1. Project preparation and creation

One 、 Environment building

1 - Qt install

• Qt edition ：Qt 5.9.8
• Qt Development environment construction ： Reference address -> https://blog.csdn.net/qq23001186/article/details/125469147

2 - FFmpeg install

• FFmpeg：4.4.2-2
• FFmpeg Installation tutorial ： Reference address ->

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Two 、Qt Project composition and management

• Qt Project management window ： stay Qt Creator Click... In the left toolbar “ edit ” Button , You can enter the project management window ;Qt Creator You can open multiple projects , But there is only one activity , The active project name is bold
• Under the project name node , Groups manage various source files , The files and groups are as follows
  • xxx.pro file ： It's a project management document , Including some settings for the project
  • Headers grouping ： Under this node are all header files in the project (.h)
  • Sources grouping ： Under this node are all items in the project C++ Source file (.cpp)
  • Resources grouping ： Various resource files in the project under this node , Such as QML file , Icon （ picture ） file , Translation of documents, etc ; Use qrc File load resource

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3、 ... and 、.pro Introduction to project documents

• .pro File Comments ： Use # Annotate

keyword	paraphrase
TEMPLATE	Appoint qmake What kind of... Is generated for this application makefile
QT	Specify the... To use Qt modular ( The default is core gui, Corresponding to QtCore and QtGui modular )
CONFIG	The configuration variable specifies the options to be used by the compiler and the libraries to be connected
TARGET	Specify the base file name of the executable or library , It doesn't contain any extensions 、 Prefix or version number （ The default is the current directory name ）
DEFINES	List of additional preprocessor definitions required by the application
SOURCES	List of all source files in the application
HEADERS	In the application C++ The header file (.h)
FORMS	All... In the application .ui file （ from Qt Designer generation ） A list of
DESTDIR	The directory where the executable object is placed
INCLUDEPATH	Additional list of include paths required by the application
DEPENDPATH	The search path the application depends on
VPATH	Search path for supplementary files
DEF_FILE	Only Windows need ： What the application wants to connect to .def file
RC_FILE	Only Windows need ： Resource files for the application
RES_FILE	Only Windows need ： The resource file to which the application will connect

• TEMPLATE Key type

TEMPLATE Keyword content	paraphrase
app	Build an application of makefile. This is the default , So if the template is not specified , This will be used .
lib	Build a library of makefile. When using this template , except “app” System variables are mentioned in the template , One more VERSION Is supported by . You need to specify specific information for the library .pro Use them in files .VERSION - Version number of the target library , such as ,2.3.1
vcapp	Build an application of Visual Studio Project documents
vclib	Build a library of Visual Studio Project documents
subdirs	This is a special template , It can create a directory that can enter a specific directory and generate... For a project file makefile And call... For it make Of makefile. There is only one system variable in this template SUBDIRS Can be identified . This variable contains the list of subdirectories containing project files to be processed . The name of this project file is the same as the subdirectory , such qmake You can find it . for example , If it's in the subhead “myapp”, So the project file in this directory should be called myapp.pro

• CONFIG Key type ： Configuration variables specify the options to be used by the compiler and the libraries to be connected . Anything can be added to the configuration variable , But only the following options can be qmake distinguish

CONFIG Keyword content	paraphrase
release	The application will use release Pattern serialization . If “debug” To be designated , It will be ignored
debug	The application will use debug Pattern serialization
warn_on	The compiler will output as many warnings as possible . If “warn_off” To be designated , It will be ignored
warn_off	The compiler will output as few warnings as possible
qt	The application is a Qt Applications , also Qt The library will be connected
thread	An application is a multithreaded application
x11	The application is a X11 Application or library
windows	Used only for “app” Templates ： The application is a Windows Next window application
console	Used only for “app” Templates ： The application is a Windows The console application under
dll	Used only for “lib” Templates ： A library is a shared library （dll）
staticlib	Used only for “lib” Templates ： A library is a static library
plugin	Used only for “lib” Templates ： Library is a plug-in , This will make dll Options to take effect

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Four 、Qt Meta object system

• Qt Introduction to meta object system ：Qt Meta object system （Meta-Object System） Provides signals and slot base addresses for communication between objects 、 Runtime type information and dynamic attribute system
• Qt The meta object system consists of the following three foundations
  • QObject Class is the base class of all classes that use the meta object system
  • In a class private Partial declaration Q_OBJECT macro , Enables classes to use the properties of meta objects , Such as dynamic properties 、 Signal and slot
  • MOC（ Meta object editor ） For each QObject Subclasses of provide the necessary code to implement the characteristics of the meta object system ; When building a project ,MOC Tool reading C++ Source file , When it finds that the class definition has Q_OBJECT Macro time , It will generate another class with meta object support code for this class C++ Source file , The generated source file is compiled and connected with similar implementation files

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5、 ... and 、Qt Basic modules

modular	describe
Qt Core	QtCore Modules are all based on Qt The foundation of the application , Core non graphical classes used by other modules . Provides a mechanism for communication between signals and slots , Concurrency and multithreading , Containers , The event system , Plug ins and I/O facilities
Qt GUI	The most important GUI modular . Graphical user interface (GUI) The base class of the component . Include OpenGL
Qt widgets	Used to build GUI Interface C++ Graphics component class , Include based on GUI Typical widget classes for applications and QSceneGraph class . stay Qt 5 In the from QtGui Separate from
Qt Multimedia	Audio 、 video 、 Broadcast and camera functions
Qt Multimedia Widgets	Realize the multimedia function and get the interface component class
Qt Network	Use a simpler and lighter class for network programming
Qt QML	Qt QML The module is used for QML and JavaScript Language
Qt Quick	This module is used to QML2 Compiling GUI Applications . Declarative framework for building highly dynamic applications with custom user interfaces
Qt Quick Controls	Offer lightweight QML type , For desktop 、 Embedded and mobile devices create high-performance user interfaces . These types have a simple style architecture and are very efficient
Qt Quick Dialogs	For from Qt Quick The type with which the application creates and interacts with the system dialog
Qt Quick Layouts	Used in Qt Quick Arrange the layout of the project in
Qt SQL	Include use SQL Classes for database integration
Qt Test	For unit testing Qt Application and library classes . Be careful ： The binary compatibility guarantee does not apply to Qt test . however , It will remain source compatible

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6、 ... and 、 Project new

1 - New projects

• New projects
  
  
  
  
  
  
  

2 - Use vs Open the project

• Use vs Open the project

  • qml Of ui Some suggestions are in qt In the development
  • For debugging, you can choose vs, Easier to debug

• newly build bat File generation vs Project documents ：qmake -tp vc DemoProl.pro（ Use qmake Based on the current .pro File generation is suitable for Visual Stdio Engineering documents of ）
  
  

• win10 Run under bat Set up ： Add the variable name to the system environment variable -> %path%, A variable's value -> C:/windows/system32

• function GeneVS.bat Report errors ：
  

• Set up cl.exe Environment variables of ： Search the computer cl.exe; My computer path is D:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\VC\Tools\MSVC\14.16.27023\bin\Hostx64\x64; In environment variable -> System -> PATH Add a path to

• Use VS Open the project file .vcxproj
  

3 - QT Inheritance system

• QGuiApplication app(argc, argv);： stay main.cpp Can be seen in app yes QGuiApplication class , View source discovery QGuiApplication Inherit QCoreApplication, And uses macros Q_OBJECT; and QCoreApplication Inherited QT Base class of QObject

• QQmlApplicationEngine engine：QQmlApplicationEngine Inherited QQmlEngine, And also uses macros Q_OBJECT;QQmlEngine Inherited QJSEngine;QJSEngine In the end, he inherited it QT Base class of QObject
  
  
  

4 - vs Run the project

• The following error reporting solutions ： project -> Retarget the solution

1>------  Build started :  project : DemoProl,  To configure : Debug x64 ------
1>D:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\Common7\IDE\VC\VCTargets\Microsoft.Cpp.WindowsSDK.targets(46,5): error MSB8036:  Can't find  Windows SDK  edition 8.1. Please install the required version of  Windows SDK  Either in the project property page or by right clicking the solution and selecting “ Retarget the solution ” To change the  SDK  edition .
1> The build project is complete “DemoProl.vcxproj” The operation of  -  Failure .
==========  Generate :  success  0  individual , Failure  1  individual , newest  0  individual , skip  0  individual  ==========

5 - vs Set the default encoding to UTF-8

• Why do I need to change it to UTF-8： because Qt The default code in is UTF-8, And most of the others IDE All codes are UTF-8; and VS The default encoding for is GB2312
• vs Set the default encoding to UTF-8： Tools -> Expansion and update -> online -> Search for force UTF-8（No BOM) -> close vs It will be installed automatically after -> Just reopen the project
  
• An error message may appear after modifying the character encoding ：warning C4819: The file contains cannot be in the current code page (936) The characters represented in . Please save this file as Unicode Format to prevent data loss

 Solution ：
1. Modify character encoding format  （ recommend ）
Visual Studio Provide advanced save options , It can specify the encoding specification of a specific code file and the newline character used at the end of the line .
 stay Visual Studio 2017 in , This command is not displayed by default in “ file ” The menu . You need to set it manually , To display the command .
 The operation method is as follows ：

（1） single click “ Tools ”|“ Customize ” command , eject “ Customize ” Dialog box .
（2） single click “ command ” label , Get into “ command ” tab .
（3） stay “ menu bar ” In the drop-down list , choice “ file ” Options .
（4） single click “ Add command ” Button , eject “ Add command ” Dialog box .
（5） stay “ Category ” In the list , choice “ file ” Options ; stay “ command ” In the list , choice “ Advanced save options ” Options .
（6） single click “ determine ” Button , close “ Add command ” Dialog box .
（7） Choose “ Control ” In the list “ Advanced save options ” Options , single click “ Move upward ” perhaps “ Move down ” Button , Adjust the position of the command .
（8） single click “ close ” Button , complete “ Advanced save options ” Add operation of command .
（9） open “ file ” Under the menu “ Advanced save options ”, Set encoding  Unicode（utf-8 Signed ）-  code page  65001