/*!

     Closes this widget. Returns \c true if the widget was closed;

     otherwise returns \c false.

     First it sends the widget a QCloseEvent. The widget is

     \l{hide()}{hidden} if it \l{QCloseEvent::accept()}{accepts}

     the close event. If it \l{QCloseEvent::ignore()}{ignores}

     the event, nothing happens. The default

     implementation of QWidget::closeEvent() accepts the close event.

     If the widget has the Qt::WA_DeleteOnClose flag, the widget

     is also deleted. A close events is delivered to the widget no

     matter if the widget is visible or not.

     The \l QApplication::lastWindowClosed() signal is emitted when the

     last visible primary window (i.e. window with no parent) with the

     Qt::WA_QuitOnClose attribute set is closed. By default this

     attribute is set for all widgets except transient windows such as

     splash screens, tool windows, and popup menus.

 */

 bool QWidget::close()

 {

     return d_func()->close_helper(QWidgetPrivate::CloseWithEvent);

 }

 /*!

     This event handler is called with the given \a event when Qt receives a window

     close request for a top-level widget from the window system.

     By default, the event is accepted and the widget is closed. You can reimplement

     this function to change the way the widget responds to window close requests.

     For example, you can prevent the window from closing by calling \l{QEvent::}{ignore()}

     on all events.

     Main window applications typically use reimplementations of this function to check

     whether the user's work has been saved and ask for permission before closing.

     For example, the \l{Application Example} uses a helper function to determine whether

     or not to close the window:

     \snippet mainwindows/application/mainwindow.cpp 3

     \snippet mainwindows/application/mainwindow.cpp 4

     \sa event(), hide(), close(), QCloseEvent, {Application Example}

 */

 void QWidget::closeEvent(QCloseEvent *event)

 {

     event->accept();

 }

 #ifndef TWIDGET_H

 #define TWIDGET_H

 #include <QWidget>

 #include <QDebug>

 namespace Ui

 {

     class TWidget;

 }

 class MyWidget : public QWidget

 {

 public:

     MyWidget(QWidget *parent = NULL);

     ~MyWidget();

 };

 class TWidget : public QWidget

 {

     Q_OBJECT

 public:

     explicit TWidget(QWidget *parent = );

     ~TWidget();

 private slots:

     void onPushButtonPressed();

 private:

     Ui::TWidget *m_pUI;

     MyWidget *m_pMyWidget;

 };

 #endif // TWIDGET_H

 #include "TWidget.h"

 #include "ui_TWidget.h"

 MyWidget::MyWidget(QWidget *parent)

     : QWidget(parent)

 {

     qDebug() << "construct :: MyWidget";

 }

 MyWidget::~MyWidget()

 {

     qDebug() << "destruct :: ~MyWidget";

 }

 TWidget::TWidget(QWidget *parent)

     : QWidget(parent)

     , m_pUI(new Ui::TWidget)

     , m_pMyWidget(NULL)

 {

     m_pUI->setupUi(this);

     m_pMyWidget = new MyWidget();

     m_pMyWidget->setFixedSize(, );

     m_pMyWidget->setAttribute(Qt::WA_DeleteOnClose); // 设置属性Qt::WA_DeleteOnClose

     connect(m_pUI->pushButton, &QPushButton::pressed, this, &TWidget::onPushButtonPressed);

 }

 TWidget::~TWidget()

 {

     if (m_pUI != NULL)

     {

         delete m_pUI;

         m_pUI = NULL;

     }

     if (m_pMyWidget != NULL)

     {

         delete m_pMyWidget;

         m_pMyWidget = NULL;

     }

 }

 void TWidget::onPushButtonPressed()

 {

     if (m_pMyWidget != NULL)

     {

         m_pMyWidget->show();

     }

 }

 #include "TWidget.h"

 #include <QApplication>

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

 {

     QApplication a(argc, argv);

     TWidget w;

     w.show();

     return a.exec();

 }

 construct :: MyWidget

 destruct :: ~MyWidget