Unity中AddListener绑定EventManager委托事件报错，求正确格式

Hey there! Let's break down why you're hitting that error and fix your code step by step.

Your issue stems from two key misunderstandings:

1. You can't directly call an event like a regular method: EventManager.OnGenerateNewDriftSetClicked is defined as an event, not a standard method. Events only support += (subscribe) or -= (unsubscribe) operations from outside their defining class—direct invocation like you tried isn't allowed.
2. Unity Button's onClick expects a parameterless delegate: The AddListener method for UI Buttons requires an Action (a delegate with no parameters), but your event uses a delegate that takes two parameters (int and string). These don't match directly.

Here's the corrected way to hook up your button click to trigger the event:

public void AddListeners() 
{
    // Use a lambda expression to wrap the event trigger logic, matching Button's parameterless requirement
    newDriftBtn.onClick.AddListener(() => 
    {
        // Safely invoke the event with your parameters (null check avoids crashes if no subscribers exist)
        EventManager.OnGenerateNewDriftSetClicked?.Invoke(driftNumSteps, driftName);
    });
}

Key Notes: #

• The ?.Invoke() syntax is crucial: If no scripts have subscribed to OnGenerateNewDriftSetClicked (e.g., if GenerateNewDrift is disabled), calling Invoke() directly would throw a null reference error. The ?. operator checks if the event has subscribers first.
• Your existing code in EventManager.cs and GenerateNewDrift.cs is correct! The +=/-= logic in GenerateNewDrift properly subscribes/unsubscribes to the event, and it will receive the driftNumSteps and driftName parameters when the event is triggered.

For better encapsulation, you can add a dedicated method in EventManager to handle triggering the event, instead of invoking it directly from outside the class:

Updated EventManager.cs #

public class EventManager : MonoBehaviour 
{
    public delegate void GenerateNewDriftSetHandler(int steps, string title);
    public static event GenerateNewDriftSetHandler OnGenerateNewDriftSetClicked;

    // Public static method to safely trigger the event
    public static void TriggerGenerateNewDriftSet(int steps, string title)
    {
        OnGenerateNewDriftSetClicked?.Invoke(steps, title);
    }
}

Updated GameManager.cs #

public void AddListeners() 
{
    newDriftBtn.onClick.AddListener(() => 
    {
        EventManager.TriggerGenerateNewDriftSet(driftNumSteps, driftName);
    });
}

This keeps all event-related logic contained within EventManager, making your code easier to maintain and follow.

内容的提问来源于stack exchange，提问作者greyBow