, it is hard to find out which
- call has crashed the application and which operation has introduced the
- problem.
+ The passive nature of models provides new challenges for programmers. Inconsistencies in the model can cause the application to crash. Since the model is hit by numerous calls from the view, it is hard to find out which call has crashed the application and which operation has introduced the problem.
- Qt provides software called
- \l{http://labs.qt.nokia.com/page/Projects/Itemview/Modeltest}{ModelTest},
- which checks models while your programming is running. Every time the model
- is changed, ModelTest scans the model and reports errors with an assert.
- This is especially important for tree models, since their hierarchical
- nature leaves many possibilities for subtle inconsistencies.
+ Qt provides software called \l{http://labs.qt.nokia.com/page/Projects/Itemview/Modeltest}{ModelTest}, which checks models while your programming is running. Every time the model is changed, ModelTest scans the model and reports errors with an assert. This is especially important for tree models, since their hierarchical nature leaves many possibilities for subtle inconsistencies.
- Unlike view classes, ModelTest uses out of range indexes to test the model.
- This means your application may crash with ModelTest even if it runs
- perfectly without it. So you also need to handle all of the indexes that
- are out of range when using ModelTest.
+ Unlike view classes, ModelTest uses out of range indexes to test the model. This means your application may crash with ModelTest even if it runs perfectly without it. So you also need to handle all of the indexes that are out of range when using ModelTest.
\section2 3.6 Model/View NG
@@ -601,25 +638,23 @@
<!-- wrap content table p has 0 padding and the padding for p outside of the table is 5px-->
\endraw
- Model/View was introduced in Qt 4.0 and is a frequently used technology.
- Feedback from developers and new development trends have shown that there
- is a need to further develop the model/view technology. Therefore a
- research project originated at Nokia is looking into ways to go beyond the
- current implementation.
-
- One limitation of model/view is that view classes are basically all fixed
- grids. It is possible, but really hard to make a list view with icons
- placed on a curve; or cells expanding on mouse over events to show
- additional information.
- In order to achieve graphically rich view experiences, Model/View NG will
- use QGraphicsView to render elements. Nodel/View NG also aims to make
- model/view programming more intuitive. One way to achieve this is to have
- separate models for lists, tables and trees. The current model abstraction
- is complex because it is capable of representing a list, a table or a tree.
-
- Model/View NG is a research project. You are welcome to checkout the source
- code, monitor progress and take part in discussions at the following
- address: \l{http://labs.qt.nokia.com/page/Projects/Itemview/ItemviewsNG}
+ Model/View was introduced in Qt 4.0 and is a frequently used technology. Feedback from developers and new development trends have shown that there is a need to further develop the model/view technology. Therefore a research project originated at Nokia is looking into ways to go beyond the current implementation.
+ \raw HTML
+ <br><br>
+ \endraw
+ One limitation of model/view is that view classes are basically all fixed grids. It is possible, but really hard to make a list view with icons placed on a curve; or cells expanding on mouse over events to show additional information. In order to achieve graphically rich view experiences, Model/View NG will use QGraphicsView to render elements. Nodel/View NG also aims to make model/view programming more intuitive. One way to achieve this is to have separate models for lists, tables and trees. The current model abstraction is complex because it is capable of representing a list, a table or a tree.
+ \raw HTML
+ <br><br>
+ \endraw
+ Model/View NG is a research project. You are welcome to checkout the source code, monitor progress and take part in discussions at the following address: \l{http://labs.qt.nokia.com/page/Projects/Itemview/ItemviewsNG}
+
+
+
+
+\raw HTML
+<br><br>
+\endraw
+
\raw HTML
</td><td align="right" valign="top">
@@ -630,6 +665,26 @@
\raw HTML
</td></tr></table>
\endraw
+
+\raw HTML
+<br>
+<br>
+<br>
+<br>
+\endraw
+
+
+\raw HTML
+<p style="position:absolute;left:5px;bottom:5px;">
+<a href="modelview-part2.html">previous page</a>
+</p>
+\endraw
+
+\raw HTML
+<p style="position:absolute;right:5px;bottom:5px;">
+<a href="modelview-part4.html">last page</a>
+</p>
+\endraw
*/
/*!
@@ -637,9 +692,13 @@
\contentspage {modelview-index.html}{Model/View Contents}
\previouspage {modelview-part3.html}{Intermediate Topics}
\title Model/View Chapter 4 - Good Sources of Additional Information
-
+\raw HTML
+<br>
+\endraw
\section1 4. Good Sources of Additional Information
-
+\raw HTML
+<br>
+\endraw
\section2 4.1 Books
Model/View programming is covered quite extensively in the documentation of
@@ -657,12 +716,9 @@
\o \bold{Foundations of Qt Development} / Johan Thelin, \e{Apress}, ISBN 1-59059-831-8.
\endlist
- More information about these books is available on the
- \l{Books about Qt Programming}{Qt Web site}.
+ More information about these books is available on the \l{Books about Qt Programming}{Qt Web site}.
- The following list provides an overview of example programs contained in the
- books above. Some of them make very good templates for developing similar
- applications.
+ The following list provides an overview of example programs contained in the books above. Some of them make very good templates for developing similar applications.
\table
\header
@@ -921,9 +977,7 @@
\o comprehensive custom delegate example.
\endtable
- \l{Qt Demonstrations}{Demonstrations} are similar to examples except
- that no walkthrough is provided for the code. Demonstrations are also
- sometimes more feature rich.
+ \l{Qt Demonstrations}{Demonstrations} are similar to examples except that no walkthrough is provided for the code lines. Demonstrations are also sometimes more feature rich. ( \l demos.html )
\list
\o The \bold Interview demonstration shows the same model and
@@ -933,6 +987,5 @@
each item according to the type of data it contains.
\endlist
- A \l{Model/View Programming}{reference document} for model/view technology
- is also available.
+ A \l{Model/View Programming}{reference document} for model/view technology is also available.
*/