Xamarin - Navigation.PopModalAsync() 后重新加载页面答案

【问题标题】：Xamarin - Reload Page after Navigation.PopModalAsync()Xamarin - Navigation.PopModalAsync() 后重新加载页面
【发布时间】：2017-07-19 21:52:48
【问题描述】：

我正在使用 Xamarin 为 iOS 和 Android 创建一个应用程序，我有一个用例，我按下一个按钮，它将打开一个模态，然后在模态上选择一个按钮后，它会更新一些信息，然后我需要弹出模态并重新加载它下面的主页。这怎么可能？

主页：

public partial class MainPage : ContentPage
{
    public MainPage(Object obj)
    {

        InitializeComponent();

        // do some things with obj...

        BindingContext = this;

    }

    public ButtonPressed(object sender, EventArgs args)
    {
        Navigation.PushModalAsync(new SecondaryPage(newObj));
    }

}

次要页面：

public partial class SecondaryPage : ContentPage
{
    public SecondaryPage(Object newObj)
    {

        InitializeComponent();

        BindingContext = this;

    }

    public ButtonPressed(object sender, EventArgs args)
    {
        // Do something to change newObj

        Navigation.PopModalAsync();
    }

}

所以在 PopModalAsync() 之后，我需要能够调用 MainPage() 构造函数，但将我在 SecondaryPage 中更改的“newObj”传递给它。这甚至可能吗？

【问题讨论】：

要么将完成委托传递给您的模态，在它关闭时执行，要么使用 MessagingCenter 将消息从模态发送到主页

标签： android ios xamarin xamarin.forms navigation

【解决方案1】：

在 .Net 中执行此操作的正确方法是设置一个事件：

public partial class SecondaryPage : ContentPage
{
    public SecondaryPage(Object newObj)
    {

        InitializeComponent();

        BindingContext = this;

    }

    // Add an event to notify when things are updated
    public event EventHandler<EventArgs> OperationCompeleted;

    public ButtonPressed(object sender, EventArgs args)
    {
        // Do something to change newObj
        OperationCompleted?.Invoke(this, EventArgs.Empty);
        Navigation.PopModalAsync();
    }

}

public partial class MainPage : ContentPage
{
    public MainPage(Object obj)
    {

        InitializeComponent();

        // do some things with obj...

        BindingContext = this;

    }

    public ButtonPressed(object sender, EventArgs args)
    {
        var secondaryPage = new SecondaryPage(newObj);
        // Subscribe to the event when things are updated
        secondaryPage.OperationCompeleted += SecondaryPage_OperationCompleted;
        Navigation.PushModalAsync(secondaryPage);
    }

    private void SecondaryPage_OperationCompleted(object sender, EventArgs e)
    {
        // Unsubscribe to the event to prevent memory leak
        (sender as SecondaryPage).OperationCompeleted -= SecondaryPage_OperationCompleted;
        // Do something after change
    }
}

【讨论】：