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diff --git a/doc/src/tutorials/modelview.qdoc b/doc/src/tutorials/modelview.qdoc index b39a01c..65f6674 100755..100644 --- a/doc/src/tutorials/modelview.qdoc +++ b/doc/src/tutorials/modelview.qdoc @@ -29,22 +29,28 @@ \page modelview.html \startpage {index.html}{Qt Reference Documentation} - \nextpage {modelview-part1.html}{Introduction} \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. + + 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 model/view programming, in + which widgets do not maintain internal data containers. They access external + data through a standardized interface and therefore avoid data duplication. + 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 model/view programming also + become clearer. \image treeview.png - \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: @@ -52,38 +58,29 @@ \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. - - The tutorial's source code is located in Qt's \c examples/tutorials/modelview - directory. + You will also learn whether your new application can be written easier with + model/view programming or if classic widgets will work just as well. - \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 + 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. + For more detailed information you may also want to look at the + \l{model-view-programming.html}{reference documentation} -*/ + If you are completely new to Qt, please read \l{How to Learn Qt} if you + have not already done so. -/*! - \page modelview-part1.html - \contentspage {modelview.html}{Model/View Contents} - \previouspage {modelview.html}{Model/View Contents} - \nextpage {modelview-part2.html}{Developing a Simple Model/View Application} - \title An Introduction to Model/View Programming \section1 1. Introduction @@ -104,16 +101,16 @@ \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. + 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. + 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 @@ -121,14 +118,14 @@ 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. + 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 @@ -138,9 +135,10 @@ \table \header \o Widget - \o Standard Widget (a convenience class with data in - the widget) - \o Model/View View Class (for use with external data) + \o Standard Widget\br + (an item based convenience class) + \o Model/View View Class\br + (for use with external data) \row \o \inlineimage listview.png \o \l QListWidget @@ -167,47 +165,26 @@ 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. + 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 -*/ - -/*! - \page modelview-part2-main-cpp.html - \title main.cpp - \quotefile tutorials/modelview/1_readonly/main.cpp -*/ -/*! - \page modelview-part2.html - \contentspage {modelview-index.html}{Model/View Contents} - \previouspage {modelview-part1.html}{Introduction} - \nextpage {modelview-part3.html}{Intermediate Topics} - \title Model/View Chapter 2 - A Simple Model/View Application \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 @@ -216,58 +193,55 @@ \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. + add editing capabilities later. + (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: + 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. + \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. + is easier to use than the more general QAbstractItemModel. + (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. + (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 + 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. - 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. + \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. + 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 + 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 @@ -276,12 +250,14 @@ 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 + 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: + 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. + (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 @@ -290,42 +266,45 @@ \table \header - \o Role (enum Qt::ItemDataRole ) + \o \l{Qt::ItemDataRole}{enum Qt::ItemDataRole} \o Meaning - \o Type + \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 + \o \l{Qt::AlignmentFlag}{enum Qt::AlignmentFlag} \row - \o {1, 3} Qt::CheckStateRole + \o {1, 3} \l{Qt::ItemDataRole}{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} + + sets checkboxes with \l{Qt::CheckState}{Qt::Checked} + + or \l{Qt::CheckState}{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. + \l{Qt::ItemDataRole}{Qt::ItemDataRole} enum's capabilities. - Now we need to determine how using a seperated model impacts the + 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. + \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 the error output + stream. 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 @@ -339,6 +318,7 @@ We still have a read only table, but this time the content changes every second because we are showing the current time. + (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 @@ -346,17 +326,18 @@ this with a timer. In the constructor, we set its interval to 1 second and connect its timeout signal. + (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: + (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()}. + 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 @@ -366,60 +347,58 @@ The header content, however, is set via the model, so we reimplement the \l{QAbstractItemModel::headerData()}{headerData()} method: + (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. + 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 + 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()}. + (file source: examples/tutorials/modelview/5_edit/mymodel.h) \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 - - 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 \c m_gridData to store our data. + This makes \c m_gridData the core of \c 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. + (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. + will always be set to \l 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 Qt::CheckStateRole. + (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. -*/ + \l{QAbstractItemModel::flags()}{flags()}. + + Returning \l{Qt::ItemFlag}{Qt::ItemIsSelectable | Qt::ItemIsEditable | Qt::ItemIsEnabled} + is enough to show an editor that a cell can be 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. -/*! - \page modelview-part3.html - \contentspage {modelview-index.html}{Model/View Contents} - \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 \section1 3. Intermediate Topics @@ -429,28 +408,30 @@ 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 + \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. - \image list_table_tree.png + \image list_table_tree.png This is how our example model looks so far: - \image example_model.png + \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. + with \l{QStandardItem}s, which are able to hold all the standard properties + of items like text, fonts, checkboxes or brushes. + \image tree_2_with_algorithm.png - \snippet examples/tutorials/modelview/6_treeview/modelview.cpp Quoting ModelView Tutorial + (file source: examples/tutorials/modelview/6_treeview/mainwindow.cpp) + \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 @@ -462,42 +443,45 @@ We want to access a selected item's content in order to output it into the window title together with the hierarchy level. + \image selection2.png So let's create a couple of items: - \snippet examples/tutorials/modelview/7_selections/modelview.cpp quoting modelview_a + (file source: examples/tutorials/modelview/7_selections/mainwindow.cpp) + \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 + 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 + (file source: examples/tutorials/modelview/7_selections/mainwindow.cpp) + \snippet examples/tutorials/modelview/7_selections/mainwindow.cpp quoting modelview_b - We get the model index that corresponds to the selection by calling + 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 + 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()}. + 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 @@ -531,26 +515,26 @@ 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 + 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: + 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: + \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 \l{QAbstractItemView::}{setItemDelegate()} method that + replaces the default delegate and installs a custom delegate. + 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 override 2 methods. \code class StarDelegate : public QStyledItemDelegate { Q_OBJECT public: - StarDelegate(QWidget *parent = 0); + StarDelegate(QWidget *parent = 0); void paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const; QSize sizeHint(const QStyleOptionViewItem &option, @@ -558,16 +542,28 @@ }; \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 by calling + \l{QModelIndex::data()}{index.data()}. The delegate's + \l{QAbstractItemDelegate::}{sizeHint()} method is used to obtain 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 can write a custom view class. + 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: + + \list + \o \l{Spin Box Delegate Example} + \o \l{QAbstractItemDelegate}{QAbstractItemDelegate Class Reference} + \o \l{QSqlRelationalDelegate}{QSqlRelationalDelegate Class Reference} + \o \l{QStyledItemDelegate}{QStyledItemDelegate Class Reference} + \o \l{QItemDelegate}{QItemDelegate Class Reference} + \endlist + \section2 3.5 Debugging with ModelTest @@ -575,9 +571,9 @@ 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. + problem. - Qt provides software called + Qt Labs 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. @@ -586,57 +582,9 @@ 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 - - \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 - - \raw HTML - <!-- 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} - - \raw HTML - </td><td align="right" valign="top"> - \endraw - - \inlineimage path.png - - \raw HTML - </td></tr></table> - \endraw -*/ + perfectly without it. So you also need to handle all of the indexes that are + out of range when using ModelTest. -/*! - \page modelview-part4.html - \contentspage {modelview-index.html}{Model/View Contents} - \previouspage {modelview-part3.html}{Intermediate Topics} - \title Model/View Chapter 4 - Good Sources of Additional Information \section1 4. Good Sources of Additional Information @@ -666,10 +614,10 @@ \table \header - \o example name - \o view class used - \o model used - \o aspects touched + \o Example name + \o View class used + \o Model used + \o Aspects covered \o \row \o Team Leaders @@ -695,26 +643,26 @@ \o QTableView \o custom model based on QAbstractTableModel - \o read only + \o Read only \o Book 1, Chapter 10, Figure 10.10 \row \o Cities \o QTableView - \o custom model based on + \o Custom model based on QAbstractTableModel - \o read / write + \o Read / write \o Book 1, Chapter 10, Figure 10.12 \row \o Boolean Parser \o QTreeView - \o custom model based on + \o Custom model based on QAbstractItemModel - \o read only + \o Read only \o Book 1, Chapter 10, Figure 10.14 \row \o Track Editor \o {2, 1} QTableWidget - \o custom delegate providing a custom editor + \o Custom delegate providing a custom editor \o Book 1, Chapter 10, Figure 10.15 \row @@ -723,47 +671,47 @@ QTableView QTreeView \o QDirModel - \o demonstrates the use of multiple views + \o Demonstrates the use of multiple views \o Book2, Chapter 8.2 \row \o Address Book \o QListView QTableView QTreeView - \o custom model based on + \o Custom model based on QAbstractTableModel - \o read / write + \o Read / write \o Book2, Chapter 8.4 \row \o Address Book with sorting \o \o QProxyModel - \o introducing sort and filter capabilities + \o Introducing sort and filter capabilities \o Book2, Chapter 8.5 \row \o Address Book with checkboxes \o \o - \o introducing checkboxes in model/view + \o Introducing checkboxes in model/view \o Book2, Chapter 8.6 \row \o Address Book with transposed grid \o - \o custom proxy Model based on QAbstractProxyModel - \o introducing a custom model + \o Custom proxy Model based on QAbstractProxyModel + \o Introducing a custom model \o Book2, Chapter 8.7 \row \o Address Book with drag and drop \o \o - \o introducing drag and drop support + \o Introducing drag and drop support \o Book2, Chapter 8.8 \row \o Address Book with custom editor \o \o - \o introducing custom delegates + \o Introducing custom delegates \o Book2, Chapter 8.9 \row \o Views @@ -771,51 +719,51 @@ QTableView QTreeView \o QStandardItemModel - \o read only + \o Read only \o Book 3, Chapter 5, figure 5-3 \row \o Bardelegate \o QTableView \o - \o custom delegate for presentation based on QAbstractItemDelegate + \o Custom delegate for presentation based on QAbstractItemDelegate \o Book 3, Chapter 5, figure 5-5 \row \o Editdelegate \o QTableView \o - \o custom delegate for editing based on QAbstractItemDelegate + \o Custom delegate for editing based on QAbstractItemDelegate \o Book 3, Chapter 5, figure 5-6 \row \o Singleitemview - \o custom view based on QAbstractItemView + \o Custom view based on QAbstractItemView \o - \o custom view + \o Custom view \o Book 3, Chapter 5, figure 5-7 \row \o listmodel \o QTableView - \o custom Model based on QAbstractTableModel - \o read only + \o Custom Model based on QAbstractTableModel + \o Read only \o Book 3, Chapter 5, Figure 5-8 \row \o treemodel \o QTreeView - \o custom Model based on QAbstractItemModel - \o read only + \o Custom Model based on QAbstractItemModel + \o Read only \o Book 3, Chapter 5, Figure 5-10 \row \o edit integers \o QListView - \o custom Model based on QAbstractListModel - \o read / write + \o Custom Model based on QAbstractListModel + \o Read / write \o Book 3, Chapter 5, Listing 5-37, Figure 5-11 \row \o sorting \o QTableView \o QSortFilterProxyModel applied to QStringListModel - \o demonstrates sorting + \o Demonstrates sorting \o Book 3, Chapter 5, Figure 5-12 \endtable @@ -823,19 +771,20 @@ \section2 4.2 Qt Documentation Qt 4.7 comes with 17 examples and 2 Demonstrations for model/view. - The examples can be found here: \l{Item Views Examples} + The examples can be found on the \l{Item Views Examples} page. + \table \header \o Example name \o View class used \o Model used - \o Aspects touched + \o Aspects covered \row \o Address Book \o QTableView \o QAbstractTableModel QSortFilterProxyModel - \o usage of QSortFilterProxyModel to generate different + \o Usage of QSortFilterProxyModel to generate different subsets from one data pool \row \o Basic Sort/Filter Model @@ -845,41 +794,41 @@ \o \row \o Chart - \o custom view + \o Custom view \o QStandardItemModel - \o designing custom views that cooperate with selection models + \o Designing custom views that cooperate with selection models \row \o Color Editor Factory \o {2, 1} QTableWidget - \o enhancing the standard delegate with a new custom editor to choose colours + \o Enhancing the standard delegate with a new custom editor to choose colours \row \o Combo Widget Mapper \o QDataWidgetMapper to map QLineEdit, QTextEdit and QComboBox \o QStandardItemModel - \o shows how a QComboBox can serve as a view class + \o Shows how a QComboBox can serve as a view class \row \o Custom Sort/Filter Model \o QTreeView \o QStandardItemModel QSortFilterProxyModel - \o subclass QSortFilterProxyModel for advanced sorting and filtering + \o Subclass QSortFilterProxyModel for advanced sorting and filtering \row \o Dir View \o QTreeView \o QDirModel - \o very small example to demonstrate how to assign a model to a view + \o Very small example to demonstrate how to assign a model to a view \row \o Editable Tree Model \o QTreeView - \o custom tree model - \o comprehensive example for working with trees, demonstrates + \o Custom tree model + \o Comprehensive example for working with trees, demonstrates editing cells and tree structure with an underlying custom model \row \o Fetch More \o QListView - \o custom list model - \o dynamically changing model + \o Custom list model + \o Dynamically changing model \row \o Frozen Column \o QTableView @@ -888,47 +837,47 @@ \row \o Pixelator \o QTableView - \o custom table model - \o implementation of a custom delegate + \o Custom table model + \o Implementation of a custom delegate \row \o Puzzle \o QListView - \o custom list model - \o model/view with drag and drop + \o Custom list model + \o Model/view with drag and drop \row \o Simple DOM Model \o QTreeView - \o custom tree model - \o read only example for a custom tree model + \o Custom tree model + \o Read only example for a custom tree model \row \o Simple Tree Model \o QTreeView - \o custom tree model - \o read only example for a custom tree model + \o Custom tree model + \o Read only example for a custom tree model \row \o Simple Widget Mapper \o QDataWidgetMapper to map QLineEdit, QTextEdit and QSpinBox \o QStandardItemModel - \o basic QDataWidgetMapper usage + \o Basic QDataWidgetMapper usage \row \o Spin Box Delegate \o QTableView \o QStandardItemModel - \o custom delegate that uses a spin box as a cell editor + \o Custom delegate that uses a spin box as a cell editor \row \o Star Delegate \o {2, 1} QTableWidget - \o comprehensive custom delegate example. + \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. Demonstrations are typically more + feature rich than examples. \list \o The \bold Interview demonstration shows the same model and selection being shared between three different views. - \o Demonstration \bold Spreadsheet demonstrates the use of a + \o The \bold Spreadsheet demonstration illustrates the use of a table view as a spreadsheet, using custom delegates to render each item according to the type of data it contains. \endlist @@ -936,3 +885,9 @@ A \l{Model/View Programming}{reference document} for model/view technology is also available. */ + +/*! + \page modelview-part2-main-cpp.html + \title main.cpp + \quotefile tutorials/modelview/1_readonly/main.cpp +*/ |