Longpress and list scrolling

Question

Using SwiftUI (latest XCode and testing on IOS 13.3) I'm trying to implement a long press gesture on items in a list, to allow user interaction with the individual items. The problem is that when I set "onLongPressGesture" anywhere in the list (on items, on the list itself), the list cannot be scrolled anymore. I can easily get a simple tap to work but a long press blocks scrolling.

I've put together a small example that show this issue:

struct ContentView: View
{
  let data = [
    "Test 1","Test 2","Test 3","Test 4","Test 5",
    "Test 6","Test 7","Test 8","Test 9","Test 10",
    "Test 11","Test 12","Test 13","Test 14","Test 15",
    "Test 16","Test 17","Test 18","Test 19","Test 20"
  ]

  var body: some View
  {
    List
    {
      ForEach(data,id:\.self)
      {
        item in
        Text(item).onLongPressGesture{}
      }
    }
  }
}

If I try to drag the list pressing on any text, the list wont move. If I remove the longpress handler, it moves no matter where I press down.

score 33 · Answer 1 · answered Dec 27 '19 at 11:10

I asked this on the Apple Developer Forum as well and got a solution for the problem. If the view defines an onTapGesture handler before onLongPressGesture, the list will be scrollable while supporting long press on the individual items.

The onTapGesture handler can be empty as long as it is declared first.

struct ContentView: View
{
  let data = [
    "Test 1","Test 2","Test 3","Test 4","Test 5",
    "Test 6","Test 7","Test 8","Test 9","Test 10",
    "Test 11","Test 12","Test 13","Test 14","Test 15",
    "Test 16","Test 17","Test 18","Test 19","Test 20"
  ]

  var body: some View
  {
    List
    {
      ForEach(data,id:\.self)
      {
        item in
        Text(item).onTapGesture{}.onLongPressGesture{}
      }
    }
  }
}

Unfortunately this seems to add quite a bit of delay before the long press gesture starts. Otherwise, it works. — Joey C., Nov 19 '20 at 23:06

score 5 · Answer 2 · answered Sep 15 '21 at 04:44

Referring @Jensrodi's solution as it works perfect, although you can experience a higher delay than what you would expect for a Long Press Gesture by adding a .onTapGesture before the .onLongPressGesture.

To mitigate this, you can use onLongPressGesture(minimumDuration:) to reduce/increase to a duration you are comfortable with.

See the example below

List {
    ForEach(0..<100) { x in
        Text("List number -\(x)")
            .onTapGesture{}.onLongPressGesture(minimumDuration: 0.2) { // Setting the minimumDuration to ~0.2 reduces the delay
                print("long press \(x)")
            }
    }
}

score 0 · Answer 3 · answered Dec 22 '19 at 10:46

0

I think you should dig around composing with combining gestures. Here you can see, how to compose two and more gestures, but in your case I think you need exclusive behavior (which is described in this article). So you can combine DragGesture and LongPressGesture but for ScrollView (I didn't found any solution for scrolling List). Here are example 1 and example 2 of how to control ScrollView.content.offset (for scrolling on DragGesture).

answered Dec 22 '19 at 10:46

Hrabovskyi Oleksandr

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Thanks for the suggestions, it makes for interesting reading and I will definitely look more as I may need this functionality in other areas later. However, I'm not really looking to implement multiple gestures for this. I would like the list view to handle the scrolling it self, giving the correct native feel. I can add an onTapGesture without that blocks the scrolling. But not if I try the long press gesture, which to me doesn't make sense. The basic difference between these two gestures is the time that the finger is pressed without moving. – jensrodi Dec 22 '19 at 22:55

Longpress and list scrolling

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