how to set event handler Click for many buttons in xamarin android

Question

Hello

I display the content of a table in a gridview

I have an xml (grid layout) containing a button and sommes text view .

Also a base adapter class to show a list of record. for each record i display a button

This is what i display

Header 1 Header 2
text text button
text text button	|

i can have many rows according to the table

i try to set a event handler click for each button

if i write

private List< Button>  buttons = new List<Button>();
Button abutton;
            for(int i = 0; i < 10; i++) 
            {
               abutton = new Button(this);
                abutton = FindViewById<Button>(Resource.Id.buttons);
                buttons.Add (abutton);
            }
foreach (var item in buttons)
            {
                item.Click += Buttons_Click;
            }

i get an system null reference exception at line item.Click += Buttons_Click;

i think because this line abutton = FindViewById<Button>(Resource.Id.buttons);

Thanks

Answer 1

Hello,

i can't tell it can be 1 or 5 or10

Based on your needs, you do not need to reuse items and return the view directly, I removed reuse convertview code like following code.

The goal is to insert in database data (name birthdate ...) about persons and then displays in gridview and for each row a button and click will show data of the person if i have to update

If you need to insert items in the Gridview, you can invoke adapter.NotifyDataSetChanged(); method after inserting data to the List<Classdatabirth>.

If you need to update items in the Gridview when you click item, I write a simple code to update item in the following code.

public override View GetView(int position, View convertView, ViewGroup parent)
        {       
            var item = listbirthdate[position];
            View view = convertView;
            LayoutInflater inflater = (LayoutInflater)context.GetSystemService(Context.LayoutInflaterService);
            view = inflater.Inflate(Resource.Layout.tablebirthdate, null);


           //if (view == null) // otherwise create a new one
            //{
            //    // Create a new ViewHolder object
               
            //    LayoutInflater inflater = (LayoutInflater)context.GetSystemService(Context.LayoutInflaterService);
            //    view = inflater.Inflate(Resource.Layout.tablebirthdate, null);   
            //}
            //else
            //{
              
            //    view = convertView;
            //}

            view.FindViewById<TextView>(Resource.Id.tablenamebirth).Text = item.namebirth;
            view.FindViewById<TextView>(Resource.Id.tablesurname).Text = item.surname;
            view.FindViewById<TextView>(Resource.Id.tabledatebirth).Text = item.datebirth;
            view.FindViewById<TextView>(Resource.Id.tableremain).Text = item.remain;
           Button button1 = view.FindViewById<Button>(Resource.Id.button1);
            button1.Click += (o, e) =>
            {
                //if I need to change the namebirth when I click the button, set it and invoke  NotifyDataSetChanged(); method
                listbirthdate[position].namebirth="1233333444421";
                NotifyDataSetChanged();           
            };
            return view;
        }

Best Regards,

Leon Lu

---

If the answer is the right solution, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

Answer 2

Maybe i found

In the Class adapter at the

public override View GetView(int position, View convertView, ViewGroup parent)
{
     var btn = view.FindViewById<Button>(Resource.Id.buttons);
            btn.Click += Btn_Click;
private void Btn_Click(object sender, EventArgs e)
        {
            
          }

It'works