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Thread: QListWidget items swapping

  1. #1
    Join Date
    Nov 2020
    Qt products

    Question QListWidget items swapping


    I am trying to swap the content of a QListWidget. Perhaps I am not using the right methods ... or maybe I need to use the listview + model instead ?

    The context here is that I have a plotter and I am loading multple files. Each files has its own tab with the plotted data. Each tab contains an object with the filename, channelList, etc ..

    The "Channel list" is in a general QListWidget and I would like to switch the content of that widget when I switch tab.

    Each dataLog object contains the list of channels with a QList that contains items property:
    Qt Code:
    1. QList<QListWidgetItem*> itemList;
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    And here's the handler when I change tabs :

    Qt Code:
    1. void MainWindow::on_tabWidget_logs_currentChanged(int index)
    2. {
    3. foreach(logData* l, this->openedLogs)
    4. {
    5. if(l->parentWidget == ui->tabWidget_logs->widget(index))
    6. {
    8. int count = ui->listWidget_channels->count();
    10. //currentLog->itemList.clear(); // This actually deletes the items in the dataLog object so it's not good
    12. // This doesnt seem to be working since all the items are still in the QListWidget
    13. for ( int i=0; i<count; i++)
    14. {
    15. ui->listWidget_channels->takeItem(i);
    16. }
    18. currentLog = l;
    19. // Take the items from the log object and populate the QListWidget with them
    20. foreach(QListWidgetItem *i, currentLog->itemList)
    21. {
    22. ui->listWidget_channels->addItem(i);
    23. }
    24. ui->listWidget_channels->sortItems();
    25. break;
    26. }
    27. }
    28. }
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  2. #2
    Join Date
    Jan 2008
    Alameda, CA, USA
    Thanked 816 Times in 805 Posts
    Qt products
    Windows Android

    Default Re: QListWidget items swapping

    The problem with your code to remove the items from listWidget_channels is that as soon as you take one item out, "count" is no longer valid. Try this:

    Qt Code:
    1. while ( ui->listWidget_channels->count() > 0 )
    2. ui->listWidget_channels->takeItem( 0 );
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    <=== The Great Pumpkin says ===>
    Please use CODE tags when posting source code so it is more readable. Click "Go Advanced" and then the "#" icon to insert the tags. Paste your code between them.

  3. #3
    Join Date
    Nov 2020
    Qt products

    Thumbs up Re: QListWidget items swapping

    Geez ! I really missed that one .. thanks.

    I was aware of one bad thing and it always catch me ... the decreasing for loop when the count was in the if statement :
    Qt Code:
    1. for (int i=0; i< ui->listWidget_channels->count(); i++ ){ ...
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    But indeed, having a variable with count before taking items is still wrong.

    Thanks again !

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