I am a newbie in Qt and C++ programming. I have some problem in my program that i need a solution for.
I have two files MainWindow.h and ChatWindow.h, which contains two classes of MainWindow and ChatWindow.
This is chatwindow.h
namespace Ui {
class ChatWindow;
}
class ChatWindow : public QMainWindow
{
Q_OBJECT
public:
explicit ChatWindow(QWidget *parent=0);
~ChatWindow();
private slots:
void send_chat_fn(pjsua_call_id call_id);
void rcv_chat_fn(pjsua_call_id call_id);
void rcv_msg_fn(QString msg);
void on_pushButton_clicked();
void on_actionQuit_triggered();
private:
Ui::ChatWindow *ui;
};
And this is mainwindow.h
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
void add_item(QString buddy_uri);
signals:
void send_chat(pjsua_call_id call_id);
void rcv_chat(pjsua_call_id call_id);
void rcv_msg(QString msg);
private slots:
void on_actionAdd_Buddy_triggered();
void on_actionQuit_triggered();
void on_actionStatus_triggered();
void on_actionNew_Chat_triggered();
void on_action_Configuration_triggered();
void on_listWidget_doubleClicked(const QModelIndex &index);
private:
Ui::MainWindow *ui;
};
Now i want to connect signals from mainwindow.h to slots in chatwindow.h.
I have tried connection in the constructor of class ChatWindow, but it does not work (i think that is because connections work on instances not on classes). Instance of MainWindow class which i want to connect is in mainwindow.cpp. Defining instances of class ChatWindow in MainWindow gives error:
Cannot set parent, parent is in different thread
And if i create a new instance in Constructor of ChatWindow, then it doesnt connect to the desired instance.
Its a complete mess. Please help me through this.
Related
class TDF : public QMainWindow
{
Q_OBJECT
public:
explicit TDF(QWidget *parent = nullptr);
~TDF();
private slots:
void on_umwelt_clicked();
void on_regional_clicked();
void on_pushButton_clicked();
void on_autofahrt_clicked();
void on_flugzeug_clicked();
void on_bestell_clicked();
int anzahl=3;
private:
Ui::TDF *ui;
};
#endif // TDF_H
This is my header. I tried starting the application, but it keeps saying Error: Not a signal or slot declaration.
Please help me :(
Solved the Problem. Int anzahl is not a slot but was in private slots as Seen above
I need to call a method after the ui has been shown,so i want to connect
the frame with itself,in particular using the show signal.
I've created a new form with auto generated code by qtcreator.This is the auto generated header.
#define STARTWINDOW_H
#include <QMainWindow>
namespace Ui {
class StartWindow;
}
class StartWindow : public QMainWindow
{
Q_OBJECT
public:
explicit StartWindow(QWidget *parent = 0);
~StartWindow();
private:
Ui::StartWindow *ui;
public slots:
void doSomething();
};
#endif // STARTWINDOW_H
in the cpp file no one of the following codes work
connect(ui,SIGNAL(QEvent::Show),this,SLOT(doSomething()));
connect(*ui,SIGNAL(QEvent::Show),this,SLOT(doSomething()));
connect(this->ui,SIGNAL(QEvent::Show),this,SLOT(doSomething()));
What's the right way to do it?
That signal does not exist by default, we must create it, we can override the showEvent() method:
.h
protected:
void showEvent(QShowEvent *event);
signals:
void showSignal();
.cpp
connect(this, &StartWindow::showSignal, this, &StartWindow::doSomething);
void StartWindow::showEvent(QShowEvent *event)
{
emit showSignal();
QMainWindow::showEvent(event);
}
void StartWindow::doSomething()
{
qDebug()<<"show";
}
Or you can override the eventFilter method.
.h
protected:
bool eventFilter(QObject *watched, QEvent *event);
signals:
void showSignal();
.cpp
installEventFilter(this);
connect(this, &StartWindow::showSignal, this, &StartWindow::doSomething);
bool StartWindow::eventFilter(QObject *watched, QEvent *event)
{
if(watched==this && event->type() == QEvent::Show)
emit showSignal();
return QMainWindow::eventFilter(watched, event);
}
There are a few things wrong here:
There is no show() signal and
Even if there were, you aren't using connect correctly.
First, if your class were defined like this:
namespace Ui { class MainWindow; }
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
signals:
void someSignal();
public slots:
void doSomething() {}
private:
Ui::MainWindow *ui;
};
The appropriate call to connect in the constructor would be:
QWidget::connect(this, SIGNAL(someSignal()), this, SLOT(doSomething()));
Even if there were a show signal, you wouldn't get it from ui, you would get it from this. The UI classes are just dumb containers for widgets that you add through the designer.
To perform some action when your class is shown, you can either override
virtual void showEvent(QShowEvent *); (more robust, but slightly more complex)
or simply define your own show() slot that does what you want and calls QWidget::show() at the end of it. I prefer the latter, so I will show you that.
Start by defining your show slot like this:
namespace Ui { class MainWindow; }
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
public slots:
void doSomething() {}
void show();
private:
Ui::MainWindow *ui;
};
Then, in your implementation file, do this:
void MainWindow::show()
{
doSomething();
QWidget::show();
}
I have worked with the Qt framework for quite some time now, and I have never needed to override the show event; it is simply not worth it for most use cases. If you really want a show signal that others can connect to, just add a custom signal for it and emit in in MainWindow::show(). Only resort to overriding event handlers if you can't make this work for what you are doing(very rarely necessary).
in my Qt program I need the dialog to send a signal to a slot in the mainwindow. I have set the connection up correctly to the best of my knowledge and it does not give me any errors during compile or run time but for some reason it just doesn't do anything when the button that is supposed to activate the signal is clicked. Why is this happening?
beastiary.h (mainwindow header)
namespace Ui {
class Beastiary;
}
class Beastiary : public QMainWindow
{
Q_OBJECT
public:
explicit Beastiary(QWidget *parent = 0);
Ui::Beastiary *ui;
QStringList MyList;
~Beastiary();
public slots:
void refresh();
private slots:
void on_pushButton_clicked();
void on_listWidget_itemClicked(QListWidgetItem);
void on_pushButton_2_clicked();
void on_pushButton_3_clicked();
beastiary.cpp (mainwindow cpp file)
Beastiary::Beastiary(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::Beastiary)
{
ui->setupUi(this);
Dialog dialog;
connect(&dialog, SIGNAL(gorefresh()),this, SLOT(refresh())) ;
void Beastiary::refresh()
{
qDebug () << "recieved";
ui->listWidget->clear();
QString path = "C:/Program Files/Bargest/bin";
QDir myPath(path);
myPath.setFilter(QDir::Dirs | QDir::Files | QDir::NoDotAndDotDot);
MyList = myPath.entryList();
ui->listWidget->addItems(MyList);
}
dialog.h
namespace Ui {
class Dialog;
}
class Dialog : public QDialog
{
Q_OBJECT
public:
explicit Dialog(QWidget *parent = 0);
~Dialog();
signals:
void gorefresh();
private slots:
void on_pushButton_done_clicked();
void on_pushButton_cancel_clicked();
void on_pushButton_clicked();
private:
Ui::Dialog *ui;
dialog.cpp
void Dialog::on_pushButton_done_clicked()
{
emit gorefresh();
}
I did leave out large parts of the code that just have nothing to do with the actual signals and slots mechanism at play here.
You're only connecting the dialog instance you created locally in the Bestiary's constructor, which goes out of scope as the constructor finishes.
connect is connecting instances, not classes. That means you need to connect each created dialog:
void Beastiary::on_pushButton_clicked() {
Dialog* ad = new Dialog(this);
connect(ad, SIGNAL(gorefresh()), this, SLOT(refresh()));
ad->show();
}
While at it, you should seriously consider using the type-safe connect syntax that came with Qt 5:
void Beastiary::on_pushButton_clicked() {
Dialog* ad = new Dialog(this);
connect(ad, &Dialog::gorefresh, this, &Bestiary::refresh));
ad->show();
}
I have class printrectangle
class PrintRectangle : public QWidget
{
Q_OBJECT
public:
explicit PrintRectangle(QWidget *parent = 0);
private:
void resetClickedIndex();
void updateIndexFromPoint( const QPoint& point);
public:
int mXIndex;
int mYIndex;
QVector<QPoint> points;
bool clicked[5][5] = {};
teacher tech;
perceptron p[5][5];
double techconst = 0.1;
signals:
public slots:
protected:
void paintEvent(QPaintEvent *);
void mousePressEvent(QMouseEvent *eventPress);
};
and MainWindow
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
private slots:
void on_learn_clicked();
void on_classify_clicked();
private:
Ui::MainWindow *ui;
};
When I click button I call to on_learn_clicked() function. I would like to transfer clicked[5][5] array into on_learn_clicked becasue I send this array to other object when user click button. How to do this?
It is not clear what is exactly the relation between MainWindow and the PrintRectangle widget. I suppose the button signal and PrintRectangle slot are connected somewhere in the MainWindow implementation.
One way to solve the problem would be to use to use the QSignalMapper as #Noidea stated.
Another way would be to use a lambda as a slot when connecting. This way you could capture the sender/receiver or other objects in scope and use their members.
You can find some information about the connect syntax in New Signal Slot Syntax
But basically you could write something like:
connect(button, &QPushButton::clicked, this, [this, printRectangle]()
{
// do smth with clicked[5][5] from printRectangle or just
// retrieve it and call another method like:
// this->processClicked(printRectangle->clicked);
// or pass it to another object
}
This way you could modify your on_classify_clicked slot to a regular method with bool[5][5] argument to do the processing.
I'm not able to receive my custom signal in the supposed SLOT. Here is my code:
mainwindow.h:
class HistoryItem {
public:
QString channel;
};
class dbThread : public QObject
{
Q_OBJECT
public:
dbThread();
signals:
void historyLoaded(QList<HistoryItem*> innerResult);
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
public slots:
void historyLoaded(const QList<HistoryItem*> innerResult);
mainwindow.cpp:
connect(dbtrad, SIGNAL(historyLoaded(QList<HistoryItem*>*)), this, SLOT(historyLoaded(QList<HistoryItem*>*)));
void MainWindow::historyLoaded(QList<HistoryItem*> innerResult) {
qDebug() << "historyLoaded()...";
}
And this is how I emit the signal:
QList<HistoryItem*> innerResult;
while (queryInner.next()) {
QString channelIDInner = queryInner.value(0).toString();
HistoryItem* item = new HistoryItem();
item->channel = channelIDInner;
innerResult.append(item);
}
qDebug() << "DONE LOADING.....";
emit historyLoaded(innerResult);
However, qDebug() << "historyLoaded()..."; is never executed.
Any ideas what the problem could be?
It seems you're using threads. Using QList when signaling across threads (or using Qt::QueuedConnection in general) requires some extra work. Basically you need to define the QList<T> type using typedef and then register it using qRegisterMetaType:
typedef QList<HistoryItem*> HistoryList_t;
...
qRegisterMetaType<HistoryList_t>("HistoryList_t");
Then use this type in your signals and slots:
public slots:
void historyLoaded(const HistoryList_t &list);
Check return value of your connect, it should fail. There is an extra * in SIGNAL(historyLoaded(QList<HistoryItem*>*)), should be SIGNAL(historyLoaded(QList<HistoryItem*>)). Fix your SLOT() too.