编译3-1的mian.cpp报警

freigaber

买了一本霍老师的快速入门自学。编译3-1有问题。问一下为什么。以下是编译错误报告：
..\mywidget1\main.cpp: In function 'int qMain(int, char**)':

..\mywidget1\main.cpp:5:20: error: variable 'QApplication a' has initializer but incomplete type

     QApplication a(argc, argv);

                    ^

..\mywidget1\main.cpp:11:35: error: invalid use of incomplete type 'class QWidget'

     QWidget *widget = new QWidget();

                                   ^

In file included from E:\Qt\Qt5.5.1\5.5\mingw492_32\include/QtCore/qobject.h:48:0,

                 from E:\Qt\Qt5.5.1\5.5\mingw492_32\include/QtCore/qabstractanimation.h:37,

                 from E:\Qt\Qt5.5.1\5.5\mingw492_32\include/QtCore/QtCore:4,

                 from E:\Qt\Qt5.5.1\5.5\mingw492_32\include/QtGui/QtGuiDepends:3,

                 from E:\Qt\Qt5.5.1\5.5\mingw492_32\include\QtGui/QtGui:3,

                 from ..\mywidget1\main.cpp:1:

E:\Qt\Qt5.5.1\5.5\mingw492_32\include/QtCore/qmetatype.h:1314:7: error: forward declaration of 'class QWidget'

class QWidget;

       ^

..\mywidget1\main.cpp:14:11: error: invalid use of incomplete type 'class QWidget'

     widget->setWindowTitle(QObject::tr("鎴戞槸widget"));

           ^

In file included from E:\Qt\Qt5.5.1\5.5\mingw492_32\include/QtCore/qobject.h:48:0,

                 from E:\Qt\Qt5.5.1\5.5\mingw492_32\include/QtCore/qabstractanimation.h:37,

                 from E:\Qt\Qt5.5.1\5.5\mingw492_32\include/QtCore/QtCore:4,

                 from E:\Qt\Qt5.5.1\5.5\mingw492_32\include/QtGui/QtGuiDepends:3,

                 from E:\Qt\Qt5.5.1\5.5\mingw492_32\include\QtGui/QtGui:3,

                 from ..\mywidget1\main.cpp:1:

E:\Qt\Qt5.5.1\5.5\mingw492_32\include/QtCore/qmetatype.h:1314:7: error: forward declaration of 'class QWidget'

class QWidget;

       ^

..\mywidget1\main.cpp:17:5: error: 'QLabel' was not declared in this scope

     QLabel *label = new QLabel();

     ^

..\mywidget1\main.cpp:17:13: error: 'label' was not declared in this scope

     QLabel *label = new QLabel();

             ^

..\mywidget1\main.cpp:17:25: error: expected type-specifier before 'QLabel'

     QLabel *label = new QLabel();

                         ^

..\mywidget1\main.cpp:28:13: error: 'label2' was not declared in this scope

     QLabel *label2 = new QLabel(widget);

             ^

..\mywidget1\main.cpp:28:26: error: expected type-specifier before 'QLabel'

     QLabel *label2 = new QLabel(widget);

                          ^

..\mywidget1\main.cpp:36:11: error: invalid use of incomplete type 'class QWidget'

     widget->show();

           ^

In file included from E:\Qt\Qt5.5.1\5.5\mingw492_32\include/QtCore/qobject.h:48:0,

                 from E:\Qt\Qt5.5.1\5.5\mingw492_32\include/QtCore/qabstractanimation.h:37,

                 from E:\Qt\Qt5.5.1\5.5\mingw492_32\include/QtCore/QtCore:4,

                 from E:\Qt\Qt5.5.1\5.5\mingw492_32\include/QtGui/QtGuiDepends:3,

                 from E:\Qt\Qt5.5.1\5.5\mingw492_32\include\QtGui/QtGui:3,

                 from ..\mywidget1\main.cpp:1:

E:\Qt\Qt5.5.1\5.5\mingw492_32\include/QtCore/qmetatype.h:1314:7: error: forward declaration of 'class QWidget'

class QWidget;

       ^

..\mywidget1\main.cpp:39:12: error: type '<type error>' argument given to 'delete', expected pointer

     delete label;

            ^

..\mywidget1\main.cpp:40:12: warning: possible problem detected in invocation of delete operator: [-Wdelete-incomplete]

     delete widget;

            ^

..\mywidget1\main.cpp:11:14: warning: 'widget' has incomplete type

     QWidget *widget = new QWidget();

              ^

In file included from E:\Qt\Qt5.5.1\5.5\mingw492_32\include/QtCore/qobject.h:48:0,

                 from E:\Qt\Qt5.5.1\5.5\mingw492_32\include/QtCore/qabstractanimation.h:37,

                 from E:\Qt\Qt5.5.1\5.5\mingw492_32\include/QtCore/QtCore:4,

                 from E:\Qt\Qt5.5.1\5.5\mingw492_32\include/QtGui/QtGuiDepends:3,

                 from E:\Qt\Qt5.5.1\5.5\mingw492_32\include\QtGui/QtGui:3,

                 from ..\mywidget1\main.cpp:1:

E:\Qt\Qt5.5.1\5.5\mingw492_32\include/QtCore/qmetatype.h:1314:7: warning: forward declaration of 'class QWidget'

class QWidget;

       ^

..\mywidget1\main.cpp:40:12: note: neither the destructor nor the class-specific operator delete will be called, even if they are declared when the class is defined

     delete widget;

yafeilinux

这本书的示例代码是基于Qt 4的，请使用书中指定的Qt版本，在论坛下载页面Qt SDK处下载。使用Qt 5会出现很多问题。

freigaber

看来qt5不兼容qt4啊。霍老师再问一个问题。一个仿notepad的项目。里面两个ui。分别是查找和主窗口。这样编的目的主要是编写查找的界面不用语句。而用design。那么怎么将查找对话框中的查找内容用到mainwindow的textedit中？

Joey_Chan

Qt += widgets