UIView添加UIMotionEffect效果

（1）UIView+MotionEffect.h

#import <UIKit/UIKit.h>

@interface UIView (MotionEffect)

@property (nonatomic, strong) UIMotionEffectGroup *effectGroup;

- (void)addXAxisWithValue:(CGFloat)xValue YAxisWithValue:(CGFloat)yValue;
- (void)removeSelfMotionEffect;

@end

（2）UIView+MotionEffect.m

#import "UIView+MotionEffect.h"
#import <objc/runtime.h>

static char motionEffectFlag;

@implementation UIView (MotionEffect)

- (void)setEffectGroup:(UIMotionEffectGroup *)effectGroup {
    // 清除关联
    objc_setAssociatedObject(self, &motionEffectFlag, nil, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
    
    // 建立关联
    objc_setAssociatedObject(self, &motionEffectFlag, effectGroup, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

- (UIMotionEffectGroup *)effectGroup {
    // 返回关联
    return objc_getAssociatedObject(self, &motionEffectFlag);
}

- (void)addXAxisWithValue:(CGFloat)xValue YAxisWithValue:(CGFloat)yValue {  
    if ((xValue >= 0) && (yValue >= 0)) {
        UIInterpolatingMotionEffect *xAxis = [[UIInterpolatingMotionEffect alloc] initWithKeyPath:@"center.x" type:UIInterpolatingMotionEffectTypeTiltAlongHorizontalAxis];
        xAxis.minimumRelativeValue = @(-xValue);
        xAxis.maximumRelativeValue = @(xValue);
        
        UIInterpolatingMotionEffect *yAxis = [[UIInterpolatingMotionEffect alloc] initWithKeyPath:@"center.y" type:UIInterpolatingMotionEffectTypeTiltAlongVerticalAxis];
        yAxis.minimumRelativeValue = @(-yValue);
        yAxis.maximumRelativeValue = @(yValue);
        
        // 先移除效果再添加效果
        self.effectGroup.motionEffects = nil;
        [self removeMotionEffect:self.effectGroup];
        self.effectGroup.motionEffects = @[xAxis, yAxis];
        
        // 给view添加效果
        [self addMotionEffect:self.effectGroup];
    }
}

- (void)removeSelfMotionEffect {
    [self removeMotionEffect:self.effectGroup];
}

@end

（3）调用示例

- (void)viewDidLoad {
    [super viewDidLoad];
    
    UIImageView *imageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"flower"]];
    imageView.center = self.view.center;
    [self.view addSubview:imageView];
    
    imageView.effectGroup = [UIMotionEffectGroup new];
    [imageView addXAxisWithValue:15.f YAxisWithValue:15.f];
}