iOS 10.0后推出的推送扩展，主要分为两个部分
1、通知服务扩展（UNNotificationServiceExtension），功能是在收到推送后允许开发者对推送内容做修改，比如添加附件，展示图片，播放音频，加载网络数据等
2、通知内容扩展（UNNotificationContentExtension），功能是在展示通知栏的时候，可以自定义通知展示界面

UNNotificationServiceExtension 通知服务扩展
在创建这个扩展时会生成info.plist NotificationService.m/.h PushExtension.entitlements三个文件

在NotificationService.m文件中，有两个回调方法：

// 系统接到通知后，有最多30秒在这里重写通知内容（如下载附件并更新通知）
- (void)didReceiveNotificationRequest:(UNNotificationRequest *)request withContentHandler:(void (^)(UNNotificationContent *contentToDeliver))contentHandler;
// 处理过程超时，则收到的通知直接展示出来
- (void)serviceExtensionTimeWillExpire;

如上所看，具体的修改内容就是在第一个方法中，下面会提供基础的操作代码，可根据自己的项目做调整

注意！！！！！！
加载并处理附件时间上限为30秒，否则，通知按系统默认形式弹出；
UNNotificationAttachment的url接收的是本地文件的url；
服务端在处理推送内容时，最好加上媒体类型字段；
aps字符串中的mutable-content字段需要设置为1；表示可修改，否则不走扩展
在对NotificationService进行debug时，需要在Xcode顶栏选择编译运行的target为NotificationService，否则无法进行实时debug。

UNNotificationAttachment：attachment支持
1）音频5M（kUTTypeWaveformAudio/kUTTypeMP3/kUTTypeMPEG4Audio/kUTTypeAudioInterchangeFileFormat）
2）图片10M（kUTTypeJPEG/kUTTypeGIF/kUTTypePNG）
3）视频50M（kUTTypeMPEG/kUTTypeMPEG2Video/kUTTypeMPEG4/kUTTypeAVIMovie）

消息内容格式：

 {"aps":{"alert":{"title":"Title...","subtitle":"Subtitle...","body":"Body..."},"sound":"default","badge": 1,"mutable-content": 1,"category": "QiShareCategoryIdentifier",},"msgid":"123","media":{"type":"image","url":"[www.fotor.com/images2/fea…](https://link.juejin.im/?target=https%3A%2F%2Fwww.fotor.com%2Fimages2%2Ffeatures%2Fphoto_effects%2Fe_bw.jpg)"}}

UNNotificationContentExtension 通知内容扩展

通知内容扩展界面NotificationViewController的结构如下：
设置actions： 从NotificationViewController直接继承于ViewController，因此可以在这个类中重写相关方法，来修改界面的相关布局及样式。在这个界面展开之前，用户可以通过UNNotificationAction与相应推送通知交互，但是用户和这个通知内容扩展界面无法直接交互。
设置category： 推送通知内容中的category字段，与UNNotificationContentExtension的info.plist中UNNotificationExtensionCategory字段的值要匹配，系统才能找到自定义的UI。

在Info.plist添加交互标识

标识样式展示

自定义视图的大小可以通过设置NotificationViewController的preferredContentSize大小来控制，
但是用户体验稍显突兀，可以通过设置info.plist中的UNNotificationExtensionInitialContentSizeRatio属性的值来优化；
contentExtension中的info.plist中NSExtension下NSExtensionAttributes字段下可以配置以下属性的值，
UNNotificationExtensionCategory：表示自定义内容假面可以识别的category，可以为数组，也即可以为这个content绑定多个通知；
UNNotificationExtensionInitialContentSizeRatio：默认的UI界面的宽高比；
UNNotificationExtensionDefaultContentHidden：是否显示系统默认的标题栏和内容，可选参数；UNNotificationExtensionOverridesDefaultTitle：是否让系统采用消息的标题作为通知的标题，可选参数。
处理通知内容扩展的过程中关于identifier的设置共有五处（UNNotificationAction、UNNotificationCategory、bestAttemptContent、contentExtension中的info.plist中，aps字符串中），请区别不同identifier的作用。
两个扩展联合使用，在XCode中选择当前target，才能打断点看到相应log信息。

消息格式内容

 { "aps":{ "alert":"Testing...(0)","badge":1,"sound":"default","category":"QiShareCategoryIdentifier"}}

在NotificationService.m中设置category的值如下：
self.bestAttemptContent.categoryIdentifier = @"QiShareCategoryIdentifier";

info.plist中关于category的配置如下：
UNNotificationContentExtension协议：NotificationViewController 中生成时默认实现了。

NotificationService代码

#import "NotificationService.h"
#import <AVFoundation/AVFoundation.h>
 
@interface NotificationService ()
 
@property (nonatomic, strong) void (^contentHandler)(UNNotificationContent *contentToDeliver);
@property (nonatomic, strong) UNMutableNotificationContent *bestAttemptContent;
 
@end
 
@implementation NotificationService
 
- (void)didReceiveNotificationRequest:(UNNotificationRequest *)request withContentHandler:(void (^)(UNNotificationContent * _Nonnull))contentHandler {
//获取回调block ，这个回调必须实现，在修改数据后，这个回调会把修改的数据回调给系统做展示    
self.contentHandler = contentHandler;
    self.bestAttemptContent = [request.content mutableCopy];
//通知的标题
    self.bestAttemptContent.title = [NSString stringWithFormat:@"%@ [ServiceExtension modified]", self.bestAttemptContent.title];
    
    // 设置UNNotificationAction 类似于微信的回复，头条的查看等按纽，按钮仅可修改位置、颜色、大小等，添加这些按钮，必须在info.plist 文件中添加对于的标识!下面附添加标识的图片

    UNNotificationAction * actionA  =[UNNotificationAction actionWithIdentifier:@"ActionA" title:@"A_Required" options:UNNotificationActionOptionAuthenticationRequired];
    UNNotificationAction * actionB = [UNNotificationAction actionWithIdentifier:@"ActionB" title:@"B_Destructive" options:UNNotificationActionOptionDestructive];
    UNNotificationAction * actionC = [UNNotificationAction actionWithIdentifier:@"ActionC" title:@"C_Foreground" options:UNNotificationActionOptionForeground];
    UNTextInputNotificationAction * actionD = [UNTextInputNotificationAction actionWithIdentifier:@"ActionD"
                                                                                            title:@"D_InputDestructive"
                                                                                          options:UNNotificationActionOptionDestructive
                                                                             textInputButtonTitle:@"Send"
                                                                             textInputPlaceholder:@"input some words here ..."];
    NSArray *actionArr = [[NSArray alloc] initWithObjects:actionA, actionB, actionC, actionD, nil];
    NSArray *identifierArr = [[NSArray alloc] initWithObjects:@"ActionA", @"ActionB", @"ActionC", @"ActionD", nil];
    UNNotificationCategory * notficationCategory = [UNNotificationCategory categoryWithIdentifier:@"QiShareCategoryIdentifier"
                                                                                          actions:actionArr
                                                                                intentIdentifiers:identifierArr
                                                                                          options:UNNotificationCategoryOptionCustomDismissAction];
    [[UNUserNotificationCenter currentNotificationCenter] setNotificationCategories:[NSSet setWithObject:notficationCategory]];
    
    // 设置categoryIdentifier 这个就是在info.plist 中添加的标识，必须一一对应
    self.bestAttemptContent.categoryIdentifier = @"QiShareCategoryIdentifier";
    
    // 加载网络请求 比如网络图片等
    NSDictionary *userInfo =  self.bestAttemptContent.userInfo;
    NSString *mediaUrl = userInfo[@"media"][@"url"];
    NSString *mediaType = userInfo[@"media"][@"type"];
    if (!mediaUrl.length) {
        self.contentHandler(self.bestAttemptContent);
    } else {
        [self loadAttachmentForUrlString:mediaUrl withType:mediaType completionHandle:^(UNNotificationAttachment *attach) {
            
            if (attach) {
                self.bestAttemptContent.attachments = [NSArray arrayWithObject:attach];
            }
            //将数据回调给系统展示通知
            self.contentHandler(self.bestAttemptContent);
        }];
    }
}
 //加载网络图片
- (void)loadAttachmentForUrlString:(NSString *)urlStr withType:(NSString *)type completionHandle:(void(^)(UNNotificationAttachment *attach))completionHandler
{
    __block UNNotificationAttachment *attachment = nil;
    NSURL *attachmentURL = [NSURL URLWithString:urlStr];
    NSString *fileExt = [self getfileExtWithMediaType:type];
    
    NSURLSession *session = [NSURLSession sessionWithConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration]];
    [[session downloadTaskWithURL:attachmentURL completionHandler:^(NSURL *temporaryFileLocation, NSURLResponse *response, NSError *error) {
        if (error) {
            NSLog(@"加载多媒体失败 %@", error.localizedDescription);
        } else {
            NSFileManager *fileManager = [NSFileManager defaultManager];
            NSURL *localURL = [NSURL fileURLWithPath:[temporaryFileLocation.path stringByAppendingString:fileExt]];
            [fileManager moveItemAtURL:temporaryFileLocation toURL:localURL error:&error];
            
            // 自定义推送UI需要
            NSMutableDictionary * dict = [self.bestAttemptContent.userInfo mutableCopy];
            [dict setObject:[NSData dataWithContentsOfURL:localURL] forKey:@"image"];
            self.bestAttemptContent.userInfo = dict;
            
            NSError *attachmentError = nil;
            attachment = [UNNotificationAttachment attachmentWithIdentifier:@"QiShareCategoryIdentifier" URL:localURL options:nil error:&attachmentError];
            if (attachmentError) {
                NSLog(@"%@", attachmentError.localizedDescription);
            }
        }
        completionHandler(attachment);
    }] resume];
}
 
- (NSString *)getfileExtWithMediaType:(NSString *)mediaType {
    NSString *fileExt = mediaType;
    if ([mediaType isEqualToString:@"image"]) {
        fileExt = @"jpg";
    }
    if ([mediaType isEqualToString:@"video"]) {
        fileExt = @"mp4";
    }
    if ([mediaType isEqualToString:@"audio"]) {
        fileExt = @"mp3";
    }
    return [@"." stringByAppendingString:fileExt];
}
 
- (void)serviceExtensionTimeWillExpire {
    // Called just before the extension will be terminated by the system.
    // Use this as an opportunity to deliver your "best attempt" at modified content, otherwise the original push payload will be used.
    self.contentHandler(self.bestAttemptContent);
}
 
@end

NotificationView 代码

#import "NotificationViewController.h"
#import <UserNotifications/UserNotifications.h>
#import <UserNotificationsUI/UserNotificationsUI.h>
 
#define Margin      15
 
@interface NotificationViewController () <UNNotificationContentExtension>
 
@property (nonatomic, strong) UILabel *label;
@property (nonatomic, strong) UILabel *subLabel;
@property (nonatomic, strong) UIImageView *imageView;
 
@property (nonatomic, strong) UILabel *hintLabel;
 
@end
 
@implementation NotificationViewController
 
- (void)viewDidLoad {
 
    [super viewDidLoad];
    
    CGPoint origin = self.view.frame.origin;
    CGSize size = self.view.frame.size;
    
    self.label = [[UILabel alloc] initWithFrame:CGRectMake(Margin, Margin, size.width-Margin*2, 30)];
    self.label.autoresizingMask = UIViewAutoresizingFlexibleWidth;
    [self.view addSubview:self.label];
    
    self.subLabel = [[UILabel alloc] initWithFrame:CGRectMake(Margin, CGRectGetMaxY(self.label.frame)+10, size.width-Margin*2, 30)];
    self.subLabel.autoresizingMask = UIViewAutoresizingFlexibleWidth;
    [self.view addSubview:self.subLabel];
    
    self.imageView = [[UIImageView alloc] initWithFrame:CGRectMake(Margin, CGRectGetMaxY(self.subLabel.frame)+10, 100, 100)];
    [self.view addSubview:self.imageView];
    
    self.hintLabel = [[UILabel alloc] initWithFrame:CGRectMake(Margin, CGRectGetMaxY(self.imageView.frame)+10, size.width-Margin*2, 20)];
    [self.hintLabel setText:@"我是hintLabel"];
    [self.hintLabel setFont:[UIFont systemFontOfSize:14]];
    [self.hintLabel setTextAlignment:NSTextAlignmentLeft];
    [self.view addSubview:self.hintLabel];
    self.view.frame = CGRectMake(origin.x, origin.y, size.width, CGRectGetMaxY(self.imageView.frame)+Margin);
 
    // 设置控件边框颜色
    [self.label.layer setBorderColor:[UIColor redColor].CGColor];
    [self.label.layer setBorderWidth:1.0];
    [self.subLabel.layer setBorderColor:[UIColor greenColor].CGColor];
    [self.subLabel.layer setBorderWidth:1.0];
    [self.imageView.layer setBorderWidth:2.0];
    [self.imageView.layer setBorderColor:[UIColor blueColor].CGColor];
    [self.view.layer setBorderWidth:2.0];
    [self.view.layer setBorderColor:[UIColor cyanColor].CGColor];
}
 
- (void)didReceiveNotification:(UNNotification *)notification {
    
    self.label.text = notification.request.content.title;
    self.subLabel.text = [NSString stringWithFormat:@"%@ [ContentExtension modified]", notification.request.content.subtitle];
    
    NSData *data = notification.request.content.userInfo[@"image"];
    UIImage *image = [UIImage imageWithData:data];
    [self.imageView setImage:image];
}
 
- (void)didReceiveNotificationResponse:(UNNotificationResponse *)response completionHandler:(void (^)(UNNotificationContentExtensionResponseOption))completion {
    
    [self.hintLabel setText:[NSString stringWithFormat:@"触发了%@", response.actionIdentifier]];
    if ([response.actionIdentifier isEqualToString:@"ActionA"]) {
        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(1.5 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
            completion(UNNotificationContentExtensionResponseOptionDismiss);
        });
    } else if ([response.actionIdentifier isEqualToString:@"ActionB"]) {
 
    } else if ([response.actionIdentifier isEqualToString:@"ActionC"]) {
 
    }  else if ([response.actionIdentifier isEqualToString:@"ActionD"]) {
 
    } else {
        completion(UNNotificationContentExtensionResponseOptionDismiss);
    }
    completion(UNNotificationContentExtensionResponseOptionDoNotDismiss);
}
 
@end

更新，10.0-12.0 后台推送语音播报可以使用系统自带的文字合成语音播报AVSpeechSynthesisVoice或者内置几段语音进行合成后再进行播放
分别例子：
系统合成

av= [[AVSpeechSynthesizer alloc]init];
av.delegate=self;//挂上代理
AVSpeechSynthesisVoice*voice = [AVSpeechSynthesisVoicevoiceWithLanguage:@"zh-CN"];//设置发音，这是中文普通话
AVSpeechUtterance*utterance = [[AVSpeechUtterance   alloc]initWithString:@"需要播报的文字"];//需要转换的文字
utterance.rate=0.6;// 设置语速，范围0-1，注意0最慢，1最快；
utterance.voice= voice;
[avspeakUtterance:utterance];//开始

内置语音

- (void)audioMergeClick{
//1.获取本地音频素材
    NSString *audioPath1 = [[NSBundle mainBundle]pathForResource:@"一" ofType:@"mp3"];
    NSString *audioPath2 = [[NSBundle mainBundle]pathForResource:@"元" ofType:@"mp3"];
    AVURLAsset *audioAsset1 = [AVURLAsset assetWithURL:[NSURL fileURLWithPath:audioPath1]];
    AVURLAsset *audioAsset2 = [AVURLAsset assetWithURL:[NSURL fileURLWithPath:audioPath2]];
//2.创建两个音频轨道,并获取两个音频素材的轨道
    AVMutableComposition *composition = [AVMutableComposition composition];
    //音频轨道
    AVMutableCompositionTrack *audioTrack1 = [composition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:0];
    AVMutableCompositionTrack *audioTrack2 = [composition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:0];
    //获取音频素材轨道
    AVAssetTrack *audioAssetTrack1 = [[audioAsset1 tracksWithMediaType:AVMediaTypeAudio] firstObject];
    AVAssetTrack *audioAssetTrack2 = [[audioAsset2 tracksWithMediaType:AVMediaTypeAudio]firstObject];
//3.将两段音频插入音轨文件,进行合并
    //音频合并- 插入音轨文件
    // `startTime`参数要设置为第一段音频的时长，即`audioAsset1.duration`, 表示将第二段音频插入到第一段音频的尾部。

    [audioTrack1 insertTimeRange:CMTimeRangeMake(kCMTimeZero, audioAsset1.duration) ofTrack:audioAssetTrack1 atTime:kCMTimeZero error:nil];
    [audioTrack2 insertTimeRange:CMTimeRangeMake(kCMTimeZero, audioAsset2.duration) ofTrack:audioAssetTrack2 atTime:audioAsset1.duration error:nil];
//4. 导出合并后的音频文件
    //`presetName`要和之后的`session.outputFileType`相对应
    //音频文件目前只找到支持m4a 类型的
    AVAssetExportSession *session = [[AVAssetExportSession alloc]initWithAsset:composition presetName:AVAssetExportPresetAppleM4A];
    
    NSString *outPutFilePath = [[self.filePath stringByDeletingLastPathComponent] stringByAppendingPathComponent:@"xindong.m4a"];
    
    if ([[NSFileManager defaultManager] fileExistsAtPath:outPutFilePath]) {
        [[NSFileManager defaultManager] removeItemAtPath:outPutFilePath error:nil];
    }
    // 查看当前session支持的fileType类型
    NSLog(@"---%@",[session supportedFileTypes]);
    session.outputURL = [NSURL fileURLWithPath:self.filePath];
    session.outputFileType = AVFileTypeAppleM4A; //与上述的`present`相对应
    session.shouldOptimizeForNetworkUse = YES;   //优化网络
    [session exportAsynchronouslyWithCompletionHandler:^{
        if (session.status == AVAssetExportSessionStatusCompleted) {
            NSLog(@"合并成功----%@", outPutFilePath);
            _audioPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:[NSURL fileURLWithPath:outPutFilePath] error:nil];
            [_audioPlayer play];
        } else {
            // 其他情况, 具体请看这里`AVAssetExportSessionStatus`.
        }
    }];
    
}
- (NSString *)filePath {
    if (!_filePath) {
        _filePath = [NSSearchPathForDirectoriesInDomains(NSLibraryDirectory, NSUserDomainMask, YES) firstObject];
        NSString *folderName = [_filePath stringByAppendingPathComponent:@"MergeAudio"];
        BOOL isCreateSuccess = [kFileManager createDirectoryAtPath:folderName withIntermediateDirectories:YES attributes:nil error:nil];
        if (isCreateSuccess) _filePath = [folderName stringByAppendingPathComponent:@"xindong.m4a"];
    }
    return _filePath;
}

官方12.1之后，在这个推送扩展里面AVAudioPlayer失效
可以播放工程主目录和Library/Sounds,还可以播放AppGroup中Library/Sounds的音频 ，我们可以在后台合成，然后下载到AppGroup后修改sound字段进行播放，首先打开我们项目的AppGroup，在主项目和推送扩展里都要勾选AppGroup
之后接到通知，解析出下载链接，下载完在本地修改sound字段，交由系统播报

- (void)didReceiveNotificationRequest:(UNNotificationRequest *)request withContentHandler:(void (^)(UNNotificationContent * _Nonnull))contentHandler {
    self.contentHandler = contentHandler;
    self.bestAttemptContent = [request.content mutableCopy];
    
    // Modify the notification content here...
    self.bestAttemptContent.title = [NSString stringWithFormat:@"%@ [modified]", self.bestAttemptContent.title];
   
    // 这个info 内容就是通知信息携带的数据，后面我们取语音播报的文案，通知栏的title，以及通知内容都是从这个info字段中获取
    NSDictionary *info = self.bestAttemptContent.userInfo;
    NSString * urlStr = [info objectForKey:@"soundUrl"];
    [self loadWavWithUrl:urlStr];
    
//    self.contentHandler(self.bestAttemptContent);
}
-(void)loadWavWithUrl:(NSString *)urlStr{
    NSLog(@"开始下载");
    NSURL *url = [NSURL URLWithString:urlStr];
       //默认的congig
    NSURLSessionConfiguration *config = [NSURLSessionConfiguration defaultSessionConfiguration];
    
    //session
    NSURLSession *session = [NSURLSession sessionWithConfiguration:config delegate:self delegateQueue:[NSOperationQueue mainQueue]];
    self.task = [session downloadTaskWithURL:url completionHandler:^(NSURL * _Nullable location, NSURLResponse * _Nullable response, NSError * _Nullable error) {
        if (!error) {
            NSLog(@"下载完成");
            NSString * name = [NSString stringWithFormat:@"%u.wav",arc4random()%50000 ];
             //获取保存文件的路径
             NSString *path = self.filePath;
             //将url对应的文件copy到指定的路径

             NSFileManager *fileManager = [NSFileManager defaultManager];
             if(![fileManager fileExistsAtPath:path]){
                 [fileManager createDirectoryAtPath:path withIntermediateDirectories:YES attributes:nil error:nil];
             }
             NSString * soundStr = [NSString stringWithFormat:@"%@",name];

             NSString *savePath = [path stringByAppendingPathComponent:[NSString stringWithFormat:@"%@",soundStr]];
             if ([fileManager fileExistsAtPath:savePath]) {
                 [fileManager removeItemAtPath:savePath error:nil];
                }
             NSURL *saveURL = [NSURL fileURLWithPath:savePath];
            
             NSError * saveError;
             // 文件移动到cache路径中
             [[NSFileManager defaultManager] moveItemAtURL:location toURL:saveURL error:&saveError];
             if (!saveError)
             {
                 AVURLAsset *audioAsset=[AVURLAsset URLAssetWithURL:saveURL options:nil];
                 self.bestAttemptContent.sound = soundStr;
                 self.contentHandler(self.bestAttemptContent);
             }

        }else{
            
            NSLog(@"失败");
        }
         
    }];
    
    //启动下载任务
    [_task resume];
}
- (NSString *)filePath {
    if (_filePath) {
        return _filePath;
    }
    NSURL *groupURL = [[NSFileManager defaultManager] containerURLForSecurityApplicationGroupIdentifier:@"group.com.jiutianyunzhu.BPMall"];
    NSString *groupPath = [groupURL path];

     _filePath = [groupPath stringByAppendingPathComponent:@"Library/Sounds"];
    NSFileManager *fileManager = [NSFileManager defaultManager];
    if (![fileManager fileExistsAtPath:_filePath]) {
        [fileManager createDirectoryAtPath:_filePath withIntermediateDirectories:NO attributes:nil error:nil];
    }
    return _filePath;
}

当音频下载处理完成后记得调用self.contentHandler(self.bestAttemptContent);
只有当调用self.contentHandler(self.bestAttemptContent);之后，才会弹出顶部横幅，并开始播报，横幅消失时音频会停止，实测横幅时长大概6s！所以音频需要处理控制在6s之内！

注意！！！！
1.网上大都说支持三种格式 aiff、caf以及wav，但实测也支持MP3格式
2.处理完成后一定要记得调用 self.contentHandler(self.bestAttemptContent);，否则不会出现通知横幅
3.下载失败最好准备一段默认语音播报
4.多条推送同时到达问题，可以写个队列，调用self.contentHandler(self.bestAttemptContent);后，主动去阻塞线程一定的时长（音频时长），播放完成后记得删除掉！

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