C++ GUI Programming with Qt 3

Transcription

1 Welcome from Budapest Welcome from ELTE University 1 Rozália Szabó Nacsa Eötvös Loránd University, Budapest Faculty of Informatics nacsa@inf.elte.hu 2 Qt Overview Qt is a complete C++ application development framework. It includes a class library and tools for cross-platform development and internationalization. C++ GUI Programming with Qt 3 Qt applications run natively, compiled from the same source code, on all supported platforms: - Qt/Windows (Microsoft Windows XP, 2000, NT 4, Me/98/95) - Qt/X11 (Linux, Solaris, HP-UX, IRIX, AIX, and other Unix variants) - Qt/Mac (Mac OS X) - Qt/Embedded (embedded Linux) 3 4 Why Qt? expanded markets short learning curves, ease of use platform independence for developers native look and feel no runtime environment high performance (no virtual machine or emulation layers) robustness (+simple memory management) easy integration with 3rd party libraries and products (C++ libs) migration from MFC, Motif extra widgets and components available good C++ performance available source code nice documentation high-quality technical support Running Qt Assistant

2 The Qt s Welcome window Class Hierarchy Hello Qt application Hello Qt: includes QObject QWidget QFrame QLabel 1. Give the definitions of used classes QApplication

3 Hello Qt: application Hello Qt: label Qt supports command-line arguments on its own. Second parameter (0) means no parent. 1. Gives the definitions of used classes 2. Create a QApplication object. 1. Gives the definitions of used classes 2. Creates a QApplication object. 3. Create a QLabel object with no parent Hello Qt:main widget Hello Qt: show If label is said to be a main widget it vanishes from the memory AND from the screen as well when it is closed. Widgets are created hidden by default. (no flickering) 1. Gives the definitions of used classes 2. Creates a QApplication object. 3. Creates a QLabel object with no parent. 4. Set the label as the application s main widget. 1. Gives the definitions of used classes 2. Creates a QApplication object. 3. Creates a QLabel object with no parent. 4. Sets the label as the application s main widget. 5. Make the label visible Hello Qt: exec HTML - style formatting Application turns into a stand by state waiting for messages. 1. Give the definitions of used classes 2. Create a QApplication object. 3. Create a QLabel object with no parent. 4. Set the label as the application s main widget. 5. Make the label visible 6. Pass application s control on Qt. ( event loop ) 17 QLabel *label = new QLabel("<h1><i>Hello</i>" "<font color=red> Qt!</font></h2>",0); 18 3

4 Compiling & Running Directory s Contents hello.exe hello.obj hello.pro Makefile 1. qmake project 2. qmake hello.pro 3. nmake 4. hello QPushButton The Quit application QApplication Responding to User Actions #include <qpushbutton.h> int main(int argc, char *argv[]) QPushButton *button= new QPushButton("Quit",0); quit.cpp #include <qpushbutton.h> int main(int argc, char *argv[]) QPushButton *button = new QPushButton("Quit",0); QObject::connect(button,SIGNAL(clicked()),&app,SLOT(quit())); app.setmainwidget(button); button->show(); quit.cpp 21 QObject::connect(button,SIGNAL(clicked()),&app,SLOT(quit())); app.setmainwidget(button); button->show(); 1. Give the definitions of used classes 2. Create a QApplication object. 3. Create a QPushButton object with no parent. 4. Make connection to respond 5. Set the button as the application s main widget. 6. Make the button visible 7. Pass application s control on Qt. 22 Making Connections macros QObject::connect(button,SIGNAL(clicked()),&app,SLOT(quit())); button clicked() quit() application member function of the QObject class QObject::connect(button,SIGNAL(clicked()),&app,SLOT(quit()));

5 Compiling & Running Numbers application Directory s Contents quit.cpp quit.exe quit.obj quit.pro Makefile main.cpp 1. qmake project 2. qmake o Makefile quit.pro 3. nmake 4. quit Form Class repesenting the main window Form s Design Caption QVBox QHBox QSpinBox QSlider QSpinBox QHBox Classes QSlider QLineEdit QEditLine QVBox Form 27 QApplication 28 Modularization Form Class - Declaration main.cpp 29 #ifndef FORM_H #define FORM_H #include <qwidget.h> #include <qvbox.h> class QHBox; class QSpinBox; Forward declaration class QSlider; class QLineEdit; class Form: public QVBox Form inherits from QVBox public: Form(QWidget *parent=0, const char *name=0); constructor private: QVBox *vbox; QHBox *hbox; QSpinBox *spinbox; Pointers QSlider *slider; QLineEdit *lineedit; ; #endif 30 5

6 Form Class - Implementation #include <qvbox.h> #include <qhbox.h> #include <qspinbox.h> #include <qslider.h> #include <qlineedit.h> #include " Form::Form(QWidget *parent, const char *name) : QVBox(parent,name) setmargin(6); setspacing(6); hbox = new QHBox(this); lineedit = new QLineEdit(this); hbox->setmargin(6); hbox->setspacing(6); spinbox = new QSpinBox(hbox); slider = new QSlider(Qt::Horizontal,hbox); slider->setrange(0,10); spinbox->setrange(0,10); Caption QVBox QHBox QSpinBox QSlider QLineEdit Numbers application s main program #include "" int main(int argc, char *argv[]) Form *form = new Form; app.setmainwidget(form); form->show(); main.cpp Caption QVBox QHBox QSpinBox QSlider QLineEdit spinbox->setvalue(5); connect(slider,signal(valuechanged(int)),spinbox,slot(setvalue(int))); connect(spinbox,signal(valuechanged(int)),slider,slot(setvalue(int))); Creating Custom Slots - Declaration... class Form: public QVBox Q_OBJECT public: Form(QWidget *parent=0, const char *name=0); private: QHBox *hbox; QSpinBox *spinbox; QSlider *slider; QLineEdit *lineedit; Q_OBJECT macro consists of function declarations for moc. moc: meta object compiler Custom Slot Implementation 1... Form::Form(QWidget *parent, const char *name) :QVBox(parent,name) setmargin(6); setspacing(6);... connect(slider,signal(valuechanged(int)),spinbox,slot(setvalue(int))); connect(spinbox,signal(valuechanged(int)),slider,slot(setvalue(int))); connect(slider,signal(valuechanged(int)),this,slot(sayasword(int))); QString words[11]; void initwords(); public slots: void sayasword(int i); ;... Words of numbers are stored in an array. This is not a standard C++ element. It will be transferred into standard C++ code by moc. 33 initwords(); spinbox->setvalue(5); The initial value must be set AFTER establishing connections. custom slot 34 Custom Slot Implementation 2 Compiling & Running... void Form::sayAsWord(int i) lineedit->settext(words[i]); qmake project qmake numbers.pro nmake numbers.pro void Form::initWords() words[0] = "null"; words[1] = "one";... words[10] = "ten"; ########################## # Automatically generated by ########################## TEMPLATE = app INCLUDEPATH +=. # Input HEADERS += SOURCES += main.cpp

7 Memory Management & Parent-Children Relationship Form QHBox(hbox) list of children The only objects we have to delete are the objects we create with new and that have no parents. QSpinBox(spinBox) QSilder(slider) Main widget is automatically deleted after close. QLineEdit(lineEdit) We have used new but we do not have to delete them either Layout Manager Object to manage the size and position of the widget. Layout manager classes are not widgets, but they can have parent and chidren. #ifndef FORM_H #define FORM_H #include <qwidget.h> class QSpinBox; class QSlider; class QLineEdit; class Form: public QWidget public: Form(QWidget *parent=0, const char *name=0); private: QSpinBox *spinbox; QSlider *slider; QLineEdit *lineedit; ; #endif Form::Form(QWidget *parent, const char *name) : QWidget(parent,name) spinbox = new QSpinBox(this); slider = new QSlider(Qt::Horizontal,this); slider->setrange(0,10); spinbox->setrange(0,10); lineedit = new QLineEdit(this); QHBoxLayout *toplayout = new QHBoxLayout; //Layout with no parent toplayout->addwidget(spinbox); toplayout->addwidget(slider); #include <qlayout.h> #include <qspinbox.h> #include <qslider.h> #include <qlineedit.h> #include "" Caption QVBox QHBox QSpinBox QSlider Caption QSpinBox QSlider mainlayout toplayout QVBoxLayout *mainlayout = new QVBoxLayout(this); //Layout with "this" parent QLineEdit QLineEdit mainlayout->addlayout(toplayout); mainlayout->addwidget(lineedit); mainlayout->setmargin(11); mainlayout->setspacing(6); connect(slider,signal(valuechanged(int)),spinbox,slot(setvalue(int))); connect(spinbox,signal(valuechanged(int)),slider,slot(setvalue(int))); spinbox->setvalue(5); //Set value AFTER connections!!

8 Parent - children relationship Form mainlayout Caption QSpinBox QSlider QLineEdit Form QSpinBox (spinbox) QSlider (slider) QLineEdit (lineedit) QVBoxLayout(mainLayout) QSpinBox (spinbox) QSlider (slider) QLineEdit (lineedit) QVBoxLayout(mainLayout) QHBoxLayout(topLayout) First toplayout is created with no parent, but we do not have to manage its deletion, because it will be added to the mainlayout and therefore mainlayout became its parent. to delete or not to delete? toplayout Main widget and its childrens are automatically deleted after close. QHBoxLayout(topLayout) 43 QHBoxLayout *toplayout = new QHBoxLayout; //Layout with no parent toplayout->addwidget(spinbox); toplayout->addwidget(slider); QVBoxLayout *mainlayout = new QVBoxLayout(this); //Layout with "this" parent mainlayout->addlayout(toplayout); //mainlayout will be the parent for toplayout mainlayout->addwidget(lineedit); // this (Form) remains the parent for lineedit 44 The.ui file and the generated C++ code Qt designer form.ui UIC Reads and writes main.cpp Reading Generates #includes Tool Generated source file 45 Revision controlled source file 46 Qt designer The subclassing approach formbase.ui UIC formbase.h Inheritance Application specific functions can be given in form.ui.h file. The ui.h extension approach form.ui UIC Qt designer form.ui.h Reads and writes Reading Generates #includes Tool Generated source file Revision controlled source file formbase.cpp main.cpp File formbase.h és a formbase.cpp are generated after modification of the form. Application specific functions will be added in the subclass. 47 Reads and writes Reading Generates #includes Tool Generated source file Revision controlled source file main.cpp 48 8

9 The QtDesigner s screen Starting Qt Designer ProjectOverview Toolbox ObjectExplorer Properties Editor/ Signal Handlers 49 File/New/C++ Project 50 File/New/Widget Laying Out Elements

10 Conneting widgets: Edit/Connections <connections> form.ui <connection> <sender>slider</sender> <signal>valuechanged(int)</signal> <receiver>spinbox</receiver> <slot>setvalue(int)</slot> </connection> <connection> <sender>spinbox</sender> <signal>valuechanged(int)</signal> <receiver>slider</receiver> <slot>setvalue(int)</slot> </connection> </connections> Declaring variable Creating Custom Slots Edit/Slots... /New Function void Form::sayAsWord( int i) lineedit->settext(words[i]); Edit/Connections 57 Creating custom functions and the constructor 58 Adding main function File/New... /C++ Main file Edit/Slots... /New Function void Form::init() spinbox->setmaxvalue(10); slider->setmaxvalue(10); initwords(); spinbox->setvalue(5); Creating the Form init() function will be performed automatically. void Form::initWords() words[0] = "null";... words[10] = "ten";

11 The generated main.cpp program #include "" int main( int argc, char ** argv ) QApplication a( argc, argv ); Form w; w.show(); a.connect( &a, SIGNAL( lastwindowclosed() ), &a, SLOT( quit() ) ); return a.exec(); Compiling & Running 1. qmake project 2. qmake words.pro 3. make Project file of Words application Extending the functionality of the program TEMPLATE = app INCLUDEPATH +=. Task: Let us make it works vice verse. # Input HEADERS += form.ui.h INTERFACES += form.ui SOURCES += main.cpp 1. qmake project 2. qmake -o Makefile words.pro 3. nmake 4. words Typing Defining a new slot Implementing the new slot void Form::slotTextChanged_( const QString & s ) bool l=false; for (int i=0; i< (int) sizeof(words)/sizeof(words[0]) &&!l;i++) if(words[i]==s) l=true; slider->setvalue(i);

12 Connecting the widgets Compiling & Running