iOS开发之麦克风监听分贝

这里简单阐述一下开发需求，用户要上直播课之前要测试麦克风是否可用，所以首先我们要使用录音的类录音，对声音的分贝进行监控，图形化界面上为用户展示声音的变化。

一、首先我们看一张UI图，补充了解一下上述需求

• 上面是一个麦克风的开关，负责开启测试和关闭测试
• 下面是一个简单的分贝图，实时展示声音的高地（这个进度条类似mac设置里面输入设备测试的进度条）

二、开始编写

1. 首先是申请系统权限，（别忘了在plist文件里面设置相关权限）

AVAuthorizationStatus videoAuthStatus = [AVCaptureDevice authorizationStatusForMediaType:AVMediaTypeAudio];
    if (videoAuthStatus == AVAuthorizationStatusNotDetermined) {
        [[AVAudioSession sharedInstance] requestRecordPermission:^void(BOOL granted) {}];
    }

2. 定义两个全局变量，如下：

@property (nonatomic , strong) AVAudioRecorder      *audioRecorder;//录音
@property (nonatomic , strong) NSTimer              *timer;//录音定时器

3. 初始化这两个类，然后开始监听

[[AVAudioSession sharedInstance] setCategory: AVAudioSessionCategoryPlayAndRecord error: nil];
NSDictionary *settings = [NSDictionary dictionaryWithObjectsAndKeys:
                                  [NSNumber numberWithFloat: 44100.0], AVSampleRateKey,
                                  [NSNumber numberWithInt: kAudioFormatAppleLossless], AVFormatIDKey,
                                  [NSNumber numberWithInt: 2], AVNumberOfChannelsKey,
                                  [NSNumber numberWithInt: AVAudioQualityMax], AVEncoderAudioQualityKey,
                                  nil];
NSURL *url = [NSURL fileURLWithPath:@"/dev/null"];//只监听不写入，所以空地址
NSError *error;
_audioRecorder = [[AVAudioRecorder alloc] initWithURL:url settings:settings error:&error];
_audioRecorder.meteringEnabled = YES;
[_audioRecorder prepareToRecord];
[self.audioRecorder record];
_timer = [NSTimer timerWithTimeInterval:0.1 repeats:YES block:^(NSTimer * _Nonnull timer) {
                if (self.audioRecorder.isRecording) {
                    [self.audioRecorder updateMeters];
                    float peakPower = [self.audioRecorder peakPowerForChannel:0];
                    if (peakPower <= -40) {
                        self.toolView.volumeView.level = 0.01;
                    }else if (peakPower == 0){
                        self.toolView.volumeView.level = 1.0;
                    }else{
                        self.toolView.volumeView.level = (peakPower + 40)*2.5/100.0;
                    }
                }
            }];
[[NSRunLoop currentRunLoop] addTimer:_timer forMode:NSRunLoopCommonModes];

• peakPower取值范围是-160 <--> 0之间，但是经过测试背景噪音一般在-40以下，所以我这里就取值-40 <-->0之间了

录音监控的部分结束了，下面分享三角形进度条的代码，有需要的小伙伴可以直接复制使用

• SHLiveCourseVolumeDBView.h

#import <UIKit/UIKit.h>

NS_ASSUME_NONNULL_BEGIN

@interface SHLiveCourseVolumeDBView : UIView
@property (nonatomic , strong) UIView       *selectView;
@property (nonatomic , assign) CGFloat      level;
@end

NS_ASSUME_NONNULL_END

• SHLiveCourseVolumeDBView.m

#import "SHLiveCourseVolumeDBView.h"

@implementation SHLiveCourseVolumeDBView
- (instancetype)initWithFrame:(CGRect)frame
{
    if (self = [super initWithFrame:frame]) {
        self.backgroundColor = UIColor.grayColor;
        UIBezierPath *bezierPath = [UIBezierPath bezierPath];
        [bezierPath moveToPoint:CGPointMake(0, frame.size.height)];
        [bezierPath addLineToPoint:CGPointMake(frame.size.width, 0)];
        [bezierPath addLineToPoint:CGPointMake(frame.size.width,frame.size.height)];
        [bezierPath addClip];
        CAShapeLayer *maskLayer = [[CAShapeLayer alloc] init];
        maskLayer.frame = self.bounds;
        maskLayer.path = bezierPath.CGPath;
        self.layer.mask = maskLayer;
        [self addSubview:self.selectView];
    }
    return self;
}
- (void)setLevel:(CGFloat)level
{
    _level = level;
    CGRect rect = self.selectView.bounds;
    rect.size.width = self.bounds.size.width*level;
    self.selectView.frame = rect;
}
- (UIView *)selectView
{
    if (!_selectView) {
        _selectView = [[UIView alloc] initWithFrame:self.bounds];
        _selectView.backgroundColor = UIColor.lightGrayColor;
        UIBezierPath *bezierPath = [UIBezierPath bezierPath];
        [bezierPath moveToPoint:CGPointMake(0, _selectView.frame.size.height)];
        [bezierPath addLineToPoint:CGPointMake(_selectView.frame.size.width, 0)];
        [bezierPath addLineToPoint:CGPointMake(_selectView.frame.size.width,_selectView.frame.size.height)];
        [bezierPath addClip];
        CAShapeLayer *maskLayer = [[CAShapeLayer alloc] init];
        maskLayer.frame = self.bounds;
        maskLayer.path = bezierPath.CGPath;
        _selectView.layer.mask = maskLayer;
    }
    return _selectView;
}
@end

完美