Qt如何将系统中使用的qDebug、qWarning等输出的信息显示到自定义的界面上或保存到文件中

一、界面中添加一个QTextBrowser

二、相关源码
.hpp

#ifndef LOGLOOKWIDGET_H
#define LOGLOOKWIDGET_H

#include <QWidget>
#include <QMutex>
#include <iostream>
#include <QFile>
#include <QTextStream>
#include <QTime>
#include <QFontDialog>

namespace Ui {
class LogLookWidget;
}

class LogLookWidget : public QWidget
{
    Q_OBJECT
signals:
    void messageOutputSignal(QtMsgType type, int line, QString file, const QString &msg);
public:
    explicit LogLookWidget(QWidget *parent = nullptr);
    ~LogLookWidget();
private:
    void controlInit();
    static void messageOutput(QtMsgType type, const QMessageLogContext &context, const QString &msg);
private slots:
    void messageOutputSlot(QtMsgType type, int line, QString file, const QString &msg);
private:
    Ui::LogLookWidget *ui;

    static LogLookWidget *instance;
    QFile *logFile = nullptr;
    QTextStream *logStream = nullptr;
};

#endif // LOGLOOKWIDGET_H

.cpp

#include "logLookWidget.h"
#include "ui_logLookWidget.h"

LogLookWidget *LogLookWidget::instance = nullptr;


LogLookWidget::LogLookWidget(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::LogLookWidget)
{
    ui->setupUi(this);
    instance = this;
    this->controlInit();
}

LogLookWidget::~LogLookWidget()
{
    qInstallMessageHandler(nullptr);
    delete ui;
}


void LogLookWidget::controlInit()
{
    this->setWindowTitle(tr("日志查看"));

    qInstallMessageHandler(LogLookWidget::messageOutput)

connect(instance,&LogLookWidget::messageOutputSignal,this,&LogLookWidget::messageOutputSlot);
}

void LogLookWidget::messageOutput(QtMsgType type, const QMessageLogContext &context, const QString &msg)
{
    emit instance->messageOutputSignal(type,context.line,context.file,msg);
}

void LogLookWidget::messageOutputSlot(QtMsgType type, int line, QString file, const QString &msg)
{
    static QMutex mutex;
    mutex.lock();

    QString tag;
    QString time;
    QString fileAndLine;

    switch(type)
    {
    case QtDebugMsg:
        tag = QString("%1").arg("D/",-5);
        break;
    case QtInfoMsg:
        tag = QString("%1").arg("I/",-5);
        break;
    case QtWarningMsg:
        tag = QString("%1").arg("W/",-5);
        break;
    case QtCriticalMsg:
        tag = QString("%1").arg("E/",-5);
        break;
    case QtFatalMsg:
        tag = QString("%1").arg("F/",-5);
        break;
    }

    time = QString("%1").arg("["+QTime::currentTime().toString("hh:mm:ss.zzz")+"]",-15);

    fileAndLine = QString("%1").arg("("+file.split("\\").last()+":"+QString::number(line)+")",-35,' ');

    QString logMsg;
    logMsg.append(tag);
    logMsg.append("  ");
    logMsg.append(time);
    logMsg.append("  ");
    logMsg.append(fileAndLine);
    logMsg.append("  ");
    logMsg.append(msg);

   // std::cout<<logMsg.toStdString();
	//将信息显示到界面上
    this->ui->textBrowser->append(logMsg);
    logMsg.append("\n");
    //将信息保存到文件中
    if(this->logStream)
        *this->logStream<<logMsg;

    mutex.unlock();
}

注意：
1、函数messageOutput只能是静态成员函数或外部函数。
2、static LogLookWidget *instance的作用是通过信号与槽的方法将信息转到类内成员函数，从而完成将信息显示到界面。
3、qInstallMessageHandler(LogLookWidget::messageOutput)的作用是将信息输出载体转化到messageOutput这个函数上，对应的qInstallMessageHandler(nullptr);是取消。