为什么我的 Presenter 没有订阅我的 WinForms 项目中的 View 事件？

Question

我正在尝试将 MVP 模式实施到我的 WinForms 项目中。但是，我的 Presenter 中的方法 'Activate' 从我的视图订阅了我的 'ActivatedForm' 事件，当我加载表单时似乎没有触发。我只是通过在 'Activate' 方法中打印一些东西来测试它。为什么这不能正常工作？

我已经在下面发布了我的代码。

我认为这与我创建带有具体视图的演示者有关，即使_view 属性是接口类型'IHomeScreenView'。我知道 'HomeScreenView_Activated' 事件发生了，因为我也在那里放了一个打印件并且有效。 'ActivatedForm' 事件总是 returns null，这意味着没有任何内容订阅该事件。

IHomeScreenView.cs

public interface IHomeScreenView
{
    List<string> ExistingAssessments { get; set; }

    event EventHandler<EventArgs> ActivatedForm;
    event EventHandler<EventArgs> CreatingNewAssessment;
    event EventHandler<EventArgs> AddingNewStandard;
    event EventHandler<EventArgs> OpeningAssessment;
}

HomeScreenView.cs

public partial class HomeScreenView : Form, IHomeScreenView
{
    private HomeScreenPresenter homeScreenPresenter;

    public List<string> ExistingAssessments
    {
        get { return recentAssessments.Items.Cast<string>().ToList(); }
        set { recentAssessments.DataSource = value; }
    }

    public event EventHandler<EventArgs> ActivatedForm;
    public event EventHandler<EventArgs> CreatingNewAssessment;
    public event EventHandler<EventArgs> AddingNewStandard;
    public event EventHandler<EventArgs> OpeningAssessment;

    // Initialize homescreen.
    public HomeScreenView()
    {
        InitializeComponent();
    }

    // Fires the activating form event.
    private void HomeScreenView_Activated(object sender, EventArgs e)
    {
        ActivatedForm?.Invoke(this, EventArgs.Empty);
    }

HomeScreenPresenter.cs

public class HomeScreenPresenter
{
    private IHomeScreenView _view;
    private AssessmentsModel _assessmentsModel;

    public HomeScreenPresenter(IHomeScreenView view)
    {
        _assessmentsModel = new AssessmentsModel();
        _view = view;
        _view.ActivatedForm += Activate;
        _view.CreatingNewAssessment += CreateNewAssessment;
        _view.AddingNewStandard += AddNewStandard;
        _view.OpeningAssessment += OpenAssessment;
    }

    public void Activate(object sender, EventArgs e)
    {
        Debug.Print("hi");
        HashSet<string> items = new HashSet<string>(_assessmentsModel.GetDataList("Assessments", "assessment_name"));
        List<string> assessments = items.ToList();

        _view.ExistingAssessments = assessments;
    }

希望有人能帮忙，谢谢

Answer 1

Form.Activated 事件仅在表单可见时触发。参见 the documentation。

When the application is active and has multiple forms, the active form is the form with the input focus. A form that is not visible cannot be the active form. The simplest way to activate a visible form is to click it or use an appropriate keyboard combination.

如果创建演示者时您的表单已经可见，则激活事件已经触发。一旦创建了演示者并连接了事件处理程序，您就可以调用 Form.Activate()。

为什么我的 Presenter 没有订阅我的 WinForms 项目中的 View 事件？

Why is my Presenter not subscribed to my View event in my WinForms project?

c#

mvp

events

design-patterns

winforms