oc开发笔记1 录音和播放

简单尝试了下用objective-c 实现录音和播放功能：

界面很简单，点击录制按钮就开始录制，再点击就停止 并播放刚才录制的声音。

参考：http://blog.csdn.net/rhljiayou/article/details/15339335

////  ViewController.m//  SnoringTest////  Created by bai on 16/4/5.//  Copyright © 2016年 bai. All rights reserved.//#import "ViewController.h"#import <AVFoundation/AVFoundation.h>@interface ViewController ()@end@implementation ViewControllerNSDictionary *recorderSettingsDict;//录音名字NSString *playName;//定时器NSTimer *timer;AVAudioRecorder *recorder;double lowPassResults;AVAudioPlayer *player;- (void)viewDidLoad {    [super viewDidLoad];   // if ([[[UIDevice currentDevice] systemVersion] compare:@"7.0"] != NSOrderedAscending)   // {        AVAudioSession *session = [AVAudioSession sharedInstance];        NSError *sessionError;        //AVAudioSessionCategoryPlayAndRecord用于录音和播放         [session setCategory:AVAudioSessionCategoryPlayAndRecord error:&sessionError];        if(session == nil)            NSLog(@"Error creating session: %@", [sessionError description]);        else            [session setActive:YES error:nil];  //  }    // Do any additional setup after loading the view, typically from a nib.    NSString *docDir = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];    playName = [NSString stringWithFormat:@"%@/play.aac",docDir];    //录音设置 格式AVFormatIDKey 通道数AVNumberOfChannelsKey 采样率AVSampleRateKey 线性采样位数AVLinearPCMBitDepthKey    recorderSettingsDict =[[NSDictionary alloc] initWithObjectsAndKeys:                           [NSNumber numberWithInt:kAudioFormatMPEG4AAC],AVFormatIDKey,                           [NSNumber numberWithInt:1000.0],AVSampleRateKey,                           [NSNumber numberWithInt:2],AVNumberOfChannelsKey,                           [NSNumber numberWithInt:8],AVLinearPCMBitDepthKey,                           [NSNumber numberWithBool:NO],AVLinearPCMIsBigEndianKey,                           [NSNumber numberWithBool:NO],AVLinearPCMIsFloatKey,                           nil];}- (void)didReceiveMemoryWarning {    [super didReceiveMemoryWarning];    // Dispose of any resources that can be recreated.    recorder= nil;    player= nil;}- (IBAction)touchUp:(UIButton *)sender {        if ([self.recordbut.titleLabel.text  isEqual: @"录制中"]){        [self.recordbut setTitle:@"录制" forState:UIControlStateNormal];        //录音停止        [recorder stop];        recorder = nil;        //结束定时器        [timer invalidate];        timer = nil;        NSError *playerError;        //从budle路径下读取音频测试文件 这个文件名是你的歌曲名字,mp3是你的音频格式        // NSString *playName = [[NSBundle mainBundle] pathForResource:@"q" ofType:@"mp3"];        //播放        // player = [[AVAudioPlayer alloc] initWithContentsOfURL:url error:nil];        player = [[AVAudioPlayer alloc] initWithContentsOfURL:[NSURL URLWithString:playName ] error:&playerError];        //音量        player.volume = 5.0;        //切换至扬声器        [[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayback error:nil];        if (player == nil)        {            NSLog(@"ERror creating player: %@", [playerError description]);        }else{            [player play];            NSLog(@" 正在播放 音量:%f",player.volume );        }    }else{         //切换至录音         [[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryRecord error:nil];           //按下录音            NSError *error = nil;            //暂时没发现模拟器上会崩溃            recorder = [[AVAudioRecorder alloc] initWithURL:[NSURL URLWithString:playName] settings:recorderSettingsDict error:&error];                        if (recorder) {                //是否允许刷新电平表，默认是off                recorder.meteringEnabled = YES;                //创建文件，并准备录音                [recorder prepareToRecord];                //开始录音                [recorder record];                //启动定时器,为了更新电平                timer = [NSTimer scheduledTimerWithTimeInterval:0.2 target:self selector:@selector(levelTimer:) userInfo:nil repeats:YES];                            } else            {                NSLog(@"Error: %@  )" , [error localizedDescription]);            }             [self.recordbut setTitle:@"录制中" forState:UIControlStateNormal];            }}-(void)levelTimer:(NSTimer*)timer_{    //call to refresh meter values刷新平均和峰值功率,此计数是以对数刻度计量的,-160表示完全安静，0表示最大输入值    [recorder updateMeters];    const double ALPHA = 0.05;    double peakPowerForChannel = pow(10, (0.05 * [recorder peakPowerForChannel:0]));    lowPassResults = ALPHA * peakPowerForChannel + (1.0 - ALPHA) * lowPassResults;        NSLog(@"音量均值: %f 峰值: %f 电平: %f", [recorder averagePowerForChannel:0], [recorder peakPowerForChannel:0], lowPassResults);}- (IBAction)exitAction:(id)sender {    exit(0);}@end

遇到问题一：播放不出声音

一开始播放时没有声音，后来百度后知道播放器*player不能设置为局部变量，得设置成全局变量才能正常播放。

问题二：Home键返回或锁屏后不能持续录音

如果不做任何设置，homo键后或锁屏会暂停录音，解决办法是修改info.plist，增加Application does not run in background和Required background modes：

问题三：使用扬声器

 //切换至扬声器

        [[AVAudioSessionsharedInstance]setCategory:AVAudioSessionCategoryPlaybackerror:nil];

 //切换至录音

         [[AVAudioSessionsharedInstance]setCategory:AVAudioSessionCategoryRecorderror:nil];