的Qt：信號和槽錯誤：未定義的參考`虛函數表爲

Question

下面的例子此鏈接：http://developer.kde.org/documentation/books/kde-2.0-development/ch03lev1sec3.html

#include <QObject> 
#include <QPushButton> 
#include <iostream> 
using namespace std; 

class MyWindow : public QWidget 
{ 
    Q_OBJECT // Enable slots and signals 
    public: 
     MyWindow(); 
    private slots: 
     void slotButton1(); 
     void slotButton2(); 
     void slotButtons(); 
    private: 
     QPushButton *button1; 
     QPushButton *button2; 
}; 

MyWindow :: MyWindow() : QWidget() 
{ 
    // Create button1 and connect button1->clicked() to this->slotButton1() 
    button1 = new QPushButton("Button1", this); 
    button1->setGeometry(10,10,100,40); 
    button1->show(); 
    connect(button1, SIGNAL(clicked()), this, SLOT(slotButton1())); 

    // Create button2 and connect button2->clicked() to this->slotButton2() 
    button2 = new QPushButton("Button2", this); 
    button2->setGeometry(110,10,100,40); 
    button2->show(); 
    connect(button2, SIGNAL(clicked()), this, SLOT(slotButton2())); 

    // When any button is clicked, call this->slotButtons() 
    connect(button1, SIGNAL(clicked()), this, SLOT(slotButtons())); 
    connect(button2, SIGNAL(clicked()), this, SLOT(slotButtons())); 
} 

// This slot is called when button1 is clicked. 
void MyWindow::slotButton1() 
{ 
    cout << "Button1 was clicked" << endl; 
} 

// This slot is called when button2 is clicked 
void MyWindow::slotButton2() 
{ 
    cout << "Button2 was clicked" << endl; 
} 

// This slot is called when any of the buttons were clicked 
void MyWindow::slotButtons() 
{ 
    cout << "A button was clicked" << endl; 
} 

int main() 
{ 
    MyWindow a; 
} 

結果：

[13:14:34 Mon May 02] ~/junkPrograms/src/nonsense $make 
g++ -c -m64 -pipe -O2 -Wall -W -D_REENTRANT -DQT_NO_DEBUG -DQT_GUI_LIB -DQT_CORE_LIB -DQT_SHARED -I/opt/qtsdk-2010.05/qt/mkspecs/linux-g++-64 -I. -I/opt/qtsdk-2010.05/qt/include/QtCore -I/opt/qtsdk-2010.05/qt/include/QtGui -I/opt/qtsdk-2010.05/qt/include -I. -I. -o signalsSlots.o signalsSlots.cpp 
g++ -m64 -Wl,-O1 -Wl,-rpath,/opt/qtsdk-2010.05/qt/lib -o nonsense signalsSlots.o -L/opt/qtsdk-2010.05/qt/lib -lQtGui -L/opt/qtsdk-2010.05/qt/lib -L/usr/X11R6/lib64 -lQtCore -lpthread 
signalsSlots.o: In function `MyWindow::MyWindow()': 
signalsSlots.cpp:(.text+0x1a2): undefined reference to `vtable for MyWindow' 
signalsSlots.cpp:(.text+0x1aa): undefined reference to `vtable for MyWindow' 
signalsSlots.o: In function `MyWindow::MyWindow()': 
signalsSlots.cpp:(.text+0x3e2): undefined reference to `vtable for MyWindow' 
signalsSlots.cpp:(.text+0x3ea): undefined reference to `vtable for MyWindow' 
signalsSlots.o: In function `main': 
signalsSlots.cpp:(.text+0x614): undefined reference to `vtable for MyWindow' 
signalsSlots.o:signalsSlots.cpp:(.text+0x61d): more undefined references to `vtable for MyWindow' follow 
collect2: ld returned 1 exit status 
make: *** [nonsense] Error 1 

虛函數表是虛函數，據我所知，有什麼錯誤的原因在這裏？

Answer 1

看起來moc不會爲您的QObject生成代碼，因爲您在.cpp文件中聲明它。要解決這個問題最簡單的方法是到MyWindow聲明移到頭，和頭添加到HEADERS列表，在的.pro文件：

HEADERS += yourheader.h 

然後重新運行qmake。

（請注意，你看看KDE 2.0本書是大大落伍）

Answer 2

只是改變你的Main（）方法如下：

#include <QtGui/QApplication> 

int main(int argc, char *argv[]) 
{ 
    QApplication a(argc, argv); 
    MyWindow w; 

    w.show(); 

    return a.exec(); 
} 

Answer 3

基於略高於andref評論，當一切都在一個CPP文件中像stuff.cpp，你需要在文件的最後添加：

#include "moc_stuff.cpp" 

（這是使用Qt 4.7.0）

Answer 4

也許爲時已晚，但...有同樣的問題，並爭取一段時間，以找到它來自何處。

右鍵單擊您的項目並選擇「運行qmake」以獲得MOC類的新版本。它通常不會自動運行...

商務部編譯器生成的存根和moc_xxxx.cpp調用，並生成虛函數表的東西

Answer 5

此問題可能由以下一些原因造成的。我偶爾偶爾偶然發現了它們。

---

您的類標題可能缺少Q_OBJECT宏。如其他答案所述，將宏添加到標題中。

class MyWidg : public QWidget 
{ 
    Q_OBJECT 

---

你的類頭可能不是由商務部來解析。將頭文件添加到.pro（或.pri）項目文件的HEADERS定義中。

HEADERS += file.h 

---

如果以上都不是真實的，那麼你可能需要再次運行QMAKE確保商務部再次解析頭，以防萬一在頭部添加了Q_OBJECT宏QMAKE爲後跑。再次運行qmake。