Adds DragGestureRecognizer

DragGestureRecognizer.xcodeproj/project.pbxproj

@@ -7,6 +7,7 @@
 	objects = {
 
 /* Begin PBXBuildFile section */
+		2E0800EE1D78B2F2004371A1 /* DragGestureRecognizer.swift in Sources */ = {isa = PBXBuildFile; fileRef = 2E0800ED1D78B2F2004371A1 /* DragGestureRecognizer.swift */; };
 		2EA02D0D1D78A64800FEB930 /* AppDelegate.swift in Sources */ = {isa = PBXBuildFile; fileRef = 2EA02D0C1D78A64800FEB930 /* AppDelegate.swift */; };
 		2EA02D0F1D78A64800FEB930 /* ViewController.swift in Sources */ = {isa = PBXBuildFile; fileRef = 2EA02D0E1D78A64800FEB930 /* ViewController.swift */; };
 		2EA02D121D78A64800FEB930 /* Main.storyboard in Resources */ = {isa = PBXBuildFile; fileRef = 2EA02D101D78A64800FEB930 /* Main.storyboard */; };
@@ -34,6 +35,7 @@
 /* End PBXContainerItemProxy section */
 
 /* Begin PBXFileReference section */
+		2E0800ED1D78B2F2004371A1 /* DragGestureRecognizer.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = DragGestureRecognizer.swift; sourceTree = "<group>"; };
 		2EA02D091D78A64800FEB930 /* DragGestureRecognizer.app */ = {isa = PBXFileReference; explicitFileType = wrapper.application; includeInIndex = 0; path = DragGestureRecognizer.app; sourceTree = BUILT_PRODUCTS_DIR; };
 		2EA02D0C1D78A64800FEB930 /* AppDelegate.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AppDelegate.swift; sourceTree = "<group>"; };
 		2EA02D0E1D78A64800FEB930 /* ViewController.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ViewController.swift; sourceTree = "<group>"; };
@@ -103,6 +105,7 @@
 				2EA02D131D78A64800FEB930 /* Assets.xcassets */,
 				2EA02D151D78A64800FEB930 /* LaunchScreen.storyboard */,
 				2EA02D181D78A64800FEB930 /* Info.plist */,
+				2E0800ED1D78B2F2004371A1 /* DragGestureRecognizer.swift */,
 			);
 			path = DragGestureRecognizer;
 			sourceTree = "<group>";
@@ -261,6 +264,7 @@
 			files = (
 				2EA02D0F1D78A64800FEB930 /* ViewController.swift in Sources */,
 				2EA02D0D1D78A64800FEB930 /* AppDelegate.swift in Sources */,
+				2E0800EE1D78B2F2004371A1 /* DragGestureRecognizer.swift in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
@@ -505,6 +509,7 @@
 				2EA02D331D78A64800FEB930 /* Release */,
 			);
 			defaultConfigurationIsVisible = 0;
+			defaultConfigurationName = Release;
 		};
 		2EA02D341D78A64800FEB930 /* Build configuration list for PBXNativeTarget "DragGestureRecognizerTests" */ = {
 			isa = XCConfigurationList;
@@ -513,6 +518,7 @@
 				2EA02D361D78A64800FEB930 /* Release */,
 			);
 			defaultConfigurationIsVisible = 0;
+			defaultConfigurationName = Release;
 		};
 		2EA02D371D78A64800FEB930 /* Build configuration list for PBXNativeTarget "DragGestureRecognizerUITests" */ = {
 			isa = XCConfigurationList;
@@ -521,6 +527,7 @@
 				2EA02D391D78A64800FEB930 /* Release */,
 			);
 			defaultConfigurationIsVisible = 0;
+			defaultConfigurationName = Release;
 		};
 /* End XCConfigurationList section */
 	};

DragGestureRecognizer/DragGestureRecognizer.swift

@@ -0,0 +1,70 @@
+//
+//  DragGestureRecognizer.swift
+//  DragGestureRecognizer
+//
+//  Created by Wojciech Nagrodzki on 01/09/16.
+//  Copyright © 2016 Wojciech Nagrodzki. All rights reserved.
+//
+
+import UIKit
+import UIKit.UIGestureRecognizerSubclass
+
+/// `DragGestureRecognizer` is a subclass of `UILongPressGestureRecognizer` that allows for tracking translation similarly to `UIPanGestureRecognizer`.
+class DragGestureRecognizer: UILongPressGestureRecognizer {
+
+    /// The total translation of the drag gesture in the coordinate system of the specified view.
+    /// - parameters:
+    ///     - view: The view in whose coordinate system the translation of the drag gesture should be computed. Pass `nil` to indicate window.
+    func translation(in view: UIView?) -> CGPoint {
+        
+        // not attached to a view or outside window
+        guard let window = self.view?.window else { return CGPoint() }
+        // gesture not in progress
+        guard let initialTouchLocationInWindow = initialTouchLocationInWindow else { return CGPoint() }
+        
+        let inView = view ?? window
+        let initialLocation = initialTouchLocationsInViews[inView] ?? window.convert(initialTouchLocationInWindow, to: inView)
+        let currentLocation = location(in: inView)
+        
+        return CGPoint(x: currentLocation.x - initialLocation.x, y: currentLocation.y - initialLocation.y)
+    }
+    
+    /// Sets the translation value in the coordinate system of the specified view.
+    /// - parameters:
+    ///     - translation: A point that identifies the new translation value.
+    ///     - view: A view in whose coordinate system the translation is to occur. Pass `nil` to indicate window.
+    func setTranslation(_ translation: CGPoint, in view: UIView?) {
+        
+        // not attached to a view or outside window
+        guard let window = self.view?.window else { return }
+        // gesture not in progress
+        guard let _ = initialTouchLocationInWindow else { return }
+        
+        let inView = view ?? window
+        let currentLocation = location(in: inView)
+        let initialLocation = CGPoint(x: currentLocation.x - translation.x, y: currentLocation.y - translation.y)
+        initialTouchLocationsInViews[inView] = initialLocation
+    }
+    
+    override var state: UIGestureRecognizerState {
+        
+        didSet {
+            
+            switch state {
+                
+            case .began:
+                initialTouchLocationInWindow = location(in: nil)
+            
+            case .ended, .cancelled, .failed:
+                initialTouchLocationInWindow = nil
+                initialTouchLocationsInViews = [:]
+            
+            case .possible, .changed:
+                break
+            }
+        }
+    }
+    
+    private var initialTouchLocationInWindow: CGPoint?
+    private var initialTouchLocationsInViews = [UIView: CGPoint]()
+}