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  4. QML ListView does not reflect updates from its C++ data model [Solved]
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QML ListView does not reflect updates from its C++ data model [Solved]

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  • O Offline
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    ondrejandrej
    wrote on 21 Jan 2015, 16:15 last edited by
    #7

    You are creating a model, but it goes out of scope immediately after constructor terminates (I suppose your last code snippet is in a constructor).

    You should ensure that the model remains in existence while the QML view is showing, e. g. by allocating on heap:
    @MyDataModel *myDataModel = new MyDataModel(this);
    context->setContextProperty("myDataModel", myDataModel);@

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    • K Offline
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      kwisatz
      wrote on 21 Jan 2015, 17:44 last edited by
      #8

      I've tried to allocate it at the heap as well and the ui remains unchanged. Originally, myDatamodel was a private member of its parent's class. The code snippet was modified to simplify my question.

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      • O Offline
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        ondrejandrej
        wrote on 21 Jan 2015, 19:44 last edited by
        #9

        You are using "it's" wrongly. Have a look at http://www.elearnenglishlanguage.com/blog/english-mistakes/its/ . You have it also in the title.

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        • K Offline
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          kwisatz
          wrote on 21 Jan 2015, 22:01 last edited by
          #10

          :D Thanks for pointing that out!

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          • P Offline
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            p3c0
            Moderators
            wrote on 22 Jan 2015, 04:54 last edited by
            #11

            bq. I just tried inserting that, and my Application Crashed as soon as that code was invoked. Narrowed it down to endResetModel() being the culprit.

            I have been using this approach in all my projects where ListView is used. It worked all the time.
            Why are you using QDeclarativeView ? Aren't you using Qt 5 ?

            157

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            • O Offline
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              ondrejandrej
              wrote on 22 Jan 2015, 11:29 last edited by
              #12

              [quote author="kwisatz" date="1421877712"]:D Thanks for pointing that out!
              [/quote]
              It's good that you fixed it :D

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              • K Offline
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                kwisatz
                wrote on 22 Jan 2015, 17:46 last edited by
                #13

                Sorry, should have made this clear earlier on, I'm using Qt 4.8.4.

                [quote author="p3c0" date="1421902494"]bq. I just tried inserting that, and my Application Crashed as soon as that code was invoked. Narrowed it down to endResetModel() being the culprit.

                I have been using this approach in all my projects where ListView is used. It worked all the time.
                Why are you using QDeclarativeView ? Aren't you using Qt 5 ?[/quote]

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                • P Offline
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                  p3c0
                  Moderators
                  wrote on 23 Jan 2015, 05:04 last edited by
                  #14

                  Well then I'm not sure why it crashes. Qt 4.8.4 still is quite old in Qt4 series. Can you try it on Qt 4.8.6 ?

                  157

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                  • K Offline
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                    kwisatz
                    wrote on 29 Jan 2015, 21:29 last edited by
                    #15

                    I've tried this with 4.8.6 but to no avail

                    At the moment, I'm unable to move to Qt5. I'm cross-compiling for an Embedded Linux System as well, there's a fair amount of porting involved to move to Qt5.

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                    • K Offline
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                      kwisatz
                      wrote on 2 Feb 2015, 17:21 last edited by
                      #16

                      Okay, I did manage to get this to work finally.

                      When clearing data, I used:
                      @ beginResetModel();
                      m_data.clear();
                      endResetModel();@

                      When removing an individual item in the data, I used:

                      @ beginRemoveRows(QModelIndex(), index, index);
                      m_data.removeAt(index);
                      endRemoveRows();@

                      And I worked on this bit of code separately from my main application. Will have to see what kind of fun awaits when I merge the changes with the rest of the application ;)

                      Appreciate the help folks!

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                      16/16

                      2 Feb 2015, 17:21

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