多窗体关联问题：调用Main Form的changedLanguages()方法后界面不更新求助

Hey there! Let's break down why your existing Main Form isn't updating when you trigger changedLanguages() from the Languages Form, and why calling mus.Show() opens a new window instead. The core problem here is you're working with a new instance of Main Form instead of the already open one. Here's how to fix it:

1. Pass the Existing Main Form Instance to Languages Form #

Instead of creating a new Main Form when you need to call changedLanguages(), pass the currently open Main Form instance to your Languages Form when you launch it. This way, you can reference the exact window that's already visible.

Step 1: Update Languages Form's Constructor #

Add a constructor to your Languages Form that accepts a Main Form instance and stores it:

private MainForm _activeMainForm;

// Constructor for Languages Form
public LanguagesForm(MainForm mainForm)
{
    InitializeComponent();
    _activeMainForm = mainForm; // Save the reference to the open Main Form
}

Step 2: Launch Languages Form From Main Form With the Instance #

When you open the Languages Form from Main Form (e.g., via a settings button), pass this (the current Main Form instance) to the constructor:

// Inside Main Form code, when opening Languages Form
var languagesForm = new LanguagesForm(this);
languagesForm.Show();

Step 3: Call the Method on the Existing Instance #

Now, when you click the language icon in Languages Form, use the stored reference to call changedLanguages()—no new window needed:

// Inside Languages Form's language icon click event
private void languageIcon_Click(object sender, EventArgs e)
{
    // Call the method on the already open Main Form
    _activeMainForm.changedLanguages();
}

2. Ensure changedLanguages() Actually Updates the UI #

Double-check that your changedLanguages() method is directly modifying the UI elements in Main Form. For example:

// Inside Main Form's changedLanguages() method
public void changedLanguages() // Make sure this method is public or internal
{
    // Update labels, buttons, etc., with the new language values
    lblGreeting.Text = Languages.GetTranslation("Greeting");
    btnSettings.Text = Languages.GetTranslation("Settings");
    txtStatus.Text = Languages.GetTranslation("LanguageUpdated");
    
    // If needed, force a refresh (usually not required if you set properties directly)
    this.Refresh();
}

Note: If your language loading happens on a background thread, you'll need to use Invoke to update the UI safely (WinForms requires UI changes on the main thread):

public void changedLanguages()
{
    if (this.InvokeRequired)
    {
        this.Invoke(new Action(changedLanguages));
        return;
    }
    // Update UI elements here
}

3. Avoid the "New Instance" Mistake #

The reason mus.Show() opens a new window is because you're creating a fresh MainForm object with new MainForm(). This is a completely separate window from the one that's already open—so calling methods on it won't affect your original form. Always reference the existing instance instead of creating a new one.

Quick Recap #

• Pass the open Main Form instance to Languages Form via its constructor
• Store that instance and use it to call changedLanguages()
• Make sure changedLanguages() directly updates your UI elements
• Never create a new MainForm instance when you need to modify the existing one

内容的提问来源于stack exchange，提问作者Nunix Monteiro