1. 把主类指针this传给其他类，tcpClientSocket = new TcpClient(this);

//ex2.cpp
#include "ex2.h"
#include "ui_ex2.h"Ex2::Ex2(QWidget *parent): QDialog(parent), ui(new Ui::Ex2)
{ui->setupUi(this);tcpClientSocket = new TcpClient(this);}Ex2::~Ex2()
{delete ui;
}void Ex2::on_pushButtonTcpConnect_clicked()
{tcpClientSocket->Test();
}

2. 把ui类改为公共类

//ex2.h
#ifndef EX2_H
#define EX2_H#include <QDialog>
#include "tcpclient.h"QT_BEGIN_NAMESPACE
namespace Ui { class Ex2; }
QT_END_NAMESPACEclass Ex2 : public QDialog
{Q_OBJECTpublic:Ex2(QWidget *parent = nullptr);~Ex2();Ui::Ex2 *ui;		//改为公共类TcpClient *tcpClientSocket;private slots:void on_pushButtonTcpConnect_clicked();private://Ui::Ex2 *ui;		//私有类QSerialPort *serial;
};
#endif // EX2_H

3. 保存主类传来的指针保存，通过该指针调用UI中的控件

//tcpclient.cpp
#include "tcpclient.h"
#include "ex2.h"TcpClient::TcpClient(Ex2 *parent)
{socket = new QTcpSocket();pUi = parent;
}TcpClient::~TcpClient()
{delete socket;
}void TcpClient::Connect()
{}void TcpClient::Test()
{pUi->ui->textEditMy1->setText("Test");
}

//tcpclient.h
#ifndef TCPCLIENT_H
#define TCPCLIENT_H#include <QTcpSocket>
//#include "ex2.h"
#include "ui_ex2.h"class Ex2;      // 声明类
class TcpClient
{
public:TcpClient(Ex2 *parent);~TcpClient();void Connect();void Test();Ex2 *pUi;
private:QTcpSocket *socket;
};#endif // TCPCLIENT_H

4. 在pro文件中增加QT += network

//ex2.pro
QT       += core guiQT += serialportQT += network# disable C4819 warning
QMAKE_CXXFLAGS_WARN_ON += -wd4819greaterThan(QT_MAJOR_VERSION, 4): QT += widgetsCONFIG += 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 6.0.0SOURCES += \main.cpp \ex2.cpp \tcpclient.cppHEADERS += \ex2.h \tcpclient.hFORMS += \ex2.ui# Default rules for deployment.
qnx: target.path = /tmp/$${TARGET}/bin
else: unix:!android: target.path = /opt/$${TARGET}/bin
!isEmpty(target.path): INSTALLS += target

5. 效果