Passing user Input to Slots

JohnSRV

Hey Everyone,

I'm new to Qt and I find the Signal/Slot Concept in this Framework really helpful. I'm doing some GUI Programming and I'm trying to get some user Input and then do some actions with it. So I have some Qpush Buttons in my GUI when the User clicks one of them he is asked to insert a number or a String.

How can I pass the Input to a Slot that works with it ?

JonB

@JohnSRV
The slot for clicking the pushbutton does not itself do anything with/know about the number/string you are about to "ask for"; it hasn't happened yet! I trust you get that bit.

When the user has clicked the button, how do you intend to "[ask user] to insert a number or a String"? How are you going to prompt for that? Only after that can we discuss how you might use signals/slots to forward the data input onto something else.

mrjj

Hi
How do you then get this number or string?

JohnSRV

@JonB after the User clicks the Button a Dialog Window pops up where the User can insert an IP Adress for example.

void boxconec::Target_IP()
{
	QString TargetIP = QInputDialog::getText(this, "Choose Target system", "Enter the IP Address of the Target System:");
	ui->IPAdress->setText(TargetIP);
}

So I want to pass this TargetIP Variable to a Function that connects to a QTcp Server listening under the given Address. How can I pass that information to my Client Function?

mrjj

@JohnSRV
How does you client function look like ?
can you just add the new parameter and call it

void boxconec::Target_IP()
{
	QString TargetIP = QInputDialog::getText(this, "Choose Target system", "Enter the IP Address of the Target System:");
	ui->IPAdress->setText(TargetIP);
ClientFunction(TargetIP);
}

JonB

@JohnSRV
I will leave you in my colleague @mrjj's capable hands for guiding you now :)

JohnSRV

@mrjj Hey thanks for your reply and sorry for my late Reply. My Client Function is not complete so I tried to test this with a Simple QFile.

void BoxConnector::ProjectButtonPushed()
{
	QString ProjectPath_UserInput = QInputDialog::getText(this, "Project", "Enter the Path to the Project");
	ui->Project_Path->setText(ProjectPath_UserInput);
	QFile Project (Project_UserInput ); 
	if (Project.exists())
	{
		QMessageBox msgBox; 
		msgBox.setText("Opening the Project..");
	}
	else
	{
		QMessageBox ErrorBox; 
		ErrorBox.setText("couldn't find the Project..");
	}
}

I can't seem to get a Message box neither for "Opening the Project.." nor for "couldn't find with the Project". Does the User Input get passed correctly to the QFile with this Code??

mrjj

Hi
You need to call msgBox.exec(); to have it show.
Currently, you just set its text but dont tell it to show:=)
https://doc.qt.io/qt-5/qmessagebox.html

Also since you want the user to input the FULL path to a project what about using FileDialog instead so the user can browse to file and not have to type it all?

https://doc.qt.io/qt-5/qfiledialog.html

JonB

@JohnSRV
QMessageBox::setText() simply sets the text for the message box, it does not show it. You need to call QMessageBox::exec() to do that.

JohnSRV

Thank you all for your help ! I solved my problem with the snippet from @mrjj

void boxconec::Target_IP()
{
	QString TargetIP = QInputDialog::getText(this, "Choose Target system", "Enter the IP Address of the Target System:");
	ui->IPAdress->setText(TargetIP);
ClientFunction(TargetIP);
}

The Application will get more complicated where the ClientFunction returns a Value that has to be passed to another slot but I'm not there yet. As for now I'm gonna mark this question as solved.

Thank you !

JonB

@JohnSRV
What you have ended up with is fine. But be aware you have not encountered any signal/slot stuff in it. In effect, the signal/slot stuff is being hidden from you inside QInputDialog::getText(), and what you see at this level is a synchronous program.

JohnSRV

Hello Everyone,

I'm back on this topic now. I have a GUI where the User can choose which Project he wants to work with. When he pushes the Button "choose Project" a QFileDialog gets opened.

void BoxConnector::ProjectButtonPushed()
{
QString ProjectPath_UserInput = QFileDialog::getOpenFileName(this, tr("Open Project"), "C:/Users/Project");

Now I have many other buttons in my GUI where the user could manipulate the chosen project. How Can I pass the Path of the chosen Project to the other Slots?

I for example have a Button where the User could insert a Simulation Step Size

void BoxConnector::SimStepSizePushed()
{
	QString SimSize_UserInput = QInputDialog::getText(this, "Simulation Step Size", "Insert Simulation Step Size");
}

How Can I pass the Path of the chosen Project in the first Slot to this Slot for example so I could manipulate the Simulation Step Size of the chosen Project?

mrjj

Hi
Just make
QString ProjectPath_UserInput;
a member of BoxConnector
so all slots and methods has access.

JohnSRV

@mrjj I declared a QString in the BoxConnector.h.

Its Value gets set in the ProjectButtonPushed() Slot. When I call this String in another Slot it seems to be empty.

mrjj

@JohnSRV
make sure you didnt do the classic error.
you line should be be
ProjectPath_UserInput = QFileDialog::getOpenFileName(this, tr("Open Project"), "C:/Users/Project");

and NOT
QString ProjectPath_UserInput = QFileDialog::getOpenFileName(this, tr("Open Project"), "C:/Users/Project");
as then you still use local variable..

JohnSRV

As a matter of fact I did make the classic Mistake. Thanks !!!

mrjj

@JohnSRV
Thats is why its a classic, very easy to do :)