Add support for interactive transitioning

material-motion#3

Author: randcode-generator

src/MDMTransition.h

@@ -17,6 +17,7 @@
 #import <UIKit/UIKit.h>
 
 @protocol MDMTransitionContext;
+@protocol MDMInteractiveTransitionContext;
 
 /**
  A transition coordinates the animated presentation or dismissal of a view controller.
@@ -88,3 +89,9 @@ NS_SWIFT_NAME(presentationController(forPresented:presenting:source:));
 // clang-format on
 
 @end
+
+NS_SWIFT_NAME(InteractiveTransition)
+@protocol MDMInteractiveTransition <NSObject>
+- (Boolean)isInteractive:(nonnull id<MDMTransitionContext>)context;
+- (void)startWithInteractiveContext:(nonnull id<MDMInteractiveTransitionContext>)context;
+@end

src/MDMTransitionContext.h

@@ -80,3 +80,12 @@ NS_SWIFT_NAME(TransitionContext)
 @property(nonatomic, strong, readonly, nonnull) UIView *containerView;
 
 @end
+
+NS_SWIFT_NAME(InteractiveTransitionContext)
+@protocol MDMInteractiveTransitionContext
+- (void)updatePercent:(CGFloat)percent;
+- (void)finishInteractiveTransition;
+- (void)cancelInteractiveTransition;
+
+@property(nonatomic, readonly, nonnull) id<MDMTransitionContext> transitionContext;
+@end

src/MDMTransitionController.h

@@ -17,6 +17,7 @@
 #import <Foundation/Foundation.h>
 
 @protocol MDMTransition;
+@protocol MDMInteractiveTransition;
 
 /**
  A transition controller is a bridge between UIKit's view controller transitioning APIs and
@@ -37,5 +38,5 @@ NS_SWIFT_NAME(TransitionController)
  `modalPresentationStyle` property.
  */
 @property(nonatomic, strong, nullable) id<MDMTransition> transition;
-
+@property(nonatomic, strong, nullable) id<MDMInteractiveTransition> interactiveTransition;
 @end

src/UIViewController+TransitionController.h

@@ -17,6 +17,7 @@
 #import <Foundation/Foundation.h>
 
 @protocol MDMTransitionController;
+@protocol MDMInteractiveTransitionContext;
 
 @interface UIViewController (MDMTransitionController)
 
@@ -31,4 +32,5 @@
 @property(nonatomic, strong, readonly, nonnull) id<MDMTransitionController> mdm_transitionController
     NS_SWIFT_NAME(transitionController);
 
+@property(nonatomic, strong, nullable) id<MDMInteractiveTransitionContext> interactiveTransitionContext;
 @end

src/UIViewController+TransitionController.m

@@ -24,6 +24,16 @@ @implementation UIViewController (MDMTransitionController)
 
 #pragma mark - Public
 
+- (id<MDMInteractiveTransition>)interactiveTransitionContext {
+  const void *key = [self mdm_transitionControllerKey];
+  return objc_getAssociatedObject(self, key);
+}
+
+- (void)setInteractiveTransitionContext:(id<MDMInteractiveTransition>) interactiveTransition {
+  const void *key = [self mdm_transitionControllerKey];
+  objc_setAssociatedObject(self, key, interactiveTransition, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
+}
+
 - (id<MDMTransitionController>)mdm_transitionController {
   const void *key = [self mdm_transitionControllerKey];
 

src/private/MDMPresentationTransitionController.m

@@ -17,6 +17,7 @@
 #import "MDMPresentationTransitionController.h"
 
 #import "MDMTransition.h"
+#import "MDMViewControllerInteractiveTransitionContext.h"
 #import "MDMViewControllerTransitionContext.h"
 
 @interface MDMPresentationTransitionController () <UIViewControllerTransitioningDelegate, MDMViewControllerTransitionContextDelegate>
@@ -30,10 +31,12 @@ @implementation MDMPresentationTransitionController {
   UIPresentationController *_presentationController;
 
   MDMViewControllerTransitionContext *_context;
+  MDMViewControllerInteractiveTransitionContext *_interactiveContext;
   __weak UIViewController *_source;
 }
 
 @synthesize transition = _transition;
+@synthesize interactiveTransition = _interactiveTransition;
 
 - (nonnull instancetype)initWithViewController:(nonnull UIViewController *)viewController {
   self = [super init];
@@ -56,6 +59,10 @@ - (void)setTransition:(id<MDMTransition>)transition {
   }
 }
 
+- (void)setInteractiveTransition:(id<MDMInteractiveTransition>)transition {
+  _interactiveTransition = transition;
+}
+
 #pragma mark - UIViewControllerTransitioningDelegate
 
 // Animated transitions
@@ -80,6 +87,14 @@ - (void)setTransition:(id<MDMTransition>)transition {
   return _context;
 }
 
+- (nullable id<UIViewControllerInteractiveTransitioning>)interactionControllerForPresentation:(id<UIViewControllerAnimatedTransitioning>)animator {
+  return [self prepareForInteractiveTransition];
+}
+
+- (nullable id<UIViewControllerInteractiveTransitioning>)interactionControllerForDismissal:(id<UIViewControllerAnimatedTransitioning>)animator {
+  return [self prepareForInteractiveTransition];
+}
+
 // Presentation
 
 - (UIPresentationController *)presentationControllerForPresentedViewController:(UIViewController *)presented
@@ -125,4 +140,35 @@ - (void)prepareForTransitionWithSourceViewController:(nullable UIViewController
   }
 }
 
+- (nullable id<UIViewControllerInteractiveTransitioning>) prepareForInteractiveTransition {
+  Boolean isInteractive = false;
+  
+  if (_interactiveTransition) {
+    Boolean isInteractiveResponds = false;
+    Boolean startWithInteractiveResponds = false;
+    
+    if ([_interactiveTransition respondsToSelector:@selector(isInteractive:)]) {
+      isInteractiveResponds = true;
+    } else {
+      return nil;
+    }
+    
+    if ([_interactiveTransition respondsToSelector:@selector(startWithInteractiveContext:)]) {
+      startWithInteractiveResponds = true;
+    } else {
+      return nil;
+    }
+    
+    if(isInteractiveResponds && startWithInteractiveResponds) {
+      isInteractive = [_interactiveTransition isInteractive:_context];
+      if(isInteractive) {
+        _interactiveContext = [[MDMViewControllerInteractiveTransitionContext alloc] initWithTransition:_context];
+        
+        [_interactiveTransition startWithInteractiveContext:_interactiveContext];
+      }
+    }
+  }
+  
+  return isInteractive == false ? nil : [_interactiveContext getPercentIT];
+}
 @end

src/private/MDMViewControllerInteractiveTransitionContext.h

@@ -0,0 +1,25 @@
+/*
+ Copyright 2017-present The Material Motion Authors. All Rights Reserved.
+ 
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+ 
+ http://www.apache.org/licenses/LICENSE-2.0
+ 
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+ */
+
+#import <Foundation/Foundation.h>
+#import "MDMTransition.h"
+#import "MDMTransitionContext.h"
+#import "MDMViewControllerTransitionContext.h"
+
+@interface MDMViewControllerInteractiveTransitionContext : NSObject <MDMInteractiveTransitionContext>
+- (nonnull instancetype)initWithTransition:(nonnull id<MDMTransitionContext>)transitionContext;
+- (UIPercentDrivenInteractiveTransition* _Nonnull)getPercentIT;
+@end

src/private/MDMViewControllerInteractiveTransitionContext.m

@@ -0,0 +1,49 @@
+/*
+ Copyright 2017-present The Material Motion Authors. All Rights Reserved.
+ 
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+ 
+ http://www.apache.org/licenses/LICENSE-2.0
+ 
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+ */
+
+#import "MDMViewControllerInteractiveTransitionContext.h"
+
+@implementation MDMViewControllerInteractiveTransitionContext {
+  UIPercentDrivenInteractiveTransition *_percent;
+}
+
+@synthesize transitionContext = _transitionContext;
+
+- (nonnull instancetype)initWithTransition:(nonnull id<MDMTransitionContext>)transitionContext {
+  self = [super init];
+  if (self) {
+    _percent = [[UIPercentDrivenInteractiveTransition alloc] init];
+    _transitionContext = transitionContext;
+  }
+  return self;
+}
+
+- (UIPercentDrivenInteractiveTransition *_Nonnull)getPercentIT {
+  return _percent;
+}
+
+- (void)updatePercent:(CGFloat)percent {
+  [_percent updateInteractiveTransition:percent];
+}
+
+- (void)finishInteractiveTransition {
+  [_percent finishInteractiveTransition];
+}
+
+- (void)cancelInteractiveTransition {
+  [_percent cancelInteractiveTransition];
+}
+@end

src/private/MDMViewControllerTransitionContext.m

@@ -78,11 +78,18 @@ - (UIView *)containerView {
 }
 
 - (void)transitionDidEnd {
-  [_transitionContext completeTransition:true];
-
+  BOOL wasCanceled = [_transitionContext transitionWasCancelled];
+  if(wasCanceled) {
+    [_transitionContext completeTransition: false];
+  } else {
+    [_transitionContext completeTransition: true];
+  }
+  
   _transition = nil;
 
-  [_delegate transitionDidCompleteWithContext:self];
+  if(!wasCanceled) {
+    [_delegate transitionDidCompleteWithContext:self];
+  }
 }
 
 #pragma mark - Private