The address book example shows how to use proxy models to display different views onto data from a single model.
This example provides an address book that allows contacts to be grouped alphabetically into 9 groups: ABC, DEF, GHI, ... , VW, ..., XYZ. This is achieved by using multiple views on the same model, each of which is filtered using an instance of the QSortFilterProxyModel 类。
地址簿包含 5 个类：
MainWindow
,
AddressWidget
,
TableModel
,
NewAddressTab
and
AddDialog
。
MainWindow
类使用
AddressWidget
作为其中心 Widget 并提供
File
and
工具
菜单。
AddressWidget
类是
QTabWidget
subclass that is used to manipulate the 10 tabs displayed in the example: the 9 alphabet group tabs and an instance of
NewAddressTab
。
NewAddressTab
类是子类化的
QWidget
that is only used whenever the address book is empty, prompting the user to add some contacts.
AddressWidget
also interacts with an instance of
TableModel
to add, edit and remove entries to the address book.
TableModel
是子类化的
QAbstractTableModel
that provides the standard model/view API to access data. It holds a list of added contacts. However, this data is not all visible in a single tab. Instead,
QTableView
is used to provide 9 different views of the same data, according to the alphabet groups.
QSortFilterProxyModel
is the class responsible for filtering the contacts for each group of contacts. Each proxy model uses a
QRegularExpression
to filter out contacts that do not belong in the corresponding alphabetical group. The
AddDialog
class is used to obtain information from the user for the address book. This
QDialog
subclass is instantiated by
NewAddressTab
to add contacts, and by
AddressWidget
to add and edit contacts.
We begin by looking at the
TableModel
实现。
TableModel
class provides standard API to access data in its list of contacts by subclassing
QAbstractTableModel
. The basic functions that must be implemented in order to do so are:
rowCount()
,
columnCount()
,
data()
,
headerData()
。对于
TableModel
to be editable, it has to provide implementations
insertRows()
,
removeRows()
,
setData()
and
flags()
函数。
struct Contact { QString name; QString address; bool operator==(const Contact &other) const { return name == other.name && address == other.address; } }; inline QDataStream &operator<<(QDataStream &stream, const Contact &contact) { return stream << contact.name << contact.address; } inline QDataStream &operator>>(QDataStream &stream, Contact &contact) { return stream >> contact.name >> contact.address; } class TableModel : public QAbstractTableModel { Q_OBJECT public: TableModel(QObject *parent = nullptr); TableModel(const QList<Contact> &contacts, QObject *parent = nullptr); int rowCount(const QModelIndex &parent) const override; int columnCount(const QModelIndex &parent) const override; QVariant data(const QModelIndex &index, int role) const override; QVariant headerData(int section, Qt::Orientation orientation, int role) const override; Qt::ItemFlags flags(const QModelIndex &index) const override; bool setData(const QModelIndex &index, const QVariant &value, int role = Qt::EditRole) override; bool insertRows(int position, int rows, const QModelIndex &index = QModelIndex()) override; bool removeRows(int position, int rows, const QModelIndex &index = QModelIndex()) override; const QList<Contact> &getContacts() const; private: QList<Contact> contacts; };
Two constructors are used, a default constructor which uses
TableModel
's own
QList<Contact>
and one that takes
QList<Contact>
as an argument, for convenience.
We implement the two constructors as defined in the header file. The second constructor initializes the list of contacts in the model, with the parameter value.
TableModel::TableModel(QObject *parent) : QAbstractTableModel(parent) { } TableModel::TableModel(const QList<Contact> &contacts, QObject *parent) : QAbstractTableModel(parent), contacts(contacts) { }
rowCount()
and
columnCount()
functions return the dimensions of the model. Whereas,
rowCount()
's value will vary depending on the number of contacts added to the address book,
columnCount()
's value is always 2 because we only need space for the
名称
and
地址
columns.
int TableModel::rowCount(const QModelIndex &parent) const { return parent.isValid() ? 0 : contacts.size(); } int TableModel::columnCount(const QModelIndex &parent) const { return parent.isValid() ? 0 : 2; }
data()
function returns either a
名称
or
地址
, based on the contents of the model index supplied. The row number stored in the model index is used to reference an item in the list of contacts. Selection is handled by the
QItemSelectionModel
, which will be explained with
AddressWidget
.
QVariant TableModel::data(const QModelIndex &index, int role) const { if (!index.isValid()) return QVariant(); if (index.row() >= contacts.size() || index.row() < 0) return QVariant(); if (role == Qt::DisplayRole) { const auto &contact = contacts.at(index.row()); switch (index.column()) { case 0: return contact.name; case 1: return contact.address; default: break; } } return QVariant(); }
headerData()
function displays the table's header,
名称
and
地址
. If you require numbered entries for your address book, you can use a vertical header which we have hidden in this example (see the
AddressWidget
implementation).
QVariant TableModel::headerData(int section, Qt::Orientation orientation, int role) const { if (role != Qt::DisplayRole) return QVariant(); if (orientation == Qt::Horizontal) { switch (section) { case 0: return tr("Name"); case 1: return tr("Address"); default: break; } } return QVariant(); }
insertRows()
function is called before new data is added, otherwise the data will not be displayed. The
beginInsertRows()
and
endInsertRows()
functions are called to ensure all connected views are aware of the changes.
bool TableModel::insertRows(int position, int rows, const QModelIndex &index) { Q_UNUSED(index); beginInsertRows(QModelIndex(), position, position + rows - 1); for (int row = 0; row < rows; ++row) contacts.insert(position, { QString(), QString() }); endInsertRows(); return true; }
removeRows()
function is called to remove data. Again,
beginRemoveRows()
and
endRemoveRows()
are called to ensure all connected views are aware of the changes.
bool TableModel::removeRows(int position, int rows, const QModelIndex &index) { Q_UNUSED(index); beginRemoveRows(QModelIndex(), position, position + rows - 1); for (int row = 0; row < rows; ++row) contacts.removeAt(position); endRemoveRows(); return true; }
setData()
function is the function that inserts data into the table, item by item and not row by row. This means that to fill a row in the address book,
setData()
must be called twice, as each row has 2 columns. It is important to emit the
dataChanged()
signal as it tells all connected views to update their displays.
bool TableModel::setData(const QModelIndex &index, const QVariant &value, int role) { if (index.isValid() && role == Qt::EditRole) { const int row = index.row(); auto contact = contacts.value(row); switch (index.column()) { case 0: contact.name = value.toString(); break; case 1: contact.address = value.toString(); break; default: return false; } contacts.replace(row, contact); emit dataChanged(index, index, {Qt::DisplayRole, Qt::EditRole}); return true; } return false; }
flags()
function returns the item flags for the given index.
Qt::ItemFlags TableModel::flags(const QModelIndex &index) const { if (!index.isValid()) return Qt::ItemIsEnabled; return QAbstractTableModel::flags(index) | Qt::ItemIsEditable; }
We set the
Qt::ItemIsEditable
flag because we want to allow the
TableModel
to be edited. Although for this example we don't use the editing features of the
QTableView
object, we enable them here so that we can reuse the model in other programs.
The last function in
TableModel
,
getContacts()
返回
QList
<Contact> object that holds all the contacts in the address book. We use this function later to obtain the list of contacts to check for existing entries, write the contacts to a file and read them back. Further explanation is given with
AddressWidget
.
const QList<Contact> &TableModel::getContacts() const { return contacts; }
AddressWidget
class is technically the main class involved in this example as it provides functions to add, edit and remove contacts, to save the contacts to a file and to load them from a file.
class AddressWidget : public QTabWidget { Q_OBJECT public: AddressWidget(QWidget *parent = nullptr); void readFromFile(const QString &fileName); void writeToFile(const QString &fileName); public slots: void showAddEntryDialog(); void addEntry(const QString &name, const QString &address); void editEntry(); void removeEntry(); signals: void selectionChanged (const QItemSelection &selected); private: void setupTabs(); TableModel *table; NewAddressTab *newAddressTab; };
AddressWidget
extends
QTabWidget
in order to hold 10 tabs (
NewAddressTab
and the 9 alphabet group tabs) and also manipulates
table
，
TableModel
对象，
proxyModel
，
QSortFilterProxyModel
object that we use to filter the entries, and
tableView
，
QTableView
对象。
AddressWidget
constructor accepts a parent widget and instantiates
NewAddressTab
,
TableModel
and
QSortFilterProxyModel
。
NewAddressTab
object, which is used to indicate that the address book is empty, is added and the rest of the 9 tabs are set up with
setupTabs()
.
AddressWidget::AddressWidget(QWidget *parent) : QTabWidget(parent), table(new TableModel(this)), newAddressTab(new NewAddressTab(this)) { connect(newAddressTab, &NewAddressTab::sendDetails, this, &AddressWidget::addEntry); addTab(newAddressTab, tr("Address Book")); setupTabs(); }
setupTabs()
function is used to set up the 9 alphabet group tabs, table views and proxy models in
AddressWidget
. Each proxy model in turn is set to filter contact names according to the relevant alphabet group using a case-insensitive
QRegularExpression
object. The table views are also sorted in ascending order using the corresponding proxy model's
sort()
函数。
Each table view's selectionMode 被设为 QAbstractItemView::SingleSelection and selectionBehavior 被设为 QAbstractItemView::SelectRows , allowing the user to select all the items in one row at the same time. Each QTableView object is automatically given a QItemSelectionModel that keeps track of the selected indexes.
void AddressWidget::setupTabs() { const auto groups = { "ABC", "DEF", "GHI", "JKL", "MNO", "PQR", "STU", "VW", "XYZ" }; for (const QString &str : groups) { const auto regExp = QRegularExpression(QString("^[%1].*").arg(str), QRegularExpression::CaseInsensitiveOption); auto proxyModel = new QSortFilterProxyModel(this); proxyModel->setSourceModel(table); proxyModel->setFilterRegularExpression(regExp); proxyModel->setFilterKeyColumn(0); QTableView *tableView = new QTableView; tableView->setModel(proxyModel); tableView->setSelectionBehavior(QAbstractItemView::SelectRows); tableView->horizontalHeader()->setStretchLastSection(true); tableView->verticalHeader()->hide(); tableView->setEditTriggers(QAbstractItemView::NoEditTriggers); tableView->setSelectionMode(QAbstractItemView::SingleSelection); tableView->setSortingEnabled(true); connect(tableView->selectionModel(), &QItemSelectionModel::selectionChanged, this, &AddressWidget::selectionChanged); connect(this, &QTabWidget::currentChanged, this, [this, tableView](int tabIndex) { if (widget(tabIndex) == tableView) emit selectionChanged(tableView->selectionModel()->selection()); }); addTab(tableView, str); } }
QItemSelectionModel
类提供
selectionChanged
signal that is connected to
AddressWidget
's
selectionChanged()
signal. We also connect
QTabWidget::currentChanged
() signal to the lambda expression which emits
AddressWidget
's
selectionChanged()
as well. These connections are necessary to enable the
Edit Entry...
and
Remove Entry
actions in
MainWindow
's Tools menu. It is further explained in
MainWindow
's implementation.
Each table view in the address book is added as a tab to the QTabWidget with the relevant label, obtained from the QStringList of groups.
We provide two
addEntry()
functions: One which is intended to be used to accept user input, and the other which performs the actual task of adding new entries to the address book. We divide the responsibility of adding entries into two parts to allow
newAddressTab
to insert data without having to popup a dialog.
The first
addEntry()
function is a slot connected to the
MainWindow
's
Add Entry...
action. This function creates an
AddDialog
object and then calls the second
addEntry()
function to actually add the contact to
table
.
void AddressWidget::showAddEntryDialog() { AddDialog aDialog; if (aDialog.exec()) addEntry(aDialog.name(), aDialog.address()); }
Basic validation is done in the second
addEntry()
function to prevent duplicate entries in the address book. As mentioned with
TableModel
, this is part of the reason why we require the getter method
getContacts()
.
void AddressWidget::addEntry(const QString &name, const QString &address) { if (!table->getContacts().contains({ name, address })) { table->insertRows(0, 1, QModelIndex()); QModelIndex index = table->index(0, 0, QModelIndex()); table->setData(index, name, Qt::EditRole); index = table->index(0, 1, QModelIndex()); table->setData(index, address, Qt::EditRole); removeTab(indexOf(newAddressTab)); } else { QMessageBox::information(this, tr("Duplicate Name"), tr("The name \"%1\" already exists.").arg(name)); } }
If the model does not already contain an entry with the same name, we call
setData()
to insert the name and address into the first and second columns. Otherwise, we display a
QMessageBox
to inform the user.
注意：
newAddressTab
is removed once a contact is added as the address book is no longer empty.
Editing an entry is a way to update the contact's address only, as the example does not allow the user to change the name of an existing contact.
Firstly, we obtain the active tab's
QTableView
object using
QTabWidget::currentWidget
(). Then we extract the
selectionModel
从
tableView
to obtain the selected indexes.
void AddressWidget::editEntry() { QTableView *temp = static_cast<QTableView*>(currentWidget()); QSortFilterProxyModel *proxy = static_cast<QSortFilterProxyModel*>(temp->model()); QItemSelectionModel *selectionModel = temp->selectionModel(); const QModelIndexList indexes = selectionModel->selectedRows(); QString name; QString address; int row = -1; for (const QModelIndex &index : indexes) { row = proxy->mapToSource(index).row(); QModelIndex nameIndex = table->index(row, 0, QModelIndex()); QVariant varName = table->data(nameIndex, Qt::DisplayRole); name = varName.toString(); QModelIndex addressIndex = table->index(row, 1, QModelIndex()); QVariant varAddr = table->data(addressIndex, Qt::DisplayRole); address = varAddr.toString(); }
Next we extract data from the row the user intends to edit. This data is displayed in an instance of
AddDialog
with a different window title. The
table
is only updated if changes have been made to data in
aDialog
.
AddDialog aDialog;
aDialog.setWindowTitle(tr("Edit a Contact"));
aDialog.editAddress(name, address);
if (aDialog.exec()) {
const QString newAddress = aDialog.address();
if (newAddress != address) {
const QModelIndex index = table->index(row, 1, QModelIndex());
table->setData(index, newAddress, Qt::EditRole);
}
}
}
Entries are removed using the
removeEntry()
function. The selected row is removed by accessing it through the
QItemSelectionModel
对象，
selectionModel
。
newAddressTab
is re-added to the
AddressWidget
only if the user removes all the contacts in the address book.
void AddressWidget::removeEntry() { QTableView *temp = static_cast<QTableView*>(currentWidget()); QSortFilterProxyModel *proxy = static_cast<QSortFilterProxyModel*>(temp->model()); QItemSelectionModel *selectionModel = temp->selectionModel(); const QModelIndexList indexes = selectionModel->selectedRows(); for (QModelIndex index : indexes) { int row = proxy->mapToSource(index).row(); table->removeRows(row, 1, QModelIndex()); } if (table->rowCount(QModelIndex()) == 0) insertTab(0, newAddressTab, tr("Address Book")); }
writeToFile()
function is used to save a file containing all the contacts in the address book. The file is saved in a custom
.dat
format. The contents of the list of contacts are written to
file
使用
QDataStream
. If the file cannot be opened, a
QMessageBox
is displayed with the related error message.
void AddressWidget::writeToFile(const QString &fileName) { QFile file(fileName); if (!file.open(QIODevice::WriteOnly)) { QMessageBox::information(this, tr("Unable to open file"), file.errorString()); return; } QDataStream out(&file); out << table->getContacts(); }
readFromFile()
function loads a file containing all the contacts in the address book, previously saved using
writeToFile()
.
QDataStream
is used to read the contents of a
.dat
file into a list of contacts and each of these is added using
addEntry()
.
void AddressWidget::readFromFile(const QString &fileName) { QFile file(fileName); if (!file.open(QIODevice::ReadOnly)) { QMessageBox::information(this, tr("Unable to open file"), file.errorString()); return; } QList<Contact> contacts; QDataStream in(&file); in >> contacts; if (contacts.isEmpty()) { QMessageBox::information(this, tr("No contacts in file"), tr("The file you are attempting to open contains no contacts.")); } else { for (const auto &contact: qAsConst(contacts)) addEntry(contact.name, contact.address); } }
NewAddressTab
class provides an informative tab telling the user that the address book is empty. It appears and disappears according to the contents of the address book, as mentioned in
AddressWidget
's implementation.
NewAddressTab
class extends
QWidget
and contains a
QLabel
and
QPushButton
.
class NewAddressTab : public QWidget { Q_OBJECT public: NewAddressTab(QWidget *parent = nullptr); public slots: void addEntry(); signals: void sendDetails(const QString &name, const QString &address); };
The constructor instantiates the
addButton
,
descriptionLabel
and connects the
addButton
's signal to the
addEntry()
槽。
NewAddressTab::NewAddressTab(QWidget *parent) : QWidget(parent) { auto descriptionLabel = new QLabel(tr("There are currently no contacts in your address book. " "\nClick Add to add new contacts.")); auto addButton = new QPushButton(tr("Add")); connect(addButton, &QAbstractButton::clicked, this, &NewAddressTab::addEntry); auto mainLayout = new QVBoxLayout; mainLayout->addWidget(descriptionLabel); mainLayout->addWidget(addButton, 0, Qt::AlignCenter); setLayout(mainLayout); }
addEntry()
function is similar to
AddressWidget
's
addEntry()
in the sense that both functions instantiate an
AddDialog
object. Data from the dialog is extracted and sent to
AddressWidget
's
addEntry()
slot by emitting the
sendDetails()
信号。
void NewAddressTab::addEntry() { AddDialog aDialog; if (aDialog.exec()) emit sendDetails(aDialog.name(), aDialog.address()); }
AddDialog
class extends
QDialog
and provides the user with a
QLineEdit
和
QTextEdit
to input data into the address book.
class AddDialog : public QDialog { Q_OBJECT public: AddDialog(QWidget *parent = nullptr); QString name() const; QString address() const; void editAddress(const QString &name, const QString &address); private: QLineEdit *nameText; QTextEdit *addressText; };
AddDialog
's constructor sets up the user interface, creating the necessary widgets and placing them into layouts.
AddDialog::AddDialog(QWidget *parent) : QDialog(parent), nameText(new QLineEdit), addressText(new QTextEdit) { auto nameLabel = new QLabel(tr("Name")); auto addressLabel = new QLabel(tr("Address")); auto okButton = new QPushButton(tr("OK")); auto cancelButton = new QPushButton(tr("Cancel")); auto gLayout = new QGridLayout; gLayout->setColumnStretch(1, 2); gLayout->addWidget(nameLabel, 0, 0); gLayout->addWidget(nameText, 0, 1); gLayout->addWidget(addressLabel, 1, 0, Qt::AlignLeft|Qt::AlignTop); gLayout->addWidget(addressText, 1, 1, Qt::AlignLeft); auto buttonLayout = new QHBoxLayout; buttonLayout->addWidget(okButton); buttonLayout->addWidget(cancelButton); gLayout->addLayout(buttonLayout, 2, 1, Qt::AlignRight); auto mainLayout = new QVBoxLayout; mainLayout->addLayout(gLayout); setLayout(mainLayout); connect(okButton, &QAbstractButton::clicked, this, &QDialog::accept); connect(cancelButton, &QAbstractButton::clicked, this, &QDialog::reject); setWindowTitle(tr("Add a Contact")); } QString AddDialog::name() const { return nameText->text(); } QString AddDialog::address() const { return addressText->toPlainText(); } void AddDialog::editAddress(const QString &name, const QString &address) { nameText->setReadOnly(true); nameText->setText(name); addressText->setPlainText(address); }
To give the dialog the desired behavior, we connect the OK and Cancel buttons to the dialog's accept() and reject() slots. Since the dialog only acts as a container for name and address information, we do not need to implement any other functions for it.
MainWindow
class extends
QMainWindow
and implements the menus and actions necessary to manipulate the address book.
|
|
class MainWindow : public QMainWindow { Q_OBJECT public: MainWindow(); private slots: void updateActions(const QItemSelection &selection); void openFile(); void saveFile(); private: void createMenus(); AddressWidget *addressWidget; QAction *editAct; QAction *removeAct; };
MainWindow
class uses an
AddressWidget
as its central widget and provides the File menu with
打开
,
Close
and
Exit
actions, as well as the
工具
menu with
Add Entry...
,
Edit Entry...
and
Remove Entry
actions.
The constructor for
MainWindow
instantiates AddressWidget, sets it as its central widget and calls the
createMenus()
函数。
MainWindow::MainWindow() : QMainWindow(), addressWidget(new AddressWidget) { setCentralWidget(addressWidget); createMenus(); setWindowTitle(tr("Address Book")); }
createMenus()
function sets up the
File
and
工具
menus, connecting the actions to their respective slots. Both the
Edit Entry...
and
Remove Entry
actions are disabled by default as such actions cannot be carried out on an empty address book. They are only enabled when one or more contacts are added.
void MainWindow::createMenus() { QMenu *fileMenu = menuBar()->addMenu(tr("&File")); QAction *openAct = new QAction(tr("&Open..."), this); fileMenu->addAction(openAct); connect(openAct, &QAction::triggered, this, &MainWindow::openFile); ... editAct = new QAction(tr("&Edit Entry..."), this); editAct->setEnabled(false); toolMenu->addAction(editAct); connect(editAct, &QAction::triggered, addressWidget, &AddressWidget::editEntry); toolMenu->addSeparator(); removeAct = new QAction(tr("&Remove Entry"), this); removeAct->setEnabled(false); toolMenu->addAction(removeAct); connect(removeAct, &QAction::triggered, addressWidget, &AddressWidget::removeEntry); connect(addressWidget, &AddressWidget::selectionChanged, this, &MainWindow::updateActions); }
Apart from connecting all the actions' signals to their respective slots, we also connect
AddressWidget
's
selectionChanged()
signal to its
updateActions()
槽。
openFile()
function allows the user to choose a file with the
open file dialog
. The chosen file has to be a custom
.dat
file that contains address book contacts. This function is a slot connected to
openAct
在
File
菜单。
void MainWindow::openFile() { QString fileName = QFileDialog::getOpenFileName(this); if (!fileName.isEmpty()) addressWidget->readFromFile(fileName); }
saveFile()
function allows the user to save a file with the
save file dialog
. This function is a slot connected to
saveAct
在
File
菜单。
void MainWindow::saveFile() { QString fileName = QFileDialog::getSaveFileName(this); if (!fileName.isEmpty()) addressWidget->writeToFile(fileName); }
updateActions()
function enables and disables
Edit Entry...
and
Remove Entry
depending on the contents of the address book. If the address book is empty, these actions are disabled; otherwise, they are enabled. This function is a slot is connected to the
AddressWidget
's
selectionChanged()
信号。
void MainWindow::updateActions(const QItemSelection &selection) { QModelIndexList indexes = selection.indexes(); if (!indexes.isEmpty()) { removeAct->setEnabled(true); editAct->setEnabled(true); } else { removeAct->setEnabled(false); editAct->setEnabled(false); } }
The main function for the address book instantiates
QApplication
and opens a
MainWindow
before running the event loop.
int main(int argc, char *argv[]) { QApplication app(argc, argv); MainWindow mw; mw.show(); return app.exec(); }