IOS的重力感应

昨天写了重力感应的例子，我觉得这个例子比较有用处，我分享出来：

1 ）显然ios4 之后可以使用coreMotion的framework 为了向下兼容加上UIAccelerator，

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#import <Foundation/Foundation.h>
#import <CoreMotion/CoreMotion.h>
@protocol IFAccelerometerDelegate<NSObject>
- (void)accelerateWithX:(NSNumber*)x withY:(NSNumber*)y withZ:(NSNumber*)z withTimeInterval:(NSTimeInterval)timeInterval;
@end
@inte易做图ce IFAccelerometer : NSObject<UIAccelerometerDelegate>
{
    UIAccelerometer *_accelerometer;
    CMMotionManager *_motionManager;
    id<IFAccelerometerDelegate> _delegate;
}
+ (id)shareAccelerometer;
- (void)addOberser:(id)oberserer;
- (void)removeObserver;

@end

CMMotionManager 将是我们使用的Object，可以用来监测重力！
同时，咱们不能在需要监测重力感应的地方直接使用这个类，这样耦合比较严重，也不利于重用。所以抽离出来，在代码中您可以看到，我将定义一个signleton，同时将重力变化的事件回调给其代理。

2.接着往下是定义其函数，这个很简单，直接贴代码。

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#import "IFAccelerometer.h"
static IFAccelerometer *accelerometerInstance = nil;
@implementation IFAccelerometer
+ (id)shareAccelerometer
{
    if (!accelerometerInstance) {
        static dispatch_once_t onceToken;
        dispatch_once(&onceToken, ^{
            accelerometerInstance = [[[self class]alloc]init];
        });
    }
    return accelerometerInstance;
}

- (id)init
{
    self = [super init];
    if (self) {
#ifdef __IPHONE_5_0
        _motionManager = [[CMMotionManager alloc]init];
        if (_motionManager.accelerometerAvailable) {
            [_motionManager setAccelerometerUpdateInterval:1/60.f];
            NSOperationQueue *operationQueue = [NSOperationQueue mainQueue];
            [_motionManager startAccelerometerUpdatesToQueue:operationQueue withHandler:^(CMAccelerometerData *data,NSError *error)
             {
                 if ([_delegate respondsToSelector:@selector(accelerateWithX:withY:withZ:withTimeInterval:)])
                 {
                     NSNumber *x = [NSNumber numberWithDouble:data.acceleration.x];
                     NSNumber *y = [NSNumber numberWithDouble:data.acceleration.y];
                     NSNumber *z = [NSNumber numberWithDouble:data.acceleration.z];
                     [_delegate accelerateWithX:x withY:y withZ:z withTimeInterval:data.timestamp];
                 }
             }
             ];

        }
#else
#ifdef __IPHONE_4_0
               _accelerometer = [UIAccelerometer sharedAccelerometer];
               [_accelerometer setUpdateInterval:(1/60.0f)];
               _accelerometer.delegate = self;
#endif
#endif

    }
    return self;
}

- (void)addOberser:(id)oberserer
{
    _delegate = oberserer;
}

- (void)removeObserver
{
    _delegate = nil;
}

- (void)accelerometer:(UIAccelerometer *)accelerometer didAccelerate:(UIAcceleration *)acceleration
{
    if ([_delegate respondsToSelector:@selector(accelerateWithX:withY:withZ:withTimeInterval:)])
    {
        NSNumber *x = [NSNumber numberWithDouble:acceleration.x];
        NSNumber *y = [NSNumber numberWithDouble:acceleration.y];
        NSNumber *z = [NSNumber numberWithDouble:acceleration.z];
        [_delegate accelerateWithX:x withY:y withZ:z withTimeInterval:acceleration.timestamp];
    }

}
3.以ViewController 为例介绍如何使用重力感应
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- (void)viewDidLoad
{
    [super viewDidLoad];
    [[IFAccelerometer shareAccelerometer]addOberser:self];
    _imageView = [[UIImageView alloc]initWithImage:[UIImage imageNamed:@"33.png"]];
    _imageView.frame = CGRectMake(0, 0, KIMAGEWIDTH, KIMAGEHEIGHT);
    _imageView.center = self.view.center;
    [self.view addSubview:_imageView];

}

_imageView 是一个UIImageView的成员，其宽高是一个分别是我定义的宏。
注意，我在头文件添加了重力感应的代理，此时这行

[[IFAccelerometer shareAccelerometer]addOberser:self];

表明我在这个viewController中使用这个重力感应的数据。

好，现在是完成回调的时候了，继续贴代码

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- (void)accelerateWithX:(NSNumber *)x withY:(NSNumber *)y withZ:(NSNumber *)z withTimeInterval:(NSTimeInterval)timeInterval
{

    float deceleration = 0.4f;
    float sensitivity = 6.0f;
    float maxVelocity = 100.0f;

    velocity.x = velocity.x * deceleration + [x doubleValue] * sensitivity;
    velocity.y = velocity.y * deceleration + [y doubleValue] * sensitivity;

    if(velocity.x > maxVelocity){
        velocity.x = maxVelocity;
    }else if(velocity.x < -

补充：移动开发 , IOS ,