dialog.h

#ifndef DIALOG_H

#define DIALOG_H

#include <QDialog>

#include<QCheckBox>

#include<QRadioButton>

#include<QPushButton>

#include<QPlainTextEdit>

QT_BEGIN_NAMESPACE

namespace Ui { class Dialog; }

QT_END_NAMESPACE

class Dialog : public QDialog

{

    Q_OBJECT

public:

    Dialog(QWidget *parent = nullptr);

    ~Dialog();

private:

    Ui::Dialog *ui;

    QCheckBox*chkBoxUnder;

    QCheckBox*chkBoxItalic;

    QCheckBox*chkBoxBold;

    QRadioButton*radioBlack;

    QRadioButton*radioRed;

    QRadioButton*radioBlue;

    QPushButton*btnOK;

    QPushButton*btnCancel;

    QPushButton*btnClose;

    QPlainTextEdit*txtEdit;

    void initUI();

    void initSignalSlots();

private slots:

    void  do_chkBoxUnder(bool checked);

    void  do_chkBoxItalic(bool checked);

    void  do_chkBoxBold(bool checked);

    void setFontColor();//设置字体颜色

};

#endif // DIALOG_H

dialog.cpp

#include "dialog.h"

#include "ui_dialog.h"

#include<QHBoxLayout>

#include<QDebug>

#include<QTextCursor>

#include<QTextCharFormat>

Dialog::Dialog(QWidget *parent)

    : QDialog(parent)

    , ui(new Ui::Dialog)

{

    ui->setupUi(this);

    initUI();

    initSignalSlots();

}

Dialog::~Dialog()

{

    delete ui;

}

void Dialog::initUI()

{

    chkBoxUnder=new QCheckBox("Underline");

    chkBoxItalic=new QCheckBox("Italic");

    chkBoxBold=new QCheckBox("Bold");

    QHBoxLayout*Hlay1=new QHBoxLayout;

    Hlay1->addWidget(chkBoxUnder);

    Hlay1->addWidget(chkBoxItalic);

    Hlay1->addWidget(chkBoxBold);

    radioBlack=new QRadioButton("Black");

    radioBlack->setChecked(true);

    radioRed=new QRadioButton("Red");

    radioBlue=new QRadioButton("Blue");

    QHBoxLayout*Hlay2=new QHBoxLayout;

    Hlay2->addWidget(radioBlack);

    Hlay2->addWidget(radioRed);

    Hlay2->addWidget(radioBlue);

    QHBoxLayout*Hlay3=new QHBoxLayout;

    btnOK=new QPushButton("确定");

    btnCancel=new QPushButton("取消");

    btnClose=new QPushButton("退出");

    Hlay3->addStretch();

    Hlay3->addWidget(btnOK);

    Hlay3->addWidget(btnCancel);

    Hlay3->addStretch();

    Hlay3->addWidget(btnClose);

    txtEdit=new QPlainTextEdit;

    txtEdit->setPlainText("手工创建的");

    QFont font=txtEdit->font();

    font.setPointSize(16);

    txtEdit->setFont(font);

    QVBoxLayout*VLay=new QVBoxLayout(this);

    VLay->addLayout(Hlay1);

    VLay->addLayout(Hlay2);

    VLay->addWidget(txtEdit);

    VLay->addLayout(Hlay3);

    this->setLayout(VLay);

}

void Dialog::initSignalSlots()

{

    //设置颜色的单选按钮

    connect(radioBlue,&QRadioButton::clicked,this,&Dialog::setFontColor);

    connect(radioRed,&QRadioButton::clicked,this,&Dialog::setFontColor);

    connect(radioBlack,&QRadioButton::clicked,this,&Dialog::setFontColor);

    //设置字体的复选框

    connect(chkBoxBold,&QCheckBox::clicked,this,&Dialog::do_chkBoxBold);

    connect(chkBoxItalic,&QCheckBox::clicked,this,&Dialog::do_chkBoxItalic);

    connect(chkBoxUnder,&QCheckBox::clicked,this,&Dialog::do_chkBoxUnder);

    //三个按钮与窗口的槽函数关联

    connect(btnOK,&QPushButton::clicked,this,&Dialog::accept);

    connect(btnCancel,&QPushButton::clicked,this,&Dialog::reject);

    connect(btnClose,&QPushButton::clicked,this,&Dialog::close);

}

void  Dialog::do_chkBoxUnder(bool checked)

{

QFont font;

font.setUnderline(checked);

txtEdit->setFont(font);

}

void  Dialog::do_chkBoxItalic(bool checked)

{

    QFont font;

    font.setItalic(checked);

    txtEdit->setFont(font);

}

void  Dialog::do_chkBoxBold(bool checked)

{

    QFont font;

    font.setBold(checked);

    txtEdit->setFont(font);

}

void Dialog::setFontColor()

{

    // 获取文本编辑控件的光标

        QTextCursor cursor = txtEdit->textCursor();

        QTextCharFormat format;

        // 根据单选按钮选择设置颜色

        if (radioRed->isChecked()) {

            format.setForeground(QBrush(Qt::red));

            qDebug() << "Setting text color to red";

        } else if (radioBlue->isChecked()) {

            format.setForeground(QBrush(Qt::blue));

            qDebug() << "Setting text color to blue";

        } else if (radioBlack->isChecked()) {

            format.setForeground(QBrush(Qt::black));

            qDebug() << "Setting text color to black";

        }

        // 判断是否有选中内容

        if (cursor.hasSelection()) {

            // 如果有选中的内容，应用格式到选中部分

            cursor.mergeCharFormat(format);

        } else {

            // 如果没有选中内容，应用格式到当前光标所在段落

            QTextCursor tempCursor = cursor;

            tempCursor.select(QTextCursor::BlockUnderCursor);

            tempCursor.mergeCharFormat(format);

        }

        // 设置光标回到文本编辑控件中

        txtEdit->setTextCursor(cursor);

}

//设置字体颜色

main.cpp

#include "dialog.h"

#include <QApplication>

int main(int argc, char *argv[])

{

    QApplication a(argc, argv);

    Dialog w;

    w.show();

    return a.exec();

}

最终的效果