Consistent target index when reloading heights (#58)

Author: ninarg

Diff for: Sources/BottomSheetPresentationController.swift

@@ -46,7 +46,7 @@ final class BottomSheetPresentationController: UIPresentationController {
     // MARK: - Private properties
 
     private var contentHeights: [CGFloat]
-    private let startTargetIndex: Int
+    private var startTargetIndex: Int
     private let handleBackground: BottomSheetView.HandleBackground
     private let useSafeAreaInsets: Bool
     private let draggableHeight: CGFloat?
@@ -93,9 +93,12 @@ final class BottomSheetPresentationController: UIPresentationController {
         bottomSheetView?.reset()
     }
 
-    func reload(with contentHeights: [CGFloat]) {
+    func reload(with contentHeights: [CGFloat], targetIndex: Int?) {
         self.contentHeights = contentHeights
-        bottomSheetView?.reload(with: contentHeights)
+        if let targetIndex = targetIndex {
+            startTargetIndex = targetIndex
+        }
+        bottomSheetView?.reload(with: contentHeights, targetIndex: targetIndex)
     }
 
     func hideDimView() {

Diff for: Sources/BottomSheetTransitioningDelegate.swift

@@ -6,7 +6,7 @@ import UIKit
 
 public final class BottomSheetTransitioningDelegate: NSObject {
     public private(set) var contentHeights: [CGFloat]
-    private let startTargetIndex: Int
+    private var startTargetIndex: Int
     private let handleBackground: BottomSheetView.HandleBackground
     private let draggableHeight: CGFloat?
     private let useSafeAreaInsets: Bool
@@ -62,8 +62,11 @@ public final class BottomSheetTransitioningDelegate: NSObject {
     }
 
     public func reload(with contentHeights: [CGFloat]) {
+        let previousHeight = self.contentHeights[safe: startTargetIndex] ?? 0
+        let indexOfPreviousHeightInNewHeights = contentHeights.firstIndex(of: previousHeight) ?? 0
         self.contentHeights = contentHeights
-        presentationController?.reload(with: contentHeights)
+        startTargetIndex = indexOfPreviousHeightInNewHeights
+        presentationController?.reload(with: contentHeights, targetIndex: startTargetIndex)
     }
 
     public func hideBackgroundOverlay() {

Diff for: Sources/BottomSheetView.swift

@@ -249,11 +249,11 @@ public final class BottomSheetView: UIView {
         }
     }
 
-    public func reload(with contentHeights: [CGFloat]) {
-        let previousHeight = self.contentHeights[safe: currentTargetOffsetIndex] ?? 0
-        let indexOfPreviousHeightInNewHeights = contentHeights.firstIndex(of: previousHeight) ?? 0
+    public func reload(with contentHeights: [CGFloat], targetIndex: Int?) {
         self.contentHeights = contentHeights
-        currentTargetOffsetIndex = indexOfPreviousHeightInNewHeights
+        if let targetIndex = targetIndex {
+            currentTargetOffsetIndex = targetIndex
+        }
         reset()
     }