QLineEditUnit.h

#pragma once
#include <QLineEdit>
#include <QPushButton>class QLineEditUnit : public QLineEdit
{Q_OBJECT
public:QLineEditUnit(QWidget* parent = Q_NULLPTR);~QLineEditUnit();//获取编辑框单位QString UnitText()const;//设置编辑框单位void SetUnitText(const QString& unitText);private:QPushButton* m_unitButton = nullptr;//单位文本按钮
};

QUnitLineEdit.cpp

#include "QLineEditUnit.h"
#include <QLayout>
#include <QStyle>
QLineEditUnit::QLineEditUnit(QWidget* parent) : QLineEdit(parent)
{m_unitButton = new QPushButton;//单位按钮扁平无边框m_unitButton->setStyleSheet("border-style:solid;color: rgba(77, 155, 213, 1);");m_unitButton->setFlat(true);//单位加入布局QBoxLayout* layout = new QBoxLayout(QBoxLayout::LeftToRight);layout->addStretch();layout->setSpacing(0);//单位按钮的Margins//右边留了13px，留给单位(按钮)layout->setContentsMargins(0, 0, 13, 0);layout->addWidget(m_unitButton);this->setLayout(layout);
}QLineEditUnit::~QLineEditUnit()
{
}QString QLineEditUnit::UnitText() const
{return   this->m_unitButton->text();
}void QLineEditUnit::SetUnitText(const QString& unitText)
{if (unitText.isEmpty() || this->m_unitButton->text() == unitText){return;}m_unitButton->setFont(this->font());this->m_unitButton->setText(unitText);// this->m_unitButton->setVisible(true);//获得文字的宽度int width = this->fontMetrics().width(m_unitButton->text());m_unitButton->setFixedWidth(width);//到单位开头了就往下显示，防止往后输入的内容有一部分在按钮下面QBoxLayout* layout = (QBoxLayout*)this->layout();QMargins margins = layout->contentsMargins();setTextMargins(margins.left(), margins.top(), width + margins.right(), margins.bottom());
}

然后再界面，先拖拽一个lineEdit，然后右键提升

所有的lineEdit都提升为带单位的

把lineEdit的指针强制类型转换成带单位的指针
其实好像我做的强制类型转换没什么必要，多此一举
可以直接用