Check If a Uiscrollview Reached the Top or Bottom

Check if a UIScrollView reached the top or bottom

Implement the UIScrollViewDelegate in your class, and then add this:

-(void)scrollViewDidScroll: (UIScrollView*)scrollView
{
    float scrollViewHeight = scrollView.frame.size.height;
    float scrollContentSizeHeight = scrollView.contentSize.height;
    float scrollOffset = scrollView.contentOffset.y;

    if (scrollOffset == 0)
    {
        // then we are at the top
    }
    else if (scrollOffset + scrollViewHeight == scrollContentSizeHeight)
    {
        // then we are at the end
    }
}

Hope this is what you are after! Else have a tinker by adding more conditions to the above code and NSLog the value of scrollOffset.

Determine if view reached the top of the UIScrollView

Just convert the top of the scroll view and the top of v3 to the same coordinate system and now you can simply look to see which one is higher.

Let sv be the scroll view and v3 be view 3. Then:

func scrollViewDidScroll(_ sv: UIScrollView) {
    let svtop = sv.frame.origin.y
    let v3top = sv.superview!.convert(v3.bounds.origin, from:v3).y
    if v3top < svtop { print("now") }
}

Detect UIScrollview bottom reached

Have you thought of adding a boolean. update it when the method is called for the first time and maybe when user scrolls back up.

UIScrollView, reaching the bottom of the scroll view

I think what you might be able to do is to check that your contentOffset point is at the bottom of contentSize. So you could probably do something like:

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
    float bottomEdge = scrollView.contentOffset.y + scrollView.frame.size.height;
    if (bottomEdge >= scrollView.contentSize.height) {
        // we are at the end
    }
}

You'll likely also need a negative case there to show your indicator when the user scrolls back up. You might also want to add some padding to that so, for example, you could hide the indicator when the user is near the bottom, but not exactly at the bottom.

How to determine that the scroll reached to specific position(I have to determine the space from bottom should be 56 px) while scrolling in iOS swift

You need to calculate the bottomOffset first, then calculate the difference between it and the contentOffset. If it's <= 56, then you reached a specific position.

let bottomOffset = scrollView.contentSize.height - scrollView.frame.size.height

let position = bottomOffset - scrollView.contentOffset.y

if position <= 56 {
    print(" you reached at desired bottom")
    self.showPageControl(toShow: true)
} else {
    self.showPageControl(toShow: false)
}

How can I detect when iOS ScrollView is at the very top?

scrollViewDidEndDragging means the user's finger lifted, but because it has physics to simulate inertia, the view may continue to move. There is another delegate method for exactly what you are looking for: scrollViewDidScrollToTop which as the name implies fires when you get to the top of the scrollview.

EDIT:
you can also try:

  func scrollViewDidScroll(_ scrollView: UIScrollView) {
    if scrollView.contentOffset.y <= 0 {
      print("top!")
    }
  }

EDIT third time's the charm? This one only fires once, after the scroll view has stopped moving, if you are at the top.

  override func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
    if scrollView.contentOffset.y == 0 {
      print("top!")
    }
  }

How to check if a scroll view scrolled in bottom or not in ios

implement UIScrollViewDelegate in the class that hosts UIScrollView.

set the scrollView.delegate property.

implement below method.

-(void)scrollViewDidScroll: (UIScrollView*)scrollView
{
    float scrollViewHeight = scrollView.frame.size.height;
    float scrollContentSizeHeight = scrollView.contentSize.height;
    float scrollOffset = scrollView.contentOffset.y;

    if (scrollOffset + scrollViewHeight == scrollContentSizeHeight)
    {
        //This condition will be true when scrollview will reach to bottom
    }

}

How do I detect when User has reached the bottom of the ScrollView?

Wrap your whole ScrollView in your ChildSizeReader, so you can get the height of the ScrollView itself.

Because the offset starts at zero at the top, when at the bottom of the scroll view the end isn't at the top of the screen, but rather the bottom. This difference is the height of the scroll view. This means the ScrollView starts at offset 0 and goes to total content height - scroll view height.

Code:

struct ContentView: View {
    let spaceName = "scroll"

    @State var wholeSize: CGSize = .zero
    @State var scrollViewSize: CGSize = .zero

    var body: some View {
        ChildSizeReader(size: $wholeSize) {
            ScrollView {
                ChildSizeReader(size: $scrollViewSize) {
                    VStack {
                        ForEach(0..<100) { i in
                            Text("\(i)")
                        }
                    }
                    .background(
                        GeometryReader { proxy in
                            Color.clear.preference(
                                key: ViewOffsetKey.self,
                                value: -1 * proxy.frame(in: .named(spaceName)).origin.y
                            )
                        }
                    )
                    .onPreferenceChange(
                        ViewOffsetKey.self,
                        perform: { value in
                            print("offset: \(value)") // offset: 1270.3333333333333 when User has reached the bottom
                            print("height: \(scrollViewSize.height)") // height: 2033.3333333333333

                            if value >= scrollViewSize.height - wholeSize.height {
                                print("User has reached the bottom of the ScrollView.")
                            } else {
                                print("not reached.")
                            }
                        }
                    )
                }
            }
            .coordinateSpace(name: spaceName)
        }
        .onChange(
            of: scrollViewSize,
            perform: { value in
                print(value)
            }
        )
    }
}

Note your already existing scrollViewSize variable is the content's size, not the scroll view's size.

Also notice that I changed the == to >= - this is so you don't have to be exactly at the height, can be over-scrolled where it rubber-bands back.

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