android - Xamarin - 在 Navigation.PopModalAsync() 后重新加载页面

Question

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，它会打开一个模态框，然后在模态框上选择一个按钮后，它会更新一些信息，然后我需要关闭 Modal 并重新加载其下的主页。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));
    }

}

二级页面:

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();
    }

}

因此，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。这可能吗？

Answer 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
    }
}