I have a text field and a button purely designed in c++(without importing a qml doc). How do i read the text from the text field when I click the buton.
I am unable to find a function associated for that.
To hook up the button to a method, use the following code:
button = new Button();
texField = new TextField();
connect(button, SIGNAL(clicked()), this, SLOT(onClicked());
Then define the onClicked slot as so:
void ClassName::onClicked() {
qDebug() << textField->text(); //print the textField's text
}
For this to work, this method has to be marked in the class as a Q_SLOT and the object itself must be marked as a Q_OBJECT.
Related
Suppose I have a single text box and a radio button placed below the text box .
What I want is that if the user enters some text and ALSO clicks the radio button a similar text box and a radio button should appear just below. And similar thing should happen if the user does that for new UI items.
Any suggestions what classes I should be looking for?
The relevant class you need to handle the inserting of new widgets is one of the QLayout subclasses, most likely QVBoxLayout it sounds like. This will allow you to insert a new textbox and radio button at the bottom of the layout, which will then automatically expand to fit these new widgets.
Inserting the new objects is pretty straightforward. Connect a slot to a signal of the QRadioButton that's at the bottom of the layout, like the QRadioButton::toggled or QRadioButton::clicked signals. This slot will check if the above textbox has any text in it, and, if so, insert a new textbox/radio button pair below them.
To be clear, this slot should be a method of the widget that uses the layout to arrange its sub-widgets. For example, if you're putting all these objects in a QGroupBox, then that's the object to which you'd add the slot I'm describing.
Here is an (untested) example:
class Group : public QGroupBox {
Q_OBJECT
public:
Group(QWidget* parent = nullptr) : QGroupBox(parent)
{
layout = new QVBoxLayout(this);
insertNewRow();
}
private slots:
void insertNewRow(bool checked = true) {
/* You might want to make this remove the row if the button is unchecked */
if (!checked)
return;
/* Only add row if text box is non-empty */
if (textBoxes.isEmpty() || textBoxes.last()->text().isEmpty())
return;
/* Disconnect slot for previous radio button */
QObject::disconnect(radioButtons.last(), 0, 0, 0);
/* Add new text box and button, labeled Button 1, Button 2, etc. */
textBoxes.append(new QLineEdit("", this));
radioButtons.append(new QRadioButton(QString("Button %1").arg(textBoxes.size())), this));
/* Connect signal/slot to add new row when clicked */
QObject::connect(radioButtons.last(), &QRadioButton::toggled, this, &Group::insertNewRow);
}
private:
QVBoxLayout* layout;
QList<QLineEdit*> textBoxes;
QList<QRadioButton*> radioButtons;
};
I'm working on a Qt4 project. I have a QLineEdit and I want to re-use behavior that I see when I click the Escape key inside the QLineEdit, but I'm not sure how.
When I press the escape key, I get the field to reset to the value that it was before I started editing. This is useful to me and I want this behavior on-hand.
Ideally, I would like a signal I can fire off that triggers the QLineEdit to reset to the value it was before. I would prefer not to try and fake an escape key event. I can cache the old value of the line edit, but this seems more work if the behavior already exists when I click escape. Thanks.
How can I make QLineEdit widget to respond on Escape key by setting
the text programmatically?
Either by overriding QWidget::event virtual function with the child of QLineEdit or a bit more "local", like installing the event filter:
class MyLineEditEventFilter : public QObject
{
public:
explicit MyLineEditEventFilter(QLineEdit *parent) : QObject(parent)
{}
bool eventFilter(QObject *obj, QEvent *e)
{
switch (e->type())
{
case QEvent::KeyPress:
{
QKeyEvent *keyEvent = static_cast<QKeyEvent *>(e);
if (keyEvent->key() == Qt::Key_Escape)
{
// or set the other text from the variable
reinterpret_cast<QLineEdit *>(parent())->setText("Escape!");
}
break;
}
}
// standard event processing
return QObject::eventFilter(obj, e);
}
};
And the caller is like that:
m_pLineEditSearch = new QLineEdit;
auto* pLineEditEvtFilter = new MyLineEditEventFilter(m_pLineEditSearch);
m_pLineEditSearch->installEventFilter(pLineEditEvtFilter);
For getting the previous text to reset with Escape pressed you may use different methods but you need to obtain the pointer to the object holding the string somehow. That is hard to answer without seeing your code.
You can also use QDataWidgetMapper and map your QLineEdit to its model. The Esc key behavior you're mentioning is already built-in there. You can also take advantage of the other functionalities that QDataWidgetMapper provides.
Here's how you would use it:
//Your model can have multiple rows and columns, let's assume it's just one
//QLineEdit, that will mean one row and one column
QStandardItemModel *model = new QStandardItemModel(1,1,this);
QStandardItem* item = new QStandardItem("QLineEdit initial value");
QLineEdit* myLineEdit = new QLineEdit(this);
QDataWidgetMapper* dataWidgetMapper = new QDataWidgetMapper(this);
dataWidgetMapper->setModel(model);
dataWidgetMapper->addMapping(myLineEdit, 0);
dataWidgetMapper->toFirst();
Hope this helps.
UPDATE:
There have been some valid concerns raised in the comments under my section about some of the pitfalls of QDataWidgetMapper, namely the fact that it not only responds to Escape key but also other keys like Enter/Return. So what happens is that after calling QDataWidgetMapper::addMapping(QWidget*, int) an event filter will be installed on your widget, which will consume Escape and Enter/Return keys. If you are still interested in finding out whether Enter or Escape have been pressed, you can add one more event filter right after that where you can check for other keys pressed. I have tried it and it works.
I've created a custom widget plugin that is a container( it overloads the qframe). In this container i would like to add children through the code. I've succeeded in doing this. However the children aren't editable or clickable in the designer. I know for children to be editable through the designer, they should be added as code to the XML, but i don't know how to do this.
Would anybody know if it's at all possible to do this?
The code I have, with arrowedFrame as my custom widget plugin class:
arrowedFrame::arrowedFrame(QWidget *parent, Qt::WindowFlags f) : (parent, f)
{
QLabel* testLabel = new QLabel(this);
}
this adds a new Label, as member (sorry i can't yet post pictures, but imagine a box with a label in it). But as i said this label isn't at all editable through the designer.
The solution I found to this is by taking this guide. And adding some things in the initialize function:
void PlotContainerPlugin::initialize(QDesignerFormEditorInterface *formEditor)
{
if (initialized)
return;
QExtensionManager *manager = formEditor->extensionManager();
myFormEditor = formEditor;
Q_ASSERT(manager != 0);
manager->registerExtensions(factory, Q_TYPEID(QDesignerContainerExtension));
initialized = true;
}
The first part just gets a manager:
QExtensionManager *manager = formEditor->extensionManager();
And then we use this manager to,
manager->registerExtensions(factory, Q_TYPEID(QDesignerContainerExtension));
register the plugin(a plotter I my case) with the designer.
Hope this helps:)
I'm using qt-creator to build a little QT application.
I have a main window where I have some controls like a "new contact" button.
Pressing the button a QDialog is shown, it contains 3 line edits: name, mobile and email.
The dialog is shown through the Signal/Slot system. It works fine but I want to create a Contact object when OK is clicked and I want to give back that Contact to my main window in order to put it in a QList created in the main window code.
The approach is:
QMainWindow -> new contact -> QDialog is shown
QDialog -> ok -> QMainWindow
Should I pass the QList from the main window to the QDialog as argument or there is a best way?
Should I pass the QList from the main window to the QDialog as argument or there is a best way?
In my opinion, best would be a custom QDialog subclass with three QLabels and 3 QLineEdits.
The labels would get the following type of values:
Label 1: name
Label 2: mobileNumber
Label 3: email
You would use then QLabels and QLineEdits to display them with the input coming from the user.
Then, as your program probably already does, just handle the "accept" event respectively. You could use the following method to retrieve the text entered by the end user:
text : QString
This property holds the line edit's text.
Setting this property clears the selection, clears the undo/redo history, moves the cursor to the end of the line and resets the modified property to false. The text is not validated when inserted with setText().
The text is truncated to maxLength() length.
By default, this property contains an empty string.
Then, in the handler of the accepted signal, you could call three accessor methods, like:
QString name() const { return nameLineEdit->text(); }
QString mobileNumber() const { return mobileNumberLineEdit->text(); }
QString email() const { return emailLineEdit->text(); }
You could also store that in a dedicated structure depending on you build up your data representation, so the structure would be something like this:
struct Contact {
QString name;
QString mobileNumber;
QString email;
};
and then you would have the accessor for that as follows
Contact contact() const;
Make a subclass of QDialog. Call Yourclass::exec() to show the dialog (exec is a function in QDialog), then afterwards Yourclass::contactDetails() to get them. contactDetails is a perfectly ordinary member function that you have to write.
I would like to set the text of a QComboBox to some custom text (that is not in the QComboBox's list), without adding this text as an item of the QComboBox.
This behaviour is achievable on an editable QComboBox with QComboBox::setEditText(const QString & text).
On a non-editable QComboBox, however, this function does nothing.
Is it possible to programmatically set the display/edit text of a non-editable QComboBox to something that is not in its list?
Or do I have to find another way (e.g. use a QPushButton with a popup menu)
EDIT: Consider an editable QComboBox with InsertPolicy QComboBox::NoInsert. If the user types in something and hits enter, the entered value will be used but not added to the list. What I want is this behaviour to change the 'current' text programmatically, but without allowing the user to type in some text himself. The user can choose something from the QComboBox, but some time later, I may want to override the 'current' text.
I had the same problem when I subclassed QComboBox to make a combo box of check boxes. I wrote a small function to programmatically change the text displayed in the combo box, but I didn't want to enable the user to edit that text. The solution was to set the combo box as editable:
this->setEditable(true);
and the QComboBox::lineEdit() to read only. Refer to the function:
void CheckedComboBox::setText(QString text)
{
QLineEdit *displayedText = this->lineEdit();
displayedText->setText(text);
displayedText->setReadOnly(true);
}
Reimplement paintEvent : https://github.com/qt/qtbase/blob/28d1d19a526148845107b631612520a3524b402b/src/widgets/widgets/qcombobox.cpp#L2995
and add this line : opt.currentText = QString(tr("My Custom Text"));
Example :
QCustomCheckComboBoxFilter.h
...
protected:
void paintEvent(QPaintEvent *e) Q_DECL_OVERRIDE;
...
QCustomCheckComboBoxFilter.cpp
...
void QCustomCheckComboBoxFilter::paintEvent(QPaintEvent *)
{
QStylePainter painter(this);
painter.setPen(palette().color(QPalette::Text));
// draw the combobox frame, focusrect and selected etc.
QStyleOptionComboBox opt;
initStyleOption(&opt);
opt.currentText = QString(tr("My Custom Text"));
painter.drawComplexControl(QStyle::CC_ComboBox, opt);
// draw the icon and text
painter.drawControl(QStyle::CE_ComboBoxLabel, opt);
}
...
I supposed that you want to have a combo box with "A", "B", "C" as actual data and "This is A"
, "This is B" and "This is c" as what is displayed in QComboBox. Here is the code:
box.addItems(QStringList () << "This is A"<< "This is B"<< "This is C");
box.setItemData(0, "A");
box.setItemData(1, "B");
box.setItemData(2, "C");
You can get the actual data with this code :
QString actual = box.itemData(0).toString();//actual will be = "A";
qDebug()<<actual;//"A"
Note: You can almost set every data types that you want for a combo box Item. Even more, you can set more that just one additional data for each item with the third parameter of setItemData.
I ended up using a QPushButton with a popup menu.
I added the items I had in the list of my QComboBox as QActions to the menu.
A menu can be set on a QPushButton with
QPushButton::setMenu(QMenu* menu)
.
The text on the button can easily be set with
QPushButton::setText(const QString &)
and is unrelated to the text in the popup menu, which is what I wanted.