最終效果圖：【文章最後會放上程式碼】

一：不要勾選Generate Form

二：標頭檔案中宣告  控制元件  宣告初始化UI介面的函式

三：構建控制元件

四：宣告槽函式，定義槽函式

程式碼：

dialog.h檔案

#ifndef DIALOG_H

#define DIALOG_H

#include <QDialog>

#include<QCheckBox>

#include<QRadioButton>

#include<QPushButton>

#include<QPlainTextEdit>

class Dialog : public QDialog
 

{

    Q_OBJECT

private:

        QCheckBox *checkBoxUnderLine;

        QCheckBox *checkBoxItalic;

        QCheckBox *checkBoxBold;

        QRadioButton *rBtnBlack;

        QRadioButton *rBtnBlue;

        QRadioButton *rBtnRed;

        QPlainTextEdit *plainTxtEdit;

        QPushButton *btnOK;

        QPushButton *btnCancel;
 

        QPushButton *btnClose;

        void initUI();

        void initSignalSlot();

private slots:

        void onCheckUnderline(bool checked);

        void onCheckItalic(bool checked);

        void onCheckBold(bool checked);

        void setTextFontColor();

public:

    Dialog(QWidget *parent = nullptr);
 

    ~Dialog();

};

#endif // DIALOG_H

dialog.cpp檔案

#include "dialog.h"

#include<QHBoxLayout>

#include<QVBoxLayout>

void Dialog::initUI()

{

    checkBoxUnderLine = new QCheckBox(tr("UnderLine"));

    checkBoxItalic = new QCheckBox(tr("Italic"));

    checkBoxBold= new QCheckBox(tr("Bold"));;

    QHBoxLayout *HLayout1 = new QHBoxLayout;

    HLayout1->addWidget(checkBoxUnderLine);

    HLayout1->addWidget(checkBoxItalic);

    HLayout1->addWidget(checkBoxBold);

    rBtnBlack = new QRadioButton(tr("Black"));

    rBtnBlue = new QRadioButton(tr("Blue"));

    rBtnRed = new QRadioButton(tr("Red"));

    QHBoxLayout *HLayout2 = new QHBoxLayout;

    HLayout2->addWidget(rBtnBlack);

    HLayout2->addWidget(rBtnBlue);

    HLayout2->addWidget(rBtnRed);

    plainTxtEdit = new QPlainTextEdit();

    QFont font = plainTxtEdit->font();

    font.setPointSize(20);

    plainTxtEdit->setFont(font);

    plainTxtEdit->setPlainText("Hello Allen\n This is a sample");

    btnOK = new QPushButton(tr("ok"));

    btnCancel = new QPushButton(tr("Cancel"));

    btnClose = new QPushButton(tr("Close"));

    QHBoxLayout *HLayout3 = new QHBoxLayout;

    HLayout3->addStretch();

    HLayout3->addWidget(btnOK);

    HLayout3->addWidget(btnCancel);

    HLayout3->addStretch();

    HLayout3->addWidget(btnClose);

    QVBoxLayout *VLayout = new QVBoxLayout;

    VLayout->addLayout(HLayout1);

    VLayout->addLayout(HLayout2);

    VLayout->addWidget(plainTxtEdit);

    VLayout->addLayout(HLayout3);

    setLayout(VLayout);

}

void Dialog::initSignalSlot()

{

    connect(btnOK,SIGNAL(clicked()),this,SLOT(accept()));

    connect(btnCancel,SIGNAL(clicked()),this,SLOT(reject()));

    connect(btnClose,SIGNAL(clicked()),this,SLOT(close()));

    connect(checkBoxUnderLine,SIGNAL(clicked(bool)),this,SLOT(onCheckUnderline(bool)));

    connect(checkBoxItalic,SIGNAL(clicked(bool)),this,SLOT(onCheckItalic(bool)));

    connect(checkBoxBold,SIGNAL(clicked(bool)),this,SLOT(onCheckBold(bool)));

    connect(rBtnBlack,SIGNAL(clicked()),this,SLOT(setTextFontColor()));

    connect(rBtnBlue,SIGNAL(clicked()),this,SLOT(setTextFontColor()));

    connect(rBtnRed,SIGNAL(clicked()),this,SLOT(setTextFontColor()));

}

void Dialog::onCheckUnderline(bool checked)

{

    QFont font = plainTxtEdit->font();

    font.setUnderline(checked);

    plainTxtEdit->setFont(font);

}

void Dialog::onCheckItalic(bool checked)

{

    QFont font = plainTxtEdit->font();

    font.setItalic(checked);

    plainTxtEdit->setFont(font);

}

void Dialog::onCheckBold(bool checked)

{

    QFont font = plainTxtEdit->font();

    font.setBold(checked);

    plainTxtEdit->setFont(font);

}

void Dialog::setTextFontColor()

{

    QPalette plet = plainTxtEdit->palette();

    if(rBtnBlack->isChecked())

        plet.setColor(QPalette::Text,Qt::black);

    else if(rBtnBlue->isChecked())

        plet.setColor(QPalette::Text,Qt::blue);

    else if(rBtnRed->isChecked())

        plet.setColor(QPalette::Text,Qt::red);

    else

        plet.setColor(QPalette::Text,Qt::black);

    plainTxtEdit->setPalette(plet);

}

Dialog::Dialog(QWidget *parent)

    : QDialog(parent)

{

   initUI();

   initSignalSlot();

}

Dialog::~Dialog()

{

}