Pass data back from Maui shell navigation - maui

Question

The App navigates to a view in which the user selects an item on a CollectionView and then navigates back. How do I get the SelectedItem on the page that initiated the navigation?
await Shell.Current.GoToAsync("//SelectAnItem");
//Get the selected item

Answer 1

The App navigates to a view in which the user selects an item on a
CollectionView and then navigates back.
There are several ways to achieve this.
Method 1:A common approach is to use EventHandler.
You can define EventHandler in this view(Suppose the name is SelectedPage), just as follows:
public static EventHandler<Item> mEventHandler; // define a static EventHandler
After you select an item, you can pass the selected item with the following code:
private void Button_Clicked(object sender, EventArgs e)
{
EventHandler<Item> handler = mEventHandler;
if (handler != null)
{
Item item = new Item { Name= "Hello." };
mEventHandler(this, item);
}
Navigation.PopAsync();
}
In the previous page, you can add the following code in the constructor of YourPreviousPage :
SelectedPage.mEventHandler += delegate (object s, Item a)
{
BackCall(s, a);
};
And the code of function BackCall is:
private void BackCall(object send, Item a)
{
if (a == null)
{
throw new ArgumentNullException(nameof(a));
}
else {
DisplayAlert("Alert", "call back value is : " + a.Name, "OK");
}
}
method 2
You can also use MessagingCenter to achieve this function.
Please refer to the following code:
public partial class PreviousPage: ContentPage
{
public PreviousPage()
{
InitializeComponent();
// method 2
MessagingCenter.Subscribe<SelectedPage, Item>(this, "SelectedItem", (obj, item) =>
{
var newItem = item as Item;
DisplayAlert("Alert", "call back value is : " + newItem.Name, "OK");
});
}
}
SelectedPage.xaml.cs
private void Button_Clicked(object sender, EventArgs e)
{
Item item = new Item { Name = "Hello." };
MessagingCenter.Send(this, "SelectedItem", item);
Navigation.PopAsync();
}