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Thread: Problem With findchild()

  1. #1
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    Default Problem With findchild()

    Hi i am trying to use the findChlid(), and i was getting error after running it that is
    The program has unexpectedly finished

    Here is my Code:
    The Header File
    Qt Code:
    1. class menuprocess : public QWidget
    2. {
    3. Q_OBJECT
    4. public:
    5. menuprocess();
    6. ~menuprocess();
    7. private:
    8. QLabel *io_one;
    9. private slots:
    10. int tester();
    11. };
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    The CPP File
    Qt Code:
    1. menuprocess::menuprocess()
    2. {
    3. io_one = new QLabel(this);
    4. testButton = new QPushButton(this);
    5. testButton->setText("Test");
    6. testButton->setGeometry(250,130,40,30);
    7. }
    8.  
    9. int menuprocess::tester()
    10. {
    11. ios << "RFID" << "MagSwipe" << "RTC" << "IFD" <<"PM";
    12. obs << "io_one" << "io_two" << "io_three" << "io_four";
    13. QLabel *label = parentWidget()->findChild<QLabel *>(obs.at(j));[B]I have used both the Lines this one and the next one by commenting one among this[/B]
    14. QLabel *label = this->findChild<QLabel *>(obs.at(j));
    15. qDebug()<<"The OBJECT NAME is"<<label->objectName();//at this line i am getting error[B]The program has unexpectedly finished[/B]
    16. label->setText(ios.at(i));[B]//And here too the same error if i comment the QDebug Line[/B]
    17. }
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    Is it possible todo so in this manner if yes

    Please do need ful

    Thanks in advance

    Regards,
    Rohith.G

  2. #2
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    Default Re: Problem With findchild()

    Hi, findChild() uses the object name of a QObject, not the name of the variable where you store your pointer. So I guess in your case "label" is always NULL, and that's why the program crashes. Use setObjectName() when you create your label in the menuprocess-constructor.

    Ginsengelf

  3. #3
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    Default Re: Problem With findchild()

    Quote Originally Posted by gunturrohith View Post
    The program has unexpectedly finished
    Meaning it crashed.
    You should have gotten a stack trace when running this in a debugger.

    Quote Originally Posted by gunturrohith View Post
    Here is my Code:
    Don't write that when the code is not actually your code.

    Quote Originally Posted by gunturrohith View Post
    Is it possible todo so in this manner if yes
    Yes, this is possible, as Ginsengelf already wrote.

    However, what do you need this for?
    Why not just store the widgets you need access to in a way to allows you to access them directly?

    Cheers,
    _

  4. #4
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    Default Re: Problem With findchild()

    Don't write that when the code is not actually your code.
    Hi anda_soka,

    Thanks for replying and helping and apologies for asking explanation,may i know the reason behind for stating this sentence
    Don't write that when the code is not actually your code. I may not be a great programmer in Qt but all the lines i have written on my own by considering the Qt assistant as reference.

    Thanks in advance,
    Rohith.G

  5. #5
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    Default Re: Problem With findchild()

    Hi, anda_skoa probably meant that your code won't compile the way you posted it and this means that it is not your complete code. For example i and j are undeclared in menuprocess::tester()

    Ginsengelf
    Last edited by Ginsengelf; 24th June 2016 at 08:40. Reason: spelling corrections

  6. #6
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    Default Re: Problem With findchild()

    Quote Originally Posted by Ginsengelf View Post
    Hi, anda_skoa probably meant that your code won't compile the way you posted it and this means that it is not your complete code.
    Exactly!

    Cheers,
    _

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