Using Delegate Callback to pass value from the Rg pop up window to the parent.

[msmrajesh]

Hi,

I am having a situation similar to this #14

I have a Entry control on a content form and on tap event I am showing the Rg pop up window.

In this Rg pop up window I have a listview that is populated from a database. When the user selects a value from the listview, I want to pass this selected value back to the content form. As suggested by you in the thread mentioned above , I am using call back delegates to pass the value.

This is how i defined the code.

Content form that hosts the entry control.

   `//Declaring the delegate to pass the value from SearchPicker to the control that calls it
    public delegate void AddItemDelegate(string item);
  //handle the tap event of the entry control.
   var frmSearchPicker = new SearchPicker(passvalue);
   frmSearchPicker.AddItemCallback = new AddItemDelegate(this.AddItemCallBackFn);
   Navigation.PushPopupAsync(new SearchPicker(passvalue));`

Rg Popup control that hosts the listview

public MainForm.AddItemDelegate AddItemCallback;      

//the tap event of the listview control inside the Rg popup control.
private void listView_OnSelected(Object sender, SelectedItemChangedEventArgs args)
        {
            if(args.SelectedItem != null)
            {
                Country itm = (Country)args.SelectedItem;
                getSelectedCountry = itm.Name.ToString();
                AddItemCallback(getSelectedCountry);
                //AddItemCallback?.Invoke(getSelectedCountry);
            }
        }

The problem is that the debugger breaks on the line

AddItemCallback(getSelectedCountry); with this exception.

System.NullReferenceException: Object reference not set to an instance of an object.

Please let me know how to make it work correctly so that I can pass the value from the Rg popup control back to the parent form that calls it.

Thanks,

Rajesh.

[rotorgames]

@msmrajesh Hi. You have created new contructor for PushPopupAsync it is problem.

try it:

var frmSearchPicker = new SearchPicker(passvalue);
 frmSearchPicker.AddItemCallback = new AddItemDelegate(this.AddItemCallBackFn);
 Navigation.PushPopupAsync(frmSearchPicker);`

[msmrajesh]

Hi @rotorgames Thanks a lot for helping out.
Rajesh.