C# 如何使用MVP处理表单关闭

下面是：

我有这样一个观点：

public interface IAddressView
{
     void Close();
     bool IsDirty();
     bool DoesUserWantToDiscardChanges();
}

public class AddressViewPresenter
{
    private IAddressView m_addressView;
    private Address m_address;

    public AddressViewPresenter(IAddressView addressView)
    {
        m_addressView = addressView;
        m_address = new Address();
    }

    public void CancelButtonClicked()
    {
        bool canClose = true;

        if (m_addressView.IsDirty())
        {
            canClose = m_addressView.DoesUserWantToDiscardChanges();
        }

        if (canClose)
        {
            m_addressView.Close();
        }
    }

    public void SaveButtonClicked()
    {
        // saving logic goes here...removed for brevity
        m_addressView.Close();
    }
}

public bool ViewRequestingClose()
{
    bool canClose = true;
    if (m_addressView.IsDirty())
    {
        canClose = m_addressView.DoesUserWantToDiscardChanges();
    }
    return canClose;
}

我的演示者如下所示：

public interface IAddressView
{
     void Close();
     bool IsDirty();
     bool DoesUserWantToDiscardChanges();
}

public class AddressViewPresenter
{
    private IAddressView m_addressView;
    private Address m_address;

    public AddressViewPresenter(IAddressView addressView)
    {
        m_addressView = addressView;
        m_address = new Address();
    }

    public void CancelButtonClicked()
    {
        bool canClose = true;

        if (m_addressView.IsDirty())
        {
            canClose = m_addressView.DoesUserWantToDiscardChanges();
        }

        if (canClose)
        {
            m_addressView.Close();
        }
    }

    public void SaveButtonClicked()
    {
        // saving logic goes here...removed for brevity
        m_addressView.Close();
    }
}

public bool ViewRequestingClose()
{
    bool canClose = true;
    if (m_addressView.IsDirty())
    {
        canClose = m_addressView.DoesUserWantToDiscardChanges();
    }
    return canClose;
}

然后我有一个windows窗体，它有一个取消按钮、一个保存按钮和所有显示地址的控件。“取消”按钮运行：

m_addressPresenter.CancelButtonClicked();

然后检查视图是否脏，并提示用户放弃任何更改。这太好了，这正是我想要的

现在我的问题是，如果用户关闭表单而不单击取消（即，他们单击右上角的“X”，甚至单击ALT+F4），如何实现同样的效果。我曾尝试处理FormClosing事件，但最终复制了一些代码，如果单击“取消”按钮，弹出窗口会出现两次。以下是我所拥有的：

private void AddressForm_FormClosing(object sender, FormClosingEventArgs e)
{
    if (this.IsDirty())
    {
        if (!this.DoesUserWantToDiscardChanges())
        {
            e.Cancel = true;
        }
    }
}

---

您遇到的主要问题是视图包含演示者负责的逻辑，因此我将演示者上的CancelButtonClicked方法更改为类似以下内容：

public interface IAddressView
{
     void Close();
     bool IsDirty();
     bool DoesUserWantToDiscardChanges();
}

public class AddressViewPresenter
{
    private IAddressView m_addressView;
    private Address m_address;

    public AddressViewPresenter(IAddressView addressView)
    {
        m_addressView = addressView;
        m_address = new Address();
    }

    public void CancelButtonClicked()
    {
        bool canClose = true;

        if (m_addressView.IsDirty())
        {
            canClose = m_addressView.DoesUserWantToDiscardChanges();
        }

        if (canClose)
        {
            m_addressView.Close();
        }
    }

    public void SaveButtonClicked()
    {
        // saving logic goes here...removed for brevity
        m_addressView.Close();
    }
}

public bool ViewRequestingClose()
{
    bool canClose = true;
    if (m_addressView.IsDirty())
    {
        canClose = m_addressView.DoesUserWantToDiscardChanges();
    }
    return canClose;
}

返回值指示视图是否应继续关闭

视图中“取消”按钮单击和表单关闭事件的两个事件处理程序随后将查询演示者，查看它们是否应继续关闭，例如

private void AddressForm_FormClosing(object sender, FormClosingEventArgs e)
{
    if(!m_addressPresenter.ViewRequestingClose())
        e.Cancel = true;
}

private void CancelButton_Click(object sender, FormClosingEventArgs e)
{
    if(m_addressPresenter.ViewRequestingClose())
        this.Close();
}

---

我知道这已经很老了，但一开始我觉得这对我来说也是一件令人困惑的事情。我就是这样处理的。希望有人会发现这很有用

在视图的界面中

public interface IMainScreenView
{
    event BoolHandler CloseView;

    bool IsDirty { get; set; }
    bool WillDiscardChanges();
}

然后在演示者中，将关闭功能订阅到CloseView事件

public MainScreenPresenter(IView _view)
{
    _view.CloseView += Close;
}

private bool Close()
{
    bool close = true;

    if (_view.IsDirty)
        close = _view.WillDiscardChanges();

    return close;
}     

public MainForm()
{
    InitializeComponent();

    _presenter = new MainScreenPresenter(this);
    FormClosing += UxMainScreenFormClosing;
}

public bool WillDiscardChanges()
{
    return MessageBox.Show("Changes have been made without being saved. Would you like to continue?", "Exiting", MessageBoxButtons.YesNo) == DialogResult.Yes;
}

protected void UxMainScreenFormClosing(object sender, FormClosingEventArgs e)
{
    e.Cancel = !CloseView();
}

现在，在视图本身中，您可以像往常一样订阅FormClosing事件并使用CloseView事件

public MainScreenPresenter(IView _view)
{
    _view.CloseView += Close;
}

private bool Close()
{
    bool close = true;

    if (_view.IsDirty)
        close = _view.WillDiscardChanges();

    return close;
}     

public MainForm()
{
    InitializeComponent();

    _presenter = new MainScreenPresenter(this);
    FormClosing += UxMainScreenFormClosing;
}

public bool WillDiscardChanges()
{
    return MessageBox.Show("Changes have been made without being saved. Would you like to continue?", "Exiting", MessageBoxButtons.YesNo) == DialogResult.Yes;
}

protected void UxMainScreenFormClosing(object sender, FormClosingEventArgs e)
{
    e.Cancel = !CloseView();
}

---

除了完整性之外，没有其他原因，我也包括了放弃更改检查。这样可以使视图保持干净，并将逻辑隐藏在演示者中。我希望这能有所帮助

如果有人遇到这种情况，想要一个简单的解决方案

如果演示者创建了视图的实例，然后将其打开，请将其放入演示者的构造函数中：

form1.FormClosed += OnFormClose; //form1 is the name of the form that the presenter opens

和下面的处理程序：

private void OnFormClose(object sender, EventArgs e)
        {
            Application.Exit();
        }

---

这样做更有意义。但是，我仍然遇到这样的问题：当您单击“取消”按钮时，它会两次询问您是否要放弃更改。您会收到双重提示，因为当确认取消时，它将关闭表单，其逻辑与仅尝试关闭表单时的逻辑相同。您可以使用bool来跟踪关闭是从Alt+F4/“x”单击还是取消单击开始的，并且只在第一次通过时提示。是的。我只是希望能有不同的做法。它的工作原理与您描述的一样，如果我添加bool来跟踪关闭是否来自取消按钮。我想这样使用bool感觉有点“笨拙”。我想如果成功了，它也会成功。谢谢。为什么不干脆

this.Close（）在
取消按钮中单击
？它的效果与使用布尔值表示关闭来自
CancelButton\u单击