[Solved] 对《C++ GUI Programming with Qt 4 (2nd Edition)》书上例子的疑惑

nimingzhe2008

在这本书的第二章，给了一个例子
头文件finddialog.h
@#ifndef FINDDIALOG_H
#define FINDDIALOG_H

#include <QDialog>

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的部分代码
@#include <QtGui>

#include "finddialog.h"

FindDialog::FindDialog(QWidget *parent)//疑问一：parent由始至终没有使用
: 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"));

connect(lineEdit, SIGNAL(textChanged(const QString &)),
        this, SLOT(enableFindButton(const QString &)));
connect(findButton, SIGNAL(clicked()),
        this, SLOT(findClicked()));
connect(closeButton, SIGNAL(clicked()),
        this, SLOT(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);//疑问2：为什么不是“对象.setLayout(mainLayout);”的形式

setWindowTitle(tr("Find"));//疑问同上
setFixedHeight(sizeHint().height());//疑问同上

}@

dbzhang800

建议先补补C++的课再深入Qt吧。

下一行紧接着不就用了么？
@
FindDialog::FindDialog(QWidget *parent)//疑问一：parent由始至终没有使用
: QDialog(parent)
@

2 因为this可以省略
@
setLayout(mainLayout);//疑问2：为什么不是“对象.setLayout(mainLayout);”的形式

setWindowTitle(tr("Find"));//疑问同上
setFixedHeight(sizeHint().height());//疑问同上

@

nimingzhe2008

谢谢。