Qt5 plug-in mechanism (7) -- plug-in development sample code (Lower-levelAPI)

Plug-in code interface class header file MyPluginInterface. h # ifndefINTERFACES_H # defineINTERFACES_H # include # defineQtPluginDemo_iidorg.qt-project.Qt.PluginDemoclassMyPluginInterface {publ plug-in code

Interface class header file MyPluginInterface. h

# Ifndef INTERFACES_H # define INTERFACES_H # include
 
  
# Define QtPluginDemo_iid "org. qt-project.Qt.PluginDemo "class MyPluginInterface {public: virtual int add (int, int) = 0; // correct syntax // virtual int add (int, int ); // incorrect syntax (although this is also the correct virtual function declaration statement) // Note: all virtual functions in the interface class should have an entity or be set to 0 (recommended ), in this way, the/C ++ compiler can generate a virtual function table for the interface class. Otherwise, if the virtual functions that do not implement the // interface class are not set to 0, the program may fail to be linked, // or the link is successful, but the last generated library cannot be loaded (there are undefined symbols in the library)}; Q_DECLARE_INTERFACE (MyPluginInterface, QtPluginDemo_iid); # endif
 

Plug-in header file MyPlugin. h

#ifndef MYPLUGIN__H#define MYPLUGIN__H#include 
 
  #include 
  
   #include "MyPluginInterface.h"class MyPlugin : public QObject, public MyPluginInterface{    Q_OBJECT    Q_PLUGIN_METADATA ( IID QtPluginDemo_iid FILE "MyPlugin.json")    Q_INTERFACES(MyPluginInterface)public:int add(int,int);};#endif
  
 

Plug-In source file MyPlugin. cpp

#include "MyPlugin.h"int MyPlugin::add(int a , int b){return a+b ;}#include "moc_MyPlugin.cpp"

JSON file MyPlugin. json, which is empty in this example.

Project file MyPlugin. pro

TEMPLATE      = libCONFIG       += plugin consoleQT           += coreHEADERS       = MyPlugin.h MyPluginInterface.hSOURCES       = MyPlugin.cppOTHER_FILES   = MyPlugin.jsonTARGET        = MyPluginDESTDIR       = ./INCLUDEPATH  += ./# installtarget.path = ./installINSTALLS += target

Application code

Interface class header file MyPluginInterface. h, which is consistent with the plug-in code.

Main program file main. cpp

# Include "MyPluginInterface. h" # include
 
  
# Include
  
   
# Include
   
    
# Include
    
     
# Include
     
      
# Include
      
        Int main (int argc, char * argv []) {QApplication app (argc, argv); QWidget w; QObject * object; w. show (); app. addLibraryPath (QString (".. /MyPlugin/install "); // add the library path // load the plug-in to obtain the instance QPluginLoader l (QString (" MyPlugin ")); // QPluginLoader l (QString ("libMyPlugin. so "); if (object = l. instance ())! = NULL) {qDebug ("plugin loaded."); // use the plug-in int a = 14, B = 23; MyPluginInterface * plugin = qobject_cast
       
         (Object); if (plugin) qDebug ("% d + % d = % d", a, B, plugin-> add (a, B ));} else {qDebug ("failed to load plugin !! "); QString errorStr = l. errorString (); qDebug () <
        
         
MyApp. pro
         

         

         
####################################################################### Automatically generated by qmake (3.0) ?? 11? 19 02:26:33 2014######################################################################TEMPLATE = appQT += gui core widgetsCONFIG += consoleTARGET = MyAppINCLUDEPATH += .# InputHEADERS += MyPluginInterface.hSOURCES += main.cpp