Feature/scroll to view controller

Matrioska.xcodeproj/project.pbxproj

@@ -36,6 +36,7 @@
 		DE85E5AF1DEC842700DFF34A /* AppearanceSpyViewController.swift in Sources */ = {isa = PBXBuildFile; fileRef = DE85E5AE1DEC842700DFF34A /* AppearanceSpyViewController.swift */; };
 		DEA64C8B1E017D8100687658 /* UIColor+HEX.swift in Sources */ = {isa = PBXBuildFile; fileRef = DEA64C8A1E017D8100687658 /* UIColor+HEX.swift */; };
 		DEA64C8D1E01810500687658 /* UIColorHEXTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = DEA64C8C1E01810500687658 /* UIColorHEXTests.swift */; };
+		EDC724671E784EA5004EFEC4 /* Focusable.swift in Sources */ = {isa = PBXBuildFile; fileRef = EDC724661E784EA5004EFEC4 /* Focusable.swift */; };
 /* End PBXBuildFile section */
 
 /* Begin PBXContainerItemProxy section */
@@ -86,6 +87,7 @@
 		DEA64C8C1E01810500687658 /* UIColorHEXTests.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = UIColorHEXTests.swift; sourceTree = "<group>"; };
 		DEECB3B21DD47C4A00F7DFB1 /* README.md */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = net.daringfireball.markdown; lineEnding = 0; path = README.md; sourceTree = "<group>"; xcLanguageSpecificationIdentifier = xcode.lang.markdown; };
 		E08AB4E968331E4711F8DCD9 /* Pods_MatrioskaTests.framework */ = {isa = PBXFileReference; explicitFileType = wrapper.framework; includeInIndex = 0; path = Pods_MatrioskaTests.framework; sourceTree = BUILT_PRODUCTS_DIR; };
+		EDC724661E784EA5004EFEC4 /* Focusable.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = Focusable.swift; sourceTree = "<group>"; };
 /* End PBXFileReference section */
 
 /* Begin PBXFrameworksBuildPhase section */
@@ -228,6 +230,7 @@
 		DE3E8D9A1DD38D1C00417AE5 /* Source */ = {
 			isa = PBXGroup;
 			children = (
+				EDC724651E784E74004EFEC4 /* Protocols */,
 				8BCFF8AB1E28D4340053AD98 /* Components */,
 				8BCFF8A21E28D3830053AD98 /* Factories */,
 				DEA64C891E017D7300687658 /* Helpers */,
@@ -256,6 +259,14 @@
 			path = Helpers;
 			sourceTree = "<group>";
 		};
+		EDC724651E784E74004EFEC4 /* Protocols */ = {
+			isa = PBXGroup;
+			children = (
+				EDC724661E784EA5004EFEC4 /* Focusable.swift */,
+			);
+			path = Protocols;
+			sourceTree = "<group>";
+		};
 /* End PBXGroup section */
 
 /* Begin PBXHeadersBuildPhase section */
@@ -472,6 +483,7 @@
 				8BCFF8B51E28D4340053AD98 /* TabBarCluster.swift in Sources */,
 				8BB2842A1E31754400243C0A /* Rule.swift in Sources */,
 				8BCFF8B31E28D4340053AD98 /* ComponentMeta.swift in Sources */,
+				EDC724671E784EA5004EFEC4 /* Focusable.swift in Sources */,
 				DEA64C8B1E017D8100687658 /* UIColor+HEX.swift in Sources */,
 				DE067DCC1DDE017700641D1A /* IntrinsicSizeAwareScrollView.swift in Sources */,
 				8BCFF8B21E28D4340053AD98 /* Component.swift in Sources */,

Source/Components/TabBarCluster.swift

@@ -132,3 +132,9 @@ extension ClusterLayout {
         }
     }
 }
+
+extension UITabBarController: Focusable {
+    func focus(on viewController: UIViewController) {
+        selectedViewController = viewController
+    }
+}

Source/Protocols/Focusable.swift

@@ -0,0 +1,21 @@
+//
+//  Focusable.swift
+//  Matrioska
+//
+//  Created by Andreas Thenn on 14/03/2017.
+//  Copyright © 2017 runtastic. All rights reserved.
+//
+
+import Foundation
+
+/** This protocol should be implemented by every UIViewController that has some kind of focus,
+ highlight or select method. We want these to be adressable in a more generic way and
+ we don't need to care about the actual underlying method that's being called.
+ */
+protocol Focusable {
+
+    /** Try to focus on the given UIViewController, otherwise it fails silently */
+    @discardableResult
+    func focus(on viewController: UIViewController)
+
+}

Source/Views/StackViewController.swift

@@ -9,8 +9,16 @@
 import UIKit
 import SnapKit
 
+/// An enum that describes the relative position of an element. The enum should work horizontally as well as vertically.
+/// Orientation depending meaning: begin - top/left, end - bottom/right
+public enum RelativePosition {
+    case begin
+    case center
+    case end
+}
+
 /// A ViewController that contains a stackView
-final class StackViewController: UIViewController {
+final class StackViewController: UIViewController, Focusable {
 
     private let preserveParentWidth: Bool
     private let scrollView = IntrinsicSizeAwareScrollView()
@@ -24,7 +32,7 @@ final class StackViewController: UIViewController {
         self.preserveParentWidth = configuration.preserveParentWidth
 
         super.init(nibName: nil, bundle: nil)
-
+        
         title = configuration.title
         stackView.distribution = .equalSpacing
         stackView.axis = configuration.axis
@@ -33,7 +41,7 @@ final class StackViewController: UIViewController {
         if !preserveParentWidth {
             stackView.alignment = .leading
         }
-
+        
         scrollView.backgroundColor = configuration.backgroundColor
     }
 
@@ -69,4 +77,65 @@ final class StackViewController: UIViewController {
         stackView.addArrangedSubview(childViewController.view)
         childViewController.didMove(toParentViewController: self)
     }
+
+    public func focus(on viewController: UIViewController) {
+        scroll(to: viewController, at: .center, animated:  true)
+    }
+
+    /// A method to access the scrollView from outside and scroll to a given target ViewController.
+    /// If no relativePosition parameter is provided, it will try to center the target.
+    ///
+    /// - Parameters:
+    ///   - targetViewController: The ViewController which should scroll into focus
+    ///   - position: An optional parameter to specify the alignement of the target. Depending of
+    ///     the stackViews' orientation position values have different meaning:
+    ///     begin - top/left, end - bottom/right
+    private func scroll(to targetViewController: UIViewController,
+                        at position: RelativePosition = .center,
+                        animated: Bool = false) {
+
+        guard childViewControllers.contains(targetViewController) else {
+            return
+        }
+
+        var targetOffset = CGPoint.zero
+        let targetFrame = targetViewController.view.frame
+
+        if stackView.axis == .vertical {
+            // keep current horizontal offset
+            targetOffset.x = scrollView.contentOffset.x
+            let topOffset = targetFrame.origin.y - scrollView.contentInset.top
+            let bottomOffset = targetFrame.maxY - scrollView.bounds.height
+            let maxOffset = scrollView.contentSize.height - scrollView.bounds.height
+
+            switch position {
+            case .begin:
+                targetOffset.y = topOffset
+            case .center:
+                targetOffset.y = topOffset - (topOffset - bottomOffset) / 2
+            case .end:
+                targetOffset.y = bottomOffset
+            }
+
+            targetOffset.y = min(maxOffset, max(scrollView.contentInset.top, targetOffset.y))
+        } else {
+            // keep current vertical offset
+            targetOffset.y = scrollView.contentOffset.y
+            let leftOffset = targetFrame.origin.x - scrollView.contentInset.left
+            let rightOffset = targetFrame.maxX - scrollView.bounds.width
+            let maxOffset = scrollView.contentSize.width - scrollView.bounds.width
+            switch position {
+            case .begin:
+                targetOffset.x = leftOffset
+            case .center:
+                targetOffset.x = leftOffset - (leftOffset - rightOffset) / 2
+            case .end:
+                targetOffset.x = rightOffset
+            }
+
+            targetOffset.x = min(maxOffset, max(scrollView.contentInset.left, targetOffset.x))
+        }
+
+        scrollView.setContentOffset(targetOffset, animated: animated)
+    }
 }