我花了几天时间在SO和其他网站上研究,以回答这一问题,但没有任何uck。

基本上,我为自己确定的挑战是,为SOS制造一个警钟,不管用户(理由或背景)在哪里,都不会听从。 我已经完成这项工作,使用了AVAudioPlayer案,并在用户发出警报时开始使用空洞的声音,以便用户能够保持这种背景。 当警报要走的时候(例如当发射国家安全局时),已经启动并准备起作用的第二角色就开始迎来用户的警钟。

此外,我通过实施AVAudioSessionDelegate方法,通过电话、系统时间或警钟处理中断问题。 它既在背景上又在地缘上运作,但最奇怪的是:

当中断结束时,AVAudioPlayer继续玩.BUT I,除非我再次把 app子带到地下。

To get to the bottom of this, I have experimented with a much simpler project which I am posting below. What this app does is, as soon as you enter the app, an instance of the AVAudioPlayer class starts looping a certain sound. Then when you bring it to the background, the player continues to loop the sound. When an interruption occurs I pause the player and when it ends I use a dispatch to wait a couple of seconds before it calls two methods, ie (void)playPlayer, a method that contains the code to resume playing the file and (void)tester, a method that contains a timer, which is set to stop the player 5 seconds after the interruption (or 7 seconds to be exact) has ended. Both the methods get called as indicated by the NSLogs I have put in both of them, but the timer never gets fired and the player continues to play indefinitely.

The Code for the .h file:

#import <UIKit/UIKit.h>
#import <AVFoundation/AVFoundation.h>
#import <AudioToolbox/AudioToolbox.h>

@interface InterruptionTest3ViewController : UIViewController <AVAudioSessionDelegate,      AVAudioPlayerDelegate>
{
    AVAudioSession *mySession;
    AVAudioPlayer *myPlayer;
}

-(void) playPlayer;
-(void) pausePlayer;
-(void) tester;

@end

这里是:

#import "InterruptionTest3ViewController.h"

@interface InterruptionTest3ViewController ()

@end

@implementation InterruptionTest3ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    mySession = [AVAudioSession sharedInstance];
    NSError *setActiveError = nil;
    [mySession setActive:YES withFlags:AVAudioSessionSetActiveFlags_NotifyOthersOnDeactivation error:&setActiveError];
    if (setActiveError) {
        NSLog(@"Session failed to activate within viewDidLoad");
    }
    else {
        NSLog(@"Session was activated within viewDidLoad");
    }
    NSError *setCategoryError = nil;
    [mySession setCategory:AVAudioSessionCategoryPlayback error:&setCategoryError];
    if (setCategoryError) {
        NSLog(@"Category failed to be set");
    }
    else {
        NSLog(@"Category has been set");
    }

    [mySession setDelegate:self];


    NSString *path = [[NSBundle mainBundle] pathForResource:@"headspin" ofType:@"wav"];
    NSError *initMyPlayerError = nil;
    myPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:[NSURL fileURLWithPath:path]     error:&initMyPlayerError];
    if (initMyPlayerError) {
        NSLog(@"myPlayer failed to initiate");
    }
    else {
        NSLog(@"myPlayer has been initiated");
    }

    [myPlayer prepareToPlay];
    [self playPlayer];

    OSStatus propertySetError = 0;
    UInt32 allowMixing = true;

    propertySetError = AudioSessionSetProperty (
                                                kAudioSessionProperty_OverrideCategoryMixWithOthers, 
                                                sizeof (allowMixing),                                 
                                                &allowMixing                                          
                                                );

    [myPlayer setNumberOfLoops:-1];
    [[UIApplication sharedApplication] beginReceivingRemoteControlEvents];
}

-(void) beginInterruption
{
    [myPlayer pause];
}

-(void) endInterruptionWithFlags:(NSUInteger)flags
{
    if (flags) {
        if (AVAudioSessionInterruptionFlags_ShouldResume) 
        {
            {
                dispatch_after(dispatch_time(DISPATCH_TIME_NOW, 2 * NSEC_PER_SEC),dispatch_get_main_queue(), ^{

                    [self playPlayer];
                    [self tester];
                });
}
        }
    }
}

-(void) tester
{
    [NSTimer timerWithTimeInterval:5.0 target:self selector:@selector(pausePlayer) userInfo:nil repeats:NO];
    NSLog(@"tester method has been called");
}

-(void) playPlayer
{
    [NSTimer timerWithTimeInterval:5.0 target:myPlayer selector:@selector(stop) userInfo:nil repeats:NO];
    [myPlayer play];
    NSLog(@"playPlayer method has been called");
}

-(void) pausePlayer
{
    [myPlayer pause];
}



//viewDidUnload etc not listed.

因此,这是民俗。 同样,为什么在机车身为背景时,停工时间没有被发射? 我是否需要在应用DidEnterBackground方法中找到一些东西?

非常感谢你们。