QDebug在QDialog内部不起作用

Question

我有一个QT应用程序，它将qDebug（）输出导出到文件中。为此，我在主文件中使用了它：

已编辑（添加了有效的应用程序）

主要：

#include "mainwindow.h"
#include <QApplication>

#include <QString>
#include <QFile>
#include <QTextStream>
#include <QStandardPaths>
#include <QVector>
#include <QDateTime>
#include <QDebug>

void log_message(QtMsgType type, const QMessageLogContext& context, const QString &msg)
{

    QString timeStamp(QDateTime::currentDateTime().toString("dd.MM.yyyy hh:mm:ss.zzz"));


    QString app_data_path = QStandardPaths::writableLocation(QStandardPaths::AppLocalDataLocation);
    QString log_path = app_data_path + "/log/myapp.log";

    #ifdef QT_DEBUG
        log_path = "myapp.log";
    #endif

    QFile log_file(log_path);
    if(log_file.open(QIODevice::WriteOnly | QIODevice::Append))
    {
        QString final_msg;

        if (log_file.size() > 10000000) //If size is > 10MB, truncate file
        {
          log_file.close();
          log_file.open(QIODevice::WriteOnly);
        }
        switch (type) {
        case QtDebugMsg:
            final_msg = timeStamp.toUtf8() + " - Debug: " + msg.toUtf8() + "\n";
            log_file.write(final_msg.toUtf8(), final_msg.size());
            break;
        case QtWarningMsg:
            final_msg = timeStamp.toUtf8() + " - Warning: " + msg.toUtf8()+ "\n";
            log_file.write(final_msg.toUtf8(), final_msg.size());
            break;
        case QtCriticalMsg:
            final_msg = timeStamp.toUtf8() + " - Critical: " + msg.toUtf8()+ "\n";
            log_file.write(final_msg.toUtf8(), final_msg.size());
            break;
        case QtFatalMsg:
            final_msg = timeStamp.toUtf8() + " - Fatal: " + msg.toUtf8()+ "\n";
            log_file.write(final_msg.toUtf8(), final_msg.size());
            abort();
        }
    }
    log_file.close();

}

int main(int argc, char *argv[])
{

   qInstallMessageHandler(log_message);
   qDebug() << "Starting app";

    QApplication a(argc, argv);

    MainWindow w;

    w.showMaximized();

    w.show_login();

    return a.exec();
}

login_dialog.cpp

#include "login_dialog.h"
#include "ui_login_dialog.h"

#include <QDialogButtonBox>
#include <QPushButton>
#include <QDebug>
#include <QLabel>
#include <QSpacerItem>
#include <iostream>

LoginDialog::LoginDialog(QWidget *parent) :
    QDialog(parent),
    ui(new Ui::LoginDialog)
{

    ui->setupUi(this);

    this->setWindowTitle("Log In");
    this->setWindowModality(Qt::ApplicationModal); //Blocks all interaction outside this window

    //Login Layout
    _login_form_layout = new QFormLayout;
    _login_email_edit = new QLineEdit;
    _login_form_layout->addRow("Email:", _login_email_edit);

    _login_password_edit = new QLineEdit;
    _login_password_edit->setEchoMode(QLineEdit::Password);
    _login_form_layout->addRow("Contraseña:", _login_password_edit);

    QLabel *forgot_password_label = new QLabel();
    forgot_password_label->setText("<a href=\"http://localhost\">Has olvidado la contraseña?</a>");
    forgot_password_label->setTextInteractionFlags(Qt::TextBrowserInteraction);
    QObject::connect(forgot_password_label,
                     SIGNAL(linkActivated(QString)),
                     this,
                     SLOT(forgot_password(QString)));

    _login_form_layout->addWidget(forgot_password_label);

    QPushButton *login_button = new QPushButton("Login");
    QObject::connect(login_button,
                     SIGNAL(clicked()),
                     this,
                     SLOT(validate_login()));

    QLabel *no_account_label = new QLabel("No tienes una cuenta?");
    no_account_label->setSizePolicy(QSizePolicy::Fixed, QSizePolicy::Fixed);
    QPushButton *go_to_signup_button = new QPushButton("Regístrate");
    QObject::connect(go_to_signup_button,
                     SIGNAL(clicked()),
                     this,
                     SLOT(change_page()));

    no_account_label->setSizePolicy(QSizePolicy::Fixed, QSizePolicy::Fixed);
    QGridLayout *go_to_signup_button_layout = new QGridLayout;
    go_to_signup_button_layout->addWidget(no_account_label,0,0, Qt::AlignCenter);
    go_to_signup_button_layout->addWidget(go_to_signup_button,1,0, Qt::AlignCenter);

    QVBoxLayout *main_login_layout = new QVBoxLayout;
    main_login_layout->addLayout(_login_form_layout);
    main_login_layout->addWidget(login_button);
    main_login_layout->addStretch();
    main_login_layout->addLayout(go_to_signup_button_layout);
    QWidget *login_container = new QWidget;
    login_container->setLayout(main_login_layout);

    //SignUp layout
    _signup_form_layout = new QFormLayout;
    _signup_email_edit = new QLineEdit;
    _signup_form_layout->addRow("Email:", _signup_email_edit);

    _signup_password_edit = new QLineEdit;
    _signup_password_edit->setEchoMode(QLineEdit::Password);
    _signup_form_layout->addRow("Contraseña:", _signup_password_edit);

    QPushButton *signup_button = new QPushButton("Regístrate");
    QObject::connect(signup_button,
                     SIGNAL(clicked()),
                     this,
                     SLOT(validate_signup()));


    QLabel *already_account_label = new QLabel("Ya tienes una cuenta?");
    already_account_label->setSizePolicy(QSizePolicy::Fixed, QSizePolicy::Fixed);
    QPushButton *go_to_login_button = new QPushButton("Log In");
    QObject::connect(go_to_login_button,
                     SIGNAL(clicked()),
                     this,
                     SLOT(change_page()));

    already_account_label->setSizePolicy(QSizePolicy::Fixed, QSizePolicy::Fixed);
    QGridLayout *go_to_login_button_layout = new QGridLayout;
    go_to_login_button_layout->addWidget(already_account_label,0,0, Qt::AlignCenter);
    go_to_login_button_layout->addWidget(go_to_login_button,1,0, Qt::AlignCenter);

    QVBoxLayout *main_signup_layout = new QVBoxLayout;
    main_signup_layout->addLayout(_signup_form_layout);
    main_signup_layout->addWidget(signup_button);
    main_signup_layout->addStretch();
    main_signup_layout->addLayout(go_to_login_button_layout);

    QWidget *signup_container = new QWidget;
    signup_container->setLayout(main_signup_layout);

    _main_stacked_widget = new QStackedWidget;
    _main_stacked_widget->addWidget(login_container);
    _main_stacked_widget->addWidget(signup_container);

    QVBoxLayout *main_layout = new QVBoxLayout;
    main_layout->addWidget(_main_stacked_widget);
    this->setLayout(main_layout);

}

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

void LoginDialog::change_page()
{
    if(_main_stacked_widget->currentIndex() == 0)
    {
        _main_stacked_widget->setCurrentIndex(1);
        this->setWindowTitle("Registro");
    }else
    {
        _main_stacked_widget->setCurrentIndex(0);
        this->setWindowTitle("Log In");
    }
}

void LoginDialog::forgot_password(const QString &link)
{
    //Q_UNUSED(link);

    qDebug() << "Forgot password";
}

void LoginDialog::validate_login()
{
    qDebug()<< "Show this line in log file";
    std::cout << "Print this line in console\n";
}

void LoginDialog::validate_signup()
{
    std::cout << "Trty to create user";

}

login_dialog.h

#ifndef LOGIN_DIALOG_H
#define LOGIN_DIALOG_H

#include <QDialog>
#include <QStackedWidget>
#include <QFormLayout>
#include <QLineEdit>

namespace Ui {
class LoginDialog;
}

class LoginDialog : public QDialog
{
    Q_OBJECT

public:
    explicit LoginDialog(QWidget *parent = 0);
    ~LoginDialog();

private slots:
    void change_page();
    void forgot_password(const QString & link);
    void validate_login();
    void validate_signup();

private:
    Ui::LoginDialog *ui;

    //Login Layout
    QFormLayout *_login_form_layout;
    QLineEdit *_login_email_edit, *_login_password_edit;

    //SignUp Layout
    QFormLayout *_signup_form_layout;
    QLineEdit *_signup_email_edit, *_signup_password_edit;


    //Main Layout

    QStackedWidget *_main_stacked_widget;


};

#endif // LOGIN_DIALOG_H

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

#include "login_dialog.h"

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();

    void show_login();
private:
    Ui::MainWindow *ui;

    LoginDialog *_login_dialog;
};

#endif // MAINWINDOW_H

mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"

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

    _login_dialog = new LoginDialog(this);

}

MainWindow::~MainWindow()
{
    delete ui;
    delete _login_dialog;
}

void MainWindow::show_login()
{
    _login_dialog->show();
}

因此，在主要功能qDebug（）<<“启动应用程序”中运行良好，并将该消息写入日志。当我单击登录按钮时。 qdebug消息丢失，但是带有stdout的消息被打印在控制台中。