Multi Select Spinner Xamarin Android

Question

I am using a spinner and an arrayAdapter to populate items in spinner. I want to make the spinner multi-selectable but I just select one row.I searched in Google, solution available in Java, but i don't have any idea on how to implement it in Xamarin.

My code is as below,

adapterList= new ArrayAdapter<string>(this, Android.Resource.Layout.SimpleListItemMultipleChoice);

spnMultiTest.Adapter = adapterList;

Answer 1

I want to make the spinner multi-selectable but I just select one row.I searched in Google, solution available in Java, but i don't have any idea on how to implement it in Xamarin.

Basically I just translate the codes from Android Spinner with multiple choice to Xamarin codes. I have tested it and it works fine:

1. MultiSpinner.cs:

   public interface MultiSpinnerListener
   {
       void onItemsSelected(bool[] selected);
   }
   public class MultiSpinner : Spinner, IDialogInterfaceOnMultiChoiceClickListener, IDialogInterfaceOnCancelListener
   {
       Context _context;
   
       private List<String> items;
       private bool[] selected;
       private String defaultText;
       private MultiSpinnerListener listener;
   
       public MultiSpinner(Context context) : base(context)
       {
           _context = context;
       }
   
       public MultiSpinner(Context context, IAttributeSet arg1) : base(context, arg1)
       {
           _context = context;
      }
   
       public MultiSpinner(Context context, IAttributeSet arg1, int arg2) : base(context, arg1, arg2)
       {
           _context = context;
       }
   
   
       public  void OnClick(IDialogInterface dialog, int which, bool isChecked)
       {
           if (isChecked)
               selected[which] = true;
           else
               selected[which] = false;
       }
   
       public override void OnClick(IDialogInterface dialog, int which)
       {
           dialog.Cancel();
       }
   
   
       public override bool PerformClick()
       {
           AlertDialog.Builder builder = new AlertDialog.Builder(_context);
           builder.SetMultiChoiceItems(
                   items.ToArray(), selected, this);
   
           builder.SetPositiveButton("OK",this);
           builder.SetOnCancelListener(this);
           builder.Show();
           return true;
       }
   
   
       public void SetItems(List<String> items, String allText,
           MultiSpinnerListener listener)
       {
   
           this.items = items;
           this.defaultText = allText;
           this.listener = listener;
   
           // all selected by default
           selected = new bool[items.Count];
           for (int i = 0; i < selected.Length; i++)
               selected[i] = true;
           ArrayAdapter<string> adapter = new ArrayAdapter<string>(_context,Resource.Layout.simple_spinner_item,Resource.Id.tv_item,new string[] { allText });
           // all text on the spinner
           //ArrayAdapter<String> adapter = new ArrayAdapter<String>(_context,Resource.Layout.simple_spinner_item, new String[] { allText });
           Adapter = adapter;
       }
   
       public void OnCancel(IDialogInterface dialog)
       {
           Java.Lang.StringBuffer spinnerBuffer = new Java.Lang.StringBuffer();
           bool someUnselected = false;
           for (int i = 0; i < items.Count; i++)
           {
               if (selected[i] == true)
               {
                   spinnerBuffer.Append(items[i]);
                   spinnerBuffer.Append(", ");
               }
               else
               {
                   someUnselected = true;
               }
           }
           String spinnerText;
           if (someUnselected)
           {
               spinnerText = spinnerBuffer.ToString();
               if (spinnerText.Length > 2)
                   spinnerText = spinnerText.Substring(0, spinnerText.Length - 2);
           }
           else
           {
               spinnerText = defaultText;
           }
           ArrayAdapter<String> adapter = new ArrayAdapter<String>(_context,Resource.Layout.simple_spinner_item,Resource.Id.tv_item,new string[] { spinnerText });
           Adapter = adapter;
           if (listener != null)
           {
              listener.onItemsSelected(selected);
           }
   
       }
   
   
   }
   

2. simple_spinner_item.xml:

   <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
       android:orientation="vertical"
       android:layout_width="match_parent"
       android:layout_height="match_parent">
     <TextView
       android:id="@+id/tv_item"
       android:layout_width="match_parent"
       android:layout_height="wrap_content"
       />
   </LinearLayout>
   

Update:

Here is the codes for using this MultiSpinner:

Main.axml:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
  <MultiSpinner.MultiSpinner
    android:id="@+id/mSpinner"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    />
</LinearLayout>

MainActivity.cs:

public class MainActivity : Activity
{
    MultiSpinner mSpinner;
    protected override void OnCreate(Bundle savedInstanceState)
    {
        base.OnCreate(savedInstanceState);

        // Set our view from the "main" layout resource
        SetContentView(Resource.Layout.Main);
        mSpinner = FindViewById<MultiSpinner>(Resource.Id.mSpinner);
        List<string> items = new List<string> {
            "Android",
            "iOS",
            "UWP"
        };

        mSpinner.SetItems(items, "AllText", null);
    }
}