C++ Qt应用：如何将表单值传递至主窗口私有变量

Hey there! Let's break down your problem and walk through two solid solutions that fit your Qt setup perfectly—no overcomplicating things.

This is the simplest approach if your "Load" form is meant to be a one-time selection tool that closes after the user clicks OK. It works exactly like the built-in input dialogs you're familiar with.

How to implement it: #

1. Make your Load form inherit from QDialog instead of a regular QWidget. This lets you use modal execution, where the main window waits for the dialog to close before continuing.
2. Add a public method to your Load dialog class to return the selected project name.
3. In your main window's Load menu slot, create the dialog, run it modally, and grab the value if the user clicked OK.

Code Examples:

MainWindow's Load Menu Slot

void MainWindow::on_actionLoad_triggered()
{
    // Create the dialog instance (parent is main window for proper ownership)
    LoadProjectDialog loadDialog(this);
    
    // Run the dialog modally—main window waits here until dialog closes
    if (loadDialog.exec() == QDialog::Accepted) {
        // Assign the selected project to your private variable
        m_currentProjectName = loadDialog.selectedProject();
        // Optional: Give user feedback (e.g., update status bar)
        statusBar()->showMessage(tr("Loaded project: %1").arg(m_currentProjectName));
    }
}

LoadProjectDialog Class

// LoadProjectDialog.h
#include <QDialog>
#include <QComboBox>
#include <QPushButton>
#include <QVBoxLayout>
#include <QHBoxLayout>

class LoadProjectDialog : public QDialog
{
    Q_OBJECT
public:
    explicit LoadProjectDialog(QWidget *parent = nullptr);
    // Public method to get selected project
    QString selectedProject() const;

private slots:
    void onOkClicked();
    void onCancelClicked();

private:
    QComboBox* m_projectComboBox;
};

// LoadProjectDialog.cpp
LoadProjectDialog::LoadProjectDialog(QWidget *parent) : QDialog(parent)
{
    // Initialize UI components
    m_projectComboBox = new QComboBox(this);
    // Populate combo box with existing projects (replace with your DB logic)
    m_projectComboBox->addItems({"Customer Database", "Inventory Tracker", "Sales Log"});

    QPushButton* okBtn = new QPushButton("OK", this);
    QPushButton* cancelBtn = new QPushButton("Cancel", this);

    // Layout setup
    QHBoxLayout* btnLayout = new QHBoxLayout;
    btnLayout->addStretch();
    btnLayout->addWidget(okBtn);
    btnLayout->addWidget(cancelBtn);

    QVBoxLayout* mainLayout = new QVBoxLayout(this);
    mainLayout->addWidget(m_projectComboBox);
    mainLayout->addLayout(btnLayout);

    // Connect buttons to dialog actions
    connect(okBtn, &QPushButton::clicked, this, &LoadProjectDialog::onOkClicked);
    connect(cancelBtn, &QPushButton::clicked, this, &LoadProjectDialog::onCancelClicked);
}

QString LoadProjectDialog::selectedProject() const
{
    return m_projectComboBox->currentText();
}

void LoadProjectDialog::onOkClicked()
{
    // Mark dialog as "accepted" to signal user confirmed selection
    accept();
}

void LoadProjectDialog::onCancelClicked()
{
    // Mark dialog as "rejected" to signal user canceled
    reject();
}

Use this if you need the Load form to stay open (non-modal) and let the user select projects multiple times. It's more flexible for ongoing interactions.

How to implement it: #

1. Define a custom signal in your Load dialog class that emits the selected project name.
2. Emit the signal when the user clicks OK.
3. Connect the signal to a slot in your main window that updates the private variable.

Code Adjustments:

Update LoadProjectDialog to Add Signal

// LoadProjectDialog.h
signals:
    // Signal emitted when user selects a project
    void projectSelected(const QString& projectName);

Modify OK Button Slot to Emit Signal

void LoadProjectDialog::onOkClicked()
{
    // Emit the signal with the selected project
    emit projectSelected(m_projectComboBox->currentText());
    accept(); // Close dialog if needed; skip this for non-modal use
}

Connect Signal in Main Window

void MainWindow::on_actionLoad_triggered()
{
    LoadProjectDialog* loadDialog = new LoadProjectDialog(this);
    // Connect dialog's signal to a lambda (or a dedicated slot) in main window
    connect(loadDialog, &LoadProjectDialog::projectSelected, this, [this](const QString& project) {
        m_currentProjectName = project;
        statusBar()->showMessage(tr("Switched to project: %1").arg(m_currentProjectName));
    });
    
    // For non-modal: use show() instead of exec()
    // loadDialog->show();
    // For modal: keep exec()
    loadDialog->exec();
}

• Go with Option 1 if your Load form is a one-time selection tool that closes after OK. It’s simpler, matches the QInputDialog pattern you mentioned, and requires fewer moving parts.
• Go with Option 2 if you need the Load form to remain open for repeated selections. It’s more flexible for dynamic workflows.

Quick Notes: #

• Make sure your private variable m_currentProjectName is properly declared in MainWindow.h (e.g., private: QString m_currentProjectName;).
• When populating the combo box, replace the hardcoded items with your actual database query logic to load existing projects.
• For non-modal dialogs, add loadDialog->setAttribute(Qt::WA_DeleteOnClose); to auto-clean up memory when the dialog closes.

内容的提问来源于stack exchange，提问作者Nico KTMamuang