How can I make sure that a sound does not start to play if another one is already playing?
Im using the following code to play sounds:
void MainWindow::displayNotification(QString message)
{
// Play sound notification
QSound *sound = new QSound("://2_1.wav", this);
sound->play();
}
Any ideas?
Store a pointer to the playing QSound in your MainWindow, then check if it has finished with the isFinished function.
void MainWindow::MainWindow(QWidget* parent)
: QMainWindow(parent)
{
QString audiofile("://2_1.wav");
m_pSound = new QSound(audiofile, this);
if(!m_pSound)
{
qDebug() << "Failed to initialise sound file: " << audiofile;
}
}
void MainWindow::displayNotification(QString message)
{
if(!m_pSound) // check m_pSound is initialised
return;
// check if sound is playing
if(!m_pSound->isFinished)
return;
// Play sound notification
m_pSound->play();
}
Note that m_pSound is now declared as a member variable of MainWindow.
the class "QSound" has the method "isFinished()" for that reason.
if(m_pSound->isFinished())
//play
else
//wait
Related
I want to use a QTimer object to control a LED indictor status. A QLed class inherited QWidget is created to control the LED indicator. Here below its two major functions relevant:
void QLed::setLEDFlashing(bool value)
{
ledStatus = value; //Boolean value to accept a user-defined LED status
m_value = ledStatus; //m_value is used in painting LED (with QtSvgRenderer)
QTimer ledTimer;
ledTimer.setInterval(300);
if(!ledTimer.isActive())
{
ledTimer.start();
}
//Here is the connection between the timer and this (i.e., QLed*) object
connect(&ledTimer, SIGNAL(timeout()), this, SLOT(setLEDFlashingTimerHandler()));
}
//I want to use this function to make LED keep flashing
void QLed::setLEDFlashingTimerHandler()
{
//qDebug()<<"setLEDFlashingTimerHandler()";
if (ledStatus)
{
m_value = TRUE;
ledStatus = FALSE;
}
else
{
m_value = FALSE;
ledStatus =TRUE;
}
}
//This is to paint the LED widget
void QLed::paintEvent(QPaintEvent *)
{
QPainter painter(this);
painter.setRenderHint(QPainter::Antialiasing, true);
//based on m_value, different svg file is loaded
if(m_value)
ledShapeAndColor.append(colors[m_onColor]);
else
ledShapeAndColor.append(colors[m_offColor]);
renderer->load(ledShapeAndColor);
renderer->render(&painter);
//qDebug()<<"paintEvent m_value="<<m_value;
}
In the mainwindow.ui, I add a QLabel object (named led) and promote it to QLed, and in the mainwindow.cpp:
ui->led->setLEDFlashing(TRUE);
The above codes cannot result in a flashing LED indicator. Actually, the connection between ledTimer and setLEDFlashingTimerHandler does NOT take effect for some reason, and m_value is not updated in paintEvent. Anyone can help debug my codes? Thanks!
Edits:
I have solved the connection issue by using QTimer *ledTimer in stead of QTimer ledTimer. But the painting still not works as expected, since m_value is not updated in that function or the function is only invoked for the very first time?
In your function QLed::setLEDFlashing, you create a local instance of QTimer which will be destroyed at the end of your function.
You should declare your QTimer as an attribute of your class or use a inner timer with QObject::startTimer
I want to save an image of a frame from a QMediaPlayer. After reading the documentation, I understood that I should use QVideoProbe. I am using the following code :
QMediaPlayer *player = new QMediaPlayer();
QVideoProbe *probe = new QVideoProbe;
connect(probe, SIGNAL(videoFrameProbed(QVideoFrame)), this, SLOT(processFrame(QVideoFrame)));
qDebug()<<probe->setSource(player); // Returns true, hopefully.
player->setVideoOutput(myVideoSurface);
player->setMedia(QUrl::fromLocalFile("observation.mp4"));
player->play(); // Start receving frames as they get presented to myVideoSurface
But unfortunately, probe->setSource(player) always returns false for me, and thus my slot processFrame is not triggered.
What am I doing wrong ? Does anybody have a working example of QVideoProbe ?
You're not doing anything wrong. As #DYangu pointed out, your media object instance does not support monitoring video. I had the same problem (and same for QAudioProbe but it doesn't interest us here). I found a solution by looking at this answer and this one.
The main idea is to subclass QAbstractVideoSurface. Once you've done that, it will call the method QAbstractVideoSurface::present(const QVideoFrame & frame) of your implementation of QAbstractVideoSurface and you will be able to process the frames of your video.
As it is said here, usually you will just need to reimplement two methods :
supportedPixelFormats so that the producer can select an appropriate format for the QVideoFrame
present which allows to display the frame
But at the time, I searched in the Qt source code and happily found this piece of code which helped me to do a full implementation. So, here is the full code for using a "video frame grabber".
VideoFrameGrabber.cpp :
#include "VideoFrameGrabber.h"
#include <QtWidgets>
#include <qabstractvideosurface.h>
#include <qvideosurfaceformat.h>
VideoFrameGrabber::VideoFrameGrabber(QWidget *widget, QObject *parent)
: QAbstractVideoSurface(parent)
, widget(widget)
, imageFormat(QImage::Format_Invalid)
{
}
QList<QVideoFrame::PixelFormat> VideoFrameGrabber::supportedPixelFormats(QAbstractVideoBuffer::HandleType handleType) const
{
Q_UNUSED(handleType);
return QList<QVideoFrame::PixelFormat>()
<< QVideoFrame::Format_ARGB32
<< QVideoFrame::Format_ARGB32_Premultiplied
<< QVideoFrame::Format_RGB32
<< QVideoFrame::Format_RGB24
<< QVideoFrame::Format_RGB565
<< QVideoFrame::Format_RGB555
<< QVideoFrame::Format_ARGB8565_Premultiplied
<< QVideoFrame::Format_BGRA32
<< QVideoFrame::Format_BGRA32_Premultiplied
<< QVideoFrame::Format_BGR32
<< QVideoFrame::Format_BGR24
<< QVideoFrame::Format_BGR565
<< QVideoFrame::Format_BGR555
<< QVideoFrame::Format_BGRA5658_Premultiplied
<< QVideoFrame::Format_AYUV444
<< QVideoFrame::Format_AYUV444_Premultiplied
<< QVideoFrame::Format_YUV444
<< QVideoFrame::Format_YUV420P
<< QVideoFrame::Format_YV12
<< QVideoFrame::Format_UYVY
<< QVideoFrame::Format_YUYV
<< QVideoFrame::Format_NV12
<< QVideoFrame::Format_NV21
<< QVideoFrame::Format_IMC1
<< QVideoFrame::Format_IMC2
<< QVideoFrame::Format_IMC3
<< QVideoFrame::Format_IMC4
<< QVideoFrame::Format_Y8
<< QVideoFrame::Format_Y16
<< QVideoFrame::Format_Jpeg
<< QVideoFrame::Format_CameraRaw
<< QVideoFrame::Format_AdobeDng;
}
bool VideoFrameGrabber::isFormatSupported(const QVideoSurfaceFormat &format) const
{
const QImage::Format imageFormat = QVideoFrame::imageFormatFromPixelFormat(format.pixelFormat());
const QSize size = format.frameSize();
return imageFormat != QImage::Format_Invalid
&& !size.isEmpty()
&& format.handleType() == QAbstractVideoBuffer::NoHandle;
}
bool VideoFrameGrabber::start(const QVideoSurfaceFormat &format)
{
const QImage::Format imageFormat = QVideoFrame::imageFormatFromPixelFormat(format.pixelFormat());
const QSize size = format.frameSize();
if (imageFormat != QImage::Format_Invalid && !size.isEmpty()) {
this->imageFormat = imageFormat;
imageSize = size;
sourceRect = format.viewport();
QAbstractVideoSurface::start(format);
widget->updateGeometry();
updateVideoRect();
return true;
} else {
return false;
}
}
void VideoFrameGrabber::stop()
{
currentFrame = QVideoFrame();
targetRect = QRect();
QAbstractVideoSurface::stop();
widget->update();
}
bool VideoFrameGrabber::present(const QVideoFrame &frame)
{
if (frame.isValid())
{
QVideoFrame cloneFrame(frame);
cloneFrame.map(QAbstractVideoBuffer::ReadOnly);
const QImage image(cloneFrame.bits(),
cloneFrame.width(),
cloneFrame.height(),
QVideoFrame::imageFormatFromPixelFormat(cloneFrame .pixelFormat()));
emit frameAvailable(image); // this is very important
cloneFrame.unmap();
}
if (surfaceFormat().pixelFormat() != frame.pixelFormat()
|| surfaceFormat().frameSize() != frame.size()) {
setError(IncorrectFormatError);
stop();
return false;
} else {
currentFrame = frame;
widget->repaint(targetRect);
return true;
}
}
void VideoFrameGrabber::updateVideoRect()
{
QSize size = surfaceFormat().sizeHint();
size.scale(widget->size().boundedTo(size), Qt::KeepAspectRatio);
targetRect = QRect(QPoint(0, 0), size);
targetRect.moveCenter(widget->rect().center());
}
void VideoFrameGrabber::paint(QPainter *painter)
{
if (currentFrame.map(QAbstractVideoBuffer::ReadOnly)) {
const QTransform oldTransform = painter->transform();
if (surfaceFormat().scanLineDirection() == QVideoSurfaceFormat::BottomToTop) {
painter->scale(1, -1);
painter->translate(0, -widget->height());
}
QImage image(
currentFrame.bits(),
currentFrame.width(),
currentFrame.height(),
currentFrame.bytesPerLine(),
imageFormat);
painter->drawImage(targetRect, image, sourceRect);
painter->setTransform(oldTransform);
currentFrame.unmap();
}
}
VideoFrameGrabber.h
#ifndef VIDEOFRAMEGRABBER_H
#define VIDEOFRAMEGRABBER_H
#include <QtWidgets>
class VideoFrameGrabber : public QAbstractVideoSurface
{
Q_OBJECT
public:
VideoFrameGrabber(QWidget *widget, QObject *parent = 0);
QList<QVideoFrame::PixelFormat> supportedPixelFormats(
QAbstractVideoBuffer::HandleType handleType = QAbstractVideoBuffer::NoHandle) const;
bool isFormatSupported(const QVideoSurfaceFormat &format) const;
bool start(const QVideoSurfaceFormat &format);
void stop();
bool present(const QVideoFrame &frame);
QRect videoRect() const { return targetRect; }
void updateVideoRect();
void paint(QPainter *painter);
private:
QWidget *widget;
QImage::Format imageFormat;
QRect targetRect;
QSize imageSize;
QRect sourceRect;
QVideoFrame currentFrame;
signals:
void frameAvailable(QImage frame);
};
#endif //VIDEOFRAMEGRABBER_H
Note : in the .h, you will see I added a signal taking an image as a parameter. This will allow you to process your frame anywhere in your code. At the time, this signal took a QImage as a parameter, but you can of course take a QVideoFrame if you want to.
Now, we are ready to use this video frame grabber:
QMediaPlayer* player = new QMediaPlayer(this);
// no more QVideoProbe
VideoFrameGrabber* grabber = new VideoFrameGrabber(this);
player->setVideoOutput(grabber);
connect(grabber, SIGNAL(frameAvailable(QImage)), this, SLOT(processFrame(QImage)));
Now you just have to declare a slot named processFrame(QImage image) and you will receive a QImage each time you will enter the method present of your VideoFrameGrabber.
I hope that this will help you!
After Qt QVideoProbe documentation:
bool QVideoProbe::setSource(QMediaObject *mediaObject)
Starts monitoring the given mediaObject.
If there is no media object associated with mediaObject, or if it is
zero, this probe will be deactivated and this function wil return
true.
If the media object instance does not support monitoring video, this
function will return false.
Any previously monitored objects will no longer be monitored. Passing
in the same object will be ignored, but monitoring will continue.
So it seems your "media object instance does not support monitoring video"
TL;DR: https://gist.github.com/JC3/a7bab65acbd7659d1e57103d2b0021ba (only file)
I had a similar issue (5.15.2; although in my case I was on Windows, was definitely using the DirectShow back-end, the probe attachment was returning true, the sample grabber was in the graph, but the callback wasn't firing).
I never figured it out but needed to get something working so I kludged one out of a QAbstractVideoSurface, and it's been working well so far. It's a bit simpler than some of the other implementations in this post, and it's all in one file.
Note that Qt 5.15 or higher is required if you intend to both process frames and play them back with this, since the multi-surface QMediaPlayer::setVideoOutput wasn't added until 5.15. If all you want to do is process video you can still use the code below as a template for pre-5.15, just gut the formatSource_ parts.
Code:
VideoProbeSurface.h (the only file; link is to Gist)
#ifndef VIDEOPROBESURFACE_H
#define VIDEOPROBESURFACE_H
#include <QAbstractVideoSurface>
#include <QVideoSurfaceFormat>
class VideoProbeSurface : public QAbstractVideoSurface {
Q_OBJECT
public:
VideoProbeSurface (QObject *parent = nullptr)
: QAbstractVideoSurface(parent)
, formatSource_(nullptr)
{
}
void setFormatSource (QAbstractVideoSurface *source) {
formatSource_ = source;
}
QList<QVideoFrame::PixelFormat> supportedPixelFormats (QAbstractVideoBuffer::HandleType type) const override {
return formatSource_ ? formatSource_->supportedPixelFormats(type)
: QList<QVideoFrame::PixelFormat>();
}
QVideoSurfaceFormat nearestFormat (const QVideoSurfaceFormat &format) const override {
return formatSource_ ? formatSource_->nearestFormat(format)
: QAbstractVideoSurface::nearestFormat(format);
}
bool present (const QVideoFrame &frame) override {
emit videoFrameProbed(frame);
return true;
}
signals:
void videoFrameProbed (const QVideoFrame &frame);
private:
QAbstractVideoSurface *formatSource_;
};
#endif // VIDEOPROBESURFACE_H
I went for the quickest-to-write implementation possible so it just forwards supported pixel formats from another surface (my intent was to both probe and play back to a QVideoWidget) and you get whatever format you get. I just needed to grab subimages into QImages though, which handles most common formats. But you could modify this to force any formats you want (e.g. you might want to just return formats supported by QImage or filter out source formats not supported by QImage), etc.).
Example set up:
QMediaPlayer *player = ...;
QVideoWidget *widget = ...;
// forward surface formats provided by the video widget:
VideoProbeSurface *probe = new VideoProbeSurface(...);
probe->setFormatSource(widget->videoSurface());
// same signal signature as QVideoProbe's signal:
connect(probe, &VideoProbeSurface::videoFrameProbed, ...);
// the key move is to render to both the widget (for viewing)
// and probe (for processing). fortunately, QMediaPlayer can
// take a list:
player->setVideoOutput({ widget->videoSurface(), probe });
Notes
The only really sketchy thing I had to do was const_cast the QVideoFrame on the receiver side (for read-only access), since QVideoFrame::map() isn't const:
if (const_cast<QVideoFrame&>(frame).map(QAbstractVideoBuffer::ReadOnly)) {
...;
const_cast<QVideoFrame&>(frame).unmap();
}
But the real QVideoProbe would make you do the same thing so, I don't know what's up with that -- it's a strange API. I ran some tests with sw, native hw, and copy-back hw renderers and decoders and map/unmap in read mode seem to be functioning OK, so, whatever.
Performance-wise, the video will bog down if you spend too much time in the callback, so design accordingly. However, I didn't test QueuedConnection, so I don't know if that'd still have the issue (although the fact that the signal parameter is a reference would make me wary of trying it, as well as conceivable issues with the GPU releasing the memory before the slot ends up being called). I don't know how QVideoProbe behaves in this regard, either. I do know that, at least on my machine, I can pack and queue Full HD (1920 x 1080) resolution QImages to a thread pool for processing without slowing down the video.
You probably also want to implement some sort of auto-unmapper utility object for exception safe unmap(), etc. But again, that's not unique to this, same thing you'd have to do with QVideoProbe.
So hopefully that helps somebody else.
Example QImage Use
PS, example of packing arbitrarily-formatted QVideoFrames into a QImage in:
void MyVideoProcessor::onFrameProbed(const QVideoFrame &frame) {
if (const_cast<QVideoFrame&>(frame).map(QAbstractVideoBuffer::ReadOnly)) {
auto imageFormat = QVideoFrame::imageFormatFromPixelFormat(frame.pixelFormat());
QImage image(frame.bits(), frame.width(), frame.height(), frame.bytesPerLine(), imageFormat);
// *if* you want to use this elsewhere you must force detach:
image = image.copy();
// but if you don't need to use it past unmap(), you can just
// use the original image instead of a copy.
// <---- now do whatever with the image, e.g. save() it.
// if you *haven't* copied the image, then, before unmapping,
// kill any internal data pointers just to be safe:
image = QImage();
const_cast<QVideoFrame&>(frame).unmap();
}
}
Notes about that:
Constructing a QImage directly from the data is fast and essentially free: no copies are done.
The data buffers are only technically valid between map and unmap, so if you intend to use the QImage outside of that scope, you'll want to use copy() (or anything else that forces a detach) to force a deep copy.
You also probably want to ensure that the original not-copied QImage is destructed before calling unmap. It's unlikely to cause problems but it's always a good idea to minimize how many invalid pointers are hanging around at any given time, and also the QImage docs say "The buffer must remain valid throughout the life of the QImage and all copies that have not been modified or otherwise detached from the original buffer". Best to be strict about it.
I am starting a QT5 application with a rather complex design based on Qt Widgets. It runs on Beagleboard with a touchscreen. I will have a rather weird local invention instead of the LCD display. It's a laser painting on acrylic plate. It has no driver yet. To actually update a screen I must create a screenshot of the window as bitmap, turn it to grayscale and feed to a proprietary library, which will handle the laser. It should look cute, when ready. Unfortunately, the laser blinks on update, so I cannot just make screenshots on timer, or it will be jerky like hell.
I need to run a function every time a meaningful update of GUI happens, while preferably ignore things like button being pressed and released. Is there some way to create a hook without subclassing every single Qt Widget I will use? The only way to do this I know is to override paintEvent of everything. I want a simpler solution.
Possible assumptions are: the application will be running under X server with dummy display, will be the only GUI app running. Some updates happen without user input.
The code below does it. It doesn't dig too deeply into the internals of Qt, it merely leverages the fact that backing store devices are usually QImages. It could be modified to accommodate OpenGL-based backing stores as well.
The WidgetMonitor class is used to monitor the widgets for content changes. An entire top-level window is monitored no matter which particular widget is passed to the monitor(QWidget*) method. You only need to call the monitor method for one widget in the window you intend to monitor - any widget will do. The changes are sent out as a QImage of window contents.
The implementation installs itself as an event filter in the target window widget and all of its children, and monitors the repaint events. It attempts to coalesce the repaint notifications by using the zero-length timer. The additions and removals of children are tracked automagically.
When you run the example, it creates two windows: a source window, and a destination window. They may be overlapped so you need to separate them. As you resize the source window, the size of the destination's rendition of it will also change appropriately. Any changes to the source children (time label, button state) propagate automatically to the destination.
In your application, the destination could be an object that takes the QImage contents, converts them to grayscale, resizes appropriately, and passes them to your device.
I do not quite understand how your laser device works if it can't gracefully handle updates. I presume that it is a raster-scanning laser that runs continuously in a loop that looks roughly like this:
while (1) {
for (line = 0; line < nLines; ++line) {
drawLine();
}
}
You need to modify this loop so that it works as follows:
newImage = true;
QImage localImage;
while (1) {
if (newImage) localImage = newImage;
for (line = 0; line < localImage.height(); ++line) {
drawLine(line, localImage);
}
}
You'd be flipping the newImage flag from the notification slot connected to the WidgetMonitor. You may well find out that leveraging QImage, and Qt's functionality in general, in your device driver code, will make it much easier to develop. Qt provides portable timers, threads, collections, etc. I presume that your "driver" is completely userspace, and communicates via a serial port or ethernet to the micro controller that actually controls the laser device.
If you will be writing a kernel driver for the laser device, then the interface would be probably very similar, except that you end up writing the image bitmap to an open device handle.
// https://github.com/KubaO/stackoverflown/tree/master/questions/surface-20737882
#include <QtWidgets>
#include <array>
const char kFiltered[] = "WidgetMonitor_filtered";
class WidgetMonitor : public QObject {
Q_OBJECT
QVector<QPointer<QWidget>> m_awake;
QBasicTimer m_timer;
int m_counter = 0;
void queue(QWidget *window) {
Q_ASSERT(window && window->isWindow());
if (!m_awake.contains(window)) m_awake << window;
if (!m_timer.isActive()) m_timer.start(0, this);
}
void filter(QObject *obj) {
if (obj->isWidgetType() && !obj->property(kFiltered).toBool()) {
obj->installEventFilter(this);
obj->setProperty(kFiltered, true);
}
}
void unfilter(QObject *obj) {
if (obj->isWidgetType() && obj->property(kFiltered).toBool()) {
obj->removeEventFilter(this);
obj->setProperty(kFiltered, false);
}
}
bool eventFilter(QObject *obj, QEvent *ev) override {
switch (ev->type()) {
case QEvent::Paint: {
if (!obj->isWidgetType()) break;
if (auto *window = static_cast<QWidget *>(obj)->window()) queue(window);
break;
}
case QEvent::ChildAdded: {
auto *cev = static_cast<QChildEvent *>(ev);
if (auto *child = qobject_cast<QWidget *>(cev->child())) monitor(child);
break;
}
default:
break;
}
return false;
}
void timerEvent(QTimerEvent *ev) override {
if (ev->timerId() != m_timer.timerId()) return;
qDebug() << "painting: " << m_counter++ << m_awake;
for (auto w : m_awake)
if (auto *img = dynamic_cast<QImage *>(w->backingStore()->paintDevice()))
emit newContents(*img, w);
m_awake.clear();
m_timer.stop();
}
public:
explicit WidgetMonitor(QObject *parent = nullptr) : QObject{parent} {}
explicit WidgetMonitor(QWidget *w, QObject *parent = nullptr) : QObject{parent} {
monitor(w);
}
Q_SLOT void monitor(QWidget *w) {
w = w->window();
if (!w) return;
filter(w);
for (auto *obj : w->findChildren<QWidget *>()) filter(obj);
queue(w);
}
Q_SLOT void unMonitor(QWidget *w) {
w = w->window();
if (!w) return;
unfilter(w);
for (auto *obj : w->findChildren<QWidget *>()) unfilter(obj);
m_awake.removeAll(w);
}
Q_SIGNAL void newContents(const QImage &, QWidget *w);
};
class TestWidget : public QWidget {
QVBoxLayout m_layout{this};
QLabel m_time;
QBasicTimer m_timer;
void timerEvent(QTimerEvent *ev) override {
if (ev->timerId() != m_timer.timerId()) return;
m_time.setText(QTime::currentTime().toString());
}
public:
explicit TestWidget(QWidget *parent = nullptr) : QWidget{parent} {
m_layout.addWidget(&m_time);
m_layout.addWidget(new QLabel{"Static Label"});
m_layout.addWidget(new QPushButton{"A Button"});
m_timer.start(1000, this);
}
};
int main(int argc, char **argv) {
QApplication app{argc, argv};
TestWidget src;
QLabel dst;
dst.setFrameShape(QFrame::Box);
for (auto *w : std::array<QWidget *, 2>{&dst, &src}) {
w->show();
w->raise();
}
QMetaObject::invokeMethod(&dst, [&] { dst.move(src.frameGeometry().topRight()); },
Qt::QueuedConnection);
WidgetMonitor mon(&src);
src.setWindowTitle("Source");
dst.setWindowTitle("Destination");
QObject::connect(&mon, &WidgetMonitor::newContents, [&](const QImage &img) {
dst.resize(img.size());
dst.setPixmap(QPixmap::fromImage(img));
});
return app.exec();
}
#include "main.moc"
I am trying to build an QT State Maschine. I have some States, and for those States i need Transition that alter the Graphics on my gui.
The Problem i having and the only reason i am asking, i am Stuck and Point 1.
The compiler cant identifie the QTEventTransition. I have QT 4.6 wroking with QT Creator on Windows.
The compiler does not find Header #include < QtEventTransition >
This is what i did i never did this bevor but i think it should be correct, I have A Header File where i have my Transitions Declareted like this:
class validateBoatTransition : public QtEventTransition
{
public:
validateBoatTransition(Widget *widget,ServerSkeleton* server);
protected:
bool eventTest(QEvent *e);
void onTransition(QEvent *);
private:
Chart* ourChart;
Message current;
BarelySocket* myBarelySocket;
};
Than i have my Cpp File where i have this:
validateBoatTransition::validateBoatTransition(Widget *widget,ServerSkeleton* server)
{
}
void validateBoatTransition::onTransition(QEvent *e)
{
/*
My Logik should go here
*/
}
What i want is that if the Transition is activated by an Button (clicked) it should fire this transition!
I searched the net, but cant find an solution. Can i do that? I should i think.
Yours Thomas
Maybe you should take a look to signals/slot mechanism. I think this is what you need to achieve what you want.
Make your onTransition function a slot instead of an event handler and connect it to the signal clicked of the button.
class validateBoatTransition : public QtEventTransition
{
...
public slots:
void onTransition();
...
}
Somewhere in your code, connect the button to the slot:
QObject::connect(myButton, signal(clicked()), myValidateBoatTransition, slot(onTransition());
Each time the button will be clicked the execution will go through the onTransition function.
I think you're trying to use wrong classes/mechanisms to achieve your goals. If I understand you correctly, you have some GUI and after clicking some button you want to validate some stuff and if this validation is successful the state machine should change it's state. I'd write it this way:
Create some class to handle validation:
class BoatValidator : public QObject
{
Q_OBJECT
// boring stuff like constructor, etc.
public slots:
void validate()
{
if ( /*your validation logic goes here*/ ) {
emit boatTransition();
}
}
signals:
void boatTransition(); // emitted if validation is succesful
};
Then you connect your QPushButton::clicked() to BoatValidator::validate() and use BoatValidator::boatTransition() signal to drive the state machine:
QStateMachine machine;
QState *state1 = new QState(&machine);
QState *state2 = new QState(&machine);
// more state machine setup
// connect validator and button
QPushButton button;
BoatValidator validator;
connect(&button, SIGNAL(clicked()), &validator, SLOT(validate()));
// use validator to change states
state1->addTransition(&validator, SIGNAL(boatTransition()), state2);
Generally I'd use signal to drive state machine, unless some transitions are obviously event driven (for example some QEvent::Enter/QEvent::Leave on GUI widgets, etc.).
What i wanted to do is build a Qt State Machine. The Problem was that i could not trigger my own Transitions (let alone with my own Events). The answers given are good but would lead to a messy code. Why should i use a QT State Machine if i could not use the QT Transitions?
The First Problem above is solved, if you create a new Project. QT Creater is very annoying.
But here now my solution , may it help others.
First my State:
class ServerState : public QState
{
Q_OBJECT
public:
ServerState(QPushButton * pushButton);
~ServerState();
public slots:
void buttonWasClicked();
protected:
void onEntry(QEvent *e);
void onExit(QEvent *e);
private:
QPushButton * pushButton;
};
Normal, but you see i added an Slot. This slot enables me to connect a bottom signal or a Widget Mouse Press Signal to it !
Like this:
QStateMachine *machine = new QStateMachine(this);
ServerState *s1 = new ServerState(connectButton);
connect(connectButton, SIGNAL(clicked()), s1, SLOT(buttonWasClicked()));
machine->addState(s1);
s1->addTransition(connectTransition);
all i needed to to is now fire a declared Event like this one :
#define RegisterToServerEventIndex User+5
class ConnectToServerEvent : public QEvent
{
public:
ConnectToServerEvent() : QEvent(QEvent::Type(QEvent::ConnectToServerEventIndex))
{}
};
when the slot was called:
void ServerState::buttonWasClicked()
{
this->machine()->postEvent(new ConnectToServerEvent());
qDebug("ServerState::buttonWasClicked");
}
The QT State Machine would now call all the Transitions , link with this state:
ConnectToServerTransition::ConnectToServerTransition(QPushButton * pushButtonB,ServerSkeleton* serverSkeleton)
{
this->pushButtonB = pushButtonB;
this->pushButtonB->hide();
this->serverSkeleton = serverSkeleton;
qDebug("ConnectToServerTransition::ConnectToServerTransition");
}
bool ConnectToServerTransition::eventTest(QEvent *e)
{
return (e->type() == QEvent::ConnectToServerEventIndex);
}
void ConnectToServerTransition::onTransition(QEvent *e)
{
if (true == this->serverSkeleton->initalisieren())
{
this->pushButtonB->show();
}else{
qDebug("Conection to Server faild");
}
emit kill();
return;
}
Whats so great that i dare to post?
Well first you can link a Qt SM to a widget where a mouse press event , or somthing else, is called and process the raw data to a an level you need later in your program. All you then need to do is, to emit the singal:
void Widget::mousePressEvent(QMouseEvent *event){
Coordinates current;
current.line = 0;
current.row = A;
current.row = (Row) (event->x() / 30); // 30 = breite von einen Feld
current.line = event->y() / 30; // 30 = länge von einen Feld
emit this->clicked(current);
return;
}
Then this enhenced information (current) is passed to the slot at my state, where i chose to call the correct transition that does the work. You could link more transitions to it, if you need it.
But most importend you dont need to reprogramm the Transition, a think i realy disliked.
Thank you for your help , i could not done it alone.
Ok, so I'm having this problem tonight:
[...]
connect(startButton, SIGNAL(clicked()), this, SLOT(startCalculation()));
connect(stopButton, SIGNAL(clicked()), this, SLOT(stopCalculation()));
[...]
void MainWindow::startCalculation()
{
qDebug() << "hello";
this->startButton->setDisabled(true);
this->stopButton->setEnabled(true);
this->calcStatus = true;
this->calculate();
}
void MainWindow::stopCalculation()
{
this->startButton->setEnabled(true);
this->stopButton->setDisabled(true);
this->calcStatus = false;
}
void MainWindow::calculate()
{
qDebug() << "hello";
while(this->calcStatus)
{
}
}
[...]
I'm trying to make the calculate() procedure stoppable any time, but right after it is started I loose control and I can't press STOP. Of course in my future plans calculate() is going to "calculate" something real (e.g. heat transfer simulation).
Thanks for suggestions.
P.
You would need to look into threading. The calculation locks the ui.
Well, in "Introduction to Design Patterns in C++ with Qt4" they say that
"it is possible to avoid the use of
threads in favor of the Qt Event Loop
combined with QTimers"
but I've never tried it :)
Actually, I've just tried -
add:
QTimer *Timer;
in MainWindow class header and in MainWindow constructor add:
Timer = new QTimer(this);
then change calculate() from function to a signal and modify:
void MainWindow::startCalculation()
{
qDebug() << "hello";
this->startButton->setDisabled(true);
this->stopButton->setEnabled(true);
this->calcStatus = true;
connect(Timer, SIGNAL(timeout()), this, SLOT(calculate()));
Timer->start(0);
}
void MainWindow::stopCalculation()
{
this->startButton->setEnabled(true);
this->stopButton->setDisabled(true);
this->calcStatus = false;
Timer->stop();
Timer->disconnect(this,SLOT(calculate()));
}
This should work as long as you dont pass any arguments into calculate().