旋转的风车（声音越大转速越快）

添加AVFoundation.framework库文件

 

#import <UIKit/UIKit.h>

@interface AppDelegate : UIResponder <UIApplicationDelegate>

@property (strong, nonatomic) UIWindow *window;


@end

#import "AppDelegate.h"
#import "RootViewController.h"
@interface AppDelegate ()

@end

@implementation AppDelegate


- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    // Override point for customization after application launch.
    self.window.backgroundColor = [UIColor whiteColor];
    
    self.window.rootViewController = [[RootViewController alloc] initWithNibName:@"RootViewController" bundle:nil];
    
    [self.window makeKeyAndVisible];
    return YES;
}


@end

#import <UIKit/UIKit.h>
#import <AVFoundation/AVFoundation.h>
@interface RootViewController : UIViewController
{
    @private
    AVAudioRecorder *recorder;
    NSTimer *levelTimer;
    double lowPass;
}
@property (weak, nonatomic) IBOutlet UIImageView *fan;

@end

#import "RootViewController.h"

@interface RootViewController ()

@end

@implementation RootViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    [self initRecorder];
}

/**
 *  初始化AVAudioRecorder
 */
- (void)initRecorder{
    NSError *error;
    NSURL *url = [NSURL fileURLWithPath:@"/dev/null"];
    NSDictionary *settings = [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithFloat:4100.0],AVSampleRateKey,[NSNumber numberWithInt:kAudioFormatAppleLossless],AVFormatIDKey,[NSNumber numberWithInt:1],AVNumberOfChannelsKey,[NSNumber numberWithInt:AVAudioQualityMax],AVEncoderAudioQualityKey, nil];
    recorder = [[AVAudioRecorder alloc] initWithURL:url settings:settings error:&error];
    if (recorder) {
        recorder.meteringEnabled = YES;
        [recorder record];
        levelTimer = [NSTimer scheduledTimerWithTimeInterval:0.03 target:self selector:@selector(audioLevelTimerCallback:) userInfo:nil repeats:YES];
    }else{
        NSLog(@"Error:%@",[error description]);
    }
}

- (void)audioLevelTimerCallback:(NSTimer *)timer{
    [recorder updateMeters];
    double peakPowerForChannel = pow(10, 0.05*[recorder peakPowerForChannel:0]);
    lowPass = 0.05 * peakPowerForChannel + (1 - 0.05) * lowPass;
    [self rotateFanToAngle:(lowPass - 0.05)/(1 - 0.05)];

}

/**
 *  旋转风扇
 */
- (void)rotateFanToAngle:(double)angle{
   [UIView transitionWithView:self.fan duration:angle*1.2 options:UIViewAnimationCurveEaseOut animations:^{
       self.fan.transform = CGAffineTransformRotate(self.fan.transform, angle/3);
   } completion:nil];
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}



@end

在xib文件中拖入UIImageView,然后添加相应的图片