Unity. how can I get Touch by fingerID?

Question

We have the index of the touches and method Input.GetTouch(int index) which returns Touch. Also we have fingerID property of Touch structure. How can we get a Touch by fingerID?

Answer 1

For getting a specific touch by ID you have to search for it in the existing touches.

private static bool TryGetTouch(int fingerID, out Touch touch)
{
    foreach(var t in Input.touches)
    {
        if(t.fingerID == fingerID)
        {
            touch = t;
            return true;
        }
    }

    // No touch with given ID exists
   touch = default;
   return false;
}

You can also use linq and do e.g.

using System.Linq;

...

private static bool TryGetTouch(int fingerID, out Touch touch)
{
    try
    {
        touch = Input.touches.First(t => t.fingerID == fingerID);
        return true;
    }
    catch
    {
       // No touch with given ID exists
       touch = default;
       return false;
    }
}

and use it like

if(TryGetTouch (someFingerID, out var touch))
{
    // use touch here
}
else
{
    // probably use a new touch and store its fingerID 
}