在单独的线程中将DLL中的std :: cout重定向到QTextEdit [英] Redirecting std::cout from DLL in a separate thread to QTextEdit
本文介绍了在单独的线程中将DLL中的std :: cout重定向到QTextEdit的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
目标是将QtCreator中显示的所有应用程序输出显示为QTextEdit作为调试控制台窗口，因此对于同一应用程序，只有具有密码的用户才能看到控制台窗口，而普通用户则不能.有一个带有多个dll的exe.需要将所有来自DLL和qDebug的std :: cout显示在调试控制台窗口中.
The goal is to display all the application output shown in QtCreator to a QTextEdit as a debug console window so with the same application only those who have password are allowed to see the console window while normal users cannot. There is an exe with several dlls. All std::cout from DLLs and qDebug are needed to be shown in the debug console window.
要实现这一目标，我遵循了 http://www.qtforum.org/article/39768/redirecting-std-cout-std-cerf-qdebug-to-qtextedit.html
To achieve this, I have followed http://www.qtforum.org/article/39768/redirecting-std-cout-std-cerf-qdebug-to-qtextedit.html
该代码适用于单线程，但是当线程开始调用DLL中的函数时，该代码将挂起.我想知道如何解决这个问题.
The code works great for single thread but is hanged when a thread is started to call functions in DLL. I would like to know how to fix the problem.
代码
在mainwindow.cpp中
In mainwindow.cpp
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QObject>
#include <QThread>
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
m_qd = new Q_DebugStream(std::cout,ui->textEdit); //Redirect Console output to QTextEdit
m_qd->Q_DebugStream::registerQDebugMessageHandler(); //Redirect qDebug() output to QTextEdit
connect(ui->pushButtonSingleThreadTest, SIGNAL(clicked()),this,SLOT(SingleThreadTest()));
connect(ui->pushButtonMultiThreadTest, SIGNAL(clicked()),this,SLOT(MultiThreadTest()));
}
void MainWindow::SingleThreadTest()
{
run();
}
void MainWindow::MultiThreadTest()
{
QThread *workerThread= new QThread;
ThreadWorker *worker = new ThreadWorker();
worker->moveToThread(workerThread);
connect(workerThread, SIGNAL(started()), worker, SLOT(doWork()));
connect(worker, SIGNAL(finished()), workerThread, SLOT(quit()));
connect(worker, SIGNAL(finished()), worker, SLOT(deleteLater()));
connect(workerThread, SIGNAL(finished()), workerThread, SLOT(deleteLater()));
workerThread->start();
}
MainWindow::~MainWindow()
{
delete ui;
}
在mainwindow.h
In mainwindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include "q_debugstream.h"
#include "../ToyProj1/Header.h"
namespace Ui {
class MainWindow;
}
class ThreadWorker : public QObject
{
Q_OBJECT
public:
ThreadWorker()
{
}
private:
signals:
void finished();
public slots:
void doWork()
{
run();
emit finished();
}
};
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
public slots:
void SingleThreadTest();
void MultiThreadTest();
private:
Ui::MainWindow *ui;
Q_DebugStream* m_qd;
};
#endif // MAINWINDOW_H
在q_debugstream.h
in q_debugstream.h
#ifndef Q_DEBUGSTREAM_H
#define Q_DEBUGSTREAM_H
#include <iostream>
#include <streambuf>
#include <string>
#include "QTextEdit.h"
class Q_DebugStream : public std::basic_streambuf<char>
{
public:
Q_DebugStream(std::ostream &stream, QTextEdit* text_edit) : m_stream(stream)
{
log_window = text_edit;
m_old_buf = stream.rdbuf();
stream.rdbuf(this);
}
~Q_DebugStream()
{
m_stream.rdbuf(m_old_buf);
}
static void registerQDebugMessageHandler(){
qInstallMessageHandler(myQDebugMessageHandler);
}
private:
static void myQDebugMessageHandler(QtMsgType, const QMessageLogContext &, const QString &msg)
{
std::cout << msg.toStdString().c_str();
}
protected:
//This is called when a std::endl has been inserted into the stream
virtual int_type overflow(int_type v)
{
if (v == '\n')
{
log_window->append("");
}
return v;
}
virtual std::streamsize xsputn(const char *p, std::streamsize n)
{
QString str(p);
if(str.contains("\n")){
QStringList strSplitted = str.split("\n");
log_window->moveCursor (QTextCursor::End);
log_window->insertPlainText (strSplitted.at(0)); //Index 0 is still on the same old line
for(int i = 1; i < strSplitted.size(); i++){
log_window->append(strSplitted.at(i));
}
}else{
log_window->moveCursor (QTextCursor::End);
log_window->insertPlainText (str);
}
return n;
}
private:
std::ostream &m_stream;
std::streambuf *m_old_buf;
QTextEdit* log_window;
};
#endif // Q_DEBUGSTREAM_H
在DLL中，
int run()
{
std::cout << "Hello World" << std::endl;
return 0;
}
该代码示例已上传到github以供参考.重复该问题时，请构建ToyProj1和ToyProj1GUI.
The code sample is uploaded to github for reference. Build ToyProj1 and ToyProj1GUI when repeat the problem.
https://github.com/kuwt/ToyProject.git
推荐答案
使用有疑问的帮助注释，此解决方案可与信号和插槽机制很好地配合使用.std :: cout和qDebug重定向到QTextEdit.
With the help comments in question, this solution works well with signal and slot mechanism. std::cout and qDebug are redirected to QTextEdit.
main.cpp
#include "mainwindow.h"
#include <QApplication>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MainWindow w;
w.show();
// Setup QMessageCatch
/*!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!*/
qInstallMessageHandler(MainWindow::QMessageOutput);
/*!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!*/
return a.exec();
}
mainwindow.h
mainwindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include <QDebug>
#include <QTextEdit>
#include "q_debugstream.h"
namespace Ui {
class MainWindow;
}
class ThreadWorker : public QObject
{
Q_OBJECT
public:
ThreadWorker()
{
}
private:
signals:
void finished();
public slots:
void doWork()
{
std::cout<< "Hello World2" <<std::endl;
qDebug() << "Hello World2q" ;
emit finished();
}
};
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
// QMessage
/*!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!*/
static void QMessageOutput(QtMsgType , const QMessageLogContext &, const QString &msg);
/*!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!*/
public slots:
void SingleThreadTest();
void MultiThreadTest();
private:
Ui::MainWindow *ui;
// MessageHandler for display and ThreadLogStream for redirecting cout
/*!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!*/
MessageHandler *msgHandler = Q_NULLPTR;
ThreadLogStream* m_qd;
/*!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!*/
};
#endif // MAINWINDOW_H
mainwindow.cpp
mainwindow.cpp
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QObject>
#include <QThread>
// Catch QMessage, redirect to cout
/*!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!*/
void MainWindow::QMessageOutput(QtMsgType , const QMessageLogContext &, const QString &msg)
{
std::cout<<msg.toStdString().c_str()<<std::endl;
}
/*!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!*/
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
// Set up ThreadLogStream, which redirect cout to signal sendLogString
// Set up MessageHandler, wgucg catch message from sendLogString and Display
/*!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!*/
m_qd = new ThreadLogStream(std::cout); //Redirect Console output to QTextEdit
this->msgHandler = new MessageHandler(this->ui->textEdit, this);
connect(m_qd, &ThreadLogStream::sendLogString, msgHandler, &MessageHandler::catchMessage);
/*!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!*/
connect(ui->pushButtonSingleThreadTest, SIGNAL(clicked()),this,SLOT(SingleThreadTest()));
connect(ui->pushButtonMultiThreadTest, SIGNAL(clicked()),this,SLOT(MultiThreadTest()));
}
void MainWindow::SingleThreadTest()
{
std::cout<< "Hello World1" <<std::endl;
qDebug() << "Hello World1q" ;
}
void MainWindow::MultiThreadTest()
{
QThread *workerThread= new QThread;
ThreadWorker *worker = new ThreadWorker();
worker->moveToThread(workerThread);
connect(workerThread, SIGNAL(started()), worker, SLOT(doWork()));
connect(worker, SIGNAL(finished()), workerThread, SLOT(quit()));
connect(worker, SIGNAL(finished()), worker, SLOT(deleteLater()));
connect(workerThread, SIGNAL(finished()), workerThread, SLOT(deleteLater()));
workerThread->start();
}
MainWindow::~MainWindow()
{
delete ui;
}
q_debugstream.h
q_debugstream.h
#ifndef ThreadLogStream_H
#define ThreadLogStream_H
#include <iostream>
#include <streambuf>
#include <string>
#include <QScrollBar>
#include "QTextEdit"
#include "QDateTime"
// MessageHandler
/*!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!*/
class MessageHandler : public QObject
{
Q_OBJECT
public :
MessageHandler(QTextEdit *textEdit, QObject * parent = Q_NULLPTR) : QObject(parent), m_textEdit(textEdit){}
public slots:
void catchMessage(QString msg)
{
this->m_textEdit->append(msg);
}
/*!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!*/
private:
QTextEdit * m_textEdit;
};
/*!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!*/
class ThreadLogStream : public QObject, public std::basic_streambuf<char>
{
Q_OBJECT
public:
ThreadLogStream(std::ostream &stream, QObject * parent = Q_NULLPTR) :QObject(parent), m_stream(stream)
{
m_old_buf = stream.rdbuf();
stream.rdbuf(this);
}
~ThreadLogStream()
{
// output anything that is left
if (!m_string.empty())
{
emit sendLogString(QString::fromStdString(m_string));
}
m_stream.rdbuf(m_old_buf);
}
protected:
virtual int_type overflow(int_type v)
{
if (v == '\n')
{
emit sendLogString(QString::fromStdString(m_string));
m_string.erase(m_string.begin(), m_string.end());
}
else
m_string += v;
return v;
}
virtual std::streamsize xsputn(const char *p, std::streamsize n)
{
m_string.append(p, p + n);
long pos = 0;
while (pos != static_cast<long>(std::string::npos))
{
pos = static_cast<long>(m_string.find('\n'));
if (pos != static_cast<long>(std::string::npos))
{
std::string tmp(m_string.begin(), m_string.begin() + pos);
emit sendLogString(QString::fromStdString(tmp));
m_string.erase(m_string.begin(), m_string.begin() + pos + 1);
}
}
return n;
}
private:
std::ostream &m_stream;
std::streambuf *m_old_buf;
std::string m_string;
signals:
void sendLogString(const QString& str);
};
#endif // ThreadLogStream_H
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