Launch a second view on a pushed button

mrjj

@Lucian
Ok then its not a variable running out of scope.

And you have tested that
Test::Butt()
is called?

Also try
QQuickView * view = new QQuickView;
instead of
QQuickView * view = new QQuickView()

Not sure if u want the view to be inside something or in a window.
IF you dont give a Qwidget a parent it will become a window.
Else its inserted into parent.

Also the code

  QQuickView view;
    view.setSource(QUrl("qrc:/test.qml"));
    view.setResizeMode(QQuickView::SizeRootObjectToView);
    view.show();

Can work from main but if u do the same in a function, you have this problem that
as soon as functions ends, it will delete view
so right after view.show(); is called it will be deleted. ( so might not show at all)
That is why i showed
QQuickView * view = new QQuickView(this)
That wont run out of scope.

Lucian

I have try everything, it doesn't work. Every time creates a new window but is empty.
I don't understand why doesn't work..
If i remove

this->proc->start("some_executabele", QIODevice::ReadWrite);
this->proc->waitForFinished(-1);

Works ok...
My function in pushed button now looks like this:

    QQuickView* view
    view = new QQuickView();
    view->setSource(QUrl("qrc:/loading.qml"));
    view->setResizeMode(QQuickView::SizeRootObjectToView);
    view->show();
    this->proc->start("some_executabele", QIODevice::ReadWrite);
    this->proc->waitForFinished(-1);

Thank you for your help @mrjj

mrjj

@Lucian
Hi
It looks ok.
( Note, u create a new QQuickView each time. So its a leak but that u can fix later )

I would look at what
http://doc.qt.io/qt-5/qquickview.html#errors
returns.

To see if it has some issue running/loading.

Update:
Just to be sure. We are debugging the QQuickView and setSource
and nothing related to waitForFinished ?

Or are you saying that it works until you use QProcess then windows is empty?

Lucian

Yes,,works until i use QProcess.
If i let the button handle without QProcess it works.
It is possible so lunch a QQuickView in a new QProcess? Maybe current process is the reason why doesn't work .

mrjj

@Lucian

Then i think is what happens.
The setSource starts to load. its still loading when functions returns.

then waitForFinished blocks the event loop
so there is no time to draw when the QML is ready.

so I would try to use the
http://doc.qt.io/qt-5/qquickview.html#statusChanged

and if status is ready, then there in that slot i would run the QProcess.

In that way you first block the event loop when the
QML is 100% finished loading and that should work better.

Lucian

Ok, i will try to find an example and i will post if i solve this.

Lucian

Hey @mrjj

Can you give me one last hand of help ?:D
Look what i have done

class Process : public QObject
{
    Q_OBJECT
private:
    QProcess* proc = new QProcess(this);
    QQuickView* view = new QQuickView();

public slots:
    void startProcess();
};

In process.cpp

void Process::startProcess()
{
    this->proc->start("C:\\Windows\\System32\\calc.exe", QIODevice::ReadWrite);
    this->proc->waitForFinished(-1);
}

void Process::run() {
    view->setSource(QUrl("qrc:/loading.qml"));
    view->setResizeMode(QQuickView::SizeRootObjectToView);
    view->show();

    QObject::connect(view,SIGNAL(view::statusChanged),this, SLOT(Process::startProcess()));
}

Now the qml is show correct but doesn't start the calc.exe after the qml is load.
Is corect how i use QObject::connect?

mrjj

@Lucian said in Launch a second view on a pushed button:

Hi
Good work
There is a slight adjustment

QObject::connect(view,SIGNAL(view::statusChanged),this, SLOT(Process::startProcess()));

should be

QObject::connect(view,SIGNAL(statusChanged() ),this, SLOT(startProcess() ) );
( no class:: in front when using the old syntax)

And i would love if you did

qDebug() << "status sig:" << QObject::connect(view,SIGNAL(statusChanged() ),this, SLOT(startProcess() ) );

so you can check it says TRUE;

Also
void Process::startProcess() {
qDebug() << "startProcess called";
...

So we know it connects works and the startProcess is called.

Lucian

Something is wrong.
It say : "status sig: false"
So the signal is not generated.

Also say:
QObject::connect: No such signal QQuickView::statusChanged()

mrjj

@Lucian
ahh sorry.
Didnt check the docs. ( shame on me)

its just missing the parameter.

void QQuickView::statusChanged(QQuickView::Status status)

so its
QObject::connect(view,SIGNAL(statusChanged(QQuickView::Status) ),this, SLOT(startProcess(QQuickView::Status) ) );

NOte. only Type is added. NOT the paramtername

and u need/could to change slot too

void Process::startProcess( QQuickView::Status thesatus) {
so here u can actually see if its ready etc.

but u dont need to use the status :)

jsulm

@Lucian
Please check documentation: http://doc.qt.io/qt-5/qquickview.html#statusChanged
The signal has a parameter, so it should be:

qDebug() << "status sig:" << QObject::connect(view,SIGNAL(statusChanged(QQuickView::Status) ),this, SLOT(startProcess() ) );

Lucian

Thanks @mrjj , @jsulm
Now it's better.
"status sig: true"

But the startProcess() still isn't call yet.
The message from slot is not printed and the calc.exe doesn't show up, but at lest the status from QQuickView is changed.

jsulm

@Lucian Try to connect first:

void Process::run() {
    QObject::connect(view,SIGNAL(view::statusChanged),this, SLOT(Process::startProcess()));
    view->setSource(QUrl("qrc:/loading.qml"));
    view->setResizeMode(QQuickView::SizeRootObjectToView);
    view->show();
}

Lucian

Yes @jsulm .
It work but this doesn't solve my problem.
I try to connect status change with startProcess because the progress bar (loading.qml) was block by waitForFinish(-1).
Now is happening the same.
The signal and the slot are called in the right order but also loading.qml doesn't popup until i close the calc.exe.

jsulm

@Lucian Why do you wait for the process to finish?

this->proc->waitForFinished(-1);

Are you aware that this call blocks the event loop (so your app is blocked)?

Lucian

Yes @jsulm .
I need to do that because the process what will be launch will create a txt file. This file will be use farder so i need to be sore the process has finished his job and has created the txt.

jsulm

@Lucian No need to wait for this! Just connect to http://doc.qt.io/qt-5/qprocess.html#finished signal - when it is called the process has finished...
Qt is an asynchronous framework - you should adapt to asynchronous programming.

Lucian

But how will wait my application to create the txt file ? Because after the process is finished i want to read from that .txt file created by him and if i read before creation the application will fail.
So i need to connect the finish signal from QProcess with a slot that make the read from .txt file? :D

jsulm

@Lucian Yes, you simply connect a slot to that signal and do what you want with that file in this slot.

Lucian

I have made some changes and now look like this:

void Process::startProcess()
{
    qDebug() << "startProcess called";
    this->proc->start("C:\\Windows\\System32\\calc.exe", QIODevice::ReadWrite);
    qDebug() << "connect status :" << QObject::connect(proc,SIGNAL(QProcess::finished()),this, SLOT(addData()));
}

And the slot:

void Process::addData()
{
    qDebug() << "addData call:";
    SomeClasss c;    
    c.read();
}

The problem is again with type of the signal:
*QObject::connect: No such signal QProcess::QProcess::finished()

From documentation (Qt doc) doesn't seems to be something wrong.