iOS-实现后台长时间运行

前言

一般APP在按下Home键被挂起后，这时APP的 backgroundTimeRemaining 也就是后台运行时间大约只有3分钟，如果在退出APP后，过十几二十二分钟或者更长时间再回到APP，APP就会回到刚打开时的状态，也就是首页；有的项目在被挂起后需要在后台运行一段时间，使有足够的时间来完成与服务器对接的操作，或者需要一直运行的需求；如果需要，则在APP被挂起后，申请后台，来延长后台运行时间。

APP申请后台运行的方式有几种：

播放音乐

定位 

Newsstand downloads

fetch 等；

这里主要说下后台播放无声音乐（其实是不播放），采用哪种方式，对应勾选上图；我的项目中有音频播放需求，如果没有，那就找一个播放音频的理由，或者用其他方式实现。

实现

这里采用了两个单例：电话监控（XKTelManager）、后台运行（XKBGRunManager），电话监控可以忽略，视情况而用；采用单例是为了方便管理；

XKTelManager.h

#import <Foundation/Foundation.h>

@interface XKTelManager : NSObject
///是否在后台运行
@property (nonatomic,assign) BOOL inBackgroundRun;
+ (XKTelManager *)sharedManager;
/**
 来电监听
 */
- (void)startMonitor;
@end

XKTelManager.m

#import "XKTelManager.h"
#import "XKBGRunManager.h"
#import <CoreTelephony/CTCallCenter.h>
#import <CoreTelephony/CTCall.h>

static XKTelManager *_sharedManger;
@interface XKTelManager()
@property (nonatomic, strong) CTCallCenter *callCenter;
@end
@implementation XKTelManager
+ (XKTelManager *)sharedManager{
    static dispatch_once_t onceTelSingle;
    dispatch_once(&onceTelSingle, ^{
        if (!_sharedManger) {
            _sharedManger = [[XKTelManager alloc]init];
        }
    });
    return _sharedManger;
}
- (instancetype)init{
    self = [super init];
    if (self) {
        _inBackgroundRun = NO;
    }
    return self;
}
#pragma mark -********* 监听电话相关
- (void)startMonitor {
    __weak typeof(self) weakSelf = self;
    _callCenter = [[CTCallCenter alloc] init];
    _callCenter.callEventHandler = ^(CTCall * call) {
        ///如果已经进入后台了，不做任何操作
        if (weakSelf.inBackgroundRun) {
            return;
        }
        ///APP未进入后台
        if ([call.callState isEqualToString:CTCallStateDisconnected]){
            NSLog(@"电话 --- 断开连接");
            [[XKBGRunManager sharedManager] stopBGRun];
        }
        else if ([call.callState isEqualToString:CTCallStateConnected]){
            NSLog(@"电话 --- 接通");
        }
        else if ([call.callState isEqualToString:CTCallStateIncoming]){
            NSLog(@"电话 --- 待接通");
            [[XKBGRunManager sharedManager] startBGRun];
        }
        else if ([call.callState isEqualToString:CTCallStateDialing]){
            NSLog(@"电话 --- 拨号中");
            [[XKBGRunManager sharedManager] startBGRun];
        }
        else {
            NSLog(@"电话 --- 无操作");
        }
        
    };
}
@end

XKBGRunManager.h

#import <Foundation/Foundation.h>

@interface XKBGRunManager : NSObject
+ (XKBGRunManager *)sharedManager;

/**
 开启后台运行
 */
- (void)startBGRun;

/**
 关闭后台运行
 */
- (void)stopBGRun;
@end

XKBGRunManager.m

#import "XKBGRunManager.h"
///循环时间
static NSInteger _circulaDuration = 60;
static XKBGRunManager *_sharedManger;
@interface XKBGRunManager()
@property (nonatomic,assign) UIBackgroundTaskIdentifier task;
///后台播放
@property (nonatomic,strong) AVAudioPlayer *playerBack;
@property (nonatomic, strong) NSTimer *timerAD;
///用来打印测试
@property (nonatomic, strong) NSTimer *timerLog;
@property (nonatomic,assign) NSInteger count;
@end
@implementation XKBGRunManager{
    CFRunLoopRef _runloopRef;
    dispatch_queue_t _queue;
}
+ (XKBGRunManager *)sharedManager{
    static dispatch_once_t onceRunSingle;
    dispatch_once(&onceRunSingle, ^{
        if (!_sharedManger) {
            _sharedManger = [[XKBGRunManager alloc]init];
        }
    });
    return _sharedManger;
}
/// 重写init方法，初始化音乐文件
- (instancetype)init {
    if (self = [super init]) {
        [self setupAudioSession];
        _queue = dispatch_queue_create("com.audio.inBackground", NULL);
        //静音文件
        NSString *filePath = [[NSBundle mainBundle] pathForResource:@"****" ofType:@"mp3"];
        NSURL *fileURL = [[NSURL alloc] initFileURLWithPath:filePath];
        self.playerBack = [[AVAudioPlayer alloc] initWithContentsOfURL:fileURL error:nil];
        [self.playerBack prepareToPlay];
        // 0.0~1.0,默认为1.0
        self.playerBack.volume = 0.01;
        // 循环播放
        self.playerBack.numberOfLoops = -1;
    }
    return self;
}

- (void)setupAudioSession {
    // 新建AudioSession会话
    AVAudioSession *audioSession = [AVAudioSession sharedInstance];
    // 设置后台播放
    NSError *error = nil;
    [audioSession setCategory:AVAudioSessionCategoryPlayback withOptions:AVAudioSessionCategoryOptionMixWithOthers error:&error];
    if (error) {
        NSLog(@"Error setCategory AVAudioSession: %@", error);
    }
    NSLog(@"%d", audioSession.isOtherAudioPlaying);
    NSError *activeSetError = nil;
    // 启动AudioSession，如果一个前台app正在播放音频则可能会启动失败
    [audioSession setActive:YES error:&activeSetError];
    if (activeSetError) {
        NSLog(@"Error activating AVAudioSession: %@", activeSetError);
    }
}

/**
 启动后台运行
 */
- (void)startBGRun{
    [self.playerBack play];
    [self applyforBackgroundTask];
    ///确保两个定时器同时进行
    dispatch_async(_queue, ^{
        self.timerLog = [[NSTimer alloc] initWithFireDate:[NSDate date] interval:1 target:self selector:@selector(log) userInfo:nil repeats:YES];
        self.timerAD = [[NSTimer alloc] initWithFireDate:[NSDate date] interval:_circulaDuration target:self selector:@selector(startAudioPlay) userInfo:nil repeats:YES];
        _runloopRef = CFRunLoopGetCurrent();
        [[NSRunLoop currentRunLoop] addTimer:self.timerAD forMode:NSDefaultRunLoopMode];
        [[NSRunLoop currentRunLoop] addTimer:self.timerLog forMode:NSDefaultRunLoopMode];
        CFRunLoopRun();
    });
}

/**
 申请后台
 */
- (void)applyforBackgroundTask{
    _task =[[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:^{
        dispatch_async(dispatch_get_main_queue(), ^{
            [[UIApplication sharedApplication] endBackgroundTask:_task];
            _task = UIBackgroundTaskInvalid;
        });
    }];
}

/**
 打印
 */
- (void)log{
    _count = _count + 1;
    NSLog(@"_count = %ld",_count)
}

/**
 检测后台运行时间
 */
- (void)startAudioPlay{
    _count = 0;
    dispatch_async(dispatch_get_main_queue(), ^{
        if ([[UIApplication sharedApplication] backgroundTimeRemaining] < 61.0) {
            NSLog(@"后台快被杀死了");
            [self.playerBack play];
            [self applyforBackgroundTask];
        }
        else{
            NSLog(@"后台继续活跃呢");
        }///再次执行播放器停止，后台一直不会播放音乐文件
        [self.playerBack stop];
    });
}

/**
 停止后台运行
 */
- (void)stopBGRun{
    if (self.timerAD) {
        CFRunLoopStop(_runloopRef);
        [self.timerLog invalidate];
        self.timerLog = nil;
        // 关闭定时器即可
        [self.timerAD invalidate];
        self.timerAD = nil;
        [self.playerBack stop];
    }
    if (_task) {
        [[UIApplication sharedApplication] endBackgroundTask:_task];
        _task = UIBackgroundTaskInvalid;
    }
}

@end

最后在 AppDelegate.m 对应的方法中，实现开启和停止后台运行即可！