yberdnikov · August 29, 2015 14:20 · Apr 17, 2014 · Apr 17, 2014 · Apr 17, 2014 · Apr 17, 2014
diff --git a/ViewController.m b/ViewController.m
@@ -22,6 +22,7 @@ - (void)viewDidLoad
 {
   [super viewDidLoad];
 
+  // Setup a screen edge pan gesture recognizer to trigger from the right edge of the screen.
   self.edgePanGestureRecognizer = [[UIScreenEdgePanGestureRecognizer alloc] initWithTarget:self action:@selector(handleScreenEdgePanGesture:)];
   self.edgePanGestureRecognizer.edges = UIRectEdgeRight;
   [self.view addGestureRecognizer:self.edgePanGestureRecognizer];
@@ -34,13 +35,17 @@ - (void)handleScreenEdgePanGesture:(UIScreenEdgePanGestureRecognizer *)sender
 
   switch (sender.state) {
     case UIGestureRecognizerStateBegan:
+      // Configure the navigation controller to return the custom (interactive/animated) transition.
       self.navigationController.delegate = self;
+      // Trigger a segue (or push another view controller, whatevs you want).
       [self performSegueWithIdentifier:@"next" sender:sender];
       break;
     case UIGestureRecognizerStateChanged:
+      // Update the transition using a UIPercentDrivenInteractiveTransition.
       [self.percentDrivenInteractiveTransition updateInteractiveTransition:percent];
       break;
     case UIGestureRecognizerStateEnded:
+      // Cancel or finish depending on how the gesture ended.
       if (percent > 0.5 || fabs([sender velocityInView:self.view].x) > 1000)
         [self.percentDrivenInteractiveTransition finishInteractiveTransition];
       else
@@ -53,11 +58,13 @@ - (void)handleScreenEdgePanGesture:(UIScreenEdgePanGestureRecognizer *)sender
 
 - (id<UIViewControllerAnimatedTransitioning>)navigationController:(UINavigationController *)navigationController animationControllerForOperation:(UINavigationControllerOperation)operation fromViewController:(UIViewController *)fromVC toViewController:(UIViewController *)toVC
 {
+  // Have to return a custom transition here in order for the navigation controller to ask about the interactive stuff below. The SlideAnimatedTransitioning just tries to duplicate the default transition as much as possible.
   return [SlideAnimatedTransitioning new];
 }
 
 - (id<UIViewControllerInteractiveTransitioning>)navigationController:(UINavigationController *)navigationController interactionControllerForAnimationController:(id<UIViewControllerAnimatedTransitioning>)animationController
 {
+  // Unset the delegate so that all other types of transitions (back, normal animated push not initiated by a gesture) get the default behavior.
   self.navigationController.delegate = nil;
 
   if (self.edgePanGestureRecognizer.state == UIGestureRecognizerStateBegan) {

diff --git a/SlideAnimatedTransitioning.h b/SlideAnimatedTransitioning.h
@@ -0,0 +1,13 @@
+//
+//  SlideAnimatedTransitioning.h
+//  SwipeLeft
+//
+//  Created by Visnu on 4/14/14.
+//  Copyright (c) 2014 Visnu Pitiyanuvath. All rights reserved.
+//
+
+#import <Foundation/Foundation.h>
+
+@interface SlideAnimatedTransitioning : NSObject <UIViewControllerAnimatedTransitioning>
+
+@end
diff --git a/SlideAnimatedTransitioning.m b/SlideAnimatedTransitioning.m
@@ -1,15 +1,15 @@
 //
-//  SlideTransition.m
+//  SlideAnimatedTransitioning.m
 //  SwipeLeft
 //
 //  Created by Visnu on 4/14/14.
 //  Copyright (c) 2014 Visnu Pitiyanuvath. All rights reserved.
 //
 
-#import "SlideTransition.h"
+#import "SlideAnimatedTransitioning.h"
 
 // Tries to duplicate the default iOS 7 slide transition for UINavigationController
-@implementation SlideTransition
+@implementation SlideAnimatedTransitioning
 
 - (void)animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext
 {

diff --git a/SlideAnimatedTransitioning.m b/SlideAnimatedTransitioning.m
@@ -0,0 +1,50 @@
+//
+//  SlideTransition.m
+//  SwipeLeft
+//
+//  Created by Visnu on 4/14/14.
+//  Copyright (c) 2014 Visnu Pitiyanuvath. All rights reserved.
+//
+
+#import "SlideTransition.h"
+
+// Tries to duplicate the default iOS 7 slide transition for UINavigationController
+@implementation SlideTransition
+
+- (void)animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext
+{
+  UIView *containerView = [transitionContext containerView],
+         *fromView = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey].view,
+         *toView   = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey].view;
+
+  CGFloat width = containerView.frame.size.width;
+
+  CGRect offsetLeft = fromView.frame; offsetLeft.origin.x = -width/3;
+
+  CGRect offscreenRight = toView.frame; offscreenRight.origin.x = width;
+  toView.frame = offscreenRight;
+  toView.layer.shadowRadius = 5;
+  toView.layer.shadowOpacity = 0.4;
+
+  [containerView addSubview:toView];
+
+  [UIView animateWithDuration:[self transitionDuration:transitionContext] delay:0 options:UIViewAnimationOptionCurveLinear animations:^{
+    toView.frame = fromView.frame;
+
+    fromView.frame = offsetLeft;
+    fromView.layer.opacity = 0.9;
+  } completion:^(BOOL finished) {
+    fromView.layer.opacity = 1;
+    toView.layer.shadowOpacity = 0;
+    // when cancelling or completing the animation, ios simulator seems to sometimes flash black backgrounds during the animation. on devices, this doesn't seem to happen though.
+    // containerView.backgroundColor = [UIColor whiteColor];
+    [transitionContext completeTransition:![transitionContext transitionWasCancelled]];
+  }];
+}
+
+- (NSTimeInterval)transitionDuration:(id<UIViewControllerContextTransitioning>)transitionContext
+{
+  return 0.2;
+}
+
+@end
diff --git a/ViewController.m b/ViewController.m
@@ -0,0 +1,73 @@
+//
+//  ViewController.m
+//  SwipeLeft
+//
+//  Created by Visnu on 4/10/14.
+//  Copyright (c) 2014 Visnu Pitiyanuvath. All rights reserved.
+//
+
+#import "ViewController.h"
+#import "SlideAnimatedTransitioning.h"
+
+@interface ViewController ()
+
+@property UIScreenEdgePanGestureRecognizer *edgePanGestureRecognizer;
+@property UIPercentDrivenInteractiveTransition *percentDrivenInteractiveTransition;
+
+@end
+
+@implementation ViewController
+
+- (void)viewDidLoad
+{
+  [super viewDidLoad];
+
+  self.edgePanGestureRecognizer = [[UIScreenEdgePanGestureRecognizer alloc] initWithTarget:self action:@selector(handleScreenEdgePanGesture:)];
+  self.edgePanGestureRecognizer.edges = UIRectEdgeRight;
+  [self.view addGestureRecognizer:self.edgePanGestureRecognizer];
+}
+
+- (void)handleScreenEdgePanGesture:(UIScreenEdgePanGestureRecognizer *)sender
+{
+  CGFloat width = self.view.frame.size.width,
+          percent = MAX(-[sender translationInView:self.view].x, 0) / width;
+
+  switch (sender.state) {
+    case UIGestureRecognizerStateBegan:
+      self.navigationController.delegate = self;
+      [self performSegueWithIdentifier:@"next" sender:sender];
+      break;
+    case UIGestureRecognizerStateChanged:
+      [self.percentDrivenInteractiveTransition updateInteractiveTransition:percent];
+      break;
+    case UIGestureRecognizerStateEnded:
+      if (percent > 0.5 || fabs([sender velocityInView:self.view].x) > 1000)
+        [self.percentDrivenInteractiveTransition finishInteractiveTransition];
+      else
+        [self.percentDrivenInteractiveTransition cancelInteractiveTransition];
+      break;
+    default:
+      NSLog(@"unhandled state for gesture=%@", sender);
+  }
+}
+
+- (id<UIViewControllerAnimatedTransitioning>)navigationController:(UINavigationController *)navigationController animationControllerForOperation:(UINavigationControllerOperation)operation fromViewController:(UIViewController *)fromVC toViewController:(UIViewController *)toVC
+{
+  return [SlideAnimatedTransitioning new];
+}
+
+- (id<UIViewControllerInteractiveTransitioning>)navigationController:(UINavigationController *)navigationController interactionControllerForAnimationController:(id<UIViewControllerAnimatedTransitioning>)animationController
+{
+  self.navigationController.delegate = nil;
+
+  if (self.edgePanGestureRecognizer.state == UIGestureRecognizerStateBegan) {
+    self.percentDrivenInteractiveTransition = [UIPercentDrivenInteractiveTransition new];
+    self.percentDrivenInteractiveTransition.completionCurve = UIViewAnimationOptionCurveEaseOut;
+  } else {
+    self.percentDrivenInteractiveTransition = nil;
+  }
+
+  return self.percentDrivenInteractiveTransition;
+}
+
+@end