Qt5 plug-in production

One 、Qt Plug-in mechanism

1、Qt Plug in introduction

A plug-in is a program written according to a certain standard application program interface , It aims to develop programs that realize functions that the application software platform does not have .

2、Qt plug-in unit API

Qt Two types are available API Used to create plug-ins ： One is higher order API, Used to extend Qt Its own function , Such as custom database driver , Image format , Text encoding , Custom styles, etc ; One is low order API, Used to extend Qt Applications .

3、 Extend application functions through plug-ins

A、 Define an interface set ( Classes with only pure virtual functions ), Used to communicate with plug-ins .
B、 Using macros Q_DECLARE_INTERFACE() Tell the interface to Qt Meta object system .
C、 Used in applications QPluginLoader To load the plug-in .
D、 Using macros qobject_cast() To determine whether a plug-in implements the interface .

4、 Creating plug-ins

The steps to create a plug-in are as follows ：
A、 Declare the plug-in class , The plug-in class inherits from QObject Interface and plug-in implementation .
B、 Using macros Q_INTERFACES() Tell... About the plug-in interface Qt Meta object system .
C、 Using macros Q_EXPORT_PLUGIN2() Export plug-in class .
D、 Use appropriate .pro File building plug-ins .
Before loading the plug-in , QCoreApplication Object must be initialized .

Two 、 Plug in development examples

1、 Create a project

2、 establish GUI Application engineering

Here you go QWidget And QMainWindow It doesn't matter

Choose the compiler you have installed

2、 Create a plug-in interface base class

stay MyWidget Add an interface to the application MyfirstPlugin.h. The contents are as follows ：

#ifndef MYFIRSTPLUGIN_H
#define MYFIRSTPLUGIN_H
#include<QObject>
class MyfirstPlugin
{
    
public:
    virtual ~MyfirstPlugin(){
    }
    virtual QString name()=0;
};
#define MYPLUGININTERFACE_IID "com.FirstPlugin.myfirstInterface"
Q_DECLARE_INTERFACE(MyfirstPlugin, MYPLUGININTERFACE_IID)

#endif // MYFIRSTPLUGIN_H

MYPLUGININTERFACE_IID It should be a unique string with similar package name format , You can do it according to your own preferences . Be careful ： A pure virtual destructor must be defined , And all functions of this interface must be virtual functions .

3、 Create Library Project

stay First Add a sub project named MyPlugin Sub library project of .

Pay attention to CONFIG Add plugin, It's to tell Qt This is a plug-in , At the same time, load the path of the interface file made in the previous step .

…// I'll see if anyone reads it , When someone reads it, I continue to write ./