QAbstractItemModel::createIndex(0,0,0)第三个参数不能为0？

oceanqterwind

如果createIndex(0,0,0) 则出现错误   call of overloaded 'createIndex(int&, int&, int)' is ambiguous return createIndex(row, column, 0); 第三个参数 改为“createIndex(row, column, Q_NULLPTR)”就没问题，如果第三个参数为其他数字又没问题。

我是用5.7版本。

代码如下：
-------TreeModel.h-----------------------------#ifndef TREEMODEL_H#define TREEMODEL_H#include <QAbstractItemModel>
class TreeModel : public QAbstractItemModel{        Q_OBJECTpublic:        TreeModel();        int rowCount ( const QModelIndex & parent ) const;        int columnCount ( const QModelIndex & parent ) const;        QModelIndex index ( int row, int column, const QModelIndex & parent = QModelIndex() ) const;        QModelIndex parent ( const QModelIndex & index ) const;        QVariant data ( const QModelIndex & index, int role ) const;        QVariant headerData(int section, Qt::Orientation orientation, int role) const;
private:        enum {N=15};        int numbers[N];};
#endif // TREEMODEL_H-------------------treemodel.cpp-------------------------#include "treemodel.h"
TreeModel::TreeModel(){        int values[N]={36,10,26,3,7, 11,15, 1,2,3,4,5,6,7,8};        for (int i=0; i<N; i++)                numbers[i = values[i];}
int TreeModel::rowCount ( const QModelIndex & parent ) const{        if ( ! parent.isValid() )                return 1;        if (parent.internalId() < N/2 )                return 2;        return 0;}
int TreeModel::columnCount ( const QModelIndex & parent ) const {        return 1;}
QModelIndex TreeModel::index ( int row, int column, const QModelIndex & parent ) const {        if ( ! parent.isValid() )        return createIndex(row, column, 0);//        return createIndex(row, column, Q_NULLPTR);
        int parent_idx = parent.internalId();        int idx = parent_idx * 2 + ( row + 1 );        return createIndex(row, column, idx );}
QModelIndex TreeModel::parent ( const QModelIndex & index ) const{        if (index.internalId() == 0)                 return QModelIndex();                int parent_idx = (index.internalId() - 1 )/2;        return createIndex( (parent_idx+1) % 2, 0, parent_idx );}
QVariant TreeModel::data ( const QModelIndex & index, int role  ) const {        switch (role) {        case Qt::DisplayRole:                int value = numbers[ index.internalId() ];                return QVariant( value );        }        return QVariant();}
QVariant TreeModel::headerData(int section, Qt::Orientation orientation, int role) const{        if (role == Qt::DisplayRole && section==0                         && orientation == Qt::Horizontal  )                 return QString("Full Binary Tree");    return QVariant();}-------------------main.cpp-----------------------------#include "treemodel.h"#include <QApplication>#include <QTreeView>
int main(int argc, char *argv[]){        QApplication app(argc, argv);        TreeModel  treeModel;
        QTreeView treeView(0);        treeView.setModel( & treeModel );        treeView.show();        return app.exec();}
-----------------Change_header.pro--------------------------
QT       += core gui

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

TARGET = change header
TEMPLATE = app


SOURCES += main.cpp\
    treemodel.cpp

HEADERS  += treemodel.h

yafeilinux

你看看Q_NULLPTR和0的区别。

oceanqterwind

yafeilinux 发表于 2016-11-9 22:59
你看看Q_NULLPTR和0的区别。

[protected] QModelIndex QAbstractItemModel::createIndex(int row, int column, quintptr id) const
Creates a model index for the given row and column with the internal identifier, id.
This function provides a consistent interface that model subclasses must use to create model indexes.
内部id不能为0吗。
另外书上代码写的是0，发现0换成Q_NULLPTR才能运行，故有此问。