Qt生成动态链接库并使用动态链接库

项目结构

整个工程由一个主程序构成和一个模块构成(dll)。整个工程的结构目录如下

   Define.pri
   MyProject.pro
   MyProject.pro.user
+---bin
+---MainProgram
       main.cpp
       MainProgram.pro
       MainProgram.pro.user
       widget.cpp
       widget.h
       widget.ui
+---MathDll
        MathDll.pro
        MathDll.pro.user
        MyMath.cpp
        MyMath.h

qmake文件介绍

1 MyProject.pro

TEMPLATE = subdirs #多工程项目
CONFIG += ordered #指定编译顺序
SUBDIRS = MathDll \ #模块（dll）
          MainProgram #主工程

2 Define.pri

win32 {
    CONFIG(release, debug|release){
    contains(QT_ARCH, i386) {
            BIN_PATH=release_x86_
        } else {
            BIN_PATH=release_x64_
        }
    } else {
    contains(QT_ARCH, i386) {
            BIN_PATH=debug_x86_
        } else {
            BIN_PATH=debug_x64_
        }
    }
}

DESTDIR = $$PWD/bin/$$BIN_PATH #生成的二进制文件（可执行文件或者库）的目标位置，放在pri文件中，在有pro文件包含这样就不用重复写

3 MathDll.pro

QT -= gui

TEMPLATE = lib

CONFIG += c++11

# The following define makes your compiler emit warnings if you use
# any Qt feature that has been marked deprecated (the exact warnings
# depend on your compiler). Please consult the documentation of the
# deprecated API in order to know how to port your code away from it.
DEFINES += QT_DEPRECATED_WARNINGS
DEFINES += MATHDLL_LIBRARY #使用预定义来控制是导出函数符号到dll还是导出dll中的函数符号

# You can also make your code fail to compile if it uses deprecated APIs.
# In order to do so, uncomment the following line.
# You can also select to disable deprecated APIs only up to a certain version of Qt.
#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0

include($$PWD/../Define.pri) #引入pri文件

SOURCES += \
        MyMath.cpp \
        MyMath.h
#拷贝头文件到指定目录，以便其它程序能够使用该dll
QMAKE_POST_LINK += xcopy /y/F \"$$PWD/MyMath.h\" \"$$PWD/../bin/includePath\\\" $$escape_expand(\\n\\t)

# Default rules for deployment.
qnx: target.path = /tmp/$${TARGET}/bin
else: unix:!android: target.path = /opt/$${TARGET}/bin
!isEmpty(target.path): INSTALLS += target

4 MainProgram.pro

#-------------------------------------------------
#
# Project created by QtCreator 2023-12-09T17:29:33
#
#-------------------------------------------------

QT       += core gui

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

TARGET = MainProgram
TEMPLATE = app

# The following define makes your compiler emit warnings if you use
# any feature of Qt which has been marked as deprecated (the exact warnings
# depend on your compiler). Please consult the documentation of the
# deprecated API in order to know how to port your code away from it.
DEFINES += QT_DEPRECATED_WARNINGS

# You can also make your code fail to compile if you use deprecated APIs.
# In order to do so, uncomment the following line.
# You can also select to disable deprecated APIs only up to a certain version of Qt.
#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0

include($$PWD/../Define.pri) #引入pri文件
LIBS += -L$$PWD/../bin/$$BIN_PATH #设置搜索链接动态库的目录

CONFIG += c++11

INCLUDEPATH += $$PWD/../bin/includePath #设置搜索头文件目录
LIBS += -lMathDll #链接库文件


SOURCES += \
        main.cpp \
        widget.cpp

HEADERS += \
        widget.h

FORMS += \
        widget.ui

# Default rules for deployment.
qnx: target.path = /tmp/$${TARGET}/bin
else: unix:!android: target.path = /opt/$${TARGET}/bin
!isEmpty(target.path): INSTALLS += target

注意 :

LIBS += -L$$PWD/../bin/$$BIN_PATH

这句话是很重要的，在程序编译链接时会使用到动态库的 lib 文件，用于生成程序。而默认链接的位置是 MainProgram 目录下，如果没有该语句就会提示找不到 MathDll.lib 文件，可执行程序生成失败。
在这里插入图片描述

源文件分析

1 MyMath.h

#ifndef MYMATH_H_
#define MYMATH_H_
//包含QObject才能识别 Q_DECL_EXPORT Q_DECL_IMPORT
#include <QObject>
//预定义来控制导入导出符号
#if defined (MATHDLL_LIBRARY)
#define MATHDLL_LIBRRY_EXPORT Q_DECL_EXPORT
#else
#define MATHDLL_LIBRRY_EXPORT Q_DECL_IMPORT
#endif

class MATHDLL_LIBRRY_EXPORT MyMath{
public:
    MyMath();
    ~MyMath();
    int add(int a, int b);
};

#endif

2 widget.cpp

#include "widget.h"
#include "ui_widget.h"
#include "MyMath.h"

Widget::Widget(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::Widget)
{
    ui->setupUi(this);
}

Widget::~Widget()
{
    delete ui;
}

void Widget::on_pushButton_clicked()
{
    int a = ui->lineEdit->text().toInt();
    int b = ui->lineEdit_2->text().toInt();
    MyMath myMath;
    int sum = myMath.add(a, b); //使用动态链接库中的函数

    ui->label->setText(ui->label->text() + QString::number(sum));
}