Disable scrolling from bottom to top in swiftUI scroll view - ios

Question

In my iOS app (which is using SwiftUI) I am using a scroll view in which there is vertical scrolling. My issue is: I want to scroll only from top to bottom, and not bottom to top.
Is that possible?
Thank you.

Answer 1

Use LazyVGrid
and DragGesture
when changed, you only allow scroll to bottom.
struct ContentView: View {
#State private var offset: CGFloat = .zero
var columns: [GridItem] = Array(repeating: .init(.flexible()), count: 2)
var body: some View {
LazyVGrid(columns: columns) {
ForEach((0...79), id: \.self) {
let codepoint = $0 + 0x1f600
let codepointString = String(format: "%02X", codepoint)
Text("\(codepointString)")
let emoji = String(Character(UnicodeScalar(codepoint)!))
Text("\(emoji)")
}
}
.font(.largeTitle)
.offset(y: offset)
.gesture(DragGesture().onChanged {value in
let translation = value.translation.height
if translation < 1 {
offset = translation
}
})
}
}
Update
You need to track the last offset when scrolling and reset it to zero each time you stop scrolling. This fixes the issue you have addressed in your comment.
struct ContentView: View {
#State private var offset: CGFloat = .zero
#State private var lastOffset: CGFloat = .zero
var columns: [GridItem] = Array(repeating: .init(.flexible()), count: 2)
var body: some View {
LazyVGrid(columns: columns) {
ForEach((0...79), id: \.self) {
let codepoint = $0 + 0x1f600
let codepointString = String(format: "%02X", codepoint)
Text("\(codepointString)")
let emoji = String(Character(UnicodeScalar(codepoint)!))
Text("\(emoji)")
}
}
.font(.largeTitle)
.offset(y: offset)
.gesture(DragGesture().onChanged {value in
let translation = value.translation.height
if translation <= lastOffset {
offset = translation
lastOffset = translation
}
}.onEnded { value in
lastOffset = .zero
})
}
}
You do not need to use LazyVGrid if you your Views are not too many.