怎样子类化QAbstractItemView，

[goodluck365168]

怎样子类化QAbstractItemView，最好给个简单例子研究下

[ronal7do]

摘自Qt官方例子Chart Example

#ifndef PIEVIEW_H
  #define PIEVIEW_H

  #include <QAbstractItemView>

  class PieView : public QAbstractItemView
  {
      Q_OBJECT

  public:
      PieView(QWidget *parent = 0);

      QRect visualRect(const QModelIndex &index) const override;
      void scrollTo(const QModelIndex &index, ScrollHint hint = EnsureVisible) override;
      QModelIndex indexAt(const QPoint &point) const override;

  protected slots:
      void dataChanged(const QModelIndex &topLeft, const QModelIndex &bottomRight,
                       const QVector<int> &roles = QVector<int>()) override;
      void rowsInserted(const QModelIndex &parent, int start, int end) override;
      void rowsAboutToBeRemoved(const QModelIndex &parent, int start, int end) override;

  protected:
      bool edit(const QModelIndex &index, EditTrigger trigger, QEvent *event) override;
      QModelIndex moveCursor(QAbstractItemView::CursorAction cursorAction,
                             Qt::KeyboardModifiers modifiers) override;

      .....

  private:
      QRect itemRect(const QModelIndex &item) const;
      QRegion itemRegion(const QModelIndex &index) const;
      int rows(const QModelIndex &index = QModelIndex()) const;
      void updateGeometries() override;

      int margin;
      int totalSize;
      int pieSize;
      int validItems;
      double totalValue;
      QPoint origin;
      QRubberBand *rubberBand;
  };

  #endif // PIEVIEW_H

#include <QtWidgets>
  #include <cmath>

  #ifndef M_PI
  #define M_PI 3.1415927
  #endif

  #include "pieview.h"

  PieView::PieView(QWidget *parent)
      : QAbstractItemView(parent)
  {
      horizontalScrollBar()->setRange(0, 0);
      verticalScrollBar()->setRange(0, 0);

      margin = 8;
      totalSize = 300;
      pieSize = totalSize - 2 * margin;
      validItems = 0;
      totalValue = 0.0;
      rubberBand = 0;
  }

  int PieView::horizontalOffset() const
  {
      return horizontalScrollBar()->value();
  }

  void PieView::mousePressEvent(QMouseEvent *event)
  {
      QAbstractItemView::mousePressEvent(event);
      origin = event->pos();
      if (!rubberBand)
          rubberBand = new QRubberBand(QRubberBand::Rectangle, viewport());
      rubberBand->setGeometry(QRect(origin, QSize()));
      rubberBand->show();
  }

  void PieView::mouseMoveEvent(QMouseEvent *event)
  {
      if (rubberBand)
          rubberBand->setGeometry(QRect(origin, event->pos()).normalized());
      QAbstractItemView::mouseMoveEvent(event);
  }

  void PieView::mouseReleaseEvent(QMouseEvent *event)
  {
      QAbstractItemView::mouseReleaseEvent(event);
      if (rubberBand)
          rubberBand->hide();
      viewport()->update();
  }

  QModelIndex PieView::moveCursor(QAbstractItemView::CursorAction cursorAction,
                                  Qt::KeyboardModifiers /*modifiers*/)
  {
      QModelIndex current = currentIndex();

      switch (cursorAction) {
          case MoveLeft:
          case MoveUp:
              if (current.row() > 0)
                  current = model()->index(current.row() - 1, current.column(),
                                           rootIndex());
              else
                  current = model()->index(0, current.column(), rootIndex());
              break;
          case MoveRight:
          case MoveDown:
              if (current.row() < rows(current) - 1)
                  current = model()->index(current.row() + 1, current.column(),
                                           rootIndex());
              else
                  current = model()->index(rows(current) - 1, current.column(),
                                           rootIndex());
              break;
          default:
              break;
      }

      viewport()->update();
      return current;
  }

  void PieView::rowsAboutToBeRemoved(const QModelIndex &parent, int start, int end)
  {
      for (int row = start; row <= end; ++row) {
          QModelIndex index = model()->index(row, 1, rootIndex());
          double value = model()->data(index).toDouble();
          if (value > 0.0) {
              totalValue -= value;
              --validItems;
          }
      }

      QAbstractItemView::rowsAboutToBeRemoved(parent, start, end);
  }

  void PieView::scrollContentsBy(int dx, int dy)
  {
      viewport()->scroll(dx, dy);
  }

  void PieView::scrollTo(const QModelIndex &index, ScrollHint)
  {
      QRect area = viewport()->rect();
      QRect rect = visualRect(index);

      if (rect.left() < area.left()) {
          horizontalScrollBar()->setValue(
              horizontalScrollBar()->value() + rect.left() - area.left());
      } else if (rect.right() > area.right()) {
          horizontalScrollBar()->setValue(
              horizontalScrollBar()->value() + qMin(
                  rect.right() - area.right(), rect.left() - area.left()));
      }

      if (rect.top() < area.top()) {
          verticalScrollBar()->setValue(
              verticalScrollBar()->value() + rect.top() - area.top());
      } else if (rect.bottom() > area.bottom()) {
          verticalScrollBar()->setValue(
              verticalScrollBar()->value() + qMin(
                  rect.bottom() - area.bottom(), rect.top() - area.top()));
      }

      update();
  }

  /*
      Find the indices corresponding to the extent of the selection.
  */

  void PieView::setSelection(const QRect &rect, QItemSelectionModel::SelectionFlags command)
  {
      // Use content widget coordinates because we will use the itemRegion()
      // function to check for intersections.

      QRect contentsRect = rect.translated(
                              horizontalScrollBar()->value(),
                              verticalScrollBar()->value()).normalized();

      int rows = model()->rowCount(rootIndex());
      int columns = model()->columnCount(rootIndex());
      QModelIndexList indexes;

      for (int row = 0; row < rows; ++row) {
          for (int column = 0; column < columns; ++column) {
              QModelIndex index = model()->index(row, column, rootIndex());
              QRegion region = itemRegion(index);
              if (region.intersects(contentsRect))
                  indexes.append(index);
          }
      }

      if (indexes.size() > 0) {
          int firstRow = indexes[0].row();
          int lastRow = indexes[0].row();
          int firstColumn = indexes[0].column();
          int lastColumn = indexes[0].column();

          for (int i = 1; i < indexes.size(); ++i) {
              firstRow = qMin(firstRow, indexes[i].row());
              lastRow = qMax(lastRow, indexes[i].row());
              firstColumn = qMin(firstColumn, indexes[i].column());
              lastColumn = qMax(lastColumn, indexes[i].column());
          }

          QItemSelection selection(
              model()->index(firstRow, firstColumn, rootIndex()),
              model()->index(lastRow, lastColumn, rootIndex()));
          selectionModel()->select(selection, command);
      } else {
          QModelIndex noIndex;
          QItemSelection selection(noIndex, noIndex);
          selectionModel()->select(selection, command);
      }

      update();
  }

  void PieView::updateGeometries()
  {
      horizontalScrollBar()->setPageStep(viewport()->width());
      horizontalScrollBar()->setRange(0, qMax(0, 2*totalSize - viewport()->width()));
      verticalScrollBar()->setPageStep(viewport()->height());
      verticalScrollBar()->setRange(0, qMax(0, totalSize - viewport()->height()));
  }

  int PieView::verticalOffset() const
  {
      return verticalScrollBar()->value();
  }

  /*
      Returns the position of the item in viewport coordinates.
  */

  QRect PieView::visualRect(const QModelIndex &index) const
  {
      QRect rect = itemRect(index);
      if (!rect.isValid())
          return rect;

      return QRect(rect.left() - horizontalScrollBar()->value(),
                   rect.top() - verticalScrollBar()->value(),
                   rect.width(), rect.height());
  }

  /*
      Returns a region corresponding to the selection in viewport coordinates.
  */

  QRegion PieView::visualRegionForSelection(const QItemSelection &selection) const
  {
      int ranges = selection.count();

      if (ranges == 0)
          return QRect();

      QRegion region;
      for (int i = 0; i < ranges; ++i) {
          QItemSelectionRange range = selection.at(i);
          for (int row = range.top(); row <= range.bottom(); ++row) {
              for (int col = range.left(); col <= range.right(); ++col) {
                  QModelIndex index = model()->index(row, col, rootIndex());
                  region += visualRect(index);
              }
          }
      }
      return region;
  }

[goodluck365168]

还是有点复杂，不过有点启发