Qtablewidget 无法获取单元格的值

#include "dialog.h"#include "ui_dialog.h"#include <QTableWidget>Dialog::Dialog(QWidget *parent) :    QDialog(parent),    ui(new Ui::Dialog){    ui->setupUi(this);    Qt::WindowFlags flags=Qt::Dialog;    flags |=Qt::WindowMinimizeButtonHint;    flags |=Qt::WindowMaximizeButtonHint;    setWindowFlags(flags);    ui->tableWidget->setColumnCount(3);    ui->tableWidget->setRowCount(3);    QStringList headerLabels;    headerLabels << "C1" << "C2"<<"C3";    ui->tableWidget->setHorizontalHeaderLabels(headerLabels);    int i ,j;    for(i=0;i<3;i++)        for(j=0;j<3;j++)        {            QString str = QString::number(i)+","+QString::number(j);            QTableWidgetItem *item = new QTableWidgetItem(str);//每个单元格的值都要单独申请new            ui->tableWidget->setItem(i,j,item);        }    ui->label->setAutoFillBackground(true);    ui->label->setBackgroundRole(QPalette::Shadow);}Dialog::~Dialog(){    delete ui;}void Dialog::on_tableWidget_cellClicked(int row, int column){    QString str;    str = "("+QString::number(row)+","+QString::number(column)+")";    QTableWidgetItem *item = ui->tableWidget->itemAt(QPoint(row,column));    QString  str1 = item->text(); //?获取不到表格的值    str += str1;    ui->label->setText(str);}void Dialog::on_tableWidget_cellChanged(int row, int column){    QString str;    str = QString("单元格")+"("+QString::number(row)+","+QString::number(column)+")"+"已修改";    QTableWidgetItem *item = ui->tableWidget->itemAt(row,column);    QString  str1 = item->text(); //?获取不到表格的值    str += str1;    ui->label_2->setText(str);}