I have a longer wav-file, where I wanted to play smaller parts.
I stored startTime and endTime as qint64 and already loaded the audiofile:
player = new QMediaPlayer;
connect(player, SIGNAL(positionChanged(qint64)), this, SLOT(slotTick(qint64)));
player->setNotifyInterval(10);
player->setMedia(QUrl::fromLocalFile(mediasource));
...
player->setPosition(startTime);
player->play();
I observe the position with the positionChanged Signal andd use the following slot, to stop the playback once the end of the desired part is reached:
void PlayerWidget::slotTick(qint64 time){
if(endTime >= 0 && time >= endTime){
if(player->state() == QMediaPlayer::PlayingState){
player->stop();
}
}
Unfortunately, the program crashes shortly after the player stops. WHat could be the reason
Just had the same issue, and while I don't really know the underlying reason, I managed to somehow intuit a solution that actually works.
Instead of calling player->stop() directly, trigger it with a singleShot QTimer. Python code equivalent: QtCore.QTimer.singleShot(0, player.stop).
Related
I'm trying to understand the correct way to update a widget at frame-time.
The specific problem I'm trying to solve is to set the remaining time of a timer on a label.
I created and started the timer
MainTimer = new QTimer(this);
MainTimer->setSingleShot(true);
MainTimer->start(5000);
and on the QML I have a label, UI_MainTimerLabel, that I can access through ui->UI_MainTimerLabel->setNum(int).
Since the QTimer doesn't provide a OnTimerUpdate signal or callback method, I suppose I have to create some kind of loop to read the timer's value and set it to the label.
Should I do it through a QThread?
QThread::create([&]() {
while(true)
{
ui->UI_RemainingTimer->setNum(MainTimer->remainingTime());
}
})->start();
(note: I know that this won't work, but it's not a problem since I'm just trying to understand the concept)
Should I use a 0-timed QTimer?
UpdateTimer = new QTimer(this);
//{binding the UpdateTimer end signal to a ui->UI_RemainingTimer->SetNum(MainTimer->RemainingTimer() function}
UpdateTimer->start(0);
Should I use a QEventLoop (but I have yet to fully understand what is their correct usage)?
Should I use a user-created "MyTimerLabel" widget that self-updates (in which virtual overridden method?)?
Or is there some other correct way to manage a frame-time update, that I couldn't understand? (I'm trying to get the general correct approach, not the solving approach of this specific problem, though)
Thanks in advance
Is it necessary to update the GUI at every moment? No, each frame is updated every 30ms so something appropriate is to update half of that time, that is 15 ms. So the second timer is set to that period by calculating the remaining time showing it in the GUI:
#include <QtWidgets>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
QTimer main_timer;
main_timer.setSingleShot(true);
QTimer update_timer;
QLabel label;
label.setAlignment(Qt::AlignCenter);
label.resize(640, 480);
QObject::connect(&update_timer, &QTimer::timeout, [&main_timer, &update_timer, &label](){
int rem = main_timer.remainingTime();
if(rem <0){
label.setNum(0);
update_timer.stop();
}
else{
label.setNum(rem);
}
});
label.show();
main_timer.start(5000);
update_timer.start(15);
return a.exec();
}
I need to create a simple GUI which displays images, the images in this example can change and the GUI will need to update it's contents.
I wrote the following update function in my widget class:
void myClass::updatePic() {
QPixmap pix("./pic.png");
int width = ui->picLabel->width();
int height = ui->picLabel->height();
ui->picLabel->setPixmap(pix.scaled(width,height,Qt::KeepAspectRatio));}
I try to use it in the following manner:
int main(int argc, char *argv[]) {
QApplication a(argc, argv);
myClass w;
w.show();
sleep(3);
w.updatePic();
sleep(3);
w.updatePic();
sleep(3);
return a.exec();}
But the window just opens and does not display the images until we get to the a.exec() line, and then it opens the last image. What am I doing wrong?
EDIT:
Clarification, the trigger for changing the images comes from an external program (specifically, the gui will be a node in ros, and will be triggered by another node). Is there a way to push a button not from the gui via an external program? the timer will work but I dislike this "busy wait" style solutions.
Thanks for the suggestions so far
exec runs the QT event loop, which includes rendering widgets.
So move your updatePic call into your widget and activate it by for example a button or in the show event
At first learn more about event loop. In particular, you must know that all events like paintEvent or resizeEvent are usually called on corresponding events handle. The events handle is usually called by the event loop, i.e. inside of exec function.
Let's unite answers of #MohaBou and #RvdK. You need to handle timer shots after the exec call. Use QObject::timerEvent for this.
myClass::myClass()
{
<...>
// This two variables are members of myClass.
_timerId = startTimer(3000);
_updatesCount = 0;
}
myClass::~myClass()
{
<...>
// For any case. As far as I remember, otherwise the late event
// may be handled after the destructor. Maybe it is false, do
// not remember...
if (_timerId >= 0) {
killTimer(_timerId);
_timerId = - 1;
}
}
myClass::timerEvent(QTimerEvent *event)
{
if (event->timerId() == _timerId) {
if (_updatesCount < 2) {
updatePic();
++_updatesCount;
} else {
killTimer(_timerId);
_timerId = - 1;
}
}
}
The startTimer method here adds especial timer event to the event query every 3 seconds. As all events, it may be handled only when the event loop will take control and all earlier events are handled. Because of it you can have a duration if many "heavy" events are handled.
EDIT: sorry, I didn't understand #MohaBou at first read. His answer with explicit QTimer is also good enough (but I still don't understand a part about modality).
The function exec also renders the child widgets. exec() blocks the application flow while show() doesn't. So, exec is mainly used for modal dialogs.
I recommend to update it in your custom witget by using a refresh timer. Use a QTimer to update the image every 3 secs:
QTimer* timer = new QTimer(this);
timer->setInterval(3000);
connect(timer, SINGAL(timeout()), this, SLOT(updatPicture()));
Update your picture in your custom slot:
MainWindow::updatePicture() {
updatePic()
}
If you want, you could use a lambda function:
connect(timer, &QTimer::timeout, this, [&w]() {
updatePic()
});
I'm trying to create a "responsive gui", which basically means that I have an app, and on the main window there is a button. After I press this button I want the "progress bar window" to get displayed which will show the progress of the work being done, and of course this work is being done in separate thread.
Unfortunately my approach with starting a new thread in ctor of this progress_bar window doesn't seems to work and I got frozen gui.
Here is the link to this project so you can download it and run without the need for copying and pasting anything: http://www.mediafire.com/?w9b2eilc7t4yux0
Could anyone please tell me what I'm doing wrong and how to fix it?
EDIT
progress_dialog::progress_dialog(QWidget *parent) :
QDialog(parent)
{/*this is this progress dialog which is displayed from main window*/
setupUi(this);
working_thread_ = new Threaded;
connect(working_thread_,SIGNAL(counter_value(int)),progressBar,SLOT(setValue(int)),Qt::QueuedConnection);
working_thread_->start();//HERE I'M STARTING THIS THREAD
}
/*this is run fnc from the threaded class*/
void Threaded::run()
{
unsigned counter = 0;
while(true)
{
emit counter_value(counter);
counter = counter + 1 % 1000000;
}
}
Independently from the fact that tight looping is bad, you should limit the rate at which you make changes to the main GUI thread: the signals from your thread are queued as soon they are emitted on the main thread event loop, and as the GUI can't update that fast, repaint events are queued rather than executed in real time, which freezes the GUI.
And anyways updating the GUI faster than the screen refresh rate is useless.
You could try something like this:
void Threaded::run()
{
QTime time;
time.start();
unsigned counter = 0;
// initial update
emit counter_value(counter);
while(true)
{
counter = (counter + 1) % 1000000;
// 17 ms => ~ 60 fps
if(time.elapsed() > 17) {
emit counter_value(counter);
time.restart();
}
}
}
Do you try to start the thread with a parent object?
Hi all I have problem with qprogressbar. How can I make it smooth? I want it to go smoothly from 0 to 100% . I am using it with reply variable which reads data from php script and returning me data. I need to wait 3-4 seconds to get my data I want that progressbar to go smoothly from 0 to 100 and I only have instantly from 0-100.
Here is my code:
void MainWindow::updateDataTransferProgress(qint64 bytesReceived, qint64 bytesTotal)
{
ui->progressBar->setMaximum(bytesTotal);
ui->progressBar->setValue(bytesReceived);
}
void MainWindow::Citanje_korisnika()
{
init();
QUrl params;
params.addQueryItem("action","Citanje_korisnika");
QByteArray data;
data.append(params.toString());
data.remove(0,1);
QNetworkRequest request;
request.setUrl(url);
request.setHeader(QNetworkRequest::ContentTypeHeader,
QVariant("application/x-www-form-urlencoded"));
reply = manager->post(request, data);
connect(reply, SIGNAL(downloadProgress(qint64, qint64)),this, SLOT(updateDataTransferProgress(qint64,qint64)));
}
If you need more code..just tell me.
EDIT 2:
Here is my another part of code:
void MainWindow::init()
{
url = "http://127.0.0.1:8888/direkt_php_qt.php";
manager = new QNetworkAccessManager(this);
// connect(manager, SIGNAL(downloadProgress(qint64,qint64)),this,SLOT(updateDataTransferProgress(qint64,qint64)));
connect(manager, SIGNAL(finished(QNetworkReply*)),this, SLOT(replyFinished(QNetworkReply*)));
}
So program starts and first thing it goes into functionvoid MainWindow::Citanje_korisnika() then it goes to void MainWindow::init() and then void MainWindow::updateDataTransferProgress(qint64 bytesReceived, qint64 bytesTotal) problem is. I want to make this progress bar to go smoothly from the begginig of the program until he downloaded all data to my reply variable.
Now I am getting my form shown and then I waint 3-4 sec nothing is happening, I see my progress bar at 0 and nothing is filled with data and then after some time progress bar jumpes to 100% and data is show.. So I want this perios while program is loading from server to see my progress bar going from 0-100 at some normal speed. Now I only see blank fileds and then boom everything is on. I want to make it all go smoothly. If you know what I mean.
Looks like here the bytesReceived == bytesTotal and thats why its jumping from 0 to 100% immediately. If you know approximate size of bytesTotal you can set QNetworkReply::setReadBufferSize(qint64 size) to fraction of bytesTotal. Than at least you will some progress. However as mentioned in the docu this will throttle down your download speed and I see no point in that.
A song is set as static in Phonon audio player. The loop works using aboutToFinish(). The problem is that there is a 1 sec delay at the end of the song, then the song repeats.
How can we avoid the delay? I have also stored in a temporary buffer (using QBuffer), for playing it. But it is not giving solution for looping issue.
musicpath="sound/sample.mp3";
Phonon::AudioOutput *audioOutput;
Phonon::VolumeSlider *volumeSlider;
Phonon::MediaObject *mediaObject;
mediaObject = new Phonon::MediaObject(this);
mediaObject->setCurrentSource(Phonon::MediaSource( musicpath));
connect(mediaObject, SIGNAL(aboutToFinish()),mediaObject,SLOT(stop()));
connect(mediaObject, SIGNAL(aboutToFinish()),mediaObject,SLOT(play()));
Phonon::createPath(mediaObject, audioOutput);
volumeSlider->setAudioOutput(audioOutput);
mediaObject->play();
I think best choice is checking for state of video is by using timer with 1 ms and play it if end
timer = new QTimer;
QObject::connect(timer, SIGNAL(timeout()), this, SLOT(timer_overflow()));
timer->start(1);
void MainWindow::timer_overflow()
{
if(ui->videoPlayer->isPaused())
{
video=Phonon::createPlayer(Phonon::VideoCategory,Phonon::MediaSource("video/back);
ui->videoPlayer->load(Phonon::MediaSource("video/background_video.wmv"));
ui->videoPlayer->play();
}
}