finddialog.h

#ifndef FINDDIALOG_H
#define FINDDIALOG_H

#include <QDialog>
#include <QLabel>
#include <QLineEdit>
#include <QCheckBox>
#include <QPushButton>
#include <QHBoxLayout>
#include <QVBoxLayout>
/*
class QCheckBox;
class QLabel;
class QLineEdit;
class QPushButton;
*/

class FindDialog : public QDialog
{
    Q_OBJECT
public:
    FindDialog(QWidget *parent = 0);
signals:
    void findNext(const QString &str,Qt::CaseSensitivity cs);
    void findPrevious(const QString &str,Qt::CaseSensitivity cs);
private slots:
    void findClicked();
    void enableFindButton(const QString &text);
private:
    QLabel *label;
    QLineEdit *lineEdit;
    QCheckBox *caseCheckBox;
    QCheckBox *backwardCheckBox;
    QPushButton *findButton;
    QPushButton *closeButton;

};
#endif

finddialog.cpp

#include <QtGui>
#include "finddialog.h"

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"));

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

    closeButton = 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(findButton);
    rightLayout->addWidget(closeButton);
    rightLayout->addStretch();

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

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

void FindDialog::findClicked()
{
    QString text = lineEdit->text();
    Qt::CaseSensitivity cs =
            caseCheckBox->isChecked()?Qt::CaseSensitive
                                    :Qt::CaseInsensitive;
    if(backwardCheckBox->isChecked()){
        emit findPrevious(text,cs);
    }else{
        emit findNext(text,cs);
    }
}

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

main.cpp

#include <QApplication>
#include "finddialog.h"

int main(int argc,char *argv[])
{
    QApplication app(argc,argv);
    FindDialog *dialog = new FindDialog;
    dialog->show();
    return app.exec();
}

最终结果为：