iOS9的UICollisionBehavior似乎要遠離邊界1.5分：我的bug還是Apple的？

Question

在我的應用程序中，我使用包含UICollisionBehavior的UIKit Dynamics在打開和關閉時彈出一個菜單。 我正在使用的代碼如下。 這對iOS8來說一直很好用。 然而，對於iOS9（包括剛剛發布的iOS9.1 beta 2），我發現了一個奇怪的問題。 從表面上看，我正在用這個彈跳動畫彈跳的菜單在打開然后關閉之后沒有完全關閉。 仔細觀察，我發現UICollisionBehavior的邊界在iOS8和iOS9上使用相同的值計算。

菜單打開碰撞邊界： (798,330) to (1024,330)它代表一條線，在屏幕上，菜單底部應該在打開和彈跳后最終休息。

菜單關閉碰撞邊界： (798,-280) to (1024,-280)它代表一條線，關閉屏幕，菜單頂部應該在關閉和彈跳后最終休息。

問題出現在iOS9中，菜單UIView實際上並沒有最終在這些邊界處休息。 打開后，iOS9的菜單框架如下所示：

(798, -1.5; 226, 330) [這是：（x，y; w，h）]

關閉后，菜單框架如下所示：

(798, -278.5; 226, 330)

但是 ，這應該是：

(798, 0; 226, 330) （開場后）

(798, -280; 226, 330) （關閉后）

其他人看到iOS9和碰撞行為的這些問題？

我即將對我的代碼進行攻擊（在下面搜索“HACK”），我會選擇iOS9，但我真的不喜歡這些黑客！

BounceAnimation.h

//
//  BounceAnimation.h
//  Petunia
//
//  Created by Christopher Prince on 12/18/14.
//  Copyright (c) 2014 Spastic Muffin, LLC. All rights reserved.
//

// Animates an object through a straight line path, up, down, left or right until it lands, after which it bounces. This requires iOS8 or later.

#import <Foundation/Foundation.h>

@interface BounceAnimation : NSObject

// distnace is for the viewToAnimate to travel until it lands and bounces, in points. You must set this before calling run.
- (instancetype) initWithReferenceView: (UIView *) referenceView viewToAnimate: (UIView *) viewToAnimate andDistance: (CGFloat) distance;

// Direction and distance will be obtained from animateToPoint, and should be consistent with the constraints for the direction property below. I.e., the animateToPoint should be down, left, right, or up from the origin of the viewToAnimate.
- (instancetype) initWithReferenceView: (UIView *) referenceView viewToAnimate: (UIView *) viewToAnimate andFinalPoint: (CGPoint) animateToPoint;

// One shot animation. You can only call run once.
- (void) run;

// Called when animation completes, if given. Called when all the bouncing is done.
@property (nonatomic, strong) void (^completion)(void);

// Called when first contact is made with the boundary, just as the first bounce is about to begin.
@property (nonatomic, strong) void (^firstImpactCallback)(void);

// Only keeps weak references to the views passed in the init method.
@property (nonatomic, weak, readonly) UIView *referenceView;
@property (nonatomic, weak, readonly) UIView *viewToAnimate;

// Rate at which the object accelerates towards the boundary. Same units as magnitude for UIGravityBehavior. Defaults to 1.0.
@property (nonatomic) CGFloat accelerationRate;

// Defaults to 0. Units are points per second.
@property (nonatomic) CGFloat initialVelocity;

// This is a unit vector.
// dx (first component) is rightwards; e.g., dx=0, no right/left; dx=-1, is left one unit
// dy (second component) is downwards; e.g., dy=1, down one unit.
// Defaults to (0, 1), downwards.
// Right now, dx and dy can be 0, 1, or -1. One of dx and dy must be 0.
@property (nonatomic, readonly) CGVector direction;

@end

BounceAnimation.m

//
//  BounceAnimation.m
//  Petunia
//
//  Created by Christopher Prince on 12/18/14.
//  Copyright (c) 2014 Spastic Muffin, LLC. All rights reserved.
//

#import "BounceAnimation.h"
#import "Vector.h"
#import "UIDevice+Extras.h"

@interface BounceAnimation()<UIDynamicAnimatorDelegate, UICollisionBehaviorDelegate>
{
    UIDynamicAnimator *_animator;
    UIGravityBehavior *_gravityBehavior;
    UICollisionBehavior *_collision;
    UIDynamicItemBehavior *_velocity;
    CGPoint _linearVelocity;
    CGFloat _distanceInPoints;
    BOOL _calledFirstImpactCallback;
}

@property (nonatomic, weak) UIView *referenceView;
@property (nonatomic, weak) UIView *viewToAnimate;
@property (nonatomic) CGVector direction;

@end

#define INITIAL_GRAVITY_MAGNITUDE 1.0

@implementation BounceAnimation

- (void) setupWithReferenceView: (UIView *) referenceView andViewToAnimate: (UIView *) viewToAnimate;
{
    AssertIf([UIDevice ios7OrEarlier], @"Don't have at least iOS8!");

    self.referenceView = referenceView;
    self.viewToAnimate = viewToAnimate;

    _animator = [[UIDynamicAnimator alloc] initWithReferenceView:referenceView];
    _animator.delegate = self;

    _gravityBehavior = [[UIGravityBehavior alloc] initWithItems:@[viewToAnimate]];
    _gravityBehavior.magnitude = INITIAL_GRAVITY_MAGNITUDE;

    _velocity = [[UIDynamicItemBehavior alloc] initWithItems:@[viewToAnimate]];
}

// referenceView is just the view on top of which we're doing our animation. E.g., it could be self.view of a view controller. viewToAnimate must be a subview of the reference view.
- (instancetype) initWithReferenceView: (UIView *) referenceView viewToAnimate: (UIView *) viewToAnimate andDistance: (CGFloat) distanceInPoints;
{
    self = [super init];
    if (self) {
        AssertIf(distanceInPoints <= 0.0, @"Invalid distance: %f", _distanceInPoints);
        _distanceInPoints = distanceInPoints;
        [self setupWithReferenceView:referenceView andViewToAnimate:viewToAnimate];
        [self setDirection:CGVectorMake(0.0, 1.0)];
    }

    return self;
}

- (instancetype) initWithReferenceView: (UIView *) referenceView viewToAnimate: (UIView *) viewToAnimate andFinalPoint: (CGPoint) animateToPoint;
{
    self = [super init];
    if (self) {
        // Need to compute distance and direction.
        CGVector direction = [Vector subFirst:[Vector fromPoint:animateToPoint] from:[Vector fromPoint:viewToAnimate.frameOrigin]];
        SPASLogDetail(@"direction after subtraction: %@", NSStringFromCGVector(direction));

        // Special case: No direction because same start and finish.
        if (direction.dy + direction.dx == 0.0) {
            _distanceInPoints = 0.0;
        }
        else {
            direction = [Vector normalize:direction]; // vectorNormalize(direction);
            _distanceInPoints = [Vector distanceFromPoint:viewToAnimate.frameOrigin toPoint:animateToPoint];
        }

        SPASLogDetail(@"finalPoint: %@, direction: %@, distance: %f", NSStringFromCGPoint(animateToPoint), NSStringFromCGVector(direction), _distanceInPoints);

        [self setupWithReferenceView:referenceView andViewToAnimate:viewToAnimate];
        [self setDirection:direction];
    }

    return self;
}

- (void) setInitialVelocity:(CGFloat)initialVelocity;
{
    _initialVelocity = initialVelocity;
    // Only positive speeds in the velocity are relevant. Negative speeds reduce the velocity, they don't go the other direction.
    _linearVelocity =
        CGPointMake(initialVelocity * fabs(_direction.dx),
                    initialVelocity * fabs(_direction.dy));
}

- (void) setAccelerationRate:(CGFloat)accelerationRate;
{
    _accelerationRate = accelerationRate;
    _gravityBehavior.magnitude = accelerationRate;

}

// I'm only doing left, right, up, down animations because of the problem of rotating the viewToAnimate. I'm not sure I'll ever have a case where I want a rotated animated view. (Hmmm. If I want to do some kind of continuous animation, arbitrary direction with non-rotated objects could be cool!)
- (void) setDirection:(CGVector)direction;
{
    if (_collision) {
        [_animator removeBehavior:_collision];
        _collision = nil;
    }

    if (_distanceInPoints == 0.0) {
        // Why bother?
        SPASLogDetail(@"Zero distance");
        return;
    }

    // 9/24/15; HACK
    //_distanceInPoints += 1.5;

    // Since we're doing vector operations with one of the init methods above, the following seems risky!
    //AssertIf(direction.dy != 0.0 && direction.dy != -1.0 && direction.dy != 1.0, @"Invalid dy: %f", direction.dy);
    //AssertIf(direction.dx != 0.0 && direction.dx != -1.0 && direction.dx != 1.0, @"Invalid dx: %f", direction.dx);

    _direction = direction;
    _gravityBehavior.gravityDirection = direction;

    _collision = [[UICollisionBehavior alloc] initWithItems:@[self.viewToAnimate]];
    _collision.collisionDelegate = self;

    CGPoint startBoundary;
    CGPoint endBoundary;

#define SMALL_VALUE 0.05
    BOOL (^closeToZero)(CGFloat) = ^(CGFloat value) {
        if (value > -SMALL_VALUE && value < SMALL_VALUE) {
            return YES;
        }
        else {
            return NO;
        }
    };

    if (closeToZero(direction.dx)) {
        // Vertical motion.
        CGFloat yBoundary = direction.dy * _distanceInPoints + self.viewToAnimate.frameY;
        if (direction.dy > 0.0) {
            // If we're going down, then we need to add the height of the self.viewToAnimate to our boundary. This is because the origin coords are in the *upper*, left of the viewToAnimate.
            yBoundary += self.viewToAnimate.frameHeight;
        }

        startBoundary = CGPointMake(self.viewToAnimate.frameX, yBoundary);
        endBoundary = CGPointMake(self.viewToAnimate.frameX + self.viewToAnimate.frameWidth, yBoundary);
    }
    else {
        // Horizontal motion.
        CGFloat xBoundary = direction.dx * _distanceInPoints + self.viewToAnimate.frameX;
        if (direction.dx > 0.0) {
            // If we're going to the right, then we need to add the width of the self.viewToAnimate to our boundary. This is because the origin coords are in the upper, *left* of the viewToAnimate.
            xBoundary += self.viewToAnimate.frameWidth;
        }

        startBoundary = CGPointMake(xBoundary, self.viewToAnimate.frameY);
        endBoundary = CGPointMake(xBoundary, self.viewToAnimate.frameY + self.viewToAnimate.frameHeight);
    }

    SPASLog(@"startBoundary: %@, endBoundary: %@", NSStringFromCGPoint(startBoundary), NSStringFromCGPoint(endBoundary));

    [_collision addBoundaryWithIdentifier:@"barrier"
                                fromPoint:startBoundary
                                  toPoint:endBoundary];

    [_animator addBehavior:_collision];
}

- (void) run;
{
    if (_collision) {
        [_animator addBehavior:_gravityBehavior];
        [_velocity addLinearVelocity:_linearVelocity forItem:self.viewToAnimate];
        [_animator addBehavior:_velocity];
    }
    else {
        if (self.completion) {
            self.completion();
        }
    }
}

#pragma mark - UIDynamicAnimatorDelegate methods

- (void)dynamicAnimatorDidPause:(UIDynamicAnimator*)animator;
{
    if (self.completion) {
        self.completion();
    }
}

#pragma mark -

#pragma mark - UICollisionBehaviorDelegate methods

// This isn't the method that gets called in our case.
//- (void)collisionBehavior:(UICollisionBehavior*)behavior beganContactForItem:(id <UIDynamicItem>)item1 withItem:(id <UIDynamicItem>)item2 atPoint:(CGPoint)p;

- (void)collisionBehavior:(UICollisionBehavior*)behavior beganContactForItem:(id <UIDynamicItem>)item withBoundaryIdentifier:(id <NSCopying>)identifier atPoint:(CGPoint)p;
{
    if (!_calledFirstImpactCallback) {
        _calledFirstImpactCallback = YES;
        if (self.firstImpactCallback) {
            self.firstImpactCallback();
        }
    }
}

#pragma mark -


@end

Answer 1

我在Swift工作，我看到與1.5點偏移相同的行為。 它似乎與器件的分辨率無關（1x，2x或3x），都有1.5點偏移。

但是，使用基於路徑的API，問題似乎不再存在：

let collisionBehavior: UICollisionBehavior = ...
let topLeft: CGPoint = ...
let bottomLeft: CGPoint = ...

let path = CGPathCreateMutable()
CGPathMoveToPoint(path, nil, topLeft.x, topLeft.y)
CGPathAddLineToPoint(path, nil, bottomLeft.x, bottomLeft.y)
let bezierPath = UIBezierPath(CGPath: path)
collisionBehavior.addBoundaryWithIdentifier("myID", forPath: bezierPath)

將其轉換為Objective-C非常簡單：

UICollisionBehavior *collisionBehavior = ...
CGPoint topLeft = ...
CGPoint bottomLeft = ...

CGMutablePathRef path = CGPathCreateMutable();
CGPathMoveToPoint(path, nil, topLeft.x, topLeft.y);
CGPathAddLineToPoint(path, nil, bottomLeft.x, bottomLeft.y);
UIBezierPath *bezierPath = [UIBezierPath bezierPathWithCGPath: path];
[collisionBehavior addBoundaryWithIdentifier: @"myID" forPath: path];