signals-slots

问题 I am beginner to qt. I was working on calculator gui application, I have already defined slots like numPressed() when any of the number pushbutton is pressed on the calculator that will be displayed on the lineEdit. void Calculator::numPressed(){ QPushButton *button = (QPushButton *)sender(); QString buttonValue = button->text(); Qstring display = ui->lineEdit->text(); Qdouble ProcessedValue = previousValue + buttonValue.toDouble(); . . . ui->lineEdit->setText(QString::number(ProcessedValue))

问题 I am beginner to qt. I was working on calculator gui application, I have already defined slots like numPressed() when any of the number pushbutton is pressed on the calculator that will be displayed on the lineEdit. void Calculator::numPressed(){ QPushButton *button = (QPushButton *)sender(); QString buttonValue = button->text(); Qstring display = ui->lineEdit->text(); Qdouble ProcessedValue = previousValue + buttonValue.toDouble(); . . . ui->lineEdit->setText(QString::number(ProcessedValue))

问题 I am beginner to qt. I was working on calculator gui application, I have already defined slots like numPressed() when any of the number pushbutton is pressed on the calculator that will be displayed on the lineEdit. void Calculator::numPressed(){ QPushButton *button = (QPushButton *)sender(); QString buttonValue = button->text(); Qstring display = ui->lineEdit->text(); Qdouble ProcessedValue = previousValue + buttonValue.toDouble(); . . . ui->lineEdit->setText(QString::number(ProcessedValue))

问题 I have a Qt application with this kind of main()... int main(int argc, char *argv[]) { QApplication app(argc, argv); MainWindow mainWin; ... A separate, non-GUI thread is launched here mainWin.Init(); mainWin.show(); app.exec(); } This other thread that is created before the mainWin needs to know when it can start communicating with the mainWin. But since the mainWin uses Qt signals, slots, timers, etc, it's not truly ready to rock until the event loop is running (via exec()). My question is:

问题 In headers: class Clock : public QWidget { Q_OBJECT public: explicit Clock(QWidget *parent = 0); ...... } class ElecClock : virtual public Clock { Q_OBJECT public: explicit ElecClock(QWidget *parent = 0); private slots: void showTime(); //display two LCDNumber ...... } class MechClock : virtual public Clock { Q_OBJECT public: explicit MechClock(QWidget *parent = 0); ...... } class NewClock : public MechClock, public ElecClock //combination of Mechclock and ElecClock { Q_OBJECT public:

问题 I need to change my text in QLabel every time when I clicked in order to my info updates. When I change the value of A, the value of B must change, too. I have two button that can change values in two QLabel (value of A, value of B). main.cpp: Counter A, B; QObject::connect(&A, &Counter::changeValue, &B, &Counter::setValue); QObject::connect(&A, &Counter::changeValue, &B, &Counter::Increment); QObject::connect(&A, &Counter::changeValue, &B, &Counter::Decrement ); QObject::connect(Add,

问题 From a tutorial, I've seen that signals and slots can be used to make callbacks from a worker thread into the main GUI thread, but I'm uncertain how to establish bi-directional communication using signals and slots. The following is what I am working with: class RespondedToWorkerSignals(QObject): callback_from_worker = pyqtSignal() class RespondedToWorker(QRunnable): def __init__(self, func, *args, **kwargs): super(RespondedToWorker, self).__init__() self._func = func self.args = args self

问题 I have a table and move around inside with left, right, up, down buttons. Now I need to create a SIGNAL when I stay in a certain cell and press SPACE button. This SIGNAL should bring also the coordinate of that cell. I tried with standard signals of QTableWidget but it does not work. How can I solve this? 回答1: Create a separate header file i.e. "customtable.h" and then in the Designer you can Promote the existing QTableWidget to this class. class customTable:public QTableWidget { Q_OBJECT

问题 I have a table and move around inside with left, right, up, down buttons. Now I need to create a SIGNAL when I stay in a certain cell and press SPACE button. This SIGNAL should bring also the coordinate of that cell. I tried with standard signals of QTableWidget but it does not work. How can I solve this? 回答1: Create a separate header file i.e. "customtable.h" and then in the Designer you can Promote the existing QTableWidget to this class. class customTable:public QTableWidget { Q_OBJECT

问题 Lets consider this simple example: Class Emitter: public QObject { ... signal: surfaceDestroyed(QObject*); public: void emittingMethod(QObject* surface) { emit surfaceDestroyed(surface); delete surface; } } I have a queued connection for this case connect(emitterObject, SIGNAL(surfaceDestroyed(QObject*), receiverObject, SLOT(onSurfaceDestroyed(QObject*)), Qt::QueuedConnection); In onSurfaceDestroyed method the received QObject is dereferenced and used So the question is how safe this code is?