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Merge pull request exyte#33 from exyte/feature/modify_header
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Added a new function that allows you to change the size of the header…
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@f3dm76
f3dm76 authored Aug 16, 2023
2 parents 0eab689 + a043b89 commit bfaf364
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Showing 2 changed files with 76 additions and 48 deletions.
2 changes: 1 addition & 1 deletion Example/Example/Examples/ColorScalingHeader.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -15,7 +15,7 @@ struct ColorScalingHeader: View {
@Environment(\.presentationMode) var presentationMode

@State private var selectedColor: Color = .green

var body: some View {
ZStack(alignment: .topLeading) {
ScalingHeaderScrollView {
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122 changes: 75 additions & 47 deletions Source/ScalingHeaderScrollView.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -9,32 +9,49 @@
import SwiftUI
import Introspect

public enum SnapHeaderState: Equatable {
case expanded
case collapsed
case custom(CGFloat)

func getSnapValue(_ expandedValue: CGFloat, _ collapsedValue: CGFloat) -> CGFloat {
switch self {
case .expanded:
return expandedValue
case .collapsed:
return collapsedValue
case .custom(let value):
return value
}
}
}

public struct ScalingHeaderScrollView<Header: View, Content: View>: View {

/// Content on the top, which will be collapsed
public var header: Header

/// Content on the bottom
public var content: Content

/// Should the progress view be showing or not
@State private var isSpinning: Bool = false

/// UIKit's UIScrollView
@State private var uiScrollView: UIScrollView?

/// UIScrollView delegate, needed for calling didPullToRefresh or didEndDragging
@StateObject private var scrollViewDelegate = ScalingHeaderScrollViewDelegate()

/// ScrollView's header frame, needed for calculation of frame changing
// @StateObject private var headerFrame = ViewFrame()

/// ScrollView's content frame, needed for calculation of frame changing
@StateObject private var contentFrame = ViewFrame()

/// Interpolation from 0 to 1 of current collapse progress
@Binding private var progress: CGFloat


/// Use this variable to programmatically change header's visibility state
@Binding private var shouldSnapTo: SnapHeaderState

/// Current scroll offset Y value
@Binding private var scrollOffset: CGFloat

Expand All @@ -56,9 +73,12 @@ public struct ScalingHeaderScrollView<Header: View, Content: View>: View {
/// Allow collapsing while scrolling up
private var allowsHeaderCollapseFlag: Bool = false

/// Animation, when header size will be changed
private var headerAnimation: Animation?

/// Allow enlarging while pulling down
private var allowsHeaderGrowthFlag: Bool = false

/// Shows or hides the indicator for the scrollView
private var showsIndicators: Bool = true

Expand All @@ -69,23 +89,22 @@ public struct ScalingHeaderScrollView<Header: View, Content: View>: View {
/// Use this to set initial scroll position to anything other than fully expanded
/// Set a value in 0...1, 0 - fully collapsed header, 1 - fully expanded
private var initialSnapPosition: CGFloat?

/// Alignment for header content
private var headerAlignment: Alignment = .center

/// Clipped or not header
private var headerIsClipped: Bool = true

/// Private computed properties

/// Private computed properties
private var hasPullToRefresh: Bool {
didPullToRefresh != nil
}

private var contentOffset: CGFloat {
isLoading && hasPullToRefresh ? maxHeight + 32.0 : maxHeight
}

private var progressViewOffset: CGFloat {
isLoading ? maxHeight + 24.0 : maxHeight
}
Expand All @@ -99,29 +118,30 @@ public struct ScalingHeaderScrollView<Header: View, Content: View>: View {
private var headerScaleOnPullDown: CGFloat {
!hasPullToRefresh && allowsHeaderGrowthFlag ? max(1.0, getHeightForHeaderView() / maxHeight * 0.9) : 1.0
}

private var needToShowProgressView: Bool {
hasPullToRefresh && (isLoading || isSpinning)
}

// MARK: - Init

public init(@ViewBuilder header: @escaping () -> Header, @ViewBuilder content: @escaping () -> Content) {
self.header = header()
self.content = content()
_progress = .constant(0)
_scrollOffset = .constant(0)
_isLoading = .constant(false)
_scrollToTop = .constant(false)
_shouldSnapTo = .constant(.expanded)
}

// MARK: - Body builder

public var body: some View {
GeometryReader { globalGeometry in
ScrollView(showsIndicators: showsIndicators) {
content
.offset(y: contentOffset)
.offset(y: shouldSnapTo.getSnapValue(minHeight, contentOffset))
.frameGetter($contentFrame.frame)
.onChange(of: contentFrame.frame) { frame in
isSpinning = frame.minY - globalGeometry.frame(in: .global).minY > 20.0
Expand All @@ -142,9 +162,8 @@ public struct ScalingHeaderScrollView<Header: View, Content: View>: View {
.scaleEffect(1.25)
.offset(y: getOffsetForHeader() + progressViewOffset)
}

header
.frame(height: headerHeight, alignment: headerAlignment)
.frame(height: shouldSnapTo.getSnapValue(minHeight, headerHeight), alignment: headerAlignment)
.clipped(isClipped: headerIsClipped)
.offset(y: getOffsetForHeader())
.allowsHitTesting(true)
Expand All @@ -156,6 +175,7 @@ public struct ScalingHeaderScrollView<Header: View, Content: View>: View {
.frame(height: maxHeight)
.offset(y: -(contentFrame.startingRect?.maxY ?? UIScreen.main.bounds.height))
}
.animation(headerAnimation, value: shouldSnapTo)
.introspectScrollView { scrollView in
configure(scrollView: scrollView)
}
Expand All @@ -164,9 +184,9 @@ public struct ScalingHeaderScrollView<Header: View, Content: View>: View {
}
}
}

// MARK: - Private configure

private func configure(scrollView: UIScrollView) {
scrollView.delegate = scrollViewDelegate
if let didPullToRefresh = didPullToRefresh {
Expand Down Expand Up @@ -194,15 +214,15 @@ public struct ScalingHeaderScrollView<Header: View, Content: View>: View {
}
}
}

// MARK: - Private actions

private func setScrollPositionToTop() {
guard var contentOffset = uiScrollView?.contentOffset, contentOffset.y > 0 else { return }
contentOffset.y = maxHeight - minHeight
uiScrollView?.setContentOffset(contentOffset, animated: true)
}

private func snapScrollPosition() {
guard var contentOffset = uiScrollView?.contentOffset else { return }

Expand Down Expand Up @@ -233,21 +253,21 @@ public struct ScalingHeaderScrollView<Header: View, Content: View>: View {
uiScrollView?.setContentOffset(contentOffset, animated: true)
}
}

// MARK: - Private getters for heights and offsets

private func getScrollOffset() -> CGFloat {
-(uiScrollView?.contentOffset.y ?? 0)
}

private func getGeometryReaderVsScrollView(scrollGeometry: GeometryProxy, globalGeometry: GeometryProxy) -> CGFloat {
getScrollOffset() - scrollGeometry.frame(in: .global).minY + globalGeometry.frame(in: .global).minY
}

private func getOffsetForHeader() -> CGFloat {
let offset = getScrollOffset()
let extraSpace = maxHeight - minHeight

if offset < -extraSpace {
let imageOffset = abs(min(-extraSpace, offset))
return allowsHeaderCollapseFlag ? imageOffset : (minHeight - maxHeight) - offset
Expand All @@ -256,7 +276,7 @@ public struct ScalingHeaderScrollView<Header: View, Content: View>: View {
}
return maxHeight - headerHeight
}

private func getHeightForHeaderView() -> CGFloat {
let offset = getScrollOffset()
if hasPullToRefresh {
Expand All @@ -265,11 +285,11 @@ public struct ScalingHeaderScrollView<Header: View, Content: View>: View {
return max(minHeight, maxHeight + offset)
}
}

private func getCollapseProgress() -> CGFloat {
1 - min(max((getHeightForHeaderView() - minHeight) / (maxHeight - minHeight), 0), 1)
}

private func getHeightForLoadingView() -> CGFloat {
max(0, getScrollOffset())
}
Expand All @@ -278,7 +298,7 @@ public struct ScalingHeaderScrollView<Header: View, Content: View>: View {
// MARK: - Extension View

extension View {

@ViewBuilder
func clipped(isClipped: Bool) -> some View {
if isClipped {
Expand All @@ -289,7 +309,7 @@ extension View {
}
}

// MARK: - Modifiers
// MARK: - Modifiers

extension ScalingHeaderScrollView {

Expand All @@ -299,44 +319,52 @@ extension ScalingHeaderScrollView {
scalingHeaderScrollView._progress = progress
return scalingHeaderScrollView
}

/// Passes current scroll offset value into binding
public func scrollOffset(_ scrollOffset: Binding<CGFloat>) -> ScalingHeaderScrollView {
var scalingHeaderScrollView = self
scalingHeaderScrollView._scrollOffset = scrollOffset
return scalingHeaderScrollView
}

/// Allows to set up callback and `isLoading` state for pull-to-refresh action
public func pullToRefresh(isLoading: Binding<Bool>, perform: @escaping () -> Void) -> ScalingHeaderScrollView {
var scalingHeaderScrollView = self
scalingHeaderScrollView._isLoading = isLoading
scalingHeaderScrollView.didPullToRefresh = perform
return scalingHeaderScrollView
}

/// Allows content scroll reset, need to change Binding to `true`
public func scrollToTop(resetScroll: Binding<Bool>) -> ScalingHeaderScrollView {
var scalingHeaderScrollView = self
scalingHeaderScrollView._scrollToTop = resetScroll
return scalingHeaderScrollView
}

/// Changes min and max heights of Header
public func height(min: CGFloat = 150.0, max: CGFloat = 350.0) -> ScalingHeaderScrollView {
var scalingHeaderScrollView = self
scalingHeaderScrollView.minHeight = min
scalingHeaderScrollView.maxHeight = max
return scalingHeaderScrollView
}

/// When scrolling up - switch between actual header collapse and simply moving it up
public func allowsHeaderCollapse(_ allows: Bool = true) -> ScalingHeaderScrollView {
var scalingHeaderScrollView = self
scalingHeaderScrollView.allowsHeaderCollapseFlag = allows
return scalingHeaderScrollView
}

/// Сhanging the size of the header at the moment
public func snapHeaderToState(_ state: Binding<SnapHeaderState>, animated: Bool = true) -> ScalingHeaderScrollView {
var scalingHeaderScrollView = self
scalingHeaderScrollView.headerAnimation = animated ? .default : nil
scalingHeaderScrollView._shouldSnapTo = state
return scalingHeaderScrollView
}

/// When scrolling down - enable/disable header scale
public func allowsHeaderGrowth(_ allows: Bool = true) -> ScalingHeaderScrollView {
var scalingHeaderScrollView = self
Expand All @@ -350,7 +378,7 @@ extension ScalingHeaderScrollView {
scalingHeaderScrollView.headerSnappingPositions = [0, 1]
return scalingHeaderScrollView
}

/// Set positions for header snap (once you lift your finger header snaps to closest allowed position)
public func headerSnappingPositions(snapPositions: [CGFloat]) -> ScalingHeaderScrollView {
var scalingHeaderScrollView = self
Expand All @@ -364,21 +392,21 @@ extension ScalingHeaderScrollView {
scalingHeaderScrollView.initialSnapPosition = initialSnapPosition
return scalingHeaderScrollView
}

/// Hiddes scroll indicators
public func hideScrollIndicators(_ hide: Bool = false) -> ScalingHeaderScrollView {
var scalingHeaderScrollView = self
scalingHeaderScrollView.showsIndicators = hide
return scalingHeaderScrollView
}

/// Header clipped
public func headerIsClipped(_ isClipped: Bool = true) -> ScalingHeaderScrollView {
var scalingHeaderScrollView = self
scalingHeaderScrollView.headerIsClipped = isClipped
return scalingHeaderScrollView
}

/// Header alignment
public func headerAlignment(_ alignment: Alignment) -> ScalingHeaderScrollView {
var scalingHeaderScrollView = self
Expand Down

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