Qt错误：无效使用不完全类型'class QLabel' [英] Qt error: invalid use of incomplete type 'class QLabel'

问题描述

我试图使用QtCreater编译以下程序，但我得到了很多错误在这个程序。我从一本书得到了这个程序，我不能弄清楚错误在哪里。有人可以帮助调试此程序。

这里是FindDialog.h

  #ifndef FINDDIALOG_H 
 #define FINDDIALOG_H 
 
 #include< QDialog> 
 
 class QCheckbox; 
 class QLabel; 
类QLineEdit; 
 class QPushButton; 
 
 class FindDialog：public QDialog 
 {
 Q_OBJECT 
 
 public：
 FindDialog（QWidget * parent = 0）; 
 
信号：
 void findNext（const QString& str，Qt :: CaseSensitivity cs）; 
 void findPrevious（const QString& str，Qt :: CaseSensitivity cs）; 
 
私有插槽：
 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> 
 
 #includefinddialog.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））; 
 
 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）; 
 
 setWindowTitle（tr（Find）））; 
 setFixedHeight（sizeHint（）。height（））; 
} 
 
 void FindDialog :: findClicked（）
 {
 QString text = lineEdit-> text（）; 
 Qt :: CaseSensitivity cs = caseCheckBox-> isChecked（）？ Qt :: CaseSensitivity 
：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& lt; QApplication> 
 
 #includefindDialog.h
 
 int main（int argc，char * argv []）
 {
 QApplication app（argc，argv ）; 
 FindDialog * dialog = new FindDialog; 
 dialog-> show（）; 
 return app.exec（） 
} 
  

我得到的错误如下：

  finddialog.cpp：21：32：注意：候选项是：
在包含在/usr/include/qt5/QtCore/qabstractanimation.h中的文件中： 45：0，
来自/ usr / include / qt5 / QtCore / QtCore：4，
来自/ usr / include / qt5 / QtGui / QtGui：4，
来自finddialog.cpp：1 ：
 /usr/include/qt5/QtCore/qobject.h:199:36：note：static QMetaObject :: Connection QObject :: connect（const QObject *，const char *，const QObject *，const char * Qt :: ConnectionType）
 static QMetaObject :: Connection connect（const QObject * sender，const char * signal，
 ^ 
 /usr/include/qt5/QtCore/qobject.h:199： 36：注意：参数1没有已知的转换，从'QPushButton *'到'const QObject *'
 /usr/include/qt5/QtCore/qobject.h:202:36：note：static QMetaObject :: Connection QObject :: connect（const QObject *，const QMetaMethod& const QObject *，const QMetaMethod& Qt :: ConnectionType）
 static QMetaObject :: Connection connect（const QObject * sender，const QMetaMethod& signal，
 ^ 
 /usr/include/qt5/QtCore/qobject.h:202:36：注意：没有已知的从'QPushButton *'到'const QObject *'的参数1的转换
 / usr / include /qt5/QtCore/qobject.h:418:32：note：QMetaObject :: Connection QObject :: connect（const QObject *，const char *，const char *，Qt :: ConnectionType）const 
 inline QMetaObject ::连接QObject :: connect（const QObject * asender，const char * asignal，
 ^ 
 /usr/include/qt5/QtCore/qobject.h:418:32：注意：参数1没有已知的转换从'QPushButton *'到'const QObject *'
 /usr/include/qt5/QtCore/qobject.h:215:43：note：template< class Func1，class Func2> static QMetaObject :: Connection QObject :: connect（const typename QtPrivate :: FunctionPointer< Func> :: Object *，Func1，const typename QtPrivate :: FunctionPointer Func2> :: Object *，Func2，Qt :: ConnectionType）
 static inline QMetaObject :: Connection connect（const typename QtPrivate :: FunctionPointer Func1> :: Object * sender，Func1 signal，
 ^ 
 /usr/include/qt5/QtCore/qobject.h:215 ：43：note：模板参数推导/替换失败：
 /usr/include/qt5/QtCore/qobject.h：替换'template< class Func1，class Func2> static QMetaObject :: Connection QObject :: connect （const typename QtPrivate :: FunctionPointer< Func> :: Object *，Func1，const typename QtPrivate :: FunctionPointer Func2> :: Object *，Func2，Qt :: ConnectionType）[Func1 = const char *; Func2 = const char *]'：
 finddialog.cpp：21：32：从这里需要
 /usr/include/qt5/QtCore/qobject.h:215:43：错误：没有名为'Object' struct QtPrivate :: FunctionPointer< const char *>'
 /usr/include/qt5/QtCore/qobject.h:245:13：note：template< class Func1，class Func2>静态类型名QtPrivate :: QEnableIf<（（int）（QtPrivate :: FunctionPointer< Func2> :: ArgumentCount）> = 0），QMetaObject :: Connection> :: Type QObject :: connect（const typename QtPrivate :: FunctionPointer& ; :: Object *，Func1，Func2）
 connect（const typename QtPrivate :: FunctionPointer< Func1> :: Object * sender，Func1 signal，Func2 slot）
 ^ 
 / usr / include /qt5/QtCore/qobject.h:245:13：note：模板参数扣除/替换失败：
 finddialog.cpp：21：32：note：candidate期望有3个参数，4提供
 this， （findClicked（）））; 
 ^ 
在/usr/include/qt5/QtCore/qabstractanimation.h:45:0中包含的文件中，
来自/ usr / include / qt5 / QtCore / QtCore：4，
从/ usr / include / qt5 / QtGui / QtGui：4，
从finddialog.cpp：1：
 /usr/include/qt5/QtCore/qobject.h:268:13：注意： template< class Func1，class Func2>静态类型名QtPrivate :: QEnableIf<（QtPrivate :: FunctionPointer< Func2> :: ArgumentCount ==（-1）），QMetaObject :: Connection> :: Type QObject :: connect（const typename QtPrivate :: FunctionPointer Func&对象*，Func1，Func2）
 connect（const typename QtPrivate :: FunctionPointer< Func1> :: Object * sender，Func1 signal，Func2 slot）
 ^ 
 / usr / include / qt5 / QtCore / qobject.h：268：13：note注意：模板参数扣除/替换失败：
 finddialog.cpp：21：32：note：candidate期望有3个参数，4提供
 this，SLOT（findClicked ）））; 
 ^ 
 finddialog.cpp：23：61：error：没有匹配的函数调用FindDialog :: connect（QPushButton *& const char [11]，FindDialog * const，const char [9] ]）'
 connect（closeButton，SIGNAL（clicked（）），this，SLOT（close（）））; 
 ^ 
 finddialog.cpp：23：61：note：候选项是：
在包含在/usr/include/qt5/QtCore/qabstractanimation.h:45:0的文件中，
从/ usr / include / qt5 / QtCore / QtCore：4，
从/ usr / include / qt5 / QtGui / QtGui：4，
从finddialog.cpp：1：
 / usr /include/qt5/QtCore/qobject.h:199:36：note：static QMetaObject :: Connection QObject :: connect（const QObject *，const char *，const QObject *，const char *，Qt :: ConnectionType）
 static QMetaObject :: Connection connect（const QObject * sender，const char * signal，
 ^ 
 /usr/include/qt5/QtCore/qobject.h:199:36：note：没有已知的转换参数1从'QPushButton *'到'const QObject *'
 /usr/include/qt5/QtCore/qobject.h:202:36：note：static QMetaObject :: Connection QObject :: connect（const QObject * ，const QMetaMethod& const QObject *，const QMetaMethod& Qt :: ConnectionType）
 static QMetaObject :: Connection connect（const QObject * sender，const QMetaMethod& signal，
 ^ 
 / usr / include / qt5 / QtCore / qobject.h：202：36：注意：没有已知的从'QPushButton *'到'const QObject *'
 / usr / include / qt5 / QtCore / qobject的转换。 h：418：32：note：QMetaObject :: Connection QObject :: connect（const QObject *，const char *，const char *，Qt :: ConnectionType）const 
 inline QMetaObject :: Connection QObject :: connect QObject * asender，const char * asignal，
 ^ 
 /usr/include/qt5/QtCore/qobject.h:418:32：注意：没有已知的参数1从'QPushButton *'转换为' const QObject *'
 /usr/include/qt5/QtCore/qobject.h:215:43：note：template< class Func1，class Func2> static QMetaObject :: Connection QObject :: connect（const typename QtPrivate :: FunctionPointer< Func> :: Object *，Func1，const typename QtPrivate :: FunctionPointer Func2> :: Object *，Func2，Qt :: ConnectionType）
 static inline QMetaObject :: Connection connect（const typename QtPrivate :: FunctionPointer Func1> :: Object * sender，Func1 signal，
 ^ 
 /usr/include/qt5/QtCore/qobject.h:215 ：43：note：模板参数推导/替换失败：
 /usr/include/qt5/QtCore/qobject.h：替换'template< class Func1，class Func2> static QMetaObject :: Connection QObject :: connect （const typename QtPrivate :: FunctionPointer< Func> :: Object *，Func1，const typename QtPrivate :: FunctionPointer Func2> :: Object *，Func2，Qt :: ConnectionType）[Func1 = const char *; Func2 = const char *]'：
 finddialog.cpp：23：61：从这里需要
 /usr/include/qt5/QtCore/qobject.h:215:43：错误：没有名为'Object' struct QtPrivate :: FunctionPointer< const char *>'
 /usr/include/qt5/QtCore/qobject.h:245:13：note：template< class Func1，class Func2>静态类型名QtPrivate :: QEnableIf<（（int）（QtPrivate :: FunctionPointer< Func2> :: ArgumentCount）> = 0），QMetaObject :: Connection> :: Type QObject :: connect（const typename QtPrivate :: FunctionPointer& ; :: Object *，Func1，Func2）
 connect（const typename QtPrivate :: FunctionPointer Func1> :: Object * sender，Func1 signal，Func2 slot）
 ^ 
 / usr / include /qt5/QtCore/qobject.h:245:13：注意：模板参数扣除/替换失败：
 finddialog.cpp：23：61：note：candidate期望有3个参数，4提供
 connect（closeButton ，SIGNAL（clicked（）），this，SLOT（close（）））; 
 ^ 
在/usr/include/qt5/QtCore/qabstractanimation.h:45:0中包含的文件中，
来自/ usr / include / qt5 / QtCore / QtCore：4，
从/ usr / include / qt5 / QtGui / QtGui：4，
从finddialog.cpp：1：
 /usr/include/qt5/QtCore/qobject.h:268:13：注意： template< class Func1，class Func2>静态类型名QtPrivate :: QEnableIf<（QtPrivate :: FunctionPointer< Func2> :: ArgumentCount ==（-1）），QMetaObject :: Connection> :: Type QObject :: connect（const typename QtPrivate :: FunctionPointer Func&对象*，Func1，Func2）
 connect（const typename QtPrivate :: FunctionPointer< Func1> :: Object * sender，Func1 signal，Func2 slot）
 ^ 
 / usr / include / qt5 / QtCore / qobject.h：268：13：注意：模板参数扣除/替换失败：
 finddialog.cpp：23：61：note：candidate期望3个参数，4提供
 connect（closeButton，SIGNAL clicked（）），this，SLOT（close（）））; 
 ^ 
 finddialog.cpp：25：2：error：'QHBoxLayout'没有在这个范围内声明
 QHBoxLayout * topLeftLayout = new QHBoxLayout; 
 ^ 
 finddialog.cpp：25：15：error：'topLeftLayout'没有在这个范围内声明
 QHBoxLayout * topLeftLayout = new QHBoxLayout; 
 ^ 
 finddialog.cpp：25：35：error：'QHBoxLayout'之前的类型说明符
 QHBoxLayout * topLeftLayout = new QHBoxLayout; 
 ^ 
 finddialog.cpp：25：35：error：expected';'before'QHBoxLayout'
 finddialog.cpp：29：2：error：'QVBoxLayout' 
 QVBoxLayout * leftLayout = new QVBoxLayout; 
 ^ 
 finddialog.cpp：29：15：error：'leftLayout'没有在这个范围内声明
 QVBoxLayout * leftLayout = new QVBoxLayout; 
 ^ 
 finddialog.cpp：29：32：error：'QVBoxLayout'之前的类型说明符
 QVBoxLayout * leftLayout = new QVBoxLayout; 
 ^ 
 finddialog.cpp：29：32：error：expected';'before'QVBoxLayout'
 finddialog.cpp：34：15：error：'rightLayout' 
 QVBoxLayout * rightLayout = new QVBoxLayout; 
 ^ 
 finddialog.cpp：34：33：error：'QVBoxLayout'之前的类型说明符
 QVBoxLayout * rightLayout = new QVBoxLayout; 
 ^ 
 finddialog.cpp：34：33：error：expected';'before'QVBoxLayout'
 finddialog.cpp：39：15：error：'mainLayout' 
 QHBoxLayout * mainLayout = new QHBoxLayout; 
 ^ 
 finddialog.cpp：39：32：error：expect'QHBoxLayout'之前的类型说明
 QHBoxLayout * mainLayout = new QHBoxLayout; 
 ^ 
 finddialog.cpp：39：32：error：expected';'before'QHBoxLayout'
 finddialog.cpp：在成员函数'void FindDialog :: findClicked（）'：
 finddialog.cpp：50：25：error：invalid use of incomplete type'class QLineEdit'
 QString text = lineEdit-> text（）; 
 ^ 
在finddialog.cpp中包含的文件中：3：0：
 finddialog.h：8：7：error：'QLineEdit'类的向前声明
 class QLineEdit; 
 ^ 
 finddialog.cpp：51：39：error：无效使用不完整的类'QCheckbox'
 Qt :: CaseSensitivity cs = caseCheckBox-> isChecked Qt :: CaseSensitivity 
 ^ 
在finddialog.cpp：3：0包含的文件中：
 finddialog.h：6：7：error：'QCheckbox'类的向前声明
类QCheckbox; 
 ^ 
 finddialog.cpp：52：17：error：期望的主表达式'：'token 
：Qt :: CaseInsensitive; 
 ^ 
 finddialog.cpp：53：21：error：无效使用不完整的类'QCheckbox'
 if（backwardCheckBox-> isChecked（））{
 ^ 
在从finddialog.cpp：3：0包含的文件中：
 finddialog.h：6：7：error：'QCheckbox'的向前声明
 class QCheckbox; 
 ^ 
 finddialog.cpp：在成员函数'void FindDialog :: enableFindButton（const QString&）'：
 finddialog.cpp：62：12：error：invalid use of incomplete type' QPushButton'
 findButton-> setEnabled（！text.isEmpty（））; 
 ^ 
在/ usr / include / qt5 / QtWidgets / QDialog：1：0，
从finddialog.h：4，
从finddialog.cpp： 
 /usr/include/qt5/QtWidgets/qdialog.h:52:7：error：向前声明'class QPushButton'
 class QPushButton; 
 ^ 
 make：*** [finddialog.o]错误1 
  

解决方案

我在读同一本书。有2个事情需要修复，以使此示例工作。

1. findDialog.h头文件中的'类'转发声明不起作用，因此QLabel等的构造函数发现。使用相应的#include替换每个类，如下所示。 （在finddialog.h文件中不需要QHBoxLayout和QVBoxLayout，但为了方便起见，我移动了这些，所有必需的包含在同一个地方。）

     #include< QDialog> 
    #include< QCheckbox> // class QCheckBox; 
    #include< QLabel> // class QLabel; 
    #include< QLineEdit> // class QLineEdit; 
    #include< QPushButton> // class QPushButton; 
    #include< QHBoxLayout> // in the finddialog.cpp 
    #include< QVBoxLayout> // in the finddialog.cpp 
     




2. 将.pro文件修改为：

     greaterThan（QT_MAJOR_VERSION，4）：QT + = widgets 
    
    TARGET = find 
    $ b b TEMPLATE = app 
    
    HEADERS = finddialog.h 
    
    SOURCES = finddialog.cpp \ 
    main.cpp 
     
    



/ ol>


I'm trying to compile the following program using QtCreater but I get a lots of errors in this program. I got this program from a book and I'm not able to figure out where the error is. Can someone help debug this program.

Here is the 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

#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"));

    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);

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

void FindDialog::findClicked()
{
    QString text = lineEdit->text();
    Qt::CaseSensitivity cs = caseCheckBox->isChecked() ? Qt::CaseSensitivity
                                                       : 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();
}

The errors I get are the following:

finddialog.cpp:21:32: note: candidates are:
In file included from /usr/include/qt5/QtCore/qabstractanimation.h:45:0,
                 from /usr/include/qt5/QtCore/QtCore:4,
                 from /usr/include/qt5/QtGui/QtGui:4,
                 from finddialog.cpp:1:
/usr/include/qt5/QtCore/qobject.h:199:36: note: static QMetaObject::Connection QObject::connect(const QObject*, const char*, const QObject*, const char*, Qt::ConnectionType)
     static QMetaObject::Connection connect(const QObject *sender, const char *signal,
                                    ^
/usr/include/qt5/QtCore/qobject.h:199:36: note:   no known conversion for argument 1 from ‘QPushButton*’ to ‘const QObject*’
/usr/include/qt5/QtCore/qobject.h:202:36: note: static QMetaObject::Connection QObject::connect(const QObject*, const QMetaMethod&, const QObject*, const QMetaMethod&, Qt::ConnectionType)
     static QMetaObject::Connection connect(const QObject *sender, const QMetaMethod &signal,
                                    ^
/usr/include/qt5/QtCore/qobject.h:202:36: note:   no known conversion for argument 1 from ‘QPushButton*’ to ‘const QObject*’
/usr/include/qt5/QtCore/qobject.h:418:32: note: QMetaObject::Connection QObject::connect(const QObject*, const char*, const char*, Qt::ConnectionType) const
 inline QMetaObject::Connection QObject::connect(const QObject *asender, const char *asignal,
                                ^
/usr/include/qt5/QtCore/qobject.h:418:32: note:   no known conversion for argument 1 from ‘QPushButton*’ to ‘const QObject*’
/usr/include/qt5/QtCore/qobject.h:215:43: note: template<class Func1, class Func2> static QMetaObject::Connection QObject::connect(const typename QtPrivate::FunctionPointer<Func>::Object*, Func1, const typename QtPrivate::FunctionPointer<Func2>::Object*, Func2, Qt::ConnectionType)
     static inline QMetaObject::Connection connect(const typename QtPrivate::FunctionPointer<Func1>::Object *sender, Func1 signal,
                                           ^
/usr/include/qt5/QtCore/qobject.h:215:43: note:   template argument deduction/substitution failed:
/usr/include/qt5/QtCore/qobject.h: In substitution of ‘template<class Func1, class Func2> static QMetaObject::Connection QObject::connect(const typename QtPrivate::FunctionPointer<Func>::Object*, Func1, const typename QtPrivate::FunctionPointer<Func2>::Object*, Func2, Qt::ConnectionType) [with Func1 = const char*; Func2 = const char*]’:
finddialog.cpp:21:32:   required from here
/usr/include/qt5/QtCore/qobject.h:215:43: error: no type named ‘Object’ in ‘struct QtPrivate::FunctionPointer<const char*>’
/usr/include/qt5/QtCore/qobject.h:245:13: note: template<class Func1, class Func2> static typename QtPrivate::QEnableIf<((int)(QtPrivate::FunctionPointer<Func2>::ArgumentCount) >= 0), QMetaObject::Connection>::Type QObject::connect(const typename QtPrivate::FunctionPointer<Func>::Object*, Func1, Func2)
             connect(const typename QtPrivate::FunctionPointer<Func1>::Object *sender, Func1 signal, Func2 slot)
             ^
/usr/include/qt5/QtCore/qobject.h:245:13: note:   template argument deduction/substitution failed:
finddialog.cpp:21:32: note:   candidate expects 3 arguments, 4 provided
       this, SLOT(findClicked()));
                                ^
In file included from /usr/include/qt5/QtCore/qabstractanimation.h:45:0,
                 from /usr/include/qt5/QtCore/QtCore:4,
                 from /usr/include/qt5/QtGui/QtGui:4,
                 from finddialog.cpp:1:
/usr/include/qt5/QtCore/qobject.h:268:13: note: template<class Func1, class Func2> static typename QtPrivate::QEnableIf<(QtPrivate::FunctionPointer<Func2>::ArgumentCount == (-1)), QMetaObject::Connection>::Type QObject::connect(const typename QtPrivate::FunctionPointer<Func>::Object*, Func1, Func2)
             connect(const typename QtPrivate::FunctionPointer<Func1>::Object *sender, Func1 signal, Func2 slot)
             ^
/usr/include/qt5/QtCore/qobject.h:268:13: note:   template argument deduction/substitution failed:
finddialog.cpp:21:32: note:   candidate expects 3 arguments, 4 provided
       this, SLOT(findClicked()));
                                ^
finddialog.cpp:23:61: error: no matching function for call to ‘FindDialog::connect(QPushButton*&, const char [11], FindDialog* const, const char [9])’
  connect(closeButton, SIGNAL(clicked()), this, SLOT(close()));
                                                             ^
finddialog.cpp:23:61: note: candidates are:
In file included from /usr/include/qt5/QtCore/qabstractanimation.h:45:0,
                 from /usr/include/qt5/QtCore/QtCore:4,
                 from /usr/include/qt5/QtGui/QtGui:4,
                 from finddialog.cpp:1:
/usr/include/qt5/QtCore/qobject.h:199:36: note: static QMetaObject::Connection QObject::connect(const QObject*, const char*, const QObject*, const char*, Qt::ConnectionType)
     static QMetaObject::Connection connect(const QObject *sender, const char *signal,
                                    ^
/usr/include/qt5/QtCore/qobject.h:199:36: note:   no known conversion for argument 1 from ‘QPushButton*’ to ‘const QObject*’
/usr/include/qt5/QtCore/qobject.h:202:36: note: static QMetaObject::Connection QObject::connect(const QObject*, const QMetaMethod&, const QObject*, const QMetaMethod&, Qt::ConnectionType)
     static QMetaObject::Connection connect(const QObject *sender, const QMetaMethod &signal,
                                    ^
/usr/include/qt5/QtCore/qobject.h:202:36: note:   no known conversion for argument 1 from ‘QPushButton*’ to ‘const QObject*’
/usr/include/qt5/QtCore/qobject.h:418:32: note: QMetaObject::Connection QObject::connect(const QObject*, const char*, const char*, Qt::ConnectionType) const
 inline QMetaObject::Connection QObject::connect(const QObject *asender, const char *asignal,
                                ^
/usr/include/qt5/QtCore/qobject.h:418:32: note:   no known conversion for argument 1 from ‘QPushButton*’ to ‘const QObject*’
/usr/include/qt5/QtCore/qobject.h:215:43: note: template<class Func1, class Func2> static QMetaObject::Connection QObject::connect(const typename QtPrivate::FunctionPointer<Func>::Object*, Func1, const typename QtPrivate::FunctionPointer<Func2>::Object*, Func2, Qt::ConnectionType)
     static inline QMetaObject::Connection connect(const typename QtPrivate::FunctionPointer<Func1>::Object *sender, Func1 signal,
                                           ^
/usr/include/qt5/QtCore/qobject.h:215:43: note:   template argument deduction/substitution failed:
/usr/include/qt5/QtCore/qobject.h: In substitution of ‘template<class Func1, class Func2> static QMetaObject::Connection QObject::connect(const typename QtPrivate::FunctionPointer<Func>::Object*, Func1, const typename QtPrivate::FunctionPointer<Func2>::Object*, Func2, Qt::ConnectionType) [with Func1 = const char*; Func2 = const char*]’:
finddialog.cpp:23:61:   required from here
/usr/include/qt5/QtCore/qobject.h:215:43: error: no type named ‘Object’ in ‘struct QtPrivate::FunctionPointer<const char*>’
/usr/include/qt5/QtCore/qobject.h:245:13: note: template<class Func1, class Func2> static typename QtPrivate::QEnableIf<((int)(QtPrivate::FunctionPointer<Func2>::ArgumentCount) >= 0), QMetaObject::Connection>::Type QObject::connect(const typename QtPrivate::FunctionPointer<Func>::Object*, Func1, Func2)
             connect(const typename QtPrivate::FunctionPointer<Func1>::Object *sender, Func1 signal, Func2 slot)
             ^
/usr/include/qt5/QtCore/qobject.h:245:13: note:   template argument deduction/substitution failed:
finddialog.cpp:23:61: note:   candidate expects 3 arguments, 4 provided
  connect(closeButton, SIGNAL(clicked()), this, SLOT(close()));
                                                             ^
In file included from /usr/include/qt5/QtCore/qabstractanimation.h:45:0,
                 from /usr/include/qt5/QtCore/QtCore:4,
                 from /usr/include/qt5/QtGui/QtGui:4,
                 from finddialog.cpp:1:
/usr/include/qt5/QtCore/qobject.h:268:13: note: template<class Func1, class Func2> static typename QtPrivate::QEnableIf<(QtPrivate::FunctionPointer<Func2>::ArgumentCount == (-1)), QMetaObject::Connection>::Type QObject::connect(const typename QtPrivate::FunctionPointer<Func>::Object*, Func1, Func2)
             connect(const typename QtPrivate::FunctionPointer<Func1>::Object *sender, Func1 signal, Func2 slot)
             ^
/usr/include/qt5/QtCore/qobject.h:268:13: note:   template argument deduction/substitution failed:
finddialog.cpp:23:61: note:   candidate expects 3 arguments, 4 provided
  connect(closeButton, SIGNAL(clicked()), this, SLOT(close()));
                                                             ^
finddialog.cpp:25:2: error: ‘QHBoxLayout’ was not declared in this scope
  QHBoxLayout *topLeftLayout = new QHBoxLayout;
  ^
finddialog.cpp:25:15: error: ‘topLeftLayout’ was not declared in this scope
  QHBoxLayout *topLeftLayout = new QHBoxLayout;
               ^
finddialog.cpp:25:35: error: expected type-specifier before ‘QHBoxLayout’
  QHBoxLayout *topLeftLayout = new QHBoxLayout;
                                   ^
finddialog.cpp:25:35: error: expected ‘;’ before ‘QHBoxLayout’
finddialog.cpp:29:2: error: ‘QVBoxLayout’ was not declared in this scope
  QVBoxLayout *leftLayout = new QVBoxLayout;
  ^
finddialog.cpp:29:15: error: ‘leftLayout’ was not declared in this scope
  QVBoxLayout *leftLayout = new QVBoxLayout;
               ^
finddialog.cpp:29:32: error: expected type-specifier before ‘QVBoxLayout’
  QVBoxLayout *leftLayout = new QVBoxLayout;
                                ^
finddialog.cpp:29:32: error: expected ‘;’ before ‘QVBoxLayout’
finddialog.cpp:34:15: error: ‘rightLayout’ was not declared in this scope
  QVBoxLayout *rightLayout = new QVBoxLayout;
               ^
finddialog.cpp:34:33: error: expected type-specifier before ‘QVBoxLayout’
  QVBoxLayout *rightLayout = new QVBoxLayout;
                                 ^
finddialog.cpp:34:33: error: expected ‘;’ before ‘QVBoxLayout’
finddialog.cpp:39:15: error: ‘mainLayout’ was not declared in this scope
  QHBoxLayout *mainLayout = new QHBoxLayout;
               ^
finddialog.cpp:39:32: error: expected type-specifier before ‘QHBoxLayout’
  QHBoxLayout *mainLayout = new QHBoxLayout;
                                ^
finddialog.cpp:39:32: error: expected ‘;’ before ‘QHBoxLayout’
finddialog.cpp: In member function ‘void FindDialog::findClicked()’:
finddialog.cpp:50:25: error: invalid use of incomplete type ‘class QLineEdit’
  QString text = lineEdit->text();
                         ^
In file included from finddialog.cpp:3:0:
finddialog.h:8:7: error: forward declaration of ‘class QLineEdit’
 class QLineEdit;
       ^
finddialog.cpp:51:39: error: invalid use of incomplete type ‘class QCheckbox’
  Qt::CaseSensitivity cs = caseCheckBox->isChecked() ? Qt::CaseSensitivity
                                       ^
In file included from finddialog.cpp:3:0:
finddialog.h:6:7: error: forward declaration of ‘class QCheckbox’
 class QCheckbox;
       ^
finddialog.cpp:52:17: error: expected primary-expression before ‘:’ token
                 : Qt::CaseInsensitive;
                 ^
finddialog.cpp:53:21: error: invalid use of incomplete type ‘class QCheckbox’
  if(backwardCheckBox->isChecked()) {
                     ^
In file included from finddialog.cpp:3:0:
finddialog.h:6:7: error: forward declaration of ‘class QCheckbox’
 class QCheckbox;
       ^
finddialog.cpp: In member function ‘void FindDialog::enableFindButton(const QString&)’:
finddialog.cpp:62:12: error: invalid use of incomplete type ‘class QPushButton’
  findButton->setEnabled(!text.isEmpty());
            ^
In file included from /usr/include/qt5/QtWidgets/QDialog:1:0,
                 from finddialog.h:4,
                 from finddialog.cpp:3:
/usr/include/qt5/QtWidgets/qdialog.h:52:7: error: forward declaration of ‘class QPushButton’
 class QPushButton;
       ^
make: *** [finddialog.o] Error 1

解决方案

I'm reading the same book. There are 2 things that need to fixed to get this sample to work.

1. The 'class' forward declarations in the findDialog.h header file do not work, so no constructor for QLabel etc can be found. Replace each class with the corresponding #include as follows. (The QHBoxLayout and QVBoxLayout are not needed in the finddialog.h file but for convenience I moved those too so that all required includes are in the same place.)

   #include < QDialog>
   #include < QCheckBox>    //class QCheckBox;  
   #include < QLabel>       //class QLabel;     
   #include < QLineEdit>    //class QLineEdit;  
   #include < QPushButton>  //class QPushButton; 
   #include < QHBoxLayout>   //in the finddialog.cpp
   #include < QVBoxLayout>   //in the finddialog.cpp
   

2. Edit the .pro file to this:

   greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
   
   TARGET   = find 
   
   TEMPLATE = app
   
   HEADERS  = finddialog.h
   
   SOURCES  = finddialog.cpp \
                   main.cpp
   

3. Delete all the old makefiles and find.pro.user and rebuild the project.

这篇关于Qt错误：无效使用不完全类型'class QLabel'的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！