App在后臺的情況希望通知用戶看到信息時使用本地推送通知實現(xiàn)。
1.導(dǎo)入系統(tǒng)框架

#import <UserNotifications/UserNotifications.h>

2.注冊本地通知樣式

UIApplication* application = [UIApplication sharedApplication];
    if ([application currentUserNotificationSettings]) {
      UIUserNotificationSettings* setting = [UIUserNotificationSettings
          settingsForTypes:UIUserNotificationTypeBadge |
                           UIUserNotificationTypeSound |
                           UIUserNotificationTypeAlert
                categories:nil];
      [application registerUserNotificationSettings:setting];
    }

3.清除之前注冊通知

[application cancelAllLocalNotifications];

如果不清除歷史通知，可能會收到之前的全部通知。
4.設(shè)置本次通知內(nèi)容

UILocalNotification* localNotif = [[UILocalNotification alloc] init];
// 發(fā)送時間
    localNotif.fireDate =[NSDate dateWithTimeIntervalSinceNow:0];
// 在通知中心要展示的通知內(nèi)容
    localNotif.alertBody = @"本地推送通知";
// 通知攜帶的內(nèi)容信息，開發(fā)者自行處理
    localNotif.userInfo = @{@"userid":@(123), @"message":@"通知"};
// 自定義同事提示聲音，必須是.caf格式音頻文件
    localNotif.soundName = @"voip_call.caf";
// 通知唯一標識，可以是msgId，用戶刪除、查找通知
    localNotif.alertAction = @"notificationId";
    [application scheduleLocalNotification:localNotif];

以上方法在 iOS10之后被棄用，iOS 開始使用UNUserNotificationCenter
具體邏輯大概類似。UNUserNotificationCenter的內(nèi)容更加豐富，可以通過它自行定義通知顯示樣式，功能更加強大。

UNUserNotificationCenter* center =
      [UNUserNotificationCenter currentNotificationCenter];
  UNMutableNotificationContent* content =
      [[UNMutableNotificationContent alloc] init];
  content.body =  @"本地推送通知";
  UNNotificationSound* sound =
      [UNNotificationSound soundNamed:@"voip_call.caf"];
  content.sound = sound;
  content.userInfo = @{@"userid":@(123), @"message":@"通知"};
  UNTimeIntervalNotificationTrigger* tirgger =
      [UNTimeIntervalNotificationTrigger triggerWithTimeInterval:0.1
                                                         repeats:NO];
/// Identifier 通知唯一標識，用于刪除、查找通知
  UNNotificationRequest* request =
      [UNNotificationRequest requestWithIdentifier:@"notificationId"
                                           content:content
                                           trigger:tirgger];

  [center addNotificationRequest:request
           withCompletionHandler:^(NSError* _Nullable error) {
             NSLog(@"%@本地推送 :( 報錯 %@", @"notificationKey", error);
           }];

最后接收本地推送通知

- (void)application:(UIApplication*)application
    didReceiveLocalNotification:(UILocalNotification*)notification {
  
}

iOS10之后
// 點擊推送消息后回調(diào)

- (void)userNotificationCenter:(UNUserNotificationCenter*)center
    didReceiveNotificationResponse:(UNNotificationResponse*)response
             withCompletionHandler:(void (^)(void))completionHandler {
  NSLog(@"center content : %@", response.notification.request.content.userInfo);
  
}

有時候需要刪除通知中心的通知，類似微信撤回消息時會撤回通知

- (void)deleteAVChatLocalNotificationId:(NSString *)notificationId {
    __block BOOL has = NO;
    UIApplication* application = [UIApplication sharedApplication];
    if (@available(iOS 10.0, *)) {
        UNUserNotificationCenter* center =
        [UNUserNotificationCenter currentNotificationCenter];
        [center getPendingNotificationRequestsWithCompletionHandler:^(
                                                                      NSArray<UNNotificationRequest*>* _Nonnull requests) {
                                                                          for (UNNotificationRequest* request in requests) {
                                                                              if ([request.identifier isEqualToString:notificationId]) {
                                                                                  has = YES;
                                                                                  break;
                                                                              }
                                                                          }
                                                                      }];
        if (has) {
            [center
             removeDeliveredNotificationsWithIdentifiers:@[notificationId]];
        }
    } else {
        NSArray* localNotifications = [application scheduledLocalNotifications];
        for (UILocalNotification* local in localNotifications) {
            if ([local.alertAction isEqualToString:notificationId]) {
                [application cancelLocalNotification:local];
                has = YES;
                break;
            }
        }
    }
    if (has) {
        NSInteger num = [application applicationIconBadgeNumber];
        if (num > 1) {
            [application setApplicationIconBadgeNumber:num - 1];
        } else {
            [application setApplicationIconBadgeNumber:0];
        }
    }
}

mp3轉(zhuǎn) caf
第一步：獲取MP3文件路徑，為了方便測試，這里把文件放到了桌面上，地址為 ：/Users/Mina/Desktop/1.mp3

第二步：設(shè)置CAF文件的輸出路徑，這里也放到了桌面上，路徑為：/Users/Mina/Desktop/2.caf

第三步：打開終端輸入命令：
afconvert /Users/Mina/Desktop/1.mp3 /Users/Mina/Desktop/2.caf -d ima4 -f caff -v
(注：不要忘記空格)