一、头文件finddialog.h

#ifndef FINDDIALOG_H
#define FINDDIALOG_H

#include <QDialog>

class QLabel;
class QLineEdit;
class QCheckBox;
class QPushButton;

class FindDialog : public QDialog
{
    Q_OBJECT

public:
    FindDialog(QWidget *parent = nullptr);
    ~FindDialog();

signals:
    void findNext(const QString& str, Qt::CaseSensitivity cs);   // 信号函数无需定义
    void findPrevious(const QString& str, Qt::CaseSensitivity cs); // 信号函数无需定义

private slots:
    void findClicked();
    void enbaleFindButton(const QString& next);

private:
    void createConnect();

private:
    QLabel* label;
    QLineEdit* lineEdit;
    QCheckBox* caseCheckBox;
    QCheckBox* backwardCheckBox;
    QPushButton* findBtn;
    QPushButton* closeBtn;
};

#endif // FINDDIALOG_H

二、实现文件finddialog.cpp

#include "finddialog.h"
#include <QLabel>
#include <QLineEdit>
#include <QCheckBox>
#include <QPushButton>
#include <QHBoxLayout>
#include <QDebug>

FindDialog::FindDialog(QWidget *parent)
    : QDialog(parent)
{
    label = new QLabel(tr("Find &what:"));
    lineEdit = new QLineEdit;
    label->setBuddy(lineEdit);
    caseCheckBox = new QCheckBox(tr("Match &case"));
    backwardCheckBox = new QCheckBox(tr("Search &backward"));

    findBtn = new QPushButton(tr("&Find"));
    findBtn->setDefault(true);
    findBtn->setEnabled(false);

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

    QHBoxLayout* topLeftLayout = new QHBoxLayout;
    topLeftLayout->addWidget(label);
    topLeftLayout->addWidget(lineEdit);

    QVBoxLayout* leftLayout = new QVBoxLayout;
    leftLayout->addLayout(topLeftLayout);
    leftLayout->addWidget(caseCheckBox);
    leftLayout->addWidget(backwardCheckBox);

    QVBoxLayout* rightLayout = new QVBoxLayout;
    rightLayout->addWidget(findBtn);
    rightLayout->addWidget(closeBtn);
    rightLayout->addStretch();

    QHBoxLayout* mainLayout = new QHBoxLayout(this);
    mainLayout->addLayout(leftLayout);
    mainLayout->addLayout(rightLayout);

    createConnect();

    setWindowTitle("Find");
    setFixedHeight(sizeHint().height());
}

FindDialog::~FindDialog()
{
}

void FindDialog::createConnect()
{
    connect(lineEdit, &QLineEdit::textChanged, this, &FindDialog::enbaleFindButton);
    connect(findBtn, &QPushButton::clicked, this, &FindDialog::findClicked);
    connect(closeBtn, &QPushButton::clicked, this, &FindDialog::close);
}

void FindDialog::findClicked()
{
    QString text = lineEdit->text();
    Qt::CaseSensitivity cs = caseCheckBox->isChecked() ? Qt::CaseSensitive
                                   : Qt::CaseInsensitive;
    if (backwardCheckBox->isChecked())
    {
        qDebug() << 1 << ": " << text << " " << cs;
        emit findPrevious(text, cs);   // emit关键字，连接signal和slot
    }
    else
    {
        qDebug() << 2 << ": " << text << " " << cs;
        emit findNext(text, cs);
    }
}

void FindDialog::enbaleFindButton(const QString& text)
{
    findBtn->setEnabled(!text.isEmpty());
}

三、main函数

#include "finddialog.h"

#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    FindDialog w;
    w.show();
    return a.exec();
}

四、运行结果

五、Dialog窗口布局