I need to post an Event from an thread to an QtreeView in my Mainwindow. Now to post an event we need the pointer to the Qobject (i.e. our qtreeview inside main window).
For this i have to take the pointer to my mainwindow in constructor MainWindow::MainWindow().
sharedobj.h file contains pointer to mainwindow :----
#include "ui_mainwindow.h"
/*!
Shared object among threads.
*/
class cntrlObj
{
public:
cntrlObj();
~ctrlObj();
/// Thread run control
bool m_bQuit;
/*!
Pointer to mainwindow window
*/
Ui::MainWindow *ui;
}
Mainwindow class contains following object :---
cntrlObj cntrlObj_obj;
Mainwindow constructor :-----
/*!
Take Pointer to Mainwindow session window
*/
cntrlObj_obj->ui_ptr->setupUi(this);
Please suggest is it an right way to take an pointer to Mainwindow ?
Also can i include file "ui_mainwindow.h" inside another sharedobj.h file to access namespace UI of mainwindow to declare an pointer as i have done in "sharedobj.h" file ?
You need to localize the knowledge within the Mainwindow, and post the event to it.
So:
Post the event to the Mainwindow instance.
Reimplement MainWindow::customEvent(...) as follows (if it's a custom QEvent, otherwise you'd reimplement event(...):
void MainWindow::customEvent(QEvent * ev) {
if (ev->type() == MyEventType) {
QCoreApplication::sendEvent(ui->treeView, ev);
}
}
Alas, why on Earth would you need to send an event to a view?
Related
I notice that QML's StatusBar type doesn't include the SizeGrip like QStatusBar does.
In order to get a size grip, I had to instead embed the QML into a QMainWindow with a QStatusBar. Although this works, it complicates the rest of the app and it's not really the design I'm after.
Would it be possible to implement the QStatusBar directly in QML by subclassing it and how would QML be able to recognise/use the SizeGrip?
EDIT:
I've attempted to derive QQuickPaintedItem to try and render a QStatusBar in QML, but so far haven't had any luck. An error is being triggered in the render call: ASSERT failure in QCoreApplication::sendEvent: "Cannot send events to objects owned by a different thread. Current thread 399d3d8. Receiver '' (of type 'QStatusBar') was created in thread 8c9f00", file kernel\qcoreapplication.cpp, line 553
.h
class WindowStatusBar : public QQuickPaintedItem
{
Q_OBJECT
public:
explicit WindowStatusBar(QQuickItem *parent = 0);
virtual ~WindowStatusBar();
void paint(QPainter *painter);
protected:
QStatusBar *statusBar_;
};
.cpp
WindowStatusBar::WindowStatusBar(QQuickItem *parent)
: QQuickPaintedItem(parent)
, statusBar_(NULL)
{
setOpaquePainting(true);
setAcceptHoverEvents(true);
setAcceptedMouseButtons(Qt::AllButtons);
statusBar_ = new QStatusBar;
}
WindowStatusBar::~WindowStatusBar()
{
delete statusBar_;
}
void WindowStatusBar::paint(QPainter *painter)
{
statusBar_->render(painter, QPoint(), QRegion(),
QStatusBar::DrawWindowBackground | QStatusBar::DrawChildren);
}
Yes, you can derive your own statusbar QML type from StatusBar or you can use the standard QML StatusBar with a contentItem that you designed. To implement the size grip you would put a MouseArea at the right border- in the onPositionChanged you would emit a signal that is interpreted by the mainwindow as a resize command. Avoiding feedback loops (because resizing the main window may change the position in the MouseArea) is left as an exercise for the reader.
I'm new in Qt and have a question.
I have QLabel and QLineEdit objects, and when QLabel text is clicked on, I want to set this text in QLineEdit.
Also I have read that QLabel has not clicked signal.
Can you explain how can I do this and write code for me ?!
Either style another type of QWidget such as a specific QPushButton to look like a QLabel and use its clicked() signal or inherit QLabel yourself and emit your own clicked() signal.
See this example:
https://wiki.qt.io/Clickable_QLabel
If you choose the latter option you can pass the text in the signal. Then connect the necessary signals/slots up between the QLabel and the QLineEdit like so:
QObject::connect(&label, SIGNAL(clicked(const QString& text)),
&lineEdit, SLOT(setText(const QString& text)));
A simple way to accomplish that, without a need for any subclassing, is a signal source that monitors the events on some object and emits relevant signals:
// main.cpp - this is a single-file example
#include <QtWidgets>
class MouseButtonSignaler : public QObject {
Q_OBJECT
bool eventFilter(QObject * obj, QEvent * ev) Q_DECL_OVERRIDE {
if ((ev->type() == QEvent::MouseButtonPress
|| ev->type() == QEvent::MouseButtonRelease
|| ev->type() == QEvent::MouseButtonDblClick)
&& obj->isWidgetType())
emit mouseButtonEvent(static_cast<QWidget*>(obj),
static_cast<QMouseEvent*>(ev));
return false;
}
public:
Q_SIGNAL void mouseButtonEvent(QWidget *, QMouseEvent *);
MouseButtonSignaler(QObject * parent = 0) : QObject(parent) {}
void installOn(QWidget * widget) {
widget->installEventFilter(this);
}
};
The emit keyword is an empty macro, Qt defines it as follows:
#define emit
It is for use by humans as a documentation aid prefix only, the compiler and moc ignore it. As a documentation aid, it means: the following method call is a signal emission. The signals are simply methods whose implementation is generated for you by moc - that's why we have to #include "main.moc" below to include all the implementations that moc has generated for the object class(es) in this file. There's otherwise nothing special or magical to a signal. In this example, you could look in the build folder for a file called main.moc and see the implementation (definition) of void MouseButtonSignaler::mouseButtonEvent( .. ).
You can then install such a signaler on any number of widgets, such as a QLabel:
int main(int argc, char ** argv) {
QApplication app(argc, argv);
MouseButtonSignaler signaler;
QWidget w;
QVBoxLayout layout(&w);
QLabel label("text");
QLineEdit edit;
layout.addWidget(&label);
layout.addWidget(&edit);
signaler.installOn(&label);
QObject::connect(&signaler, &MouseButtonSignaler::mouseButtonEvent,
[&label, &edit](QWidget*, QMouseEvent * event) {
if (event->type() == QEvent::MouseButtonPress)
edit.setText(label.text());
});
w.show();
return app.exec();
}
#include "main.moc"
You need to create one Custom Label class, which will inherit QLabel. Then you can use MouseButtonRelease event to check clicking of Label and emit your custom signal and catch in one SLOT.
Your .h file will be as below:
class YourLabelClass : public QLabel{
signals:
void myLabelClicked(); // Signal to emit
public slots:
void slotLabelClicked(); // Slot which will consume signal
protected:
bool event(QEvent *myEvent); // This method will give all kind of events on Label Widget
};
In your .cpp file, your constructor will connect signal & slot as below :
YourLabelClass :: YourLabelClass(QWidget* parent) : QLabel(parent) {
connect(this, SIGNAL(myLabelClicked()), this, SLOT(slotLabelClicked()));
}
Remaining event method and SLOT method will be implemented as below:
bool YourLabelClass :: event(QEvent *myEvent)
{
switch(myEvent->type())
{
case(QEvent :: MouseButtonRelease): // Identify Mouse press Event
{
qDebug() << "Got Mouse Event";
emit myLabelClicked();
break;
}
}
return QWidget::event(myEvent);
}
void YourLabelClass :: slotLabelClicked() // Implementation of Slot which will consume signal
{
qDebug() << "Clicked Label";
}
For Changing a Text on QLineEdit, you need to create a Custom Class and share object pointer with custom QLabel Class. Please check test code at this link
In the above example the header needs Q_OBJECT:
class YourLabelClass : public QLabel{
Q_OBJECT
signals:
I am new to QT. I have been trying to see the bridge between javascript and Qt Class.
What I did:
1) I have a button and connected clicked signal to on_pushButton_clicked, also I have qwebview instance.
In on_pushButton_clicked:
...
QUrl url = QUrl::fromLocalFile("C:\\whoami\\sd\\index.html");
QObject::connect(ui->webView->page()->mainFrame(), SIGNAL(javaScriptWindowObjectCleared()),
this, SLOT(addJSObject()));
ui->webView->page()->mainFrame()->load(QUrl(url));
....
and in addJSObject,
void MainWindow::addJSObject()
{
qDebug () <<"Inside addJSObject";
ui->webView->page()->mainFrame()->addToJavaScriptWindowObject(QString("mBridge"), m_bridge);
qDebug () <<"Nooo. I m not invoked..";
}
Problem:
It compiles without error, and html file is displayed in the qwebview, but addJSObject callback is not invoked.
Could someone help me in order to resolve this issue?.. I must have done some silly mistake. :(.
Make sure, that your MainWindow: 1) inherits QObject 2) has Q_OBJECT macro 3) has a slot addJSObject().
For example mainwindow.h:
class MainWindow : public QObject
{
Q_OBJECT
public:
MainWindow();
private slots:
void addJSObject();
};
If this is correct, you should be able to connect to addJSObject() without static QObject::connect(). Just use connect() when referring to this as signal target object.
One way to just check, that your signalling works is to try using QTimer timeout signal:
QTimer::singleShot(5000, this, SLOT(addJSObject()));
The application I am writting as unique instantiation of some classes which have to be accessible easily. For that i use singletons.
For exemple my Core is defined as :
class Core : public QObject
{
Q_OBJECT
public:
Core();
~Core();
static Core& getCore()
{
static Core mycore;
return mycore;
}
(...)
};
and it works just great. However I tried to do the same with my MainWindow class, which interits from QMainWindow. I need that in order to access methods such as geometry() from other objects
However Core works great, MainWindow makes error when clossing the programe. The main window destructor is called and executed apparently once ( debug using qDebug() ) but i still have a SIGSEGV signal. What's happening? How to solve it?
Here is the code of MainWindow
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
MainWindow(QWidget *parent = 0);
~MainWindow();
static MainWindow& getUi()
{
static MainWindow myUi;
return myUi;
}
public slots:
void refreshImage();
private:
Ui::MainWindow *ui;
};
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
connect(&appCore(), SIGNAL(refreshed()), this, SLOT(refreshImage()));
}
MainWindow::~MainWindow()
{
delete ui;
}
And the main code
QApplication app(argc, argv);
try
{
appCore().setDevice(MDMA::Kinect);
appUi().show();
return app.exec();
} catch(MDMA::exn e) {
(...)
}
where appCore and appUi are macros for Core::getCore and MainWindow::getUi()
This crash probably results from your QApplication being destroyed before the MainWindow.
If you cannot pass your MainWindow via other ways to the code where it is needed (e.g. as argument or via QObjecg::parent()), you could employ a technique similar to what QApplication does with it's instance method (a non-owning global reference):
Construct your MainWindow as an ordinary local variable on the stack, after the QApplication. Then set a global pointer (maybe better a QPointer; e.g. a static member of MainWindow), which you initially initialize to 0, to this in the constructor of MainWindow. You can also check if it was already initialized here to enforce the uniqueness. Via a public accessor method (instance?) for the global pointer, you can access the class from everywhere while ensuring destruction before QApplication.
If you want to make singletone, try to use general technics, for example, as described here:
http://www.qtcentre.org/wiki/index.php?title=Singleton_pattern
Hope, lot of questions will dissappear after reading all of that article.
As for me, there is nice and simple realization of singletone.
Good luck!
I have a custom class derived from QGraphicsPixmapItem. Its called GraphPixmapItemCustom and it's overloaded method is:
void GraphPixmapItemCustom::mousePressEvent(QGraphicsSceneMouseEvent *event)
{
QGraphicsPixmapItem::mousePressEvent(event);
GraphMarkItemCustom *ptr;
if(event->button() == Qt::RightButton)
{
qDebug("Before emit");
emit addPoint(QPointF(event->pos().x(), event->pos().y()));
qDebug("After emit");
markList.append(new GraphMarkItemCustom(QPointF(event->pos().x(), event->pos().y())));
ptr = markList.last();
markGroup->addToGroup(ptr);
//this->scene()->addItem(ptr);
}
}
the signal is declared at header:
signals:
void addPoint(QPointF position);
In main class that has a pointer to object of class GraphPixmapItemCustom called
private:
GraphPixmapItemCustom *pixItemRGB;
and in the main class I have a slot called:
private slots:
void pointAdd(QPointF position);
In the main class constructor I have a connection:
connect(pixItemRGB, SIGNAL(addPoint(QPointF)), this, SLOT(pointAdd(QPointF)));
In the slot I have only qDebug("YUPPY IT ACTUALLY WORKS!");
But the slot is not beeing fired. Why? I have deleted all moc files and everything that didn't have to be there. So only .pro, .h and .cpp files along with .ui forms where neccesary were left.
I have checked most hits at Google. What is the best (I'm not sured - maybe i modified something) that it worked! I remember the working effects of this connection. Help!
You have to connect the signal after creating the GraphPixmapItemCustom object with the new operator.