Hi,

I don't want to use tree items for my tree view so I have designed my model as below.

I need to build tree based on 0's & 1's
All zeros are top level items, and 1's followed by 0 are child's for 0 & all 2's followed by 1 are child's of 1.


Qt Code: 
  1. class Model : public QAbstractItemModel {
  2.  
  3.     Q_OBJECT
  4. public:
  5.     //all necessary functions for model
  6. private:
  7.      mutable QVector<int> m_vector;                
  8.      mutable QVector< QVector<int> > childs;   // childs for top level items  ex:  if vector of vectors is  [1 1 1] [1 1 1] [1 1 1] -> 1st top level items has 3 child's & 2nd, 3rd top level items also have 3 childs 
  9. };
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So my model is:

Qt Code: 
  1. int Model::rowCount(const QModelIndex &parent) const
  2. {
  3.   if(!parent.isValid()){
  4.       return 5000;       // 5000 top level items
  5.   }
  6.   else if(!parent.parent().isValid()) //limited to 2 levels
  7.   {
  8.      return childs.at(parent.row()).count(1);   // count no.of 1's for top level items which are 0 initially but when data() called there I am inserting 2 child's (1's), so when next time rowCount() is called it returns 2, but first time it would be 0.  I am doing this because rowCount() calls for all the top level items initially that time I am simply passing 0, but again when data() is called rowCount() will be called one more time (for visible items only) that time I am inserting 2 items for top level item in data() function so rowCount() will return 2 this time.
  9.   }
  10.   return 0;
  11. }
  12.  
  13. QVariant Model::data(const QModelIndex &index, int role ) const
  14. {
  15.     if(index.isValid()){
  16.         QVector<int> row;
  17.         row << 1 << 1;
  18.         childs[index.row()] = row;   // for all top level items inserting 2 child's 
  19.     }
  20.  
  21.   if(role == Qt::DisplayRole)
  22.       return index.row()+1;
  23.  
  24.   return QVariant();
  25. }
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But my problem is I am not able to see plus sign for all the top level items in tree view (except 1st top level item).
But if i double click on visible top level item it is expanding with 2 child's (as expected) but there is no + sign which indicates that there are child's.
I implemented hasChildren() also and checked it did not work.

Any idea/suggestions for this ?? (I tested this with Qt4.8.6 & 5.4.0 on windows8)
Thanks in advance.

My complete model is here, if any one want to test:

Qt Code: 
  1. Model::Model(QObject *parent): QAbstractItemModel(parent)
  2. {
  3.     childs.resize(5000);
  4. }
  5.  
  6. Model::~Model()
  7. {
  8. }
  9.  
  10. bool Model::hasChildren(const QModelIndex &parent) const
  11. {
  12.     if(!parent.isValid())
  13.         return true;
  14.     if(!parent.parent().isValid()){
  15.         int val = childs.at(parent.row()).count(1);
  16.         return ( (0 != val) ?  true : false);
  17.     }
  18.     return false;
  19. }
  20.  
  21. QVariant Model::data(const QModelIndex &index, int role ) const
  22. {
  23.     if(index.isValid()){
  24.         QVector<int> row;
  25.         row << 1 << 1;
  26.         childs[index.row()] = row;
  27.     }
  28.  
  29.   if(role == Qt::DisplayRole)
  30.       return index.row()+1;
  31.  
  32.   return QVariant();
  33. }
  34.  
  35. int Model::columnCount(const QModelIndex &parent) const
  36. {
  37.     return 1; //m_head.size();
  38. }
  39.  
  40. int Model::rowCount(const QModelIndex &parent) const
  41. {
  42.   if(!parent.isValid()){
  43.       return 5000;
  44.   }
  45.   else if(!parent.parent().isValid()) //limited to 2 levels
  46.   {
  47.      return childs.at(parent.row()).count(1);
  48.   }
  49.   return 0;
  50. }
  51.  
  52. QModelIndex Model::index(int row, int column, const QModelIndex &parent) const
  53. {
  54.   if(!parent.isValid())
  55.   {
  56.       return createIndex(row, column, -1); // top level item has invalid parent
  57.   }
  58.   // we only need id of the parent since it identifies the item
  59.   return createIndex(row, column, parent.row());
  60. }
  61.  
  62. QModelIndex Model::parent(const QModelIndex &ind) const
  63. {
  64.  if(!ind.isValid()) return QModelIndex();
  65.   int id = ind.internalId();
  66.   if( id == -1) return QModelIndex();
  67.   return index(id, 0); // return top-level item
  68. }
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