Login screen (How to?)

cxam

Hi! I designed my Qt Gui application using QtDesigner and in order to make diverse layers inside the application (login, main menu, settings, etc.) I made diverse QWidgets for each layer and depending which button inside the GUI was pressed the layers where showing or hiding... Now I have to make all this cool buttons functional and I have to make the login screen usable but I don't know how, in my login screen I have 4 elements: 1: the logo, 2&3: Username and Password QLineEdits and 4: The "Enter" button. I have to make all those funcitional.

Thanks in advance:

Carlos.

SGaist

Hi,

What are you going to validate your username/password ? Database ? Local file ?

cxam

Just a string, the username and pasword wont be changed

kshegunov

@cxam

Just a string, the username and pasword wont be changed

Just to put a note here - if you use a C++ string for the username and password suppose like this:

const char * password = "my very secret password";

No one can stop me (or anyone else) from loading your application/library in the disassembler and extracting that string. So do consider this, when thinking about passwords.

cxam

Yeah I know that it may not be really secure but I just want it to work the easiest way posible, anyways I still dont know how to make the username / password validation system

kshegunov

@cxam
It's an ordinary dialog, is it not?

cxam

no, it's not the login takes places in the only window of the software: "mainwindow" when you enter the correct credentials then the login disappears and show the whole thing.

SGaist

Well since it's only a very light login, put the logic in the widget and emit a signal when the login is successful. Then in your main window react on that signal and do the changes needed.

cxam

@SGaist I have, really little C++ knowledge, would you please tell me the code I have to add ? Thanks in advance

SGaist

Do you mean the comparison logic ?

cxam

@SGaist Yes.

SGaist

Something like

void MyLoginWidget::onOkButtonClicked() 
{
    if (_usernameLineEdit->text() == MyValidUserName &&
        _passwordLineEdit->text() == MyTopSecretPassword) {
        emit loginSuccessful();
    } else (
        QMessageBox::warning(this, tr("Error"), tr("Invalid username/password combination");
        _usernameLineEdit->clear();
        _passwordLineEdit->clear();
    }
}

WARNING: this is just a quick and dirty sample code.

cxam

@SGaist So I have to add that code on "mainwindow.ccp" right ? (Sorry about my C++ knowledge haha)

SGaist

No, in the login widget. The MainWindow widget should only react on the loginSuccessful signal.

cxam

@SGaist I hope this will show you more or less how I have my project structured: http://postimg.org/gallery/oeciyc12/660b7d39/

SGaist

Ok… So you are trying to have everything in only once widget. Not a good idea. You should following the "Single Responsibility" paradigm. Create one widget per "complex" widget you will have in your main window. Otherwise you will end up with a monster class that does way to much things for its own good and yours to maintain.

cxam

@SGaist Yeah, I knew that my weird distribution would bring problems hahah. So I'll have to change it. Can you tell me which is the best distribution since I want that EVERYTHING happens in just one window (When I have the project finished I will embed it) ?

SGaist

Creating several widgets doesn't mean to you will have one application window per widget. What I'm suggesting is to separate things code-wise. You will still have only one MainWindow in the end containing everything but cleanly separated from a coding point of view.

cxam

@SGaist Ok, I've created a new project > application > QtWidgets application then it created the "MainWindow" class, "MainWindow" header and "MainWindow" Ui.
So for each "screen" I have to create a new C++ class ? Or... How? I don't understand the way to create widgets...

SGaist

Yes, create a new C++ class. You will have the option to "pre-populate" it for design development. You should take the time to look at Qt Creator/Designer and Qt's tutorial about how to create UI with Designer.

cxam

@SGaist So... http://postimg.org/image/7djf0eb6v/ like this?

SGaist

Looks like it but why do you have two different projects ?

cxam

@SGaist I'm sorry, The first one is the old one and the second one is the new one. Ok now I think I understand how it works hahah, thanks for your help. Let's see if I can learn how Qt works. By the way... Do you know any good tutorial for qt ?

SGaist

Well, you can start by looking at Qt's own documentation for tutorials. Since you are using Designer it also has a nice documentation to help you get started.

cxam

@SGaist Well, I did start from there but I found it too complicated I mean, the documentation seems that is the place where you go to double check things or to search a certain thing but I need something more like a guide or a book or something like that hahah

mrjj

Hi
I find this book good for inspiration on how classes fits together.
http://www.bogotobogo.com/cplusplus/files/c-gui-programming-with-qt-4-2ndedition.pdf

Look for "Signals and Slots in Depth".

This is for Qt4 and its important to know that you can make use of Designers ability to
auto connect instead of code as shown in book.

Right click and select Goto Slot. Then choose released() .
It will then create a function (slot) for you that will be called when button is pressed and released.
The name is important so no rename. (for auto connect to work)

Also, there many good videos on youtube for how to use Designer.