參考：Qt中LineEdit編輯框限制數(shù)字輸入整理
運行環(huán)境：win10，VS2022，QT6.3
2022/1/12 添加槽函數(shù)版本，要獲取發(fā)送者。方便復用，可多個lineedit連同一個槽函數(shù)。

ui界面布局，就放了一個qlineEdit和一個button

undoTest.h

#pragma once

#include <QtWidgets/QMainWindow>
#include "ui_undoTest.h"

class undoTest : public QMainWindow
{
    Q_OBJECT

public:
    undoTest(QWidget *parent = Q_NULLPTR);
    
	// 設置lineedit輸入范圍
	void SlotLineEditLimit();
private:
    Ui::undoTestClass ui;
};

undoTest.cpp

//#pragma execution_character_set("utf-8")
#include "undoTest.h"
#include <QRegularExpression>
#include <QRegularExpressionValidator>
#include <QtCore5Compat\QRegExp>
#include <QMessageBox>
#include <QObject>
#include <QValidator>

undoTest::undoTest(QWidget *parent)
    : QMainWindow(parent)
{
    ui.setupUi(this);

    //qt5方法
    //QRegExp qregexp("[0-9\\.-]+$");
    //QValidator* validator = new QRegExpValidator(qregexp);
    //qt6方法
    QRegularExpression regExp("[0-9\\.-]+$");
    QRegularExpressionValidator* validator = new QRegularExpressionValidator(regExp, this);
    ui.lineEdit->setValidator(validator);

    connect(ui.lineEdit, &QLineEdit::editingFinished, [=](void) {
        double val = ui.lineEdit->text().toDouble();
        if (val<0||val>100)
        {
            QMessageBox box(QMessageBox::Information, QString::fromUtf8("提示"),
                QString::fromUtf8("請輸入1-100范圍內的數(shù)字！"), QMessageBox::Ok, this);
            box.exec();
            ui.lineEdit->setFocus();
            ui.lineEdit->setCursorPosition(ui.lineEdit->text().size());
            ui.lineEdit->selectAll();
            ui.lineEdit->undo();
        }
    });
    // or
    connect(ui.lineEdit, &QLineEdit::editingFinished, this, &undoTest::SlotLineEditLimit);

}
void undoTest::SlotLineEditLimit()
{
	QLineEdit * this_lineedit = qobject_cast<QLineEdit*>(sender());
	double val = this_lineedit->text().toDouble();
	if (val < 1 || val>100)
	{
		QMessageBox box(QMessageBox::Information, QString::fromUtf8("提示"),
			QString::fromUtf8("請輸入1-100范圍內的數(shù)字！"), QMessageBox::Ok, this);
		box.exec();
		this_lineedit->setFocus();
		this_lineedit->setCursorPosition(this_lineedit->text().size());
		this_lineedit->selectAll();
		this_lineedit->undo();
	}
}

main.cpp文章來源地址http://www.zghlxwxcb.cn/news/detail-647374.html

#include "undoTest.h"
#include <QtWidgets/QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    undoTest w;
    w.show();
    return a.exec();
}

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