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    Solved How to update QTableView when rows are inserted to it

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    • Ratzz
      Ratzz last edited by Ratzz

      I am trying to insert rows to QTableView set to QAbstractTableModel using drag of item from another TreeView on to the QTableView.

         //Constructor of Tableview 
          model= new TableModel();
          TableRowCount=0;
          model->rCount=TableRowCount;
          this->setModel(model);
          setAcceptDrops(true);
      
         //dropEvent
              QTreeView * view= dynamic_cast<QTreeView*>(event->source());
              QModelIndexList list= view->selectionModel()->selectedIndexes();
              for(int i=0;i<list.count();i++)
              {
                  QModelIndex dragIndex=list.at(i);
                  if(dragIndex.parent().isValid())
                  {
                      TableRowCount++;
                     model->rCount=TableRowCount;
                      
                      TableStruct Tstruct;
                      Tstruct.DeviceName=dragIndex.parent().data(Qt::DisplayRole).toString();
                      Tstruct.MessageName=dragIndex.parent().data(Qt::DisplayRole).toString();
                      Tstruct.TagName=dragIndex.data(Qt::DisplayRole).toString();
                      Tstruct.Value=QString::number(0);
                      Tstruct.Units=QString::number(0);
                      
                      TableStrList.append(Tstruct);
                      model->TableList=TableStrList;
                      model->insertRows(TableRowCount,1,dragIndex);
      

      And model looks like

      QVariant Model::data(const QModelIndex &index, int role) const
      {
          if (role == Qt::DisplayRole)
          {
              int column = index.column();
              int row  = index.row();
      
              switch(column)
              {
              case 0:
                  return   TableList.at(row).DeviceName;
                  break;
              case 1:
                  return   TableList.at(row).MessageName;
                  break;
              case 2:
                  return   TableList.at(row).TagName;
                  break;
              case 3:
                  return   TableList.at(row).Value;
                  break;
              case 4:
                  return   TableList.at(row).Units;
                  break;
              }
          }
      
          if(role == Qt::TextAlignmentRole)
          {
              return Qt::AlignCenter;
          }
      
          return QVariant();
      }
      
      int Model::rowCount(const QModelIndex & /*parent*/) const
      {
          qDebug()<< "row count "<<rCount;
          return rCount;
      }
      
      int Model::columnCount(const QModelIndex & /*parent*/) const
      {
          return 5;
      }
      
      QVariant Model::headerData( int section,Qt::Orientation orientation,int role ) const
      {
          if((role == Qt::DisplayRole || role ==Qt::ToolTipRole))
          {
              if(orientation == Qt::Horizontal)
              {
                  switch( section )
                  {
                  case 0: return( QString( "Device Name" ) );
                  case 1: return( QString( "Message Name" ) );
                  case 2: return( QString( "Tag Name" ) );
                  case 3: return( QString( "Value" ) );
                  case 4:return (QString("units"));
                  }
              }
          }
          return QAbstractItemModel::headerData( section, orientation, role );
      }
      
      bool Model::insertRows(int row, int count, const QModelIndex &parent)
      {
          beginInsertRows(parent,row,row+count-1);
          endInsertRows();
          return true;
      }
      

      Row count in the model is updated properly on drop of item but the view is not getting updated. How will the will know that the new rows re inserted??

      --Alles ist gut.

      kshegunov 1 Reply Last reply Reply Quote 0
      • kshegunov
        kshegunov Moderators @Ratzz last edited by kshegunov

        @Ratzz
        Hello,
        I believe you should emit the QAbstractItemModel::rowsInserted signal from the model (after your call to endInsertRows), so the view knows to adapt to the changes.

        Kind regards.


        PS:

        switch(column)
        {
            case 0:
        

        You should really use (possibly unnamed) enums for that kind of switch constructs.

        Read and abide by the Qt Code of Conduct

        Ratzz 1 Reply Last reply Reply Quote 1
        • Ratzz
          Ratzz @kshegunov last edited by

          @kshegunov
          Thanks for the reply.
          But doc says

          Note: This is a private signal. It can be used in signal connections but cannot be emitted by the user.
          

          What does this mean?

          --Alles ist gut.

          kshegunov 1 Reply Last reply Reply Quote 0
          • kshegunov
            kshegunov Moderators @Ratzz last edited by

            @Ratzz
            It means it can't be emitted from the user of the class. Since you're not the user of the class, but rather the designer, I think you should just ignore the note. ;)

            Read and abide by the Qt Code of Conduct

            Ratzz 1 Reply Last reply Reply Quote 0
            • Ratzz
              Ratzz @kshegunov last edited by

              @kshegunov
              It asks for QPrivateSignal http://postimg.org/image/bjpuc4bep/

              --Alles ist gut.

              kshegunov 2 Replies Last reply Reply Quote 0
              • kshegunov
                kshegunov Moderators @Ratzz last edited by

                @Ratzz
                Oops, sorry. The note above the one you cited states:

                It can only be emitted by the QAbstractItemModel implementation, and cannot be explicitly emitted in subclass code.
                

                Hm, in that case I'm not sure ... The documentation is somewhat cryptic whether endInsertRows() actually emits the aforementioned signal ...

                Read and abide by the Qt Code of Conduct

                Ratzz 1 Reply Last reply Reply Quote 0
                • kshegunov
                  kshegunov Moderators @Ratzz last edited by

                  @Ratzz
                  Possibly, you could try implementing QAbstractItemModel::dropMimeData without intercepting the drop event?

                  Read and abide by the Qt Code of Conduct

                  1 Reply Last reply Reply Quote 2
                  • Ratzz
                    Ratzz @kshegunov last edited by Ratzz

                    @kshegunov
                    The beginInsertRows doc http://doc.qt.io/qt-4.8/qabstractitemmodel.html#beginInsertRows says

                    Note: This function emits the rowsAboutToBeInserted() signal which connected views (or proxies) must handle before the data is inserted. Otherwise, the views may end up in an invalid state.
                    

                    Will it help?

                    --Alles ist gut.

                    kshegunov 1 Reply Last reply Reply Quote 0
                    • kshegunov
                      kshegunov Moderators @Ratzz last edited by kshegunov

                      @Ratzz
                      Yes, I saw that, but this is to notify the view insertions will be happening. The question is whether endInsertRows() emits rowsInserted() thus telling the view the insertion has finished and it can actually update itself. Unfortunately, the documentation doesn't state anything specific about endInsertRows(), unless I completely missed it ...

                      PS. I just noticed something in your code:

                      QTreeView * view= dynamic_cast<QTreeView*>(event->source());
                      

                      Is this a typo?

                      Read and abide by the Qt Code of Conduct

                      Ratzz 1 Reply Last reply Reply Quote 1
                      • SGaist
                        SGaist Lifetime Qt Champion last edited by

                        Hi,

                        The documentation doesn't specify but the implementation does emit rowsInserted. However in this case insertRows doesn't do anything so I wonder if there isn't a caching mechanism that avoids to update the view if in fact nothing has changed.

                        Interested in AI ? www.idiap.ch
                        Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

                        Ratzz kshegunov 2 Replies Last reply Reply Quote 1
                        • Ratzz
                          Ratzz @kshegunov last edited by

                          @kshegunov said:

                          Is this a typo?

                          I drag the items from another QTreeView .The cast is for that..
                          Did you mean that?

                          --Alles ist gut.

                          1 Reply Last reply Reply Quote 0
                          • Ratzz
                            Ratzz @SGaist last edited by

                            @SGaist said:
                            Thanks for the reply.
                            So there is no way with insertRows?

                            --Alles ist gut.

                            1 Reply Last reply Reply Quote 0
                            • kshegunov
                              kshegunov Moderators @SGaist last edited by kshegunov

                              @SGaist

                              However in this case insertRows doesn't do anything so I wonder if there isn't a caching mechanism that avoids to update the view if in fact nothing has changed.

                              After a quick look (without pretense to be complete) I couldn't clearly see any such caching done.
                              Here's what I peeked at (for Qt 5.6):
                              http://code.qt.io/cgit/qt/qtbase.git/tree/src/corelib/itemmodels/qabstractitemmodel.cpp#n2601
                              http://code.qt.io/cgit/qt/qtbase.git/tree/src/corelib/itemmodels/qabstractitemmodel.cpp#n582

                              @Ratzz

                              I drag the items from another QTreeView .The cast is for that..
                              Did you mean that?

                              Indeed I did. Have you considered handling the drag/drop events through the ordinary mechanism? Serializing on drag, then deserializing the mime data on drop?

                              Read and abide by the Qt Code of Conduct

                              Ratzz 1 Reply Last reply Reply Quote 1
                              • Ratzz
                                Ratzz @kshegunov last edited by

                                @kshegunov said:

                                Serializing on drag, then deserializing the mime data on drop?

                                No i have not considered this part.

                                --Alles ist gut.

                                kshegunov 1 Reply Last reply Reply Quote 0
                                • SGaist
                                  SGaist Lifetime Qt Champion last edited by

                                  @kshegunov : I mean't view side caching.

                                  @Ratzz currently you are not inserting anything through it. Like @kshegunov suggested, implement the drag and drop through the mechanism provided for model/view classes. It's described here

                                  Interested in AI ? www.idiap.ch
                                  Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

                                  Ratzz 1 Reply Last reply Reply Quote 0
                                  • Ratzz
                                    Ratzz @SGaist last edited by

                                    @SGaist
                                    I will try to implement through (link you provided ) this.

                                    --Alles ist gut.

                                    1 Reply Last reply Reply Quote 0
                                    • kshegunov
                                      kshegunov Moderators @Ratzz last edited by kshegunov

                                      @Ratzz

                                      No i have not considered this part.

                                      Then I suggest you try it out. It may prove to be easier and better behaved than pulling the records directly from the tree widget. As for your current implementation, I'm at a loss why it doesn't work. Maybe the tree view is losing the selection when dragging and the selection model returns no records?

                                      @SGaist

                                      I mean't view side caching.

                                      I see, well I didn't look at the view (obviously) but I suppose it's possible.

                                      Read and abide by the Qt Code of Conduct

                                      Ratzz 1 Reply Last reply Reply Quote 1
                                      • mrjj
                                        mrjj Lifetime Qt Champion last edited by

                                        Hi
                                        I am still wondering. Sorry.
                                        Lets say If I dont have drag&drop.

                                        I simply append to my internal list used in model.

                                        How will I tell the view(s) that?

                                        I though dataChanged would do it but not even begin/endInsertRow
                                        does it.

                                        Thanks

                                        kshegunov 1 Reply Last reply Reply Quote 0
                                        • Ratzz
                                          Ratzz @kshegunov last edited by

                                          @kshegunov said:

                                          Maybe the tree view is losing the selection when dragging and the selection model returns no records?

                                          I don't think so because the rowCount is getting updated as and when the new drop takes place.

                                          --Alles ist gut.

                                          1 Reply Last reply Reply Quote 0
                                          • kshegunov
                                            kshegunov Moderators @mrjj last edited by

                                            @mrjj

                                            I simply append to my internal list used in model.

                                            I'm by no means an expert, but possibly calling submit() (I don't know if it works I'm just guessing)?

                                            Read and abide by the Qt Code of Conduct

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