Change value in a list during runtime

Hello everyone,

I have a button and a list displayed. When clicking on the button, I want to change the value of a specific item within that list. Please see following aimed output example:

[Program Start]

Item Name	Value
Item Number 1	Original Value
Item Number 2	Original Value
Item Number 3	Original Value

[Button Click]

Item Name	Value
Item Number 1	Original Value
Item Number 2	Changed Value
Item Number 3	Original Value

So how can I do this? What does my `private void OnButtonClick(object sender, EventArgs e)` have to look like? How can I access a specific entry in that list?

To be better able to help me, I will share my code following:

public class MyActivity : Activity
{
List List = null;
protected override void OnCreate(Bundle bundle)
{
base.OnCreate(bundle);
SetContentView(Resource.Layout.MyActivity);
List = PopulateList();
var lv = FindViewById(Resource.Id.list);
var adapter = new ListAdapter(this, Resource.Layout.List, List);
lv.Adapter = adapter;
FindViewById(Resource.Id.button).Click += OnButtonClick;
}
}

class ListAdapter : ArrayAdapter
{
List List;
public ListAdapter(Context Context, int ListId, List List) : base(Context, ListId, List)
{
this.List = List;
}
public override int Count
{
get { return List.Count; }
}
public override View GetView(int position, View convertView, ViewGroup parent)
{
View v = convertView;
if (v == null)
{
LayoutInflater inflater = (LayoutInflater)Context.GetSystemService(Context.LayoutInflaterService);
v = inflater.Inflate(Resource.Layout.List, parent, false);
}
v.FindViewById(Resource.Id.name).Text = List[position].Name;
v.FindViewById(Resource.Id.value).Text = "Original Value";
return v;
}
}

Using following *.axml-files:

"utf-8"?>
xmlns:android ="http://schemas.android.com/apk/res/android"
android:orientation ="vertical"
android:layout_width ="match_parent"
android:layout_height="match_parent">
android:layout_width ="match_parent"
android:layout_height="wrap_content"
android:text="Click Me"
android:id="@+id/button" />
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/list" />

"utf-8"?>
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
android:id="@+id/name"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
android:id="@+id/value"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />

When simply doing

private void OnButtonClick(object sender, EventArgs e)
{
FindViewById(Resource.Id.value).Text = "Changed Value";
}

only the first item changes. So how to pass the position through the adapter? Can anyone maybe help?

Thanks in advance,

Best regards

Edit: I found out that I have to do `adapter.NotifyDataSetChanged();` somewhere in the end. But when adding this, unfortunately nothing happens anymore when clicking the button.

1 Reply

Know the answer? Post it — somebody with the same question will find it here.

Jefferson S. Motta7y ago
Look the source code:

https://pt.stackoverflow.com/questions/275825/findviewbyid-com-uma-variável-dentro-do-método

It is necessary to pass the ID (which is an int), to capture the View via the findViewById method, but you can use a similar method. With findViewWithTag you can capture the views that have a tag. Just add the android: tag = "custom" attribute in your view. Ex:
0