Qt-QTextEdit限制输入个数

相关资料：

https://blog.csdn.net/xiezhongyuan07/article/details/80611363?utm_source=blogxgwz6    原作

https://download.csdn.net/download/zhujianqiangqq/13756816    代码包下载

.pro

QT       += core gui

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

CONFIG += c++11

# The following define makes your compiler emit warnings if you use
# any Qt feature that has been marked deprecated (the exact warnings
# depend on your compiler). Please consult the documentation of the
# deprecated API in order to know how to port your code away from it.
DEFINES += QT_DEPRECATED_WARNINGS

# You can also make your code fail to compile if it uses deprecated APIs.
# In order to do so, uncomment the following line.
# You can also select to disable deprecated APIs only up to a certain version of Qt.
#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0

SOURCES += 
    main.cpp 
    mainwindow.cpp

HEADERS += 
    mainwindow.h

FORMS += 
    mainwindow.ui

TARGET = ../../QtTreeViewCheckable/bin/QtTreeViewCheckable

# Default rules for deployment.
qnx: target.path = /tmp/$${TARGET}/bin
else: unix:!android: target.path = /opt/$${TARGET}/bin
!isEmpty(target.path): INSTALLS += target

RESOURCES += 
    resource.qrc

main.cpp

#include "mainwindow.h"

#include <QApplication>

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

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QStandardItemModel>
#include <QDebug>
#include <QMessageBox>
#include <QFileSystemModel>
#include <QException>
#include <QButtonGroup>

QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();
private slots:
    void on_textEdit_textChanged();

private:
    Ui::MainWindow *ui;
};
#endif // MAINWINDOW_H

mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    setWindowTitle(QStringLiteral("QTextEdit限制输入个数"));
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::on_textEdit_textChanged()
{
    const int MAX_SIZE =10;
    QString textContent = ui->textEdit->toPlainText();
    int length = textContent.count();
    int maxLength = MAX_SIZE; // 最大字符数
    if(length > maxLength)
    {
        int position = ui->textEdit->textCursor().position();
        QTextCursor textCursor = ui->textEdit->textCursor();
        textContent.remove(position - (length - maxLength), length - maxLength);
        ui->textEdit->setText(textContent);
        textCursor.setPosition(position - (length - maxLength));
        ui->textEdit->setTextCursor(textCursor);
    }
    length = textContent.count();
    ui->label->setText(QString("%1/%2").arg(MAX_SIZE-length).arg(MAX_SIZE));
}