convert Java.Lang.Object to .net type

I'm trying to cast a spinner.SelectedItem to string in monodroid. Since SelectedItem is a Java.Lang.Object, I need to know how can I cast a Java.Lang.Object to a native .net type. 开发者_JAVA百科Thank you, Alex

You didn't provide any context into what you're binding to the spinner, but I'm assuming it's just a list of strings? If that's the case, one possibility is to just do

spinner.SelectedItem.ToString()

That won't be very useful if the underlying object is not a string, though. You have some other options available as well. You can use spinner.SelectedItemPosition to get the item out of the spinner adapter's source. Something like:

var source = new List<string> { "a", "b", "c" };
spinner.Adapter = new ArrayAdapter<string>(this, Resource.Layout.Item, Resource.Id.Name, source);
var selectedString = source[spinner.SelectedItemPosition];

You could also do:

var selectedString = spinner.GetItemAtPosition[spinner.SelectedItemPosition].ToString();

It all depends on what you're trying to do and when. Xamarin has a tutorial up here that goes through the basics of using a spinner.

http://docs.xamarin.com/android/advanced_topics/architecture

This is a link to Xaramin's documentation for Mono's runtime architecture, which doesn't not directly answer the java to .net "casting" issue, it is certainly a starting point (and is where I stand myself in searching and producing solution).

I'll post anything useful if/when I come up with something.

I have a similar problem; particularly because I have a DataLayer PCL which I want to share between the various platforms. And I don't want to transform my DataLayer objects each time into a Java object, or an IOS object etc...

So, for the Android solution, this Wrapper/Decorator pattern has worked nicely;

1. Imagine you have your PCL object

   public class GoldList
   {
       public string UniqueId { get; set; }
       public string Name { get; set; }
       public string Owner { get; set; }
   
       public GoldList()
       {
       }
   }
   

2. Create an IJavaWrapper interface and JavaWrapper object which inherits from Java.Lang.Object:

   public abstract class JavaWrapper<T> : Java.Lang.Object, IJavaWrapper
   {
       private readonly T _item;
   
       protected JavaWrapper(T item)
       {
           _item = item;
       }
   
       public T Item
       {
           get { return _item; }
       }
   
       object IJavaWrapper.Item
       {
           get { return _item; }
       }
   }
   
   public interface IJavaWrapper
   {
       object Item { get; }
   }
   

3. Create a concrete instance of this; wrapping your data object

   class GoldListJO : JavaWrapper<GoldList>
   {
       public GoldListJO() : this(new GoldList())
       {
       }
   
       public GoldListJO(GoldList item) : base(item)
       {
       }
   }
   

4. Bind to the items (using example code):

   List<GoldListJO> items = new List<GoldListJO>();
   items.Add(new GoldListJO(new GoldList { Name = "1", UniqueId = "U1", Owner = "O1" }));
   items.Add(new GoldListJO(new GoldList { Name = "2", UniqueId = "U2", Owner = "O2" }));
   items.Add(new GoldListJO(new GoldList { Name = "3", UniqueId = "U3", Owner = "O3" }));
   list.SetAdapter(new GoldListAdapter(items));
   

5. When you call "GetItem" and it returns a Java.Lang.Object, no problem, just refer to the .Item:

   GoldListJO item = (GoldListJO)GetItem(position);
   
   vh.txtName.Text = item.Item.Name;
   vh.txtUniqueId.Text = Java.Lang.String.Format("UniqueId: %s", item.Item.UniqueId);
   vh.txtOwner.Text = Java.Lang.String.Format("Owner: %s", item.Item.Owner);