Xamarin Forms Android OnAppearing 在 PopModalAsync 后不触发

Question

是否有解决方法可以解决在仍然使用模态页面时调用 PopModalAsync 后 Android 不触发的问题。这是一个例子:

using System;
using Xamarin.Forms;

namespace XamarinForms
{
    public class OnAppearingBug : ContentPage
    {
        Label label;
        public OnAppearingBug ()
        {
            label = new Label {
                Text = "Page"
            };
            Button button = new Button {
                Text = "PushModal"
            };
            button.Clicked += (sender, e) => Navigation.PushModalAsync (new PopModalBug ());

            Content = new StackLayout {
                Children = { label, button }
            };
        }
        protected override void OnAppearing(){
            label.Text = "OnAppearing";
        }
    }
}

using System;
using Xamarin.Forms;

namespace XamarinForms
{
    public class PopModalBug : ContentPage
    {
        public PopModalBug ()
        {
            Button button = new Button {
                Text = "Pop Back"
            };
            //Bug: This will not trigger OnAppearing on Android
            button.Clicked += (sender, e) => Navigation.PopModalAsync();

            Content = new StackLayout {
                Children = { button }
            };
        }
    }
}

Answer 1

另请参阅http://forums.xamarin.com/discussion/21417/navigationpage-push-pop-event-sequence-different-across-platforms和 http://forums.xamarin.com/discussion/18781/ios-and-android-different-behaviors-for-onappearing

但目前(Xamarin.Forms 1.2.2)唯一/最好的解决方案是上面 CrisWebb 提出的解决方案:

在您的主页上 - MessagingCenter.Subscribe(这个, "弹出", (发件人) => { //要运行的代码 });

在您的模态页面上 - MessagingCenter.Send(this, "弹出");