Qt Code: 
  1. #include <qapplication.h>
  2. #include <q3scrollview.h>
  3. #include <q3multilineedit.h>
  4. #include <qpushbutton.h>
  5. #include <qfont.h>
  6.  
  7. class MyMainWindow : public Q3ScrollView
  8. {
  9.  public:
  10. 	 MyMainWindow();
  11.  private:
  12.  	 QWidget *main;
  18. 	 Q3MultiLineEdit *edit;
  19. };
  20.  
  21. MyMainWindow::MyMainWindow()
  22. {
  23.  setGeometry(100, 100, 470, 410);
  24.  
  25.  main = new QWidget(this);
  26.  main->resize(400, 400);
  27.  
  28.  b1 = new QPushButton("new", main); 
  29.  b1->setGeometry(10, 10, 80, 30);
  30.  b1->setFont(QFont("Times", 18, QFont::Bold));
  31.  
  32.  b2 = new QPushButton("open", main);
  33.  b2->setGeometry(100, 10, 80, 30);
  34.  b2->setFont(QFont("Times", 18, QFont::Bold));
  35.  
  36.  b3 = new QPushButton("print", main);
  37.  b3->setGeometry(190, 10, 80, 30);
  38.  b3->setFont(QFont("Times", 18, QFont::Bold));
  39.  
  40.  b4 = new QPushButton("save", main);
  41.  b4->setGeometry(280, 10, 80, 30);
  42.  b4->setFont(QFont("Times", 18, QFont::Bold));
  43.  
  44.  b5 = new QPushButton("close", main);
  45.  b5->setGeometry(370, 10, 80, 30);
  46.  b5->setFont(QFont("Times", 18, QFont::Bold));
  47.  
  48.  edit = new Q3MultiLineEdit(main);
  49.  edit->setGeometry(0, 50, 440, 340);
  50.  edit->setText("Text edit");
  51.  
  52.  addChild(main);
  53.  
  54. }
  55.  
  56. int main(int argc, char **argv)
  57. {
  58.  QApplication a(argc, argv);
  59.  MyMainWindow w;
  60.  a.setMainWidget(&w);
  61.  w.show();
  62.  return a.exec(); 
  63. }
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Qt Code: 
  1. main.cpp:2:26: q3scrollview.h: No such file or directory
  2. main.cpp:3:29: q3multilineedit.h: No such file or directory
  3. main.cpp:8: error: expected class-name before '{' token
  4. main.cpp:18: error: ISO C++ forbids declaration of `Q3MultiLineEdit' with no type
  5. main.cpp:18: error: expected `;' before '*' token
  6. main.cpp: In constructor `MyMainWindow::MyMainWindow()':
  7. main.cpp:23: error: `setGeometry' undeclared (first use this function)
  8. main.cpp:23: error: (Each undeclared identifier is reported only once for each function it appears in.)
  9. main.cpp:25: error: no matching function for call to `QWidget::QWidget(MyMainWindow* const)'
  10. C:/Qt/4.1.2/include/QtGui/../../src/gui/kernel/qwidget.h:635: note: candidates are: QWidget::QWidget(const QWidget&)
  11. C:/Qt/4.1.2/include/QtGui/../../src/gui/kernel/qwidget.h:596: note:                 QWidget::QWidget(QWidgetPrivate&, QWidge
  12. *, Qt::WFlags)
  13. C:/Qt/4.1.2/include/QtGui/../../src/gui/kernel/qwidget.h:183: note:                 QWidget::QWidget(QWidget*, Qt::WFlags)
  14. main.cpp:48: error: `edit' undeclared (first use this function)
  15. main.cpp:48: error: `Q3MultiLineEdit' has not been declared
  16. main.cpp:52: error: `addChild' undeclared (first use this function)
  17. main.cpp: In function `int qMain(int, char**)':
  18. main.cpp:60: error: 'class QApplication' has no member named 'setMainWidget'
  19. main.cpp:61: error: 'class MyMainWindow' has no member named 'show'
  20. main.cpp:63:2: warning: no newline at end of file
  21. mingw32-make[1]: *** [tmp\obj\debug_shared\main.o] Error 1
  22. mingw32-make[1]: Leaving directory `C:/Qt/4.1.2/test/scroll/scrollview'
  23. mingw32-make: *** [debug-all] Error 2
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1) why the compile cant find q3scrollview.h and q3multilineedit.h
2) class MyMainWindow : public Q3ScrollView , and Q3ScrollView is inherit QWidget,
why it cant call the funtion setGeometry
3)error: no matching function for call to `QWidget::QWidget(MyMainWindow* const)'
i find the construct is QWidget ( QWidget * parent = 0, Qt::WFlags f = 0 ), but i cant understand it, and why dose it reference
QWidget::QWidget(const QWidget&)
QWidget::QWidget(QWidgetPrivate&, QWidge*, Qt::WFlags)
QWidget::QWidget(QWidget*, Qt::WFlags)