树模型补全器范例

The Tree Model Completer example shows how to provide completion facilities for a hierarchical model, using a period as the separator to access Child, GrandChild and GrandGrandChild level objects.

类似于补全器范例，提供 QComboBox objects to enable selection for completion mode and case sensitivity, as well as a QCheckBox for wrap completions.

资源文件

The contents of the TreeModelCompleter is read from treemodel.txt . This file is embedded within the treemodelcompleter.qrc resource file, which contains the following:

<!DOCTYPE RCC><RCC version="1.0">
<qresource prefix="/">
   <file>resources/treemodel.txt</file>
</qresource>
</RCC>

TreeModelCompleter 类定义

The TreeModelCompleter 是子类化的 QCompleter with two constructors - one with parent as an argument and another with parent and model as arguments.

class TreeModelCompleter : public QCompleter
{
    Q_OBJECT
    Q_PROPERTY(QString separator READ separator WRITE setSeparator)
public:
    explicit TreeModelCompleter(QObject *parent = 0);
    explicit TreeModelCompleter(QAbstractItemModel *model, QObject *parent = 0);
    QString separator() const;
public slots:
    void setSeparator(const QString &separator);
protected:
    QStringList splitPath(const QString &path) const override;
    QString pathFromIndex(const QModelIndex &index) const override;
private:
    QString sep;
};

The class reimplements the protected functions splitPath() and pathFromIndex() to suit a tree model. For more information on customizing QCompleter to suit tree models, refer to 处理树模型 .

TreeModelCompleter also has a separator property which is declared using the Q_PROPERTY () macro. The separator has READ and WRITE attributes and the corresponding functions separator() and setSeparator() . For more information on Q_PROPERTY (), refer to Qt 的特性系统 .

TreeModelCompleter 类实现

The first constructor constructs a TreeModelCompleter object with a parent while the second constructor constructs an object with a parent and a QAbstractItemModel , model .

TreeModelCompleter::TreeModelCompleter(QObject *parent)
    : QCompleter(parent)
{
}
TreeModelCompleter::TreeModelCompleter(QAbstractItemModel *model, QObject *parent)
    : QCompleter(model, parent)
{
}

The separator() function is a getter function that returns the separator string.

QString TreeModelCompleter::separator() const
{
    return sep;
}

As mentioned earlier, the splitPath() function is reimplemented because the default implementation is more suited to QFileSystemModel or list models. In order for QCompleter to split the path into a list of strings that are matched at each level, we split it using QString::split () 采用 sep as its separator.

QStringList TreeModelCompleter::splitPath(const QString &path) const
{
    if (sep.isNull()) {
        return QCompleter::splitPath(path);
    }
    return path.split(sep);
}

The pathFromIndex() function returns data for the completionRole() for a tree model. This function is reimplemented as its default implementation is more suitable for list models. If there is no separator, we use QCompleter 's default implementation, otherwise we use the prepend() function to navigate upwards and accumulate the data. The function then returns a QStringList , dataList , using a separator to join objects of different levels.

QString TreeModelCompleter::pathFromIndex(const QModelIndex &index) const
{
    if (sep.isNull()) {
        return QCompleter::pathFromIndex(index);
    }
    // navigate up and accumulate data
    QStringList dataList;
    for (QModelIndex i = index; i.isValid(); i = i.parent()) {
        dataList.prepend(model()->data(i, completionRole()).toString());
    }
    return dataList.join(sep);
}

MainWindow 类定义

The MainWindow 类是子类化的 QMainWindow and implements five custom slots: about() , changeCase() , changeMode() , highlight() ，和 updateContentsLabel() .

class MainWindow : public QMainWindow
{
    Q_OBJECT
public:
    MainWindow(QWidget *parent = 0);
private slots:
    void about();
    void changeCase(int);
    void changeMode(int);
    void highlight(const QModelIndex&);
    void updateContentsLabel(const QString&);

In addition, the class has two private functions, createMenu() and modelFromFile() , as well as private instances of QTreeView , QComboBox , QLabel , TreeModelCompleter and QLineEdit .

private:
    void createMenu();
    QAbstractItemModel *modelFromFile(const QString& fileName);
    QTreeView *treeView;
    QComboBox *caseCombo;
    QComboBox *modeCombo;
    QLabel *contentsLabel;
    TreeModelCompleter *completer;
    QLineEdit *lineEdit;
};

MainWindow 类实现

The MainWindow 's constructor creates a MainWindow object with a parent and initializes the completer and lineEdit 。 createMenu() function is invoked to set up the "File" menu and "Help" menu. The completer 's model is set to the QAbstractItemModel obtained from modelFromFile() ，和 highlighted() signal is connected to MainWindow 's highlight() 槽。

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent), completer(0), lineEdit(0)
{
    createMenu();
    completer = new TreeModelCompleter(this);
    completer->setModel(modelFromFile(":/resources/treemodel.txt"));
    completer->setSeparator(QLatin1String("."));
    QObject::connect(completer, SIGNAL(highlighted(QModelIndex)),
                     this, SLOT(highlight(QModelIndex)));
    QWidget *centralWidget = new QWidget;
    QLabel *modelLabel = new QLabel;
    modelLabel->setText(tr("Tree Model<br>(Double click items to edit)"));
    QLabel *modeLabel = new QLabel;
    modeLabel->setText(tr("Completion Mode"));
    modeCombo = new QComboBox;
    modeCombo->addItem(tr("Inline"));
    modeCombo->addItem(tr("Filtered Popup"));
    modeCombo->addItem(tr("Unfiltered Popup"));
    modeCombo->setCurrentIndex(1);
    QLabel *caseLabel = new QLabel;
    caseLabel->setText(tr("Case Sensitivity"));
    caseCombo = new QComboBox;
    caseCombo->addItem(tr("Case Insensitive"));
    caseCombo->addItem(tr("Case Sensitive"));
    caseCombo->setCurrentIndex(0);

The QLabel 对象 modelLabel , modeLabel and caseLabel are instantiated. Also, the QComboBox 对象， modeCombo and caseCombo , are instantiated and populated. By default, the completer 's mode is "Filtered Popup" and the case is insensitive.

    QLabel *separatorLabel = new QLabel;
    separatorLabel->setText(tr("Tree Separator"));
    QLineEdit *separatorLineEdit = new QLineEdit;
    separatorLineEdit->setText(completer->separator());
    connect(separatorLineEdit, SIGNAL(textChanged(QString)),
            completer, SLOT(setSeparator(QString)));
    QCheckBox *wrapCheckBox = new QCheckBox;
    wrapCheckBox->setText(tr("Wrap around completions"));
    wrapCheckBox->setChecked(completer->wrapAround());
    connect(wrapCheckBox, SIGNAL(clicked(bool)), completer, SLOT(setWrapAround(bool)));
    contentsLabel = new QLabel;
    contentsLabel->setSizePolicy(QSizePolicy::Fixed, QSizePolicy::Fixed);
    connect(separatorLineEdit, SIGNAL(textChanged(QString)),
            this, SLOT(updateContentsLabel(QString)));
    treeView = new QTreeView;
    treeView->setModel(completer->model());
    treeView->header()->hide();
    treeView->expandAll();
    connect(modeCombo, SIGNAL(activated(int)), this, SLOT(changeMode(int)));
    connect(caseCombo, SIGNAL(activated(int)), this, SLOT(changeCase(int)));
    lineEdit = new QLineEdit;
    lineEdit->setCompleter(completer);

使用 QGridLayout to place all the objects in the MainWindow .

    QGridLayout *layout = new QGridLayout;
    layout->addWidget(modelLabel, 0, 0); layout->addWidget(treeView, 0, 1);
    layout->addWidget(modeLabel, 1, 0);  layout->addWidget(modeCombo, 1, 1);
    layout->addWidget(caseLabel, 2, 0);  layout->addWidget(caseCombo, 2, 1);
    layout->addWidget(separatorLabel, 3, 0); layout->addWidget(separatorLineEdit, 3, 1);
    layout->addWidget(wrapCheckBox, 4, 0);
    layout->addWidget(contentsLabel, 5, 0, 1, 2);
    layout->addWidget(lineEdit, 6, 0, 1, 2);
    centralWidget->setLayout(layout);
    setCentralWidget(centralWidget);
    changeCase(caseCombo->currentIndex());
    changeMode(modeCombo->currentIndex());
    setWindowTitle(tr("Tree Model Completer"));
    lineEdit->setFocus();
}

The createMenu() function sets up the QAction objects required and adds them to the "File" menu and "Help" menu. The triggered() signals from these actions are connected to their respective slots.

void MainWindow::createMenu()
{
    QAction *exitAction = new QAction(tr("Exit"), this);
    QAction *aboutAct = new QAction(tr("About"), this);
    QAction *aboutQtAct = new QAction(tr("About Qt"), this);
    connect(exitAction, SIGNAL(triggered()), qApp, SLOT(quit()));
    connect(aboutAct, SIGNAL(triggered()), this, SLOT(about()));
    connect(aboutQtAct, SIGNAL(triggered()), qApp, SLOT(aboutQt()));
    QMenu* fileMenu = menuBar()->addMenu(tr("File"));
    fileMenu->addAction(exitAction);
    QMenu* helpMenu = menuBar()->addMenu(tr("About"));
    helpMenu->addAction(aboutAct);
    helpMenu->addAction(aboutQtAct);
}

The changeMode() function accepts an index corresponding to the user's choice of completion mode and changes the completer 's mode accordingly.

void MainWindow::changeMode(int index)
{
    QCompleter::CompletionMode mode;
    if (index == 0)
        mode = QCompleter::InlineCompletion;
    else if (index == 1)
        mode = QCompleter::PopupCompletion;
    else
        mode = QCompleter::UnfilteredPopupCompletion;
    completer->setCompletionMode(mode);
}

The about() function provides a brief description on the Tree Model Completer example.

void MainWindow::about()
{
    QMessageBox::about(this, tr("About"), tr("This example demonstrates how "
        "to use a QCompleter with a custom tree model."));
}

The changeCase() function alternates between 区分大小写 and 不区分大小写 modes, depending on the value of cs .

void MainWindow::changeCase(int cs)
{
    completer->setCaseSensitivity(cs ? Qt::CaseSensitive : Qt::CaseInsensitive);
}

`main()` 函数

The main() function instantiates MainWindow and invokes the show() function to display it.

int main(int argc, char *argv[])
{
    Q_INIT_RESOURCE(treemodelcompleter);
    QApplication app(argc, argv);
    MainWindow window;
    window.show();
    return app.exec();
}

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