绘制播放音乐时的音波图形的View

//
//  MusicView.h
//  Music
//
//  Copyright (c) 2014年 Y.X. All rights reserved.
//

#import <UIKit/UIKit.h>

@interface MusicView : UIView

@property (nonatomic, assign) CGFloat  progress;      // 进程百分比,取值为[0,1]
@property (nonatomic, assign) CGFloat  timeInterval;  // 时间间隔

@end

//
//  MusicView.m
//  Music
//
//  Copyright (c) 2014年 Y.X. All rights reserved.
//

#import "MusicView.h"

@interface MusicView ()

@property (nonatomic, assign) CGRect  baseRect; // 备份原始的frame值

@end

@implementation MusicView

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        _baseRect = frame;
    }
    return self;
}

@synthesize progress = _progress;
- (void)setProgress:(CGFloat)progress
{
    if (progress <= 0) {
        _progress = 0;
    } else if (progress >= 1) {
        _progress = 1;
    } else {
        _progress = progress;
    }
    
    [UIView animateWithDuration:(_timeInterval > 0 ? _timeInterval : 0.99) animations:^{
        CGRect rect       = _baseRect;
        rect.size.height *=  _progress;
        self.frame        = rect;
    }];
}
- (CGFloat)progress
{
    return _progress;
}

@end

//
//  RootViewController.m
//  Music
//
//  Copyright (c) 2014年 Y.X. All rights reserved.
//

#import "RootViewController.h"
#import "MusicView.h"

@interface RootViewController ()

@property (nonatomic, strong) NSTimer    *timer;
@property (nonatomic, strong) MusicView  *musicViewLine1;
@property (nonatomic, strong) MusicView  *musicViewLine2;
@property (nonatomic, strong) MusicView  *musicViewLine3;

@end

@implementation RootViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    
    // 线条1
    _musicViewLine1 = [[MusicView alloc] initWithFrame:CGRectMake(100, 100, 4, 20)];
    _musicViewLine1.backgroundColor = [UIColor redColor];
    _musicViewLine1.timeInterval    = 0.5f;
    [self.view addSubview:_musicViewLine1];
    
    // 线条2
    _musicViewLine2 = [[MusicView alloc] initWithFrame:CGRectMake(108, 100, 4, 20)];
    _musicViewLine2.backgroundColor = [UIColor redColor];
    _musicViewLine2.timeInterval    = 0.5f;
    [self.view addSubview:_musicViewLine2];
    
    // 线条3
    _musicViewLine3 = [[MusicView alloc] initWithFrame:CGRectMake(116, 100, 4, 20)];
    _musicViewLine3.backgroundColor = [UIColor redColor];
    _musicViewLine3.timeInterval    = 0.5f;
    [self.view addSubview:_musicViewLine3];
    
    _timer = [NSTimer scheduledTimerWithTimeInterval:0.5f
                                              target:self
                                            selector:@selector(timerEvent)
                                            userInfo:nil
                                             repeats:YES];
}

- (void)timerEvent
{
    _musicViewLine1.progress = arc4random()%100/100.f;
    _musicViewLine2.progress = arc4random()%100/100.f;
    _musicViewLine3.progress = arc4random()%100/100.f;
}

@end