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How to use QTableView & Model

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  • C Offline
    C Offline
    cherple
    wrote on last edited by
    #10

    Oh wow! I didn't know the debug statement uses so much resource.. Speed wise is all good now, still a little slower with the widget but definitely a lot faster as compared to previously. Thanks! :))

    But how would u suggest I do this then? I will have a variable to store a users selection from a drop down list, then based on this variable's value, when a user selects a cell it should appear as a different color, probably from a predefined set of colors.

    For example: 0=red,1=blue,2=green
    So when user picked 1, and select a cell, the cell within be blue, then the user proceed with choosing 2, then select the cell next to it, and that cell should be green. So you should see the two boxes side by side one being blue and one being green.

    A 1 Reply Last reply
    0
    • A alex_malyu

      @cherple

      data(...) is called every time cell has to be re-drawn.
      Even though it is always a good idea to keep your code robust it may be as fast as simple returning array value at specified index and is not going to cause any visible delay cause drawing cell will be always slower.

      Remove your debug statements from there and you will see no delays there if you do not do complex computation within it.

      Mentioned by bsomervi QStandardItemModel to my mind is too heavy if you want simply display predefined data. But most of the time , especially if your code would run only on desktops with relatively small number of rows/columns you will not notice any difference.

      B Offline
      B Offline
      bsomervi
      wrote on last edited by
      #11

      @alex_malyu What is so heavyweight?

      #include <QApplication>
      #include <QString>
      #include <QStandardItemModel>
      #include <QtWidgets>
      #include <QDebug>
      
      int main (int argc, char * argv[]) {
        QApplication app {argc, argv};
        QStandardItemModel model;
        model.appendRow (QList<QStandardItem *> {
            new QStandardItem {QStringLiteral ("item 1")}
            , new QStandardItem {QStringLiteral ("item 2")}
            , new QStandardItem {QStringLiteral ("item 3")}});
        auto yellow_item = new QStandardItem {QStringLiteral ("item 4")};
        yellow_item->setBackground (Qt::yellow);
        model.appendRow (QList<QStandardItem *> {
            yellow_item
            , new QStandardItem {QStringLiteral ("item 5")}
            , new QStandardItem {QStringLiteral ("item 6")}});
        model.connect (&model, &QStandardItemModel::itemChanged, [] (QStandardItem *item) {
            qDebug () << QStringLiteral ("item(%1, %2) value[%3]")
      	.arg (item->row ())
      	.arg (item->column ())
      	.arg (item->text ());
          });
        QTableView view;
        view.setModel (&model);
        view.connect (&view, &QTableView::clicked, [&model] (QModelIndex const& index) {
            auto * item = model.itemFromIndex (index);
            qDebug () << QStringLiteral ("item(%1, %2) value[%3] clicked")
      	.arg (item->row ())
      	.arg (item->column ())
      	.arg (item->text ());
          });
        view.show ();
        QObject::connect (&app, &QApplication::lastWindowClosed, &app, &QApplication::quit);
        return app.exec ();
      }
      
      A 1 Reply Last reply
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      • B bsomervi

        @alex_malyu What is so heavyweight?

        #include <QApplication>
        #include <QString>
        #include <QStandardItemModel>
        #include <QtWidgets>
        #include <QDebug>
        
        int main (int argc, char * argv[]) {
          QApplication app {argc, argv};
          QStandardItemModel model;
          model.appendRow (QList<QStandardItem *> {
              new QStandardItem {QStringLiteral ("item 1")}
              , new QStandardItem {QStringLiteral ("item 2")}
              , new QStandardItem {QStringLiteral ("item 3")}});
          auto yellow_item = new QStandardItem {QStringLiteral ("item 4")};
          yellow_item->setBackground (Qt::yellow);
          model.appendRow (QList<QStandardItem *> {
              yellow_item
              , new QStandardItem {QStringLiteral ("item 5")}
              , new QStandardItem {QStringLiteral ("item 6")}});
          model.connect (&model, &QStandardItemModel::itemChanged, [] (QStandardItem *item) {
              qDebug () << QStringLiteral ("item(%1, %2) value[%3]")
        	.arg (item->row ())
        	.arg (item->column ())
        	.arg (item->text ());
            });
          QTableView view;
          view.setModel (&model);
          view.connect (&view, &QTableView::clicked, [&model] (QModelIndex const& index) {
              auto * item = model.itemFromIndex (index);
              qDebug () << QStringLiteral ("item(%1, %2) value[%3] clicked")
        	.arg (item->row ())
        	.arg (item->column ())
        	.arg (item->text ());
            });
          view.show ();
          QObject::connect (&app, &QApplication::lastWindowClosed, &app, &QApplication::quit);
          return app.exec ();
        }
        
        A Offline
        A Offline
        alex_malyu
        wrote on last edited by alex_malyu
        #12

        @bsomervi said:

        new QStandardItem {QStringLiteral ("item 1")}

        Simplicity of usage has nothing to do with complexity of implementation or memory used and efficiency in general.
        When you have values already stored somewhere and all you need is to return the specific value does not make any sense create an additional array or do any additional memory allocation etc.
        Functionality provided by QStandardItemModel is not needed for such trivial tasks.
        All you need is to return value.
        With the same results you could suggest to use QTableWidget.
        Or better example - you are not using stl vector when using one variable is sufficient.
        Do not take it as an offence.

        1 Reply Last reply
        0
        • C cherple

          Oh wow! I didn't know the debug statement uses so much resource.. Speed wise is all good now, still a little slower with the widget but definitely a lot faster as compared to previously. Thanks! :))

          But how would u suggest I do this then? I will have a variable to store a users selection from a drop down list, then based on this variable's value, when a user selects a cell it should appear as a different color, probably from a predefined set of colors.

          For example: 0=red,1=blue,2=green
          So when user picked 1, and select a cell, the cell within be blue, then the user proceed with choosing 2, then select the cell next to it, and that cell should be green. So you should see the two boxes side by side one being blue and one being green.

          A Offline
          A Offline
          alex_malyu
          wrote on last edited by
          #13

          @cherple said:

          But how would u suggest I do this then? I will have a variable to store a users selection from a drop down list, then based on this variable's value, when a user selects a cell it should appear as a different color, probably from a predefined set of colors.

          For example: 0=red,1=blue,2=green
          So when user picked 1, and select a cell, the cell within be blue, then the user proceed with choosing 2, then select the cell next to it, and that cell should be green. So you should see the two boxes side by side one being blue and one being green.

          To specify color you need in the in the same data(... ) handle Qt::DecorationRole
          I will assume you already know value (v) below:

          int v =....
          if (role == Qt::DecorationRole)
          {
          if ( v == 0 )
          return QVariant(QColor(Qt::red));
          else if( .... )
          ....
          else
          ,,, ;
          }

          .........

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          • C Offline
            C Offline
            cherple
            wrote on last edited by
            #14

            Well I tried the decoration role, but all the cells are now red. I want only cells to become red when I select them. Also, all the boxes have a checkbox inside them now.

            A 1 Reply Last reply
            0
            • C cherple

              Well I tried the decoration role, but all the cells are now red. I want only cells to become red when I select them. Also, all the boxes have a checkbox inside them now.

              A Offline
              A Offline
              alex_malyu
              wrote on last edited by alex_malyu
              #15

              @cherple

              You had to return color you wanted depending on a row, column or value.
              I returned red as an example.

              As for check status you probably handle more than Qt::DisplayRole and Qt::DecorationRole.
              From the top of my head it might be Qt::CheckStateRole

              Post code of your data(...) function.

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              • C Offline
                C Offline
                cherple
                wrote on last edited by
                #16

                This is my data:

                if (role == Qt::DisplayRole)
                {
                Return data[row][col];
                }
                Else if (role = Qt::DecorationRole)
                {
                //if ( selectionVar == 0 )
                return QVariant(QColor(Qt::red));
                //else if( .... )
                }

                For now I just wanted to test the functionality so I just set it as red irregardless of my selection mode. I wanted to see if only my selected cell will be red.. But all the cells become a checkbox with red back ground.. I tried the checkstaterole before and it's the same.. The cells become a check box with the colored background.. I will try to take a screenshot later

                A 1 Reply Last reply
                0
                • C cherple

                  This is my data:

                  if (role == Qt::DisplayRole)
                  {
                  Return data[row][col];
                  }
                  Else if (role = Qt::DecorationRole)
                  {
                  //if ( selectionVar == 0 )
                  return QVariant(QColor(Qt::red));
                  //else if( .... )
                  }

                  For now I just wanted to test the functionality so I just set it as red irregardless of my selection mode. I wanted to see if only my selected cell will be red.. But all the cells become a checkbox with red back ground.. I tried the checkstaterole before and it's the same.. The cells become a check box with the colored background.. I will try to take a screenshot later

                  A Offline
                  A Offline
                  alex_malyu
                  wrote on last edited by alex_malyu
                  #17

                  @cherple

                  I am a bit surprised handling decoration role has such effect (checkbox),
                  bu t I believe overriding
                  virtual Qt::ItemFlags flags ( const QModelIndex & index ) const
                  should solve it. Something like :

                  Qt::ItemFlags myClass::flags ( const QModelIndex & index ) const
                  {
                  return Qt::ItemIsSelectable|Qt::ItemIsEnabled; // make sure not to return Qt::ItemIsUserCheckable
                  }

                  As for color, model can define cell color, but it does not have any idea what is selected in specific view.

                  So, if you want to change color of only selected cell you need to do it on QTableView level.
                  Or at least you can let model know that this cell is selected and need custom color every time
                  selection is changed. For example add array or map which will keep color per cell and set values there, use this container in data to define cell color.
                  In this case it had to be used with a single view, but I do not think it is a problem for you.

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                  • C Offline
                    C Offline
                    cherple
                    wrote on last edited by
                    #18

                    I'm unable to link the image at the moment. I've reimplemented the flags function as u suggested but it remains the same. In my cell, there will be a check box on the left and the whole cell will be painted red.

                    Just to confirm, all I had to do was to include the flags function in my model's header file and the flags function in the cpp right? I'm not sure why this is happening :/

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                    0
                    • C Offline
                      C Offline
                      cherple
                      wrote on last edited by
                      #19

                      This is what i see, and what i typed. I have also included the Flags function as u mentioned(not shown).

                      Code
                      Result

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                      • A Offline
                        A Offline
                        alex_malyu
                        wrote on last edited by alex_malyu
                        #20

                        Sorry that was my fault - DecorationRole displays icon/picmap.
                        So these are not checkboxes.

                        Replace Qt::DecorationRole with role == Qt::BackgroundColorRole.
                        Something like:

                        QVariant MyModel::data ( const QModelIndex & index, int role )  const
                        {
                        	if ( index.isValid() )
                        	{
                        		if( role == Qt::DisplayRole )
                        		{
                        			QString str = QString("%1:%2").arg (index.row()).arg (index.column());
                        			return QVariant( str );
                        		}
                        		else if( role == Qt::BackgroundColorRole )
                        		{
                        			if( index.row() == index.column() )
                        				return QVariant(QColor(Qt::red));
                        			else if( index.row() < index.column() )
                        				return QVariant(QColor(Qt::yellow));
                        			else 
                        				return QVariant(QColor(Qt::green));
                        		}
                        
                        	}
                        	return QVariant();
                        }
                        

                        And you do not need flags anymore.

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                        • C Offline
                          C Offline
                          cherple
                          wrote on last edited by
                          #21

                          No worries, it isn't your fault, because I tried backgroundcolorrole and it returned the same results before.

                          After entering ur code, this is what it looks like:
                          http://img.photobucket.com/albums/v483/dragonlancer/D6781CF8-2598-46CA-9290-167CB12FF98C.jpg
                          The code:
                          http://img.photobucket.com/albums/v483/dragonlancer/64707ED7-6081-466D-AE35-48263E2A959D.jpg
                          My table view settings:
                          http://img.photobucket.com/albums/v483/dragonlancer/74A8A89E-97ED-4A1F-8E68-92AF0101CFA9.jpg

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                          • A Offline
                            A Offline
                            alex_malyu
                            wrote on last edited by alex_malyu
                            #22

                            Could you post all code for whole model class and may be table view subclass?

                            As for now I can only see one potential problem -
                            you do not check that index passed to data is valid,
                            which you should do,

                            Code I posted works for me when my model subclass is set to QTableView.
                            Check if it works for you,

                            cpp:

                            #include "mymodel.h"
                            #include<QColor>
                            #include<QVariant>
                            
                            
                            MyModel::MyModel(QObject *parent)
                            	: QAbstractTableModel(parent)
                            {
                            
                            }
                            
                            MyModel::~MyModel()
                            {
                            
                            }
                            
                            int MyModel::rowCount ( const QModelIndex & parent ) const
                            {
                            	return 5;
                            }
                            
                            int MyModel::columnCount ( const QModelIndex & parent ) const
                            {
                            	return 7;
                            }
                            
                            QVariant MyModel::data ( const QModelIndex & index, int role )  const
                            {
                            	if ( index.isValid() )
                            	{
                            		if( role == Qt::DisplayRole )
                            		{
                            			QString str = QString("%1:%2").arg (index.row()).arg (index.column());
                            			return QVariant( str );
                            		}
                            		else if( role == Qt::BackgroundColorRole )
                            		{
                            			if( index.row() == index.column() )
                            				return QVariant(QColor(Qt::red));
                            			else if( index.row() < index.column() )
                            				return QVariant(QColor(Qt::yellow));
                            			else 
                            				return QVariant(QColor(Qt::green));
                            		}
                            
                            	}
                            	return QVariant();
                            }
                            

                            .h:

                            #pragma once
                            
                            #ifndef MYMODEL_H
                            #define MYMODEL_H
                            
                            #include <QAbstractTableModel>
                            
                            class MyModel : public QAbstractTableModel
                            {
                            	Q_OBJECT
                            
                            public:;
                            	MyModel(QObject *parent=NULL);
                            	~MyModel();
                            
                            	int rowCount ( const QModelIndex & parent = QModelIndex() ) const;
                            	int columnCount ( const QModelIndex & parent = QModelIndex() ) const;
                            	QVariant data ( const QModelIndex & index, int role = Qt::DisplayRole ) const;
                            
                            private:
                            
                            };
                            
                            #endif // MYMODEL_H
                            
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                            • C Offline
                              C Offline
                              cherple
                              wrote on last edited by
                              #23

                              The only difference between our code is the number of row and column returned, as well as this:

                              MyModel::MyModel(QObject *parent)
                              : QAbstractTableModel(parent)
                              {

                              My code uses QWidget instead of QObject. My constructor only sets data into gridNum[r][c] which is being returned in data(). Other than that I don't see any difference.. Damn this is frustrating..

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                              • A Offline
                                A Offline
                                alex_malyu
                                wrote on last edited by alex_malyu
                                #24
                                1. Try to replace your data() , rowCount, columnCount with mine.
                                2. Did you override QTableView? If yes try to see what happens if you use QTableView class instead of your view with default options set.
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                                • C Offline
                                  C Offline
                                  cherple
                                  wrote on last edited by
                                  #25

                                  I copied your code exactly and it's the same. Could the difference I. at version be the problem? I'm using Qt 4.8.1

                                  A 1 Reply Last reply
                                  0
                                  • C cherple

                                    I copied your code exactly and it's the same. Could the difference I. at version be the problem? I'm using Qt 4.8.1

                                    A Offline
                                    A Offline
                                    alex_malyu
                                    wrote on last edited by alex_malyu
                                    #26

                                    @cherple It works with Qt 4.8.6. I do not have earlier version to check .
                                    It might be a Qt problem. But I doubt it.
                                    Have you tried my suggestion to use my model as it is together with QTableView?
                                    All you need on top of code above is main like:

                                    #include "mymodel.h"
                                    #include <QtGui/QApplication>
                                    #include <QTableView>
                                    
                                    int main(int argc, char *argv[])
                                    {
                                    	QApplication a(argc, argv);
                                    	QTableView w;
                                        MyModel* model = new MyModel();
                                     	w.setModel( model );
                                    
                                    	w.show();
                                    	return a.exec();
                                    }
                                    
                                    1 Reply Last reply
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