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The Completer example shows how to provide string-completion facilities for an input widget based on data provided by a model.
<!DOCTYPE RCC><RCC version="1.0"> <qresource prefix="/"> <file>resources/countries.txt</file> <file>resources/wordlist.txt</file> </qresource> </RCC>
class DirModel : public QDirModel { public: DirModel(QObject *parent = 0); QVariant data(const QModelIndex &index, int role = Qt::DisplayRole) const; };This class only has a constructor and a data() function as it is only created to enable data() to return the entire file path for the display role, unlike QDirModel's data() function that only returns the folder and not the drive label. This is further explained in DirModel's implementation.
DirModel::DirModel(QObject *parent) : QDirModel(parent) { }As mentioned earlier, the data() function is reimplemented in order to get it to return the entire file parth for the display role. For example, with a QDirModel, you will see "Program Files" in the view. However, with DirModel, you will see "C:\Program Files".
QVariant DirModel::data(const QModelIndex &index, int role) const { if (role == Qt::DisplayRole && index.column() == 0) { QString path = QDir::toNativeSeparators(filePath(index)); if (path.endsWith(QDir::separator())) path.chop(1); return path; } return QDirModel::data(index, role); }The screenshots below illustrate this difference:
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class MainWindow : public QMainWindow { Q_OBJECT public: MainWindow(QWidget *parent = 0); private slots: void about(); void changeCase(int); void changeMode(int); void changeModel();Within the MainWindow class, we have two private functions: createMenu() and modelFromFile(). We also declare the private widgets needed - three QComboBox objects, a QCheckBox, a QCompleter, a QLabel, and a QLineEdit.
private: void createMenu(); QAbstractItemModel *modelFromFile(const QString& fileName); QComboBox *caseCombo; QComboBox *modeCombo; QComboBox *modelCombo; QCheckBox *wrapCheckBox; QCompleter *completer; QLabel *contentsLabel; QLineEdit *lineEdit; };
We set up three QComboBox objects, modelComb, modeCombo and caseCombo. By default, the modelCombo is set to QDirModel, the modeCombo is set to "Filtered Popup" and the caseCombo is set to "Case Insensitive".
The following code example is written in c++.
MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent), completer(0), lineEdit(0) { createMenu(); QWidget *centralWidget = new QWidget; QLabel *modelLabel = new QLabel; modelLabel->setText(tr("Model")); modelCombo = new QComboBox; modelCombo->addItem(tr("QDirModel")); modelCombo->addItem(tr("QDirModel that shows full path")); modelCombo->addItem(tr("Country list")); modelCombo->addItem(tr("Word list")); modelCombo->setCurrentIndex(0); 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 wrapCheckBox is then set up. This checkBox determines if the completer's setWrapAround() property is enabled or disabled.
wrapCheckBox = new QCheckBox; wrapCheckBox->setText(tr("Wrap around completions")); wrapCheckBox->setChecked(true);We instantiate contentsLabel and set its size policy to fixed. The combo boxes' activated() signals are then connected to their respective slots.
contentsLabel = new QLabel; contentsLabel->setSizePolicy(QSizePolicy::Fixed, QSizePolicy::Fixed); connect(modelCombo, SIGNAL(activated(int)), this, SLOT(changeModel())); connect(modeCombo, SIGNAL(activated(int)), this, SLOT(changeMode(int))); connect(caseCombo, SIGNAL(activated(int)), this, SLOT(changeCase(int)));The lineEdit is set up and then we arrange all the widgets using a QGridLayout. The changeModel() function is called, to initialize the completer.
lineEdit = new QLineEdit; QGridLayout *layout = new QGridLayout; layout->addWidget(modelLabel, 0, 0); layout->addWidget(modelCombo, 0, 1); layout->addWidget(modeLabel, 1, 0); layout->addWidget(modeCombo, 1, 1); layout->addWidget(caseLabel, 2, 0); layout->addWidget(caseCombo, 2, 1); layout->addWidget(wrapCheckBox, 3, 0); layout->addWidget(contentsLabel, 4, 0, 1, 2); layout->addWidget(lineEdit, 5, 0, 1, 2); centralWidget->setLayout(layout); setCentralWidget(centralWidget); changeModel(); setWindowTitle(tr("Completer")); lineEdit->setFocus(); }The createMenu() function is used to instantiate the QAction objects needed to fill the fileMenu and helpMenu. The actions' triggered() signals 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 modelFromFile() function accepts the fileName of a file and processes it depending on its contents.
We first validate the file to ensure that it can be opened in QFile::ReadOnly mode. If this is unsuccessful, the function returns an empty QStringListModel.
The following code example is written in c++.
QAbstractItemModel *MainWindow::modelFromFile(const QString& fileName) { QFile file(fileName); if (!file.open(QFile::ReadOnly)) return new QStringListModel(completer);The mouse cursor is then overriden with Qt::WaitCursor before we fill a QStringList object, words, with the contents of file. Once this is done, we restore the mouse cursor.
#ifndef QT_NO_CURSOR QApplication::setOverrideCursor(QCursor(Qt::WaitCursor)); #endif QStringList words; while (!file.atEnd()) { QByteArray line = file.readLine(); if (!line.isEmpty()) words << line.trimmed(); } #ifndef QT_NO_CURSOR QApplication::restoreOverrideCursor(); #endifAs mentioned earlier, the resources file contains two files - countries.txt and words.txt. If the file read is words.txt, we return a QStringListModel with words as its QStringList and completer as its parent.
if (!fileName.contains(QLatin1String("countries.txt"))) return new QStringListModel(words, completer);If the file read is countries.txt, then we require a QStandardItemModel with words.count() rows, 2 columns, and completer as its parent.
QStandardItemModel *m = new QStandardItemModel(words.count(), 2, completer);A standard line in countries.txt is:Norway NO Hence, to populate the QStandardItemModel object, m, we have to split the country name and its symbol. Once this is done, we return m.
for (int i = 0; i < words.count(); ++i) { QModelIndex countryIdx = m->index(i, 0); QModelIndex symbolIdx = m->index(i, 1); QString country = words[i].mid(0, words[i].length() - 2).trimmed(); QString symbol = words[i].right(2); m->setData(countryIdx, country); m->setData(symbolIdx, symbol); } return m; }The changeMode() function sets the completer's mode, depending on the value of index.
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 changeModel() function changes the item model used based on the model selected by the user.
A switch statement is used to change the item model based on the index of modelCombo. If case is 0, we use an unsorted QDirModel, providing us with a file path excluding the drive label.
The following code example is written in c++.
void MainWindow::changeModel() { delete completer; completer = new QCompleter(this); switch (modelCombo->currentIndex()) { default: case 0: { // Unsorted QDirModel QDirModel *dirModel = new QDirModel(completer); completer->setModel(dirModel); contentsLabel->setText(tr("Enter file path")); } break;Note that we create the model with completer as the parent as this allows us to replace the model with a new model. The completer will ensure that the old one is deleted the moment a new model is assigned to it.
If case is 1, we use the DirModel we defined earlier, resulting in full paths for the files.
The following code example is written in c++.
case 1: { // DirModel that shows full paths DirModel *dirModel = new DirModel(completer); completer->setModel(dirModel); contentsLabel->setText(tr("Enter file path")); } break;When case is 2, we attempt to complete names of countries. This requires a QTreeView object, treeView. The country names are extracted from countries.txt and set the popup used to display completions to treeView.
case 2: { // Country List completer->setModel(modelFromFile(":/resources/countries.txt")); QTreeView *treeView = new QTreeView; completer->setPopup(treeView); treeView->setRootIsDecorated(false); treeView->header()->hide(); treeView->header()->setStretchLastSection(false); treeView->header()->setResizeMode(0, QHeaderView::Stretch); treeView->header()->setResizeMode(1, QHeaderView::ResizeToContents); contentsLabel->setText(tr("Enter name of your country")); } break;The screenshot below shows the Completer with the country list model.
The screenshot below shows the Completer with the word list model.
case 3: { // Word list completer->setModel(modelFromFile(":/resources/wordlist.txt")); completer->setModelSorting(QCompleter::CaseInsensitivelySortedModel); contentsLabel->setText(tr("Enter a word")); } break; } changeMode(modeCombo->currentIndex()); changeCase(caseCombo->currentIndex()); completer->setWrapAround(wrapCheckBox->isChecked()); lineEdit->setCompleter(completer); connect(wrapCheckBox, SIGNAL(clicked(bool)), completer, SLOT(setWrapAround(bool))); }The about() function provides a brief description about the example.
void MainWindow::about() { QMessageBox::about(this, tr("About"), tr("This example demonstrates the " "different features of the QCompleter class.")); }
int main(int argc, char *argv[]) { Q_INIT_RESOURCE(completer); QApplication app(argc, argv); MainWindow window; window.show(); return app.exec(); }
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