Qt实现带字数限制的文字输入框

// 首先连接信号
connect(ui->textEdit, &QTextEdit::textChanged,
            this, &LimitTextEdit::slot_handleInput);

void LimitTextEdit::slot_handleInput()
{
    auto textEdit = static_cast<QTextEdit*>(sender());

    int currentNum = textEdit->toPlainText().length();
    // 判断是不是超出了字数限制
    if (currentNum > m_maxWordNum) {
        QString text = textEdit->toPlainText();
        text = text.mid(0, m_maxWordNum);
        int position = textEdit->textCursor().position();

        textEdit->setText(text);

        // 获取光标位置
        QTextCursor cursor = textEdit->textCursor();
        if (position > m_maxWordNum) {
            // 如果当前输入位置为末尾的话，就直接跳到最后一个字符。
            position = m_maxWordNum;
        }
        cursor.setPosition(position);
        textEdit->setTextCursor(cursor);
        currentNum = m_maxWordNum;
    }

    ui->labelCurrentNum->setNum(currentNum);
}