【发布时间】：2021-05-28 17:39:48
【问题描述】：
我正在尝试创建一个 QT DLL 以在 InnoSetup 安装程序中使用它（InnoSetup 是用 Delphi Pascal 编写的）。
当从 InnoSetup 调用时，该 DLL 应该具有从 Internet 下载文件的功能。
InnoSetup 调用如下：
procedure downloadFile();
external 'doDownload@files:testdll.dll,libssl-1_1.dll,libcrypto-1_1.dll stdcall loadwithalteredsearchpath delayload';
然后，我用这个来称呼它：
function InitializeSetup(): Boolean;
begin
Result := True;
ExtractTemporaryFile('testdll.dll');
downloadFile();
end;
问题是，如果我需要稍后（在初次调用后）调用它，我不能重用 downloadFile(); 因为在第一次调用时，不知何故，我怀疑，QCoreApplication 没有正确关闭并保持在执行循环中。 当我第二次调用这个函数时，没有任何反应，没有文件从互联网下载。再次下载文件的唯一方法是关闭并重新打开 Inno Setup。
这是我的代码：
TESTDLL.pro
QT -= gui
QT += network
TEMPLATE = lib
DEFINES += TESTCLASS_LIBRARY
CONFIG += c++11 dll
# You can make your code fail to compile if it uses deprecated APIs.
# In order to do so, uncomment the following line.
# DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000 # disables all the APIs deprecated before Qt 6.0.0
SOURCES += \
testdll.cpp \
libs\downloadThread.cpp
HEADERS += \
testdll_global.h \
testdll.h \
libs\downloadThread.h
QMAKE_LFLAGS += -Wl,--output-def,testdll.def
# Default rules for deployment.
unix {
target.path = /usr/lib
}
!isEmpty(target.path): INSTALLS += target
TESTDLL.h
#ifndef TESTDLL_H
#define TESTDLL_H
#include <QtCore>
#include "testdll_global.h"
#include "libs/downloadThread.h"
class TestDLL : public QObject
{
Q_OBJECT
public slots:
void handleResults(const QString &);
void startWThread();
void initQCoreApp();
private:
void debugMsg(QString fileName, QString message)
{
QFile file(fileName);
file.open(QIODevice::WriteOnly | QIODevice::Text);
QTextStream out(&file);
out << message;
file.close();
};
};
#endif
TESTDLL.cpp
#include "testdll.h"
namespace QCoreAppDLL
{
static int argc = 1;
static char arg0[] = "testdll.cpp";
static char * argv[] = { arg0, nullptr };
static QCoreApplication * pApp = nullptr;
}
extern "C" TESTCLASS_EXPORT void doDownload()
{
TestDLL a;
a.initQCoreApp();
}
void TestDLL::startWThread()
{
downloadThread *thread = new downloadThread(this);
connect(thread, &downloadThread::finished, thread, &QObject::deleteLater);
connect(thread, &downloadThread::resultReady, this, &TestDLL::handleResults);
thread->start();
}
void TestDLL::initQCoreApp()
{
if (!QCoreApplication::instance())
{
QCoreAppDLL::pApp = new QCoreApplication(QCoreAppDLL::argc, QCoreAppDLL::argv);
TestDLL a;
a.startWThread();
QCoreAppDLL::pApp->exec();
}
}
void TestDLL::handleResults(const QString &)
{
debugMsg("result.txt","succes!");
if (QCoreAppDLL::pApp)
QCoreAppDLL::pApp->quit();
}
DOWNLOADTHREAD.h
#ifndef downloadThread_H
#define downloadThread_H
#include <QtNetwork>
#include <QDebug>
class downloadThread : public QThread
{
Q_OBJECT
signals:
void resultReady(const QString &s);
public:
downloadThread(QObject *parent);
~downloadThread();
void run() override {
QString result;
initDownload();
emit resultReady(result);
};
void initDownload();
void doDownload(QString url);
private:
QNetworkAccessManager *networkMgr;
QNetworkReply *_reply;
public slots:
void replyFinished(QNetworkReply * reply);
};
#endif
DOWNLOADTHREAD.cpp
#include "downloadThread.h"
downloadThread::downloadThread(QObject *parent)
: QThread(parent)
{
}
downloadThread::~downloadThread()
{
quit();
wait();
}
void downloadThread::initDownload()
{
doDownload("http://www.google.com");
exec();
}
void downloadThread::doDownload(QString url)
{
networkMgr = new QNetworkAccessManager;
QNetworkRequest request;
request.setUrl(QUrl(url));
networkMgr->get(request);
connect(networkMgr, SIGNAL(finished(QNetworkReply*)), this, SLOT(replyFinished(QNetworkReply*)));
}
void downloadThread::replyFinished(QNetworkReply * reply)
{
if(reply->error() == QNetworkReply::NoError)
{
QByteArray content = reply->readAll();
QSaveFile file("output.txt");
file.open(QIODevice::WriteOnly);
file.write(content);
file.commit();
reply->deleteLater();
this->exit();
} else {
//error
reply->deleteLater();
this->exit();
}
}
我自己尝试解决问题的方法：
- 使用删除QCoreAppDLL::pApp，
void TestDLL::handleResults(const QString &)
{
debugMsg("result.txt","succes!");
if (QCoreAppDLL::pApp){
QCoreAppDLL::pApp->quit();
delete QCoreAppDLL::pApp;
}
}
正在使主机应用程序崩溃。
- QTimer和SLOT(quit())的使用，
void TestDLL::initQCoreApp()
{
if (!QCoreApplication::instance())
{
QCoreAppDLL::pApp = new QCoreApplication(QCoreAppDLL::argc, QCoreAppDLL::argv);
TestDLL a;
connect(&a, SIGNAL(finished()), QCoreAppDLL::pApp, SLOT(quit()));
QTimer::singleShot(0, &a, SLOT(startWThread));
QCoreAppDLL::pApp->exec();
}
}
什么都没有发生，就像 QCoreApplication exec 循环在 QThread 完成工作之前结束。
- 在 QThread 对象上使用插槽/信号，
void TestDLL::startWThread()
{
downloadThread *thread = new downloadThread(this);
connect(thread, &downloadThread::finished, thread, &QObject::deleteLater);
connect(thread, &downloadThread::resultReady, this, &TestDLL::handleResults);
connect(thread, SIGNAL(finished()), qApp, SLOT(quit()));
thread->start();
}
具有与以下相同的行为：
void TestDLL::handleResults(const QString &)
{
debugMsg("result.txt","succes!");
if (QCoreAppDLL::pApp)
QCoreAppDLL::pApp->quit();
}
我没有想法，我还能做些什么来解决这个问题？
提前谢谢各位！
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