// 
// ViewController.m 
// 仿百度外卖首页-重力感应 
// 
// Created by Amydom on 16/12/5. 
// Copyright © 2016年 Amydom. All rights reserved. 
// 
 
#import "ViewController.h" 
#import <CoreMotion/CoreMotion.h> 
 
@interface ViewController ()<UIScrollViewDelegate>{ 
   
  NSTimeInterval updateInterval; 
  CGFloat setx;//scroll的动态偏移量 
   
} 
@property (nonatomic,strong) CMMotionManager *mManager; 
 
@property (nonatomic , strong)UIScrollView *myScrollView; 
 
@property (nonatomic , assign)CGFloat offsetX;//初始偏移量 
 
@property (nonatomic , assign)NSInteger offset; 
 
 
@end 
 
@implementation ViewController 
 
- (void)viewDidAppear:(BOOL)animated_{ 
   
  [super viewDidAppear:animated_]; 
  //在界面已经显示后在调用方法(优化) 
  [self startUpdateAccelerometerResult:0]; 
   
} 
 
- (void)viewDidLoad { 
  [super viewDidLoad]; 
  self.view.backgroundColor = [UIColor whiteColor]; 
  [self createView]; 
   
} 
 
- (void)createView{ 
   
  //collectionView 
  UICollectionViewFlowLayout *flowLayout = [[UICollectionViewFlowLayout alloc]init]; 
  UICollectionView *myCollection = [[UICollectionView alloc]initWithFrame:[UIScreen mainScreen].bounds collectionViewLayout:flowLayout]; 
  myCollection.backgroundColor = [UIColor whiteColor]; 
  [self.view addSubview:myCollection]; 
   
   
   
  _myScrollView = [[UIScrollView alloc]initWithFrame:CGRectMake(0, 22, self.view.frame.size.width, 100)]; 
  _myScrollView.backgroundColor = [UIColor lightGrayColor]; 
  _myScrollView.delegate = self; 
  [self.view addSubview:_myScrollView]; 
   
   
  for (int i = 0; i < 8; i ++) { 
     
    NSString *name = [NSString stringWithFormat:@"%d.jpg",i + 1]; 
    UIImageView *image = [[UIImageView alloc]initWithFrame:CGRectMake(5 + 885 * i, 10, 80, 80)]; 
    image.image = [UIImage imageNamed:name]; 
    image.backgroundColor = [UIColor orangeColor]; 
    image.layer.masksToBounds = YES; 
    image.layer.cornerRadius = 40; 
    [_myScrollView addSubview:image]; 
    //偏移量为最后 image 的 frame + origin 
    _myScrollView.contentSize = CGSizeMake (image.frame.size.width + image.frame.origin.x, 10); 
     
     
  } 
   
   
 
} 
 
//手指触碰时 
- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView{ 
   
   _offsetX = scrollView.contentOffset.x; 
  [self stopUpdate]; 
   
} 
 
- (void)scrollViewDidScroll:(UIScrollView *)scrollView{ 
   
  //优化处理 
  setx = scrollView.contentOffset.x; 
   
  _offset = scrollView.contentOffset.x - _offsetX; 
   
    if (_offset > 0) { 
   
      //left 
   
    }else{ 
   
      //right 
       
    } 
   
   
} 
//手指离开时 
- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate{ 
   
  [self startUpdateAccelerometerResult:0]; 
   
} 
 
#pragma mark - 重力感应 
- (CMMotionManager *)mManager 
{ 
  if (!_mManager) { 
    updateInterval = 1.0/15.0; 
    _mManager = [[CMMotionManager alloc] init]; 
  } 
  return _mManager; 
} 
//开始 
- (void)startUpdateAccelerometerResult:(void (^)(NSInteger))result 
{ 
 
  if ([self.mManager isAccelerometerAvailable] == YES) { 
    //回调会一直调用,建议获取到就调用下面的停止方法，需要再重新开始，当然如果需求是实时不间断的话可以等离开页面之后再stop 
    [self.mManager setAccelerometerUpdateInterval:updateInterval]; 
    [self.mManager startAccelerometerUpdatesToQueue:[NSOperationQueue currentQueue] withHandler:^(CMAccelerometerData *accelerometerData, NSError *error) 
     { 
       double x = accelerometerData.acceleration.x; 
       double y = accelerometerData.acceleration.y; 
       if (fabs(y) >= fabs(x)) 
       {//前后 
         if (y >= 0){ 
           //Down 
         } 
         else{ 
           //Portrait 
         } 
          
       } else { //左右 
         
         if (x >= 0){ 
            
           setx += 10; 
            
           if (setx <= 360) { 
             //由于以10为单位改变 contentOffset, 会出现顿的现象,加上动画就可解决这个问题 
             [UIView animateWithDuration:0.1 animations:^{ 
                
               _myScrollView.contentOffset = CGPointMake(setx, 0); 
             }]; 
             //模仿 scroll 的回弹效果 
             if (setx == 360) { 
                
               [UIView animateWithDuration:0.5 animations:^{ 
                  
                 _myScrollView.contentOffset = CGPointMake(setx + 50, 0); 
                  
               } completion:^(BOOL finished) { 
                  
                 [UIView animateWithDuration:0.5 animations:^{ 
                    
                   _myScrollView.contentOffset = CGPointMake(setx , 0); 
 
                 }]; 
                  
               }]; 
                
             } 
              
           }else{ 
              
             setx = 360; 
           } 
            
     
         }else{ 
            
           setx -= 10; 
            
           if (setx >= 0) { 
              
             [UIView animateWithDuration:0.1 animations:^{ 
                
               _myScrollView.contentOffset = CGPointMake(setx, 0); 
 
             }]; 
              
             //模仿 scroll 的回弹效果 
             if (setx == 0) { 
                
               [UIView animateWithDuration:0.5 animations:^{ 
                  
                 _myScrollView.contentOffset = CGPointMake(setx - 50, 0); 
                  
               } completion:^(BOOL finished) { 
                  
                 [UIView animateWithDuration:0.5 animations:^{ 
                    
                   _myScrollView.contentOffset = CGPointMake(setx, 0); 
                    
                 }]; 
                  
               }]; 
 
             } 
              
           }else{ 
              
             setx = 0; 
              
           } 
         } 
       } 
     }]; 
  } 
} 
 
//停止感应方法 
- (void)stopUpdate 
{ 
  if ([self.mManager isAccelerometerActive] == YES) 
  { 
    [self.mManager stopAccelerometerUpdates]; 
  } 
} 
//离开页面后停止(移除 mManager) 
- (void)dealloc 
{ 
  //制空,防止野指针 
  _mManager = nil; 
} 
 
 
- (void)didReceiveMemoryWarning { 
  [super didReceiveMemoryWarning]; 
  // Dispose of any resources that can be recreated. 
} 
 
 
@end