這里簡單闡述一下開發(fā)需求，用戶要上直播課之前要測試麥克風是否可用，所以首先我們要使用錄音的類錄音，對聲音的分貝進行監(jiān)控，圖形化界面上為用戶展示聲音的變化。

一、首先我們看一張UI圖，補充了解一下上述需求

• 上面是一個麥克風的開關，負責開啟測試和關閉測試
• 下面是一個簡單的分貝圖，實時展示聲音的高地（這個進度條類似mac設置里面輸入設備測試的進度條）

二、開始編寫

1. 首先是申請系統(tǒng)權限，（別忘了在plist文件里面設置相關權限）

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

2. 定義兩個全局變量，如下：

@property (nonatomic , strong) AVAudioRecorder      *audioRecorder;//錄音
@property (nonatomic , strong) NSTimer              *timer;//錄音定時器

3. 初始化這兩個類，然后開始監(jiān)聽

[[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"];//只監(jiān)聽不寫入，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取值范圍是-160 <--> 0之間，但是經(jīng)過測試背景噪音一般在-40以下，所以我這里就取值-40 <-->0之間了

錄音監(jiān)控的部分結(jié)束了，下面分享三角形進度條的代碼，有需要的小伙伴可以直接復制使用

• 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