I have a QLineEdit widget in my menubar which shows the text "search by ID" by default. How can I implement a MouseClicked event handler for the QLineEdit, such that when I click on the LineEdit widget, the default text is cleared and user can enter the text that he wants to search?.
so far
#ifndef SEARCH_H
#define SEARCH_H
#include<QLineEdit>
class search : public QLineEdit
{
signals:
void clicked();
protected:
void mousePressEvent(QMouseEvent *);
};
#endif
You just need to connect QLineEdit::mousePressEvent ( QMouseEvent * e ) signal with function. When this signal will be emited, clear QLineEdit in your function. Simply, isn't it?
EDIT
Or if u have
void mousePressEvent(QMouseEvent *);
in your widget, all what you need is write definition for that method. When user press mouse over QLineEdit, this function will be invoked. Like:
void search::mousePressEvent(QMouseEvent *e)
{
myQLineEdit->setText("");
}
EDIT 2
Then try to do it this way:
class YourWidget : public QLineEdit
{
Q_OBJECT
protected:
void focusInEvent(QFocusEvent* e);
};
and
void YourWidget::focusInEvent(QFocusEvent* e)
{
if (e->reason() == Qt::MouseFocusReason)
{
myQLineEdit->setText("");
}
// You might also call the parent method.
QLineEdit::focusInEvent(e);
}
You'll want to use the QLineEdit::placeholderText property. It shows a grey text which disappears when the user starts editing it (i.e. when it gains focus).
QLineEdit * edit = new QLineEdit;
edit->setPlaceholderText("Search by ID");
Related
I have 10 Qlabels with an image on each. When i click on a label, its image should be cleared. I am able to identify which label was clicked theorotically, using the pixel clicked and size of each image. But how to use that information?
Eg. each label has dimension 100*100, the first label starting from 0,0. if pixel clicked is 250,50, i know that the third label was clicked, but how to use this to clear the label.
Im stuck.
There are a few ways how to implement it.
First. I would recommend to use a new class that inherits QLabel and overloads mouseReleaseEvent() handler where you just call clear() method. In this case the label will detect the mouse clicks itself and will clear its content internally.
class SelfClearingLabel : public QLabel
{
public:
using QLabel::QLabel;
protected:
void mouseReleaseEvent(QMouseEvent * event)
{
if (event->button()==Qt::LeftButton)
// process only clicks on the left button
{
clear();
}
QLabel::mouseReleaseEvent(event);
}
};
Second. You can catch mouseReleaseEvent() in your top widget and iterate over all of your child QLabel widgets and check which one is currently under mouse and clear the one. If you have other labels on this widget that shouldn't be cleared on mouse clicks then you can add some property to the QLabels that are under your interest.
void SomeTopFrame::createImageLabels(int count)
{
for (int i=0;i<count;i++)
{
QLabel* label=new QLabel(this);
label->setProperty("clear_on_click",true);
// assume that labels are added to layout *m_labelsLayout;
m_labelsLayout->addWidget(label);
}
}
void SomeTopFrame::mouseReleaseEvent(QMouseEvent * event)
{
if (event->button()==Qt::LeftButton)
// process only clicks on the left button
{
QList<QLabel*> labels=findChildren<QLabel*>();
foreach (QLabel* label, labels)
{
if (label->property("clear_on_click")&&label->underMouse())
{
label->clear();
break;
}
}
}
QFrame::mouseReleaseEvent(event);
}
It is a sample code just to show the principle. In production you can add a check that mouseReleaseEvent() is on the same widget as the mousePressEvent() to avoid triggering on drag and drop events.
Create the custom class that inherit QLabel :
ClickableLabel.h
class ClickableLabel : public QLabel
{
Q_OBJECT
public:
explicit ClickableLabel( const QString& text="", QWidget* parent=0 );
~ClickableLabel();
signals:
void clicked();
protected:
void mousePressEvent(QMouseEvent* event);
};
ClickableLabel.cpp
ClickableLabel::ClickableLabel(const QString& text, QWidget* parent)
: QLabel(parent)
{
setText(text);
}
ClickableLabel::~ClickableLabel()
{
}
void ClickableLabel::mousePressEvent(QMouseEvent* event)
{
emit clicked();
}
Just connect all labels clicked signal to following slot :
MyClass::labelClicked()
{
ClickableLabel *label = (ClickableLabel*)QObject::sender;
if(label)
label->clear();
}
I want to show osk.exe(onscreenkeyboard) when click on the QLineEdit and when focus out osk.exe hide or minimized?
how can i do?
thanks
You need to use a QProcess and reimplement the methods QLineEdit::focusInEvent and QLineEdit::focusOutEvent. Try implement a class inheriting from QLineEdit like this:
#include <QLineEdit>
#include <QProcess>
class MyLineEdit: public QLineEdit
{
public:
MyLineEdit(QWidget * parent = 0): QLineEdit(parent)
{
process_ = new QProcess();
}
protected:
void focusInEvent(QFocusEvent * e)
{
QLineEdit::focusInEvent(e);
process_->start("start C:\\osk.exe");
}
void focusOutEvent(QFocusEvent * e)
{
QLineEdit::focusOutEvent(e);
process_->kill();
}
private:
QProcess * process_;
}
(Of course replace C:\\osk.exe by the exact address of this osk.exe).
Then just use a MyLineEdit instead of a QLineEdit, it should work. I do not know how to hide or minimize the process, so I decided to kill it and restart it if necessary instead ;-)
I'm using Qt Creator to create a gui for a mineseeper game.
How can I know a QpushButton clicked with rightclick? for flag in the game.
In other word, which signal used for rightclick?
Create your own button with filter at mousePressEvent slot.
qrightclickbutton.h
#ifndef QRIGHTCLICKBUTTON_H
#define QRIGHTCLICKBUTTON_H
#include <QPushButton>
#include <QMouseEvent>
class QRightClickButton : public QPushButton
{
Q_OBJECT
public:
explicit QRightClickButton(QWidget *parent = 0);
private slots:
void mousePressEvent(QMouseEvent *e);
signals:
void rightClicked();
public slots:
};
#endif // QRIGHTCLICKBUTTON_H
qrightclickbutton.cpp
#include "qrightclickbutton.h"
QRightClickButton::QRightClickButton(QWidget *parent) :
QPushButton(parent)
{
}
void QRightClickButton::mousePressEvent(QMouseEvent *e)
{
if(e->button()==Qt::RightButton)
emit rightClicked();
}
Now connect like this
QRightClickButton *button = new QRightClickButton(this);
ui->gridLayout->addWidget(button);
connect(button, SIGNAL(rightClicked()), this, SLOT(onRightClicked()));
Create a slot in MainWindow.cpp.
void MainWindow::onRightClicked()
{
qDebug() << "User right clicked me";
}
It works for me!
I think QPushButton is internally implemented to listen to left mouse clicks only. But you can easily extend QPushButton and re-implement let's say the mouse release event and do your thing if the right mouse button was pressed, e.g. emit a custom rightClicked() signal for example:
signals:
void rightClicked();
protected:
void mouseReleaseEvent(QMouseEvent *e) {
if (e->button() == Qt::RightButton) emit rightClicked();
else if (e->button() == Qt::LeftButton) emit clicked();
}
... or you can create an overload of the clicked signal that forwards the mouseEvent pointer so you can do the same check outside of the button.
signals:
void clicked(QMouseEvent *);
protected:
void mouseReleaseEvent(QMouseEvent *e) {
emit clicked(e);
}
Then you do the check in the slot you connect the button's clicked(QMouseEvent *) signal to and proceed accordingly.
I just wrote this little helper adapter to make any existing button right-clickable with no need to subclass it:
class CRightClickEnabler : public QObject
{
public:
CRightClickEnabler(QAbstractButton * button): QObject(button), _button(button) {
button->installEventFilter(this);
};
protected:
inline bool eventFilter(QObject *watched, QEvent *event) override {
if (event->type() == QEvent::MouseButtonPress)
{
auto mouseEvent = (QMouseEvent*)event;
if (mouseEvent->button() == Qt::RightButton)
_button->click();
}
return false;
}
private:
QAbstractButton* _button;
};
Usage:
connect(ui->pushButton, &QPushButton::clicked, [](){qDebug() << "Button clicked";});
new CRightClickEnabler(ui->pushButton);
From now on, the clicked signal will be triggered by the right click as well as left click. There's no need to delete this object - it uses ui->pushButton as parent and will be auto-deleted by Qt when the parent is destroyed.
Obviously, you can write 2 lines of code (literally) to declare a new signal here and emit that signal upon right click instead of clicked, if desired.
I'd like to suggest this option as well, without need for event filter/other stuffs...
self.button.released.connect(self.doStuff)
self.button.setContextMenuPolicy(Qt.ContextMenuPolicy.CustomContextMenu)
self.button.customContextMenuRequested.connect(partial(self.doStuff, False))
def doStuff(self,state=True,p=QPoint()):
print("True for left, False for right!",state)
I have a custom QGraphicsView and a custom QGraphicsItem. I want the Item to handle my click if I click in the item, else I want the click to be handled by the View.
But when I click on the item, the item handles the click. This is ok. But if I click somewhere else the click isn't handled at all. All the code in my classes that have anything to do with mouseEvents is below.
class CustomView : public QGraphicsView
{
Q_OBJECT
public:
void mousePressEvent(QGraphicsSceneMouseEvent *event);
};
void CustomView::mousePressEvent(QGraphicsSceneMouseEvent *event){
cout << "pressing in view";
}
class CustomItem : public QGraphicsItem
{
public:
CustomItem(CustomView* widget)
void mousePressEvent(QGraphicsSceneMouseEvent *event);
};
CustomItem::CustomItem(CustomView* widget){
setFlag(ItemIsSelectable);
setFlag(ItemIsMovable);
}
void CustomItem::mousePressEvent(QGraphicsSceneMouseEvent *event){
cout << "pressing in item";
}
It seems that when I remove the mousePressEvent function from the CustomItem class and change in the CustomView the mousePressEvent function to:
void CustomView::mousePressEvent(QMouseEvent *event){
cout << "pressing in view";
}
the CustomView handles all the mouseEvents.
How can I let the CustomItem handles the clicks in the items and the CustomView handle all the other clicks?
Thank you.
EDIT
So now I have changed it to:
class CustomView : public QGraphicsView
{
Q_OBJECT
public:
};
class CustomScene : public QGraphicsScene
{
protected:
void mousePressEvent(QGraphicsSceneMouseEvent *event);
};
void CustomScene::mousePressEvent(QGraphicsSceneMouseEvent *event){
cout << "pressing in scene";
}
class CustomItem : public QGraphicsItem
{
public:
CustomItem(CustomView* widget)
protected:
void mousePressEvent(QGraphicsSceneMouseEvent *event);
};
CustomItem::CustomItem(CustomView* widget){
setFlag(ItemIsSelectable);
setFlag(ItemIsMovable);
}
void CustomItem::mousePressEvent(QGraphicsSceneMouseEvent *event){
cout << "pressing in item";
}
A Click in the scene but not in an item get handled by the scene. But clicks in the items
dont get handled by the items itself, instead it get handled by the scene. Unless if you click 2 times really fast on the items it gets handled by the scene and the item.
Any ideas?
QGraphicsView isn't really a good place to handle scene-specific events. Instead, you'll need to override QGraphicsScene::mousePressEvent. I would recommend something like this:
void CustomScene::mousePressEvent(QGraphicsSceneMouseEvent *event)
{
if (itemAt(event) == NULL)
{
// do stuff if not clicked on an item
}
else
{
QGraphicsScene::mousePressEvent(event); // this forwards the event to the item
}
}
Note that QGraphicsScene::itemAt might give you difficulties if you have items with the ItemIgnoresTransformations flag set to true. Look to the docs for QGraphicsScene::itemAt for how to resolve this.
I have a QTableView to display a bunch of data, which is stored in a QAbstractTableModel. I also want to edit the data sometime, so I use a QStyledItemDelegate to create an editor (of QTextEdit type) when I double click on the cell. However, I want to handle the key Press event myself, but I never catch Key_Escape pressing in the Text Edit editor (Other keys such as Enter and Ascii can be captured). I checked the code, and found that Escape is directly connected to QTableView's closeEditor() function, which is a virtual method and is automatically invoked. As far as I know, key press event is the bottom layer of event handling, but it is not true with such case.
I do need to capture the Escape key press event so that I can handle it myself, can anyone tell me how to do this? Thanks!
I got the answer, and I think would help others:
Override QStyledItemDelegate::eventFilter() method:
MyItemDelegate::eventFilter(QObject* editor, QEvent* event)
{
if(event->type()==QEvent::KeyPress)
return false;
return QStyledItemDelegate::eventFilter(editor, event);
}
According to Qt's documentation, QStyledItemDelegate::eventFilter() returns true if the given editor is a valid QWidget and the given event is handled; otherwise returns false. Tab, Backtab, Enter, Return and Ecs are handled by default. So, if you want to handle the key press event yourself, you must let eventFilter return false when KeyPress event occurs. So that the editor's keyPressEvent() method will be invoked instead.
QStyledItemDelegate::eventFilter is not a possibility beacuse is virtual protected
In order to get the events you should subclass your own QEditLine and override ::keyPressEvent there. Take notice of the code. I pass actual row and colum of my QTableWidget cell in order to know what we are editing in the overrided QLineEditor.
//.h
class MyStyledItemDelegate : public QStyledItemDelegate
{
public:
MyStyledItemDelegate(QObject *parent = 0);
QWidget* createEditor(QWidget* parent,const QStyleOptionViewItem &option,const QModelIndex &index) const;
};
//.cpp
#include "mylineedit.h"
MyStyledItemDelegate::MyStyledItemDelegate(QObject *parent)
:QStyledItemDelegate(parent)
{
}
QWidget* MyStyledItemDelegate::createEditor(QWidget* parent,const QStyleOptionViewItem &option,const QModelIndex &index) const
{
MyLineEdit* editor = new MyLineEdit(parent,index.row(),index.column());
return editor;
}
/////////////////////////////////////////////////////////////
//My own QLineEdit
/////////////////////////////////////////////////////////////
//.h
class MyLineEdit : public QLineEdit
{
Q_OBJECT
public:
int _nRow;
int _nCol;
public:
MyLineEdit(QWidget *parent = 0,int nRow=-1, int nCol=-1);
virtual void keyPressEvent(QKeyEvent* event);
signals:
void mySignal(const QVector<QVariant> &);
public slots:
};
//.cpp
MyLineEdit::MyLineEdit(QWidget *parent, int nRow,int nCol):
QLineEdit(parent)
{
_nRow=nRow;
_nCol=nCol;
}
/////////////////////////////////////////////////////////////////////////
void MyLineEdit::keyPressEvent(QKeyEvent* event)
{
qDebug() << "MyLineEdit::OnKeyPressEvent:"<<event->text()<< " row="<<_nRow<<" col=" <<_nCol;
///SET YOUR CODE HERE
QLineEdit::keyPressEvent(event);
}