ActionListener 应该驻留在 MVC 架构中的什么位置？

MVC and GUI: Where do ActionListeners belong according to MVC pattern?

Background:

As you mentioned, this question relates to the placement of ActionListeners in the Model-View-Controller (MVC) architectural pattern. Swing, used for creating GUIs in Java, doesn't strictly follow MVC.

Placement of ActionListeners:

1. View Responsibility:

Technically, the View should be responsible for maintaining ActionListeners attached to UI controls. The View should then inform the Controller about actions taken. This way, the Controller is isolated from UI components and can work with any implemented View.

2. Dedicated View Listener:

Instead of直接将 ActionListeners 附加到 UI 控件中，您还可以创建一个专门的 View Listener。此侦听器将描述视图可能产生的操作，例如：

public interface MainViewListener {
    void didPerformClose(MainView mainView);
}

The Controller would then subscribe to the View via this listener, and the View would call didPerformClose when the close button is pressed.

Managing Inter-Layer Communication:

Ideally, layers in an MVC architecture should communicate via interfaces. This establishes loose coupling, allowing layers to be replaced independently. You want to minimize the awareness each layer has about the others.

Updated Example:

Login View Example with Loose Coupling:

Consider a login example, where the CredentialsView and LoginView have specific responsibilities:

CredentialsView:

• Gathers credentials (username and password)
• Notifies the controller when credentials change
• Disables/enables fields during authentication

LoginView:

• Manages the CredentialsView
• Notifies the controller of authentication requests/cancels
• Dismisses the view on successful/failed authentication

By using interfaces for communication, both views and the controller can be easily replaced or updated without breaking the system.

ActionListeners Placement:

In the updated example, the ActionListeners for the authenticate and cancel buttons are still in the LoginView. However, the LoginView acts as both the controller for the CredentialsView and the view for the LoginViewController. This approach simplifies the logic while maintaining a clear separation of responsibilities.

In Conclusion:

• ActionListeners应该由View维护，通知Controller动作。
• 层之间的通信应该通过接口来促进松散耦合。
• 仔细设计视图职责，控制器职责和层间通信有助于维护 MVC 模式的完整性。

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