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iOS 关于后台持续运行

未分类 云聊IM 36℃

在日常的工作开发中,有时会遇到需要在后台持续运行的需求。对于这个需求,安卓实现起来比较简单,而iOS来说就比较复杂了。前段时间我们公司就有后台持续定位,并且上传上传地理坐标的需求(可能听起来有点流氓)。趁现在有空总结下。

先小结下:

  • 一般来说,没有进行过任何设置的app,默认退到后台极短的几秒后就变成挂起状态
  • 当设置了UIBackgroundTaskIdentifier后台任务标记时,程序后台保活会延迟到三分钟左右
  • 再设置后台持续定位,或者持续voip播放模式后,会长时间保活,这个时间从原理上可以无限(参考网易、酷狗等音乐播放器),我自己用的后台持续定位模式所持续的时间基本都在2小时以上

下面来说下主要操作和原理

 这里我测试后台持续时间是用APP角标计数的,因为发现如果本地调试退到后台和拔出线正常跑的时间结果不一样,在上面的第二种情况(UIBackgroundTaskIdentifier)情况下,如果本地连线调试,也可以很久,但是拔出线设置角标也就三分钟

先起个定时器用来改变角标(显示角标需要先注册)以记录时间,并在退到后台时启动

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    //注册推送
    UNUserNotificationCenter *center = [UNUserNotificationCenter currentNotificationCenter];
    [center requestAuthorizationWithOptions:(UNAuthorizationOptionBadge | UNAuthorizationOptionSound | UNAuthorizationOptionAlert) completionHandler:^(BOOL granted, NSError * _Nullable error) {
        if (!error) {
            NSLog(@"request authorization succeeded!");
        }
    }];
    
    return YES;
}

- (void)applicationDidEnterBackground:(UIApplication *)application {
    [self stratBadgeNumberCount];
}

- (void)stratBadgeNumberCount{
    [UIApplication sharedApplication].applicationIconBadgeNumber = 0;

    _badgeTimer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, dispatch_get_main_queue());
    dispatch_source_set_timer(_badgeTimer, DISPATCH_TIME_NOW, 1 * NSEC_PER_SEC, 1 * NSEC_PER_SEC);
    dispatch_source_set_event_handler(_badgeTimer, ^{
        [UIApplication sharedApplication].applicationIconBadgeNumber ++;
    });
    dispatch_resume(_badgeTimer);
}

正常未设置情况

代码和上面一样,角标在退出后台情况下只增加了一次

未设置情况下

设置bgtask

在进行代码实验前,先对UIBackgroundTaskIdentifier 进行了解下。
beginBackgroundTaskWithExpirationHandler这个方法是开启后台延迟挂起的操作方法,这个时间是有限的。通过UIApplication中的backgroundTimeRemaining值判断系统给你剩余的时间。

在前台运行时,backgroundTimeRemaining这个值是doule_max,就是说无限,在后台时这个值大约在180s左右,然后系统额外时间结束,开始进入挂起状态,注意这里不要在线本地调试

 - (void)applicationDidEnterBackground:(UIApplication *)application {
    [self stratBadgeNumberCount];
    [self startBgTask];
}

- (void)startBgTask{
    UIApplication *application = [UIApplication sharedApplication];
    __block    UIBackgroundTaskIdentifier bgTask;
    bgTask = [application beginBackgroundTaskWithExpirationHandler:^{
        //这里延迟的系统时间结束
        NSLog(@"%f",application.backgroundTimeRemaining);
    }];
}

果然值持续了180s左右

重复启动Bgtask

然后在以上基础思考这个问题的时候想,能不能在刚好快结束的时候,通过dispatch_after或者在block里重新开启一次bgtask 来获取新一轮的延长时间,所以进行了如下设置

死循环执行
延迟一段时间后重新开一个

这两种姿势都还是只能撑180s,所有我在想是不是就算重新开了一个bgtask也不会增加系统剩余时间

设置系统标志的后台任务 — voip、location

location模式

我先用的后台定位,这个需要在

  • 这里勾选一下后台定位更新
  • 添加定位隐私描述 Privacy – Location Always and When In Use Usage Description 我这里是11的系统,就直接用这个了
  • 开启定时器调用系统定位方法进行定位,并设置后台更新模式为YES,iOS9系统才能用
  • 去吃午饭,回来看依然在跑

code如下

#import "AppDelegate.h"
#import <UserNotifications/UserNotifications.h>
#import <CoreLocation/CoreLocation.h>
@interface AppDelegate ()<CLLocationManagerDelegate>
@property (nonatomic) dispatch_source_t badgeTimer;
@end

@implementation AppDelegate{
    CLLocationManager *appleLocationManager;
}


- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    //注册推送
    UNUserNotificationCenter *center = [UNUserNotificationCenter currentNotificationCenter];
    [center requestAuthorizationWithOptions:(UNAuthorizationOptionBadge | UNAuthorizationOptionSound | UNAuthorizationOptionAlert) completionHandler:^(BOOL granted, NSError * _Nullable error) {
        if (!error) {
            NSLog(@"request authorization succeeded!");
        }
    }];    
    return YES;
}

- (void)applicationDidEnterBackground:(UIApplication *)application {
    [self stratBadgeNumberCount];
    [self startBgTask];
}

- (void)startBgTask{
    UIApplication *application = [UIApplication sharedApplication];
    __block    UIBackgroundTaskIdentifier bgTask;
    bgTask = [application beginBackgroundTaskWithExpirationHandler:^{
        //这里延迟的系统时间结束
        [application endBackgroundTask:bgTask];
        NSLog(@"%f",application.backgroundTimeRemaining);
    }];

}

- (void)stratBadgeNumberCount{
    [UIApplication sharedApplication].applicationIconBadgeNumber = 0;
//UIApplication *application = [UIApplication sharedApplication];
    _badgeTimer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, dispatch_get_main_queue());
    dispatch_source_set_timer(_badgeTimer, DISPATCH_TIME_NOW, 1 * NSEC_PER_SEC, 1 * NSEC_PER_SEC);
    dispatch_source_set_event_handler(_badgeTimer, ^{

        [UIApplication sharedApplication].applicationIconBadgeNumber++;
        
        appleLocationManager = [[CLLocationManager alloc] init];
        appleLocationManager.allowsBackgroundLocationUpdates = YES;
        appleLocationManager.desiredAccuracy = kCLLocationAccuracyBest;
        appleLocationManager.delegate = self;
        [appleLocationManager requestAlwaysAuthorization];
        [appleLocationManager startUpdatingLocation];
    });
    dispatch_resume(_badgeTimer);
}



/** 苹果_用户位置更新后,会调用此函数 */
- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray<CLLocation *> *)locations{
    [appleLocationManager stopUpdatingLocation];
    appleLocationManager.delegate = nil;
    NSLog(@"success");
}

/** 苹果_定位失败后,会调用此函数 */
- (void)locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error{
    [appleLocationManager stopUpdatingLocation];
    appleLocationManager.delegate = nil;
    NSLog(@"error");
}
@end

到这里功能就基本实现了,下面看使用voip进行调用的实现

后台播放静默语音模式

  • 和定位一样,勾选后台声音选项
  • 播放静默声音,无限循环

代码如下

#import "AppDelegate.h"
#import <UserNotifications/UserNotifications.h>
#import <CoreLocation/CoreLocation.h>
#import <AVFoundation/AVFoundation.h>
//#import "TestUserVoice.h"
@interface AppDelegate ()<CLLocationManagerDelegate>
@property (nonatomic) dispatch_source_t badgeTimer;
@property (nonatomic, strong) AVAudioPlayer *player;
@end

@implementation AppDelegate{
    CLLocationManager *appleLocationManager;
}


- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    //注册推送
    UNUserNotificationCenter *center = [UNUserNotificationCenter currentNotificationCenter];
    [center requestAuthorizationWithOptions:(UNAuthorizationOptionBadge | UNAuthorizationOptionSound | UNAuthorizationOptionAlert) completionHandler:^(BOOL granted, NSError * _Nullable error) {
        if (!error) {
            NSLog(@"request authorization succeeded!");
        }
    }];
    [self player];
    return YES;
}

- (void)applicationDidEnterBackground:(UIApplication *)application {
    [self stratBadgeNumberCount];
    [self startBgTask];
    /** 播放声音 */
    [self.player play];
}

- (AVAudioPlayer *)player{
    if (!_player){
        NSURL *url=[[NSBundle mainBundle]URLForResource:@"work5.mp3" withExtension:nil];
        _player = [[AVAudioPlayer alloc]initWithContentsOfURL:url error:nil];
        [_player prepareToPlay];
        //一直循环播放
        _player.numberOfLoops = -1;
        AVAudioSession *session = [AVAudioSession sharedInstance];
        [session setCategory:AVAudioSessionCategoryPlayback error:nil];
        
        [session setActive:YES error:nil];
    }
    return _player;
}


- (void)startBgTask{
    UIApplication *application = [UIApplication sharedApplication];
    __block    UIBackgroundTaskIdentifier bgTask;
    bgTask = [application beginBackgroundTaskWithExpirationHandler:^{
        //这里延迟的系统时间结束
        [application endBackgroundTask:bgTask];
        NSLog(@"%f",application.backgroundTimeRemaining);
    }];

}

- (void)stratBadgeNumberCount{
    [UIApplication sharedApplication].applicationIconBadgeNumber = 0;

    _badgeTimer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, dispatch_get_main_queue());
    dispatch_source_set_timer(_badgeTimer, DISPATCH_TIME_NOW, 1 * NSEC_PER_SEC, 1 * NSEC_PER_SEC);
    dispatch_source_set_event_handler(_badgeTimer, ^{

        [UIApplication sharedApplication].applicationIconBadgeNumber++;
//        appleLocationManager = [[CLLocationManager alloc] init];
//        appleLocationManager.allowsBackgroundLocationUpdates = YES;
//        appleLocationManager.desiredAccuracy = kCLLocationAccuracyBest;
//        appleLocationManager.delegate = self;
//        [appleLocationManager requestAlwaysAuthorization];
//        [appleLocationManager startUpdatingLocation];

    });
    dispatch_resume(_badgeTimer);
}
@end

以上两种后台模式都可以支持无限运行,但是都有两个很尴尬的问题

  • 比较费电
  • 审核人员会问你你想干啥

第一种后台定位的情况我们是打电话进行交流,说明了我们软件需要采集用户信息展示出来(和滴滴展示轨迹一样),后台语音那个,我们是录取一个视频给审核人员看的,虽然我觉得这个功能可能还是被拒,但是审核人员对这个好像不太严格,看了一下视频就过了

总结

以上就是对后台持续运行的探讨,个人意见是,如果不需要后台持续做一些操作的话,不需要开启capabilities的后天模式,三分钟已经足够做很多事了。
      但是如果有需求的话,就需要设置后台模式,并且应对苹果的审核人员

Demo:https://github.com/MoonMD/BgTaskDemo.git

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